01584nas a2200145   4500008004100000245010200041210006900143300001200212490000600224520097800230100002101208700002201229700002301251856016401274       2022                        eng d00aApplying Machine Learning and Dynamic Resource Allocation Techniques in Fifth Generation Networks0 aApplying Machine Learning and Dynamic Resource Allocation Techni  a662-6730 v13 aAccording to Internet of Things (IoT) Analytics, soon, the online devices in IoT networks will range from 25 up to 50 billion. Thus, it is expected that IoT will require more effective and efficient analysis methods than ever before with the use of Machine Learning (ML) powered by Fifth Generation (5G) networks. In this paper, we incorporate the K-means algorithm inside a 5G network infrastructure to better associate devices with Base Stations (BSs). We use multiple datasets consisting of user distribution in our area of focus and propose a Dynamic Resource Allocation (DRA) technique to learn their movement and predict the optimal position, RB usage and optimize their resource allocation. Users can experience significantly higher data rates and extended coverage with minimized interference and in fact, the DRA mechanism can mitigate the need for small cell infrastructure and prove a cost-effective solution, due to the resources transferred within the network.1 aBouras, Christos1 aMichos, Evangelos1 aProkopiou, Ioannis  uhttp://telematics.upatras.gr/telematics/publications/applying-machine-learning-and-dynamic-resource-allocation-techniques-fifth-generation-networks?language=en01631nas a2200145   4500008004100000245007900041210006900120520104400189100002401233700002101257700002401278700002201302700002601324856013501350       2022                        eng d00aA Game Theoretic Approach for Efficient Resource Allocation in 5G Networks0 aGame Theoretic Approach for Efficient Resource Allocation in 5G 3 aHeterogeneous Networks (HetNets) have been lauded as a key technology for 5G communications, enabling fast growth in mobile traffic. HetNets may also expand the network’s capacity and serve more users. However, interference between small cells and macro-cells makes Quality of Service (QoS) more difficult to achieve, and thus novel protocols, new technologies, and future trends should also be included in order to provide efficiency in Resource Allocation (RA). Game Theory (GT) concepts have been widely used in a variety of engineering design challenges in which one component’s activity affects and perhaps conflicts with the actions of other components. As a result, game formulations are utilized, and the idea of equilibrium is applied to find a stable solution for the participants. In this paper, we compare two algorithms used for RA, the first being a classical RA algorithm and the second being a game theoretic one. The game implemented is called “Tragedy of the Commons”, and is applied in a non-cooperative network.1 aKoukouvela, Aspasia1 aBouras, Christos1 aKokkinos, Vasileios1 aGkamas, Apostolos1 aPouyioutas, Philippos  uhttp://telematics.upatras.gr/telematics/publications/game-theoretic-approach-efficient-resource-allocation-5g-networks?language=en01791nas a2200205   4500008004100000245009000041210006900131520101500200100002101215700002601236700002601262700001701288700002401305700002301329700002301352700002401375700002101399700002001420856014501440       2022                        eng d00aHoney discrimination based on the bee feeding by Laser Induced Breakdown Spectroscopy0 aHoney discrimination based on the bee feeding by Laser Induced B3 aIn the present work, the effects of artificial feeding of bees on the honey are investigated by employing for the first time, Laser Induced Breakdown Spectroscopy (LIBS) by analyzing the emission spectral characteristics of the plasma created on the surface of honey samples. Correlation plots indicating the importance of spectral lines of elements as e.g., Calcium (Ca), Magnesium (Mg), Sodium (Na) and Potassium (K) are constructed, while machine learning algorithms based on Linear Discriminant Analysis (LDA) and Random Forest Classifiers (RFC) are employed to classify the honey samples in terms of the bee food used. The constructed machine learning
models were validated by both cross-validation and external validation, while the obtained accuracies exceeded 90% of correct classification, indicating the potential of LIBS technique for honey discrimination. The obtained results by LIBS were also validated by HPLC-RID, which is the standard technique used for the analysis of the main honey sugars.1 aStefas, Dimitris1 aGyftokostas, Nikolaos1 aKourelias, Panagiotis1 aNanou, Eleni1 aTananaki, Chrysoula1 aKanelis, Dimitrios1 aLiolios, Vasileios1 aKokkinos, Vasileios1 aBouras, Christos1 aCouris, Stelios  uhttp://telematics.upatras.gr/telematics/publications/honey-discrimination-based-bee-feeding-laser-induced-breakdown-spectroscopy?language=en01989nas a2200193   4500008004100000245008500041210006900126300001200195490000700207520128800214100002101502700002401523700002201547700002201569700001801591700002301609700002301632856014001655       2022                        eng d00aAn Introduction of Upcoming Radio Resource Management Techniques for 5G Networks0 aIntroduction of Upcoming Radio Resource Management Techniques fo  a147-1880 v463 a5G networks are the next generation of mobile internet connectivity, that are able to offer vastly increased speeds, more reliable connections, minimal latency and more supported devices. 5G networks are expected to supercharge Internet of Things (IoT) technology, so as to provide the infrastructure needed in order to support and transfer large data amounts that will enable a smarter and more connected world. To this direction, 5G incorporates many technologies and mechanisms that aid towards the overall goal, such as Multiple-Input and Multiple-Output (MIMO), Downlink (DL) and Uplink (UL) Decoupling (DUDe) and Machine Learning (ML). These technologies can significantly help towards more efficient resource allocation inside the next generation networks, offering increased spectral efficiency and data rates, better signal coverage, reduced latencies and many more. In this chapter, we will provide insights over the aforementioned technologies through firstly a literature review and later on by analyzing their architecture and their models. We will explain how these technologies can be taken advantage of in order to support the 5G networks and why they are core components of future networks, as it is expected that also 5G and Beyond networks will capitalize on them.1 aBouras, Christos1 aKokkinos, Vasileios1 aGkamas, Apostolos1 aMichos, Evangelos1 aSina, Ioannis1 aProkopiou, Ioannis1 aAllayiotis, Foivos  uhttp://telematics.upatras.gr/telematics/publications/introduction-upcoming-radio-resource-management-techniques-5g-networks?language=en01351nas a2200145   4500008004100000245006600041210006400107520079800171100002000969700002400989700002201013700002601035700002101061856012301082       2022                        eng d00aA Machine Learning Approach to User Assignment in 5G Networks0 aMachine Learning Approach to User Assignment in 5G Networks3 aWith the advancement of wireless networks the data needs of the wireless internet have become so great, and the use of 4G and 5G so ubiquitous, that challenges arise in the availability and distribution of resources. In this paper we examine an application of Machine Learning and subsequently Neural Networks to offer a solution to this problem. The, now more than ever, profound availability of processing power greatly empowers and makes the deployment of these tools easier than ever, even in problems where in the past their application would not be feasible. The use of machine learning techniques to distribute resources in wireless networks is investigated and contrasted to a traditional algorithmic method. Scenarios are also entertained in which such approaches might be applicable.1 aKouris, Michael1 aKokkinos, Vasileios1 aGkamas, Apostolos1 aPouyioutas, Philippos1 aBouras, Christos  uhttp://telematics.upatras.gr/telematics/publications/machine-learning-approach-user-assignment-5g-networks?language=en01492nas a2200109   4500008004100000245006800041210006400109520104000173100002101213700002201234856012601256       2022                        eng d00aAn online real-time face recognition system for police purposes0 aonline realtime face recognition system for police purposes3 aIn general, face recognition algorithms are often utilized in order to identify or authenticate a human through a camera feed. However, face recognition algorithms must adapt to real-life uncertainties and noisy environments. This work targets upon extending the existing work of facial recognition algorithms by proposing an online platform that can be used from the police forces towards effective real-time human recognition. The approach on facial recognition is to use and extend the Haar Cascade algorithm for real-time purposes, which is widely considered one for the most efficient and used algorithms for that cause. As for the criminal identification, it will made possible through image pattern recognition between the provided criminal’s image and snapshots of identified faces from the livestream feed. The platform will include a live feed section with different options for video filters, enabling the user to select the best filter, depending on relevant situation of the physical surroundings for better recognition.1 aBouras, Christos1 aMichos, Evangelos  uhttp://telematics.upatras.gr/telematics/publications/online-real-time-face-recognition-system-police-purposes?language=en01584nas a2200133   4500008004100000245007100041210006900112520104900181100002101230700002301251700002201274700002401296856013001320       2022                        eng d00aPerformance Analysis of MIMO using Machine Learning in 5G Networks0 aPerformance Analysis of MIMO using Machine Learning in 5G Networ3 aMassive Multiple-Input Multiple-output (MIMO) is an important radio antenna technology for mobile wireless networks, such as 5th Generation (5G) with high potential. The use of hybrid analog and digital precoding to minimize the energy consumption as well as the hardware complexity of mixed signal components is an essential strategy. Machine Learning (ML) could be able to boost 5G technologies due to the rising difficulty of configuring cellular networks. More than ever, a ML computational framework focused on successfully processing the expected huge data generated normally by 5G networks with high subscriber cell density, is required. In the Ultra-Dense Networks (UDNs) of 5G and beyond high demanding networks paired with beamforming and massive MIMO technologies, ML struggles to define network traffic aspects distinctively, especially when they are projected to be much more dynamic and complicated. This paper presents a state-of-the-art analysis of the combined and multiple uses of ML along with MIMO technology in 5G Networks.1 aBouras, Christos1 aProkopiou, Ioannis1 aGkamas, Apostolos1 aKokkinos, Vasileios  uhttp://telematics.upatras.gr/telematics/publications/performance-analysis-mimo-using-machine-learning-5g-networks?language=en02104nas a2200109   4500008004100000245008800041210006900129520159800198100002101796700002701817856015001844       2022                        eng d00aPrediction Mechanisms to Improve 5G Network User allocation and Resource management0 aPrediction Mechanisms to Improve 5G Network User allocation and 3 aAs technology rapidly advances, the number of devices constantly communicating, transmitting and receiving data through the cellular networks keeps rising, posing an unprecedented load on them. Such an increase calls for establishing new methods to manage these devices as well as utilize the data produced by them to establish network architectures that can prevent cellular networks from overloading. To achieve the desired results, we need to optimally allocate network resources to existing users. Resource allocation has traditionally been considered an optimization problem where proposed solutions are hard to implement in real time, resulting in the use of inferior solutions with reduced produced performance. With the introduction of Machine Learning, we propose three mechanisms, intending to utilize network data to improve real time network performance. The first mechanism, a Decision Trees based mechanism aims to improve real time decision making by predicting the optimal matching of users and Base Stations. The second mechanism, a K-means based mechanism intends to tackle network congestion and ensure uninterrupted Quality of Service by predicting the optimal coordinates for placing Base Stations along the network based on traffic data. Finally, a Regression based mechanism manages to predict user movement along the network, resulting in improved resource management and reduced energy waste. These mechanisms can work cooperatively, essentially establishing a network architecture that utilizes prediction to efficiently allocate users and manage available resources.1 aBouras, Christos1 aKalogeropoulos, Rafail  uhttp://telematics.upatras.gr/telematics/publications/prediction-mechanisms-improve-5g-network-user-allocation-and-resource-management?language=en01783nas a2200145   4500008004100000245007000041210006900111520122000180100001801400700002101418700002201439700002401461700002401485856012801509       2022                        eng d00aResource Allocation In 5G and Beyond Networks for Mu-MIMO Systems0 aResource Allocation In 5G and Beyond Networks for MuMIMO Systems3 aThe resource allocation problem focuses on finding an optimal allocation of a specific number of resources to maintain Quality of Service (QoS). That is where Multiple-Input Multiple-Output (MIMO) come in as a radio antenna technology. In order to, optimize data speed, minimize errors and improve the radio transmission capacity MIMO utilizes multiple antennas at both the transmitter and the receiver. This technology uses a variety of antennas and paths that carry the data. Each antenna uses different paths. Multi-user MIMO (mu-MIMO) stands for a technology that allows routers to communicate simultaneously with multiple endpoint devices and it is the next evolutionary step of single user MIMO. Over the past decade, significant advances have been made to improve the performance of mu-MIMO. Although non-negligible progress has been achieved so far, optimal algorithms for Resource Allocation (RA) will help better the performance of mu-MIMO by increasing the system’s performance in terms of throughput, fairness, and QoS. The purpose of this paper is to provide a comparison of different beamforming techniques used for resource allocation and list them in ascending order depending on their efficiency.1 aBarri, Eirini1 aBouras, Christos1 aGkamas, Apostolos1 aKokkinos, Vasileios1 aKoukouvela, Aspasia  uhttp://telematics.upatras.gr/telematics/publications/resource-allocation-5g-and-beyond-networks-mu-mimo-systems?language=en01672nas a2200133   4500008004100000245011400041210006900155520104600224100002101270700003201291700002201323700002601345856016701371       2022                        eng d00aTechno-economic analysis of Cloud Computing supported by 5G: A Cloud vs On Premise based solutions comparison0 aTechnoeconomic analysis of Cloud Computing supported by 5G A Clo3 aCloud computing has gotten a lot of press in the IT world because it allows users to have instant access to a shared pool of configurable computer resources with no effort on their part. It is now being discussed as an enabler for more flexible, cost-effective, and powerful mobile network implementations in the communication technology (CT) sector.In this paper, a techno-economic analysis of a Cloud-based solution compared to an On-premise based one is developed. The technologies are analyzed in a technical way. Mathematical models that help determine the models’ pricing is analyzed. What is more, several experiments are conducted determining if the advantages and profits outweigh the disadvantages of each proposed solution. Also, the way 5G helps scale all these processes is analyzed. Finally, this article analyzes the conclusions of the work, as well as the result of the techno-economic study that was carried out, to explain to the reader the overall benefits provided to users by exploiting the Cloud Computing technology.1 aBouras, Christos1 aChatzigeorgiou, Charalampos1 aKollia, Anastasia1 aPouyioutas, Philippos  uhttp://telematics.upatras.gr/telematics/publications/techno-economic-analysis-cloud-computing-supported-5g-cloud-vs-premise-based-solutions-comparison?language=en01391nas a2200121   4500008004100000245008700041210006900128520085400197100002101051700002301072700002201095856015201117       2022                        eng d00aTechno-economic analysis of providers’ profit using Ultra-density in 5G networks0 aTechnoeconomic analysis of providers profit using Ultradensity i3 aFifth generation of mobile networks plays an important role internationally for the scientific community, as well as for everyday life. The challenges are rising, therefore, it is crucial to study technologies that can meet most requirements. Ultra-density is one of the technologies that appear to be a solution to the problems that arise. In this paper, authors present a techno-economic analysis of ultra-dense implementations and macrocellular deployments. In addition to structural analysis and benefits, authors develop economic models, based on parameters and factors that most affect these technologies. Furthermore, they conduct Sensitivity Analysis (SA) experiments based on those economic models, thus leading to important conclusions. Finally, there are proposals for future research and ways to reduce the higher costs of ultra-density.1 aBouras, Christos1 aFlorou, Aikaterini1 aKollia, Anastasia  uhttp://telematics.upatras.gr/telematics/publications/techno-economic-analysis-providers%E2%80%99-profit-using-ultra-density-5g-networks?language=en01268nas a2200121   4500008004100000245008400041210007000125520073700195100002300932700002100955700002400976856014601000       2022                        eng d00aΑ Machine Learning Mechanism for improved Energy Consumption in 5G Small Cells0 aΑ Machine Learning Mechanism for improved Energy Consumption in 3 aBy introducing 5G networks in our lives, we are faced with the challenge to lower energy consumption, which is expected to increase significantly. As a result, the communications sector must devise solutions to improve the energy efficiency of 5G networks while maintaining spectrum performance. We propose a Machine Learning Mechanism that provides new sleep mode functionalities, that reduce energy consumption during idle hours, on small cells. We will describe our model and examine its performance using data collected from a simulated environment. Furthermore, we present the results of our findings and conclude that such models are necessary for the introduction of 5G networks. Lastly, possible future steps, are discussed.1 aAllayiotis, Foivos1 aBouras, Christos1 aKokkinos, Vasileios  uhttp://telematics.upatras.gr/telematics/publications/%CE%B1-machine-learning-mechanism-improved-energy-consumption-5g-small-cells?language=en01115nas a2200169   4500008004100000245009000041210006900131520044400200100002100644700001800665700002200683700002500705700002400730700002300754700002300777856014500800       2021                        eng d00aAn agent-based simulation model for energy saving in large passenger and cruise ships0 aagentbased simulation model for energy saving in large passenger3 aUndoubtedly, energy saving is of paramount importance in the shipping industry, as far as both the protection of environment and the reduction of the associated operating costs are concerned. In this direction, the
International Maritime Organization aims to reduce ship emissions by at least 50% by 2050, while ships to be built by 2025 are expected to be a massive 30% more energy efficient than those built some years ago [IMO,
2018].1 aBouras, Christos1 aBarri, Eirini1 aGkamas, Apostolos1 aKaracapilidis, Nikos1 aKaradimas, Dimitris1 aKournetas, Giorgos1 aPanaretou, Yiannis  uhttp://telematics.upatras.gr/telematics/publications/agent-based-simulation-model-energy-saving-large-passenger-and-cruise-ships?language=en01787nas a2200169   4500008004100000245015200041210006900193490000700262520105700269100002601326700001701352700002201369700002401391700002101415700002001436856016101456       2021                        eng d00aClassification of Greek olive from different regions by machine learning - aided Laser - Induced Breakdown Spectroscopy and Absorption Spectroscopy0 aClassification of Greek olive from different regions by machine 0 v263 aIn the present work, the emission and the absorption spectra of numerous Greek olive oil samples and mixtures of them, obtained by two spectroscopic techniques, namely Laser-Induced Breakdown Spectroscopy (LIBS) and Absorption Spectroscopy, and aided by machine learning algorithms, were employed for the discrimination/classification of olive oils regarding their geographical origin. Both emission and absorption spectra were initially preprocessed by means of Principal Component Analysis (PCA) and were subsequently used for the construction of predictive models, employing Linear Discriminant Analysis (LDA) and Support Vector Machines (SVM). All
data analysis methodologies were validated by both “k-fold” cross-validation and external validation methods. In all cases, very high classification accuracies were found, up to 100%. The present results demonstrate the advantages of machine learning implementation for improving the capabilities of these spectroscopic techniques as tools for efficient olive oil quality monitoring and control.1 aGyftokostas, Nikolaos1 aNanou, Eleni1 aStefas, Dimitrios1 aKokkinos, Vasileios1 aBouras, Christos1 aCouris, Stelios  uhttp://telematics.upatras.gr/telematics/publications/classification-greek-olive-different-regions-machine-learning-aided-laser-induced-breakdown?language=en01382nas a2200121   4500008004100000245005200041210005200093520093500145100002101080700002701101700001801128856011401146       2021                        eng d00aClustering Based User Allocation in 5G Networks0 aClustering Based User Allocation in 5G Networks3 aMachine Learning is an extremely efficient technique for solving complex problems without the use of traditional programming but rather enabling machines to learn from an input of data and train them to cope with various problems. The rapid growth in the number of active mobile devices, mobile applications and services dictate an efficient utilization of mobile and wireless networking infrastructure. Communication networks need to evolve and valorize Machine Learning methods in order to process large volumes of data without introducing excessive time delay in these computations. Upcoming 5G systems are expected to be the first network infrastructure to support exploding mobile traffic volumes and Machine Learning techniques can be used in order to help manage the rise in data volumes. We present a mechanism for resource allocation in mobile and wireless networks, that effectively utilizes Machine Learning techniques.1 aBouras, Christos1 aKalogeropoulos, Rafail1 aSina, Ioannis  uhttp://telematics.upatras.gr/telematics/publications/clustering-based-user-allocation-5g-networks?language=en01729nas a2200157   4500008004100000245009900041210006900140300001200209490000700221520109500228100002101323700002201344700002601366700002701392856015201419       2021                        eng d00aA Comparative Study of Machine Learning Models for Spreading Factor Selection in LoRa Networks0 aComparative Study of Machine Learning Models for Spreading Facto  a100-1210 v103 aLow Power Wide Area Networks (LPWAN) technologies offer reasonably priced connectivity to a large number of low-power devices spread over great geographical ranges. Long Range (LoRa) is a LPWAN technology that empowers energy-efficient communication. In LoRaWAN networks collisions are strongly correlated with Spreading Factor (SF) assignment of end-nodes which affects network performance. In this work, SF assignment using Machine Learning models in simulation environment is presented. This work examines three approaches for the selection of the SF during LoRa transmissions a) random SF assignment b) Adaptive Data Rate (ADR) and c) SF selection through Machine Learning (ML). The main target is to study and determine the most efficient approach as well as to investigate the benefits of using ML techniques in the context of LoRa networks. In this research a library that enables the communication between ML libraries and OMNeT++ simulator was created. The performance of the approaches is evaluated for different scenarios, using the delivery ratio and energy consumption metrics.1 aBouras, Christos1 aGkamas, Apostolos1 aKatsampiris, Spyridon1 aPapachristos, Nikolaos  uhttp://telematics.upatras.gr/telematics/publications/comparative-study-machine-learning-models-spreading-factor-selection-lora-networks?language=en01676nas a2200121   4500008004100000245007100041210006900112520117900181100002101360700002201381700002201403856012901425       2021                        eng d00aComparison of Techno-Economic Solutions for 5G Networks and Beyond0 aComparison of TechnoEconomic Solutions for 5G Networks and Beyon3 aThe fifth-generation (5G) envisions a society that is constantly interconnected with a large number of devices, anywhere and anytime. The developed technologies play a substantial role, allowing low latency, large volumes of data traffic, and improved Quality of Service (QoS). The advent of 5G encourages providers and investors to develop innovative services that meet consumer demands. However, the viability of a new service should be investigated from an economic perspective. Therefore, the introduction of effective techniques concerning the financial evaluation of such services is essential. This paper analyzes 5G technologies and evaluates them in a techno-economic point of view using pricing models. In particular, the main factors used to estimate the different types of costs are Capital Expenditures (CAPEX) and Operational Expenditures (OPEX), which define the viability of each investment. Based on the results obtained, 5G is a profitable investment due to its low cost and increase in the average data consumption of each consumer. Finally, using metrics, it is found that reusing existing sites is less costly than to develop a dense macro-cell network.1 aBouras, Christos1 aKaisoudis, Fotios1 aKollia, Anastasia  uhttp://telematics.upatras.gr/telematics/publications/comparison-techno-economic-solutions-5g-networks-and-beyond?language=en01855nas a2200193   4500008004100000245015500041210006900196300000800265490000800273520105400281100002101335700002201356700002601378700002601404700001701430700002401447700002001471856017001491       2021                        eng d00aDiscrimination of olive oils based on the olive cultivar origin by machine learning employing the fusion of emission and absorption spectroscopic data0 aDiscrimination of olive oils based on the olive cultivar origin   a1-80 v1303 aIn this work Laser-Induced Breakdown Spectroscopy (LIBS) and absorption spectroscopy aided by machine learning are employed for discriminating some extra virgin Greek olive oils of different olive cultivars for the first
time. LIBS and absorption spectra of extra virgin olive oils belonging to Kolovi and Koroneiki cultivars, as well as mixtures of them, were collected, analyzed, and used to develop classification schemes employing Linear
Discriminant Analysis and Gradient Boosting, the latter allowing the determination of the most important spectral features. Both algorithms were found to provide efficient classification of the olive oil spectra with
accuracies exceeding 90%. Furthermore, for the first time, the emission spectra of LIBS were fused with the absorption spectra to create predictive models and their accuracies were found to be significantly improved. This
work demonstrates the enhanced capabilities of LIBS and absorption spectroscopy and the potential of their combination for olive oil quality monitoring and control.1 aBouras, Christos1 aStefas, Dimitrios1 aGyftokostas, Nikolaos1 aKourelias, Panagiotis1 aNanou, Eleni1 aKokkinos, Vasileios1 aCouris, Stelios  uhttp://telematics.upatras.gr/telematics/publications/discrimination-olive-oils-based-olive-cultivar-origin-machine-learning-employing-fusion-emission-and?language=en02088nas a2200145   4500008004100000245004900041210004900090300000900139490000700148520160800155100002101763700002201784700002601806856011001832       2021                        eng d00aEnergy efficient mechanism for LoRa networks0 aEnergy efficient mechanism for LoRa networks  a1-130 v133 aInternet of Things (IoT) is the ability of communication between objects and refers to a wide range of applications, such as the Search and Rescue (SAR) operations. SAR applications need long distance connectivity, thus can be benefited by Low Power Wide Area Networks (LPWAN). One LPWAN technology is called LoRa (Long Range). In this context, the WeSAR project has been created that provides a system for locating and rescuing people, especially those who belong to population groups with a very high probability of getting lost. The energy consumption of the wearable devices is important factor in the SAR operations, as the battery should last more than 45 50 hours. Therefore, the proposed system is based on LoRa technology, the user localization is based on LoRa using trilateration and Time Difference of Arrival (TDoA) instead of Geolocation Positioning System (GPS), as GPS increases the energy consumption, and we created an energy-efficient mechanism to tackle the problem of energy consumption. In this paper, an energy efficient mechanism for LoRa networks is presented, that is based on the user’s state and the battery level of the wearable device. Realistic simulations have been conducted to evaluate the system for both one wearable device, and multiple wearable devices, using different mobility models. The results from the simulations have shown a decrease in the energy consumption in various node mobility models that were tested, without compromising the delivery ratio of the network, something important as the LoRa packets are used for the localization of the lost person.1 aBouras, Christos1 aGkamas, Apostolos1 aKatsampiris, Spyridon  uhttp://telematics.upatras.gr/telematics/publications/energy-efficient-mechanism-lora-networks?language=en01599nas a2200121   4500008004100000245007300041210006900114520109100183100002101274700002201295700002601317856013401343       2021                        eng d00aEnergy Efficient Mechanism over LoRa for Search and Reuse operations0 aEnergy Efficient Mechanism over LoRa for Search and Reuse operat3 aSearch and Rescue (SAR) operations can be vastly benefited by the use of IoT and especially by Low Power Wide Area Networks (LPWAN) technologies, such as Long Range (LoRa). In this framework, the wearable device-based Search And Rescue system (WeSAR) project has been created. The main goals that WeSAR tries to improve are the localization accuracy and the energy efficiency of the wearable device. In this paper, the authors propose an energy-efficient mechanism for LoRa networks, taking into consideration the energy of a real wearable device, containing multiple sensors in a SAR scenario. In this work, we simulate the LoRa network, taking into consideration the various states of a wearable device and the impact of the sensors on the energy consumption, in order to have insights into the mechanism’s efficiency with multiple nodes, up to 500 nodes. The experiment results reveal significant reductions in the energy consumption of the wearable device and improvement of battery life, in urban and suburban conditions, and in stationary and no stationary node mobility models.1 aBouras, Christos1 aGkamas, Apostolos1 aKatsampiris, Spyridon  uhttp://telematics.upatras.gr/telematics/publications/energy-efficient-mechanism-over-lora-search-and-reuse-operations?language=en01499nas a2200133   4500008004100000245005900041210005500100300001200155520101600167100002101183700002201204700002201226856011701248       2021                        eng d00aExploring SDN & NFV in 5G Using ONOS & POX Conytollers0 aExploring SDN NFV in 5G Using ONOS POX Conytollers  a187-2033 aThis article describes how novel functionalities will take advantage of the cloud networking and will gradually replace the existing infrastructure of mobile networks with a virtualized one. Two technologies, namely software defined networking (SDN) and network function virtualization (NFV), offer their important benefits and a combination of them is an answer to the demands raised, such as central office re-architected as a data center (CORD). Open network operating system (ONOS) and POX are SDN controllers and offer an option to combine SDN and NFV addressing many ongoing problems in the field of mobile networks. In this paper, technologies and both controllers are compared and contrasted. Indicative cases of topologies are simulated and help evaluating both controllers. According to the experimental findings, ONOS is one of the most important controllers for practical, theoretical, research and educational purposes, while POX is a useful and simpler controller for other educative applications.1 aBouras, Christos1 aKollia, Anastasia1 aPapazois, Andreas  uhttp://telematics.upatras.gr/telematics/publications/exploring-sdn-nfv-5g-using-onos-pox-conytollers?language=en01497nas a2200133   4500008004100000245007900041210006900120260001800189520095100207100002101158700002201179700002601201856013601227       2021                        eng d00aExploring the energy efficiency for Search and Rescue operations over LoRa0 aExploring the energy efficiency for Search and Rescue operations  cApril 19 - 213 aThe Internet of Things (IoT) is one of the pioneering domains of Computer Science and Engineering, that comes to solve a plethora of real-life problems. One of the most promising technologies that aim to provide long-distance transmission while retaining energy consumption at low levels, is Long Range (LoRa). In this paper, a thorough study of the energy efficiency in LoRa based Search and Rescue (SAR) project for people with special needs, called Wearable based Search And Rescue system (WeSAR) is presented. After research the authors propose a LoRa based system, taking into consideration the energy efficiency. The results of the proposed mechanism are encouraging in terms of energy consumption, and the battery can last enough for the majority of the SAR operations, even when the battery is not fully charged. Also, there is no deterioration in terms of the delivery ratio of the network which is important for localization algorithms.1 aBouras, Christos1 aGkamas, Apostolos1 aKatsampiris, Spyridon  uhttp://telematics.upatras.gr/telematics/publications/exploring-energy-efficiency-search-and-rescue-operations-over-lora?language=en01840nas a2200133   4500008004100000245005800041210005700099520134700156100001801503700002101521700002201542700002601564856011601590       2021                        eng d00aGuideMe: A system for Indoor Orientation and Guidance0 aGuideMe A system for Indoor Orientation and Guidance3 aThe demand for indoor navigational systems is increasing daily. The use of navigational systems is ranging from smart cities and robots to visually impaired people support to navigate safely. The GuideMe Project aims to provide guidance and security for people suffering from blindness, and in the time being it is in the final development stage. This paper presents GuideMe Project goals GuideMe Project architecture and GuideMe final prototype. GuideMe Project architecture consists of the wearable device curried the user has, the anchors with which the wearable device works to determine the position of the user, the smartphone that is informed by the system for the route the user must follow and converts the message into audio information through the user’s headset. The headset in order to guide the user in indoor places and the local server who controls the protocols, and the information are the last parts of the architecture. It is clear that the system is quite complex, it consists of several entities and requires them to work together harmoniously to provide the prescribed functionality, in real-time. All the technologies developed to this final system, each of which has multiple sub-entities as mentioned, handle the required functionality that is the provision orientation of users who are located and moving indoors.1 aBarri, Eirini1 aBouras, Christos1 aGkamas, Apostolos1 aKatsampiris, Spyridon  uhttp://telematics.upatras.gr/telematics/publications/guideme-system-indoor-orientation-and-guidance?language=en01592nas a2200133   4500008004100000245005800041210005700099520109700156100001801253700002101271700002201292700002601314856011801340       2021                        eng d00aGuideMe: A system for Indoor Orientation and Guidance0 aGuideMe A system for Indoor Orientation and Guidance3 aThe interest for indoor navigational systems is expanding daily, and concerns among others visually impaired people that cannot navigate safely indoors. The main goal of such systems is to localize and direct the individual that has a wearable device and provide voice commands to navigate indoor buildings. This paper's aims to present the design and the implementation of the GuideMe project. GuideMe project’s goal is the design, implementation and evaluation of a navigation system focused on people that face troubles in indoor moving, utilizing a wearable device. Specifically, the focus group is people suffering from visual impairment. The person carrying the wearable device takes guidelines about the location from indoor UltraWide Band (UWB) anchors. The commands provided are about indoor direction through voice commands, assisting him to avoid obstacles in his route. We present the architecture and the details of the various modules which consist of the proposed indoor navigation system, and finally, some initial evaluations of the proposed system yield promising results.1 aBarri, Eirini1 aBouras, Christos1 aGkamas, Apostolos1 aKatsampiris, Spyridon  uhttp://telematics.upatras.gr/telematics/publications/guideme-system-indoor-orientation-and-guidance-0?language=en01261nas a2200121   4500008004100000245007300041210006900114520075500183100002100938700002200959700002600981856013201007       2021                        eng d00aHCI preliminary study and implementation for a LoRa based SAR system0 aHCI preliminary study and implementation for a LoRa based SAR sy3 aThe subject of this paper is the study and implementation of a Long Range (LoRa) based Search and Rescue system that can help in the localization of people having a high risk of going missing. These people may suffer from dementia, attention disturbance, and distraction, or disease in the autism spectrum, and it is of great importance to be found in a specific time frame, as their life can be in danger. The system is based on LoRa network architecture that enables both long-range communication and low energy consumption. In this paper aspects of the human-computer interaction were taken into consideration in contrast to the majority of the related papers, and is the proposed system is evaluated using heuristic evaluation and questionnaires.1 aBouras, Christos1 aGkamas, Apostolos1 aKatsampiris, Spyridon  uhttp://telematics.upatras.gr/telematics/publications/hci-preliminary-study-and-implementation-lora-based-sar-system?language=en01858nas a2200157   4500008004100000245013800041210006900179490000700248520116900255100002601424700002201450700002401472700002101496700002001517856016301537       2021                        eng d00aLaser-Induced Breakdown Spectroscopy coupled with machine learning as a tool for olive oil authenticity and geographic discrimination0 aLaserInduced Breakdown Spectroscopy coupled with machine learnin0 v113 aOlive oil is a basic element of the Mediterranean diet and a key product for the economies of the Mediterranean countries. Thus, there is an added incentive in the olive oil business for fraud through practices like adulteration and mislabeling. In the present work, Laser Induced Breakdown Spectroscopy (LIBS) assisted by machine learning is used for the classification of 139 virgin olive oils in terms of their geographical origin. The LIBS spectra of these olive oil samples were used to train different machine learning algorithms, namely LDA, ERTC, RFC, XGBoost, and to assess their classification performance. In addition, the variable importance of the spectral features was calculated, for the identification of the most important ones for the classification performance and to reduce their number for the algorithmic training. The algorithmic training was evaluated and tested by means of classification reports, confusion matrices and by external validation procedure as well. The present results demonstrate that machine learning aided LIBS can be a powerful and efficient tool for the rapid authentication of the geographic origin of virgin olive oil.1 aGyftokostas, Nikolaos1 aStefas, Dimitrios1 aKokkinos, Vasileios1 aBouras, Christos1 aCouris, Stelios  uhttp://telematics.upatras.gr/telematics/publications/laser-induced-breakdown-spectroscopy-coupled-machine-learning-tool-olive-oil-authenticity-and?language=en01238nas a2200169   4500008004100000245006700041210006500108520061400173100002200787700002600809700002600835700001700861700002400878700002100902700002000923856012500943       2021                        eng d00aA Laser‐Based Method for the Detection of Honey Adulteration0 aLaser‐Based Method for the Detection of Honey Adulteration3 aIn the present work, laser‐induced breakdown spectroscopy, aided by some machine learning algorithms (i.e., linear discriminant analysis (LDA) and extremely randomized trees (ERT)), is used for the detection of honey adulteration with glucose syrup. In addition, it is shown that instead of the entire LIBS spectrum, the spectral lines of inorganic ingredients of honey (i.e., calcium, sodium, and potassium) can be also used for the detection of adulteration providing efficient discrimination. The constructed predictive models attained high classification accuracies exceeding 90% correct classification.1 aStefas, Dimitrios1 aGyftokostas, Nikolaos1 aKourelias, Panagiotis1 aNanou, Eleni1 aKokkinos, Vasileios1 aBouras, Christos1 aCouris, Stelios  uhttp://telematics.upatras.gr/telematics/publications/laser%E2%80%90based-method-detection-honey-adulteration?language=en02295nas a2200229   4500008004100000245010400041210006900145490000700214520143000221100002101651700002401672700002201696700002701718700002601745700002401771700001901795700002901814700002201843700002101865700002601886856015301912       2021                        eng d00aMAES_GR: A Web-Based, Spatially Enabled Field Survey Platform for the MAES Implementation in Greece0 aMAESGR A WebBased Spatially Enabled Field Survey Platform for th0 v103 aThis study presents a standardized approach to collecting, registering, and reporting field-survey data for baseline MAES (Mapping and Assessment of Ecosystems and their Services) information in Greece. This is accomplished through a web-based platform (MAES_GR) exclusively developed under the relevant, nation-wide LIFE-IP 4 NATURA project. Based on the European Commission’s guidance for ecosystem condition (EC) and ecosystem services (ES) MAES studies, we conceptualized and structured an online platform to support EC and ES assessments, integrating all relevant fields of information needed for registering EC and ES parameters. A novel algorithm calculating EC was also developed and it is available as an integral part of the platform. The use of the MAES_GR platform was evaluated during nationwide field surveys efforts, increasing time efficiency and reducing costs. Field recording of EC and ES pinpoint spatial priorities for ecosystem restoration, conservation and sustainable development. This work highlights that MAES implementation can be favored by the use of technology tools such as mobile survey platforms, developed according to scientific needs and policy guidelines. Such tools, apart from the data inventory phase, can be used for data analysis, synthesis and extraction, providing timely, standardized information suitable for reporting at the local, regional, national and European Union scale.1 aKokoris, Ioannis1 aKokkinos, Vasileios1 aMichos, Evangelos1 aKalogeropoulos, Rafail1 aCharalambides, Marios1 aKounelis, Agisilaos1 aIliadou, Eleni1 aDamianidis, Christos, K.1 aMallinis, Giorgos1 aBouras, Christos1 aDimopoulos, Panayotis  uhttp://telematics.upatras.gr/telematics/publications/maesgr-web-based-spatially-enabled-field-survey-platform-maes-implementation-greece?language=en01567nas a2200133   4500008004100000245006800041210006600109520103700175100002601212700002301238700002401261700002101285856012701306       2021                        eng d00aA mechanism for 5G MIMO performance optimization and evaluation0 amechanism for 5G MIMO performance optimization and evaluation3 aMIMO (Multiple-Input Multiple-Output) technology has become a fundamental technique in current wireless communications, both in cellular and Wi-Fi networks. Fifth generation networks (5G) are expected to support extremely high data rates and more reliable services. The performance of 5G networks can be significantly improved with MIMO; yet the integration of optimization algorithms can further improve its performance. The purpose of this paper is to study an optimization technique for Channel State Prediction in a MIMO environment. We will examine a specific interconnection between 5G and optimization algorithms, to produce a feasible Channel State Prediction mechanism. For our experiments, we use a Dataset produced by the DeepMIMO simulator, which sets up all necessary parameters for our experiment. On this dataset we apply the Hungarian Algorithm to optimize the total throughput and based on the results we conclude that such mechanism is feasible and required for the introduction of 5G Networks in day-to-day tasks.1 aTzanakos, Dimosthenis1 aAllayiotis, Foivos1 aKokkinos, Vasileios1 aBouras, Christos  uhttp://telematics.upatras.gr/telematics/publications/mechanism-5g-mimo-performance-optimization-and-evaluation?language=en01562nas a2200133   4500008004100000245009200041210006900133520099900202100001801201700002101219700002401240700002401264856014001288       2021                        eng d00aA Mechanism for Improving the Spectral Efficiency in mu-MIMO for 5G and Beyond Networks0 aMechanism for Improving the Spectral Efficiency in muMIMO for 5G3 aThe ultimate challenge that arises in 6G and 5G and beyond networks is how the mobile networks of the future will be able to cope with the constantly increasing number of devices. In Multiuser Multiple-Input and Multiple-Output (mu-MIMO), the base station basically serves many users at the same time using the same frequency. The topic considered in this paper is the spectral performance in Downlink mu-MIMO. This paper’s goal is to improve the achieved spectral efficiency of the communication system, as well as the achieved reliability of the communication link. An algorithm based on downlink scheduling and the resource allocation is proposed to achieve maximum spectral use of the system. Considering user’s demands, this paper’s mechanism is able to allocate the potential user of the queue to the ”best antenna” based on its demands and distance. That provokes a larger number of devices that can be supported, always according to the specifications stated in IEEE 802.11ax.1 aBarri, Eirini1 aBouras, Christos1 aKokkinos, Vasileios1 aKoukouvela, Aspasia  uhttp://telematics.upatras.gr/telematics/publications/mechanism-improving-spectral-efficiency-mu-mimo-5g-and-beyond-networks?language=en02057nas a2200169   4500008004100000245013000041210006900171520132000240100002101560700001801581700002201599700002501621700002401646700002401670700002301694856017001717       2021                        eng d00aA Novel Approach to Energy Management in Large Passenger and Cruise Ships: Integrating Simulation and Machine Learning Models0 aNovel Approach to Energy Management in Large Passenger and Cruis3 aIt has been broadly admitted that the prediction of energy consumption in large passenger and cruise ships is a complex and challenging issue. Aiming to address it, this chapter reports on the development of a novel approach that builds on a sophisticated agent-based simulation model, which takes into account diverse parameters such as the size, type and behavior of the different categories of passengers onboard, the energy consuming facilities and devices of a ship, spatial data concerning the layout of a ship’s decks, and alternative ship operation modes. According to the proposed approach, outputs obtained from multiple simulation runs are then exploited by prominent Machine Learning algorithms to extract meaningful patterns between the composition of passengers and the corresponding energy demands in a ship. In this way, our approach is able to predict alternative energy consumption scenarios and trigger meaningful insights concerning the overall energy management in a ship. Overall, the proposed approach may handle the underlying uncertainty by blending the process centric character of a simulation model and the data-centric character of Machine Learning algorithms. The chapter also describes the overall architecture of the proposed solution, which is based on the microservices approach.1 aBouras, Christos1 aBarri, Eirini1 aGkamas, Apostolos1 aKaracapilidis, Nikos1 aKaradimas, Dimitris1 aKournetas, Georgios1 aPanaretou, Yiannis  uhttp://telematics.upatras.gr/telematics/publications/novel-approach-energy-management-large-passenger-and-cruise-ships-integrating-simulation-and-machine?language=en01507nas a2200109   4500008004100000245007200041210006500113520104000178100002101218700002201239856013601261       2021                        eng d00aAn Online Real – Time Face Recognition System for Police Purposes0 aOnline Real Time Face Recognition System for Police Purposes3 aIn general, face recognition algorithms are often utilized in order to identify or authenticate a human through a camera feed. However, face recognition algorithms must adapt to real-life uncertainties and noisy environments. This work targets upon extending the existing work of facial recognition algorithms by proposing an online platform that can be used from the police forces towards effective real-time human recognition. The approach on facial recognition is to use and extend the Haar Cascade algorithm for real-time purposes, which is widely considered one for the most efficient and used algorithms for that cause. As for the criminal identification, it will made possible through image pattern recognition between the provided criminal’s image and snapshots of identified faces from the livestream feed. The platform will include a live feed section with different options for video filters, enabling the user to select the best filter, depending on relevant situation of the physical surroundings for better recognition.1 aBouras, Christos1 aMichos, Evangelos  uhttp://telematics.upatras.gr/telematics/publications/online-real-%E2%80%93-time-face-recognition-system-police-purposes?language=en02482nas a2200133   4500008004100000245006700041210006700108520195000175100002102125700002202146700002402168700002702192856012902219       2021                        eng d00aPerformance Evaluation of Monitoring IoT Systems using LoRaWan0 aPerformance Evaluation of Monitoring IoT Systems using LoRaWan3 aThe proliferation of smart devices, or even better, IoT devices, has led to the widespread development of applications that take advantage of these devices. Of particular interest is the precise localization of such a device. However, these use cases become extremely difficult when connectivity to end-devices is required even in areas where the signal is too low or different technologies co-exist for the transmission of the data. In this research work, we study LoRaWan and Wi-Fi as two possible candidates for data transmission. We are particularly focused on the study of the above technologies in terms of performance as well as application development that can be used as rescue monitoring systems. For this reason, we start by describing LoRa as an ideal low power and long-distance communication protocol on the IoT devices compared to the Wi-Fi network. We perform various simulations in terms of time on air transmission, bit error rate by changing important metrics to study the behavior of the whole mechanism. Based on our simulations, the main findings highlight that the contribution of a Spreading Factor (SF) and bandwidth (BW) optimizations can be applied to real hardware for real Search and Rescue (SAR) cases giving improved results in case of coverage and battery extension applications. As a continuation of our research, we developed a monitor application that collects and visualizes data from end-nodes (wearables). These data are processed gateway and network server to The Things Network (TTN) for further analysis. The proposed solution can be used in different rescue monitor scenarios such as identifying and find individuals of vulnerable groups or those belonging to group of people with a high probability of being lost. The purpose of the above solution is to overcome monitor problems on SAR cases, compare with WiFi and suggest a module supporting both technologies in order to be used in real experiments.1 aBouras, Christos1 aGkamas, Apostolos1 aKokkinos, Vasileios1 aPapachristos, Nikolaos  uhttp://telematics.upatras.gr/telematics/publications/performance-evaluation-monitoring-iot-systems-using-lorawan?language=en01490nas a2200157   4500008004100000245007200041210006900113260002100182300001200203520089400215100002101109700002201130700002401152700002701176856012901203       2021                        eng d00aReal - Time Geolocation Approach through LoRa on Internet of Things0 aReal Time Geolocation Approach through LoRa on Internet of Thing  cJanuary 13 - 16,  a186-1913 aInternet of Things (IoT) and wireless technologies like LoRa brought more opportunities for application development in a plethora of different fields. One of these is location estimation of real-time objects and people. In this study, we focus on monitoring user’s location through a wearable IoT device with LoRa connectivity. The paper presents the development and integration of an loT ecosystem (Hardware and Software) which can be used in Search and Rescue (SAR) use cases. The proposed IoT ecosystem is evaluated and deployed inreal-scenarios with established gateways. After that we compare  the existed location-estimation methods in terms of attenuation problem, cost and operation as well to conclude to the most suitable solution that can be integrated in LoRaWAN environments. Finally, the conclusions of this work and improvements for possible future activity are described.1 aBouras, Christos1 aGkamas, Apostolos1 aKokkinos, Vasileios1 aPapachristos, Nikolaos  uhttp://telematics.upatras.gr/telematics/publications/real-time-geolocation-approach-through-lora-internet-things?language=en01738nas a2200133   4500008004100000245008000041210006900121520118000190100002101370700002201391700002601413700002701439856013801466       2021                        eng d00aSpreading Factor Analysis for LoRa networks: A supervised learning approach0 aSpreading Factor Analysis for LoRa networks A supervised learnin3 aToday, the Internet of Things (IoT) has been introduced in our lives, giving a variety of solutions and applications. The critical requirements for de-vices connected to the IoT are long battery life, long coverage, and low de-ployment cost. Some applications require the transmission of data over long distances, thus Low Power Wide Area Networks (LPWAN) have emerged, with LoRa being one of the most popular players of the market. In order, to improve energy consumption and connectivity problems, machine learning can be used in LoRa networks. In this paper, we intend to improve the energy consumption of end nodes by using machine learning models. For this reason, we present a comparison of classification algorithms, specifically, the k-NN, the Naïve Bayes, and Support Vector Machines (SVM), for the Spreading Factor (SF) as-signment in LoRa networks. The simulation results indicate that, both energy efficiency and reliability in IoT communications could be significantly im-proved using the proposed learning approach. These promising results, which are achieved using lightweight learning, make our solution favorable in many low-cost low-power IoT applications.1 aBouras, Christos1 aGkamas, Apostolos1 aKatsampiris, Spyridon1 aPapachristos, Nikolaos  uhttp://telematics.upatras.gr/telematics/publications/spreading-factor-analysis-lora-networks-supervised-learning-approach?language=en01725nas a2200145   4500008004100000245007700041210006900118300001200187520114600199100002101345700002201366700002601388700002701414856013801441       2021                        eng d00aSpreading Factor Selection Mechanism for Transmission over LoRa Networks0 aSpreading Factor Selection Mechanism for Transmission over LoRa   a344-3533 aThis paper presents a mechanism for Spreading Factor (SF) prediction in LoRa networks for more optimized data transmissions. The proposed mechanism is based on Machine Learning (ML) algorithms and assigns the node’s SF value based on prior transmission data. This paper examines three different approaches for the selection of the SF during LoRa transmissions a) Random SF assignment b) Adaptive Data Rate (ADR) and c) ML based SF selection. The main target is to study and determine the most efficient approach, as well as to investigate the exploitation of ML techniques in the context of LoRa networks. We created a simple library based on ML libraries, such as Scikit Learn that can be used with the FLoRa an OMNeT++ based LoRa simulator. With the use of this library, it is possible to predict the node’s SF using ML techniques. Two classification algorithms were tested, the k Nearest Neighbors (k-NN) and Naïve Bayes classifier. Finally, we compared the ML mechanisms with two variants of the ADR mechanism. The approaches performance is evaluated for different scenarios, using the delivery ratio and energy consumption metrics.1 aBouras, Christos1 aGkamas, Apostolos1 aKatsampiris, Spyridon1 aPapachristos, Nikolaos  uhttp://telematics.upatras.gr/telematics/publications/spreading-factor-selection-mechanism-transmission-over-lora-networks?language=en01436nas a2200145   4500008004100000245008100041210006900122260001900191300001000210490000600220520087700226100002101103700002701124856013901151       2021                        eng d00aUser Allocation in 5G Networks Using Machine Learning Methods for Clustering0 aUser Allocation in 5G Networks Using Machine Learning Methods fo  c May 12 - 14,   a13-240 v13 aThe rapid increase in the volume of devices connected to mobile networks poses unprecedented demands on existing networking infrastructures. Machine Learning is a promising technique, already applied in various sectors of our everyday lives. It enables decision making not with the use of traditional programming but rather by using data to train models to cope with various problems without explicit programming on how to do so. The integration of Machine Learning techniques is deemed necessary in as many processes as possible to help the network face congestion and enable efficient real time decision making. In this paper we present two Machine Learning based mechanisms for improving real time user allocation on the network as well as predicting the best positioning scheme for Smallcell Base Stations to provide effective utilization of the network’s resources.1 aBouras, Christos1 aKalogeropoulos, Rafail  uhttp://telematics.upatras.gr/telematics/publications/user-allocation-5g-networks-using-machine-learning-methods-clustering?language=en01576nas a2200133   4500008004100000245010700041210006900148300001000217520099400227100002101221700002401242700002501266856015101291       2021                        eng d00aUsing NOMA scheme for the management of interference and the improvement of performance in 5G networks0 aUsing NOMA scheme for the management of interference and the imp  a32-373 aThe new generation of 5G networks, compared to 4G networks, is a very important example of change in achieving very high frequencies in the carrier with huge bandwidth, high densities with a huge number of antennas and improved quality of services, making effective interference management necessary. In this paper, we present the contribution of the Non-Orthogonal Multiple Access (NOMA) scheme to improving the performance of 5G networks. We refer to the technique of sequential interference cancellation applied to some NOMA formats, compare NOMA and Orthogonal Multiple Access (OMA) formats in terms of the capabilities they offer users and NOMA's significant contribution to Multiple-Input Multiple-Output (MIMO) technology and compare three basic NOMA formats in three different resource and user reporting scenarios. Finally, we present the results of the simulations of the above comparisons and analyze the contribution of each scheme to the improvement of the system performance.1 aBouras, Christos1 aKokkinos, Vasileios1 aTzioumanis, Georgios  uhttp://telematics.upatras.gr/telematics/publications/using-noma-scheme-management-interference-and-improvement-performance-5g-networks?language=en01847nas a2200181   4500008004100000245009600041210006900137300001200206520113500218100001801353700002101371700002201392700002501414700002401439700002401463700002301487856015501510       2020                        eng d00aBlending simulation and Machine Learning models to advance energy management in large ships0 aBlending simulation and Machine Learning models to advance energ  a101-1093 aThe prediction of energy consumption in large passenger and cruise ships is certainly a complex and challenging issue. Towards addressing it, this paper reports on the development of a novel approach that builds on a sophisticated agent-based simulation model, which takes into account diverse parameters such as the size, type and behavior of the different categories of passengers onboard, the energy consuming facilities and devices of a ship, spatial data concerning the layout of a ship’s decks, and alternative ship operation modes. Outputs obtained from multiple simulation runs are then exploited by prominent Machine Learning algorithms to extract meaningful patterns between the composition of passengers and the corresponding energy demands in a ship. In this way, our approach is able to predict alternative energy consumption scenarios and trigger meaningful insights concerning the overall energy management in a ship. Overall, the proposed approach may handle the underlying uncertainty by blending the process-centric character of a simulation model and the data-centric character of Machine Learning algorithms.1 aBarri, Eirini1 aBouras, Christos1 aGkamas, Apostolos1 aKaracapilidis, Nikos1 aKaradimas, Dimitris1 aKournetas, Georgios1 aPanaretou, Yiannis  uhttp://telematics.upatras.gr/telematics/publications/blending-simulation-and-machine-learning-models-advance-energy-management-large-ships?language=en01379nas a2200157   4500008004100000245005600041210005400097300001000151490000700161520084700168100002101015700002001036700002201056700002701078856011601105       2020                        eng d00aA comparative study of 4G and 5G Network Simulators0 acomparative study of 4G and 5G Network Simulators  a11-200 v133 aNetwork simulation is a technique of utmost importance to evaluate new network performance, verify new algorithms and analyze various network topologies. It is used to find results to be expected from a hardware setup without the need for actual implementation. For this reason, there is a plethora of Network Simulation Software applied to different scenarios to evaluate theories and hypotheses. A cellular network is an example of an extremely complex system in which different components impact the overall performance in different ways. The aim of this paper is to study the most common Simulators regarding the deployment of 4G and 5G networks, provide a detailed comparison featuring their main advantages and showcasing potential defects and support the academic community, offering the required data to help choose the necessary one.1 aBouras, Christos1 aDiles, Georgios1 aGkamas, Apostolos1 aZacharopoulos, Andreas  uhttp://telematics.upatras.gr/telematics/publications/comparative-study-4g-and-5g-network-simulators?language=en01360nas a2200109   4500008004100000245006800041210006800109520091000177100002101087700001801108856012401126       2020                        eng d00aEfficient Mechanism of eNB bandwidth in D2D communication in 5G0 aEfficient Mechanism of eNB bandwidth in D2D communication in 5G3 aThe device to device (D2D)communication will be a big part of 5G and is responsible for the direct communication between users in range without the relay of Base Station (BS). There are three modes that work in D2D communication based on radio resources and how they are used. In D2D the radio resources that are the same with cellular users the mode is named as reuse mode. The other option is to specify an amount of resources only for D2D users and it is called dedicated mode. In this paper will provide how the Users Equipments (UEs) and the D2D communication itself respond in a D2D communication when an eNB serving only in dedicated mode has to change to reuse mode in order to serve more users. Considering two scenarios, reuse and dedicated the mechanism will provide the values of interference and throughput of eNB in each scenario indicating which mode is better under specific circumstances.1 aBouras, Christos1 aBarri, Eirini  uhttp://telematics.upatras.gr/telematics/publications/efficient-mechanism-enb-bandwidth-d2d-communication-5g?language=en02124nas a2200133   4500008004100000245005500041210005500096520162900151100002101780700002201801700002401823700002701847856011601874       2020                        eng d00aGeolocation analysis for SAR systems using LoRaWAN0 aGeolocation analysis for SAR systems using LoRaWAN3 aLow Power Wide Area Network (LPWAN) technologies aiming to provide power-efficient solutions to the field of
Internet of Things (IoT). Over the last years we have seen a significant development within the area of IoT applications.
For many applications, the problem of localization (i.e. determine the physical location of nodes) is critical. An area
study of such use case is also the rescue monitor systems. In this study, we start by describing a solution designed for the
Long Range Wide Area Network (LoRaWAN) to localize position of IoT modules such as wearables used from
vulnerable groups. Through performance study of the behavior of a LoRaWAN channel and using trilateration and RSSI
information, the localization of an IoT wearable can be acquired within a small range. Routing people in need is one of
the use cases the above mechanism could be integrated so as to be able to be tracked by familiar people. After that, we
evaluate the usage of mathematical model of multilateration algorithms using Time Difference of Arrival (TDoA) as a
solution for positioning over LoRaWAN. The research is carried out using simulations in Python by configuring the
constant positions of the Gateways inside an outdoor area. The proposed algorithms can be integrated in application for
tracking people at any time and especially routing people from vulnerable groups. Through multilateration and
algorithm’s prediction, we can have an accuracy of 40-60m in location positioning, ideal for search and rescue use cases.
We finally summarize the above algorithms’ estimation and general behavior in a SAR system.1 aBouras, Christos1 aGkamas, Apostolos1 aKokkinos, Vasileios1 aPapachristos, Nikolaos  uhttp://telematics.upatras.gr/telematics/publications/geolocation-analysis-sar-systems-using-lorawan?language=en01666nas a2200157   4500008004100000245006700041210006600108300001000174490000600184520110600190100001801296700002101314700002201335700002601357856012501383       2020                        eng d00aGuideMe: A Complete System for Indoor Orientation and Guidance0 aGuideMe A Complete System for Indoor Orientation and Guidance  a36-530 v13 aThe interest for indoor navigational systems is expanding daily with concerns among visually impaired people who cannot navigate safely indoors. The main goal of such systems is the localization and direction of the individual who has a wearable device that provides voice commands to navigate indoor buildings. This paper aims to present the design and the implementation of the GuideMe project. The GuideMe project’s goal is the design, implementation, and evaluation of a navigation system focused on people who face troubles in indoor moving utilizing a wearable device. Specifically, the focus group is people suffering from visual impairment. The person carrying the wearable device takes guidelines about the location from indoor ultrawide band (UWB) anchors. The commands provided are about indoor direction through voice commands, assisting him to avoid obstacles in his route. The authors present the architecture and the details of the various modules, which consist of the proposed indoor navigation system, and some initial evaluations of the proposed system yielding promising results.1 aBarri, Eirini1 aBouras, Christos1 aGkamas, Apostolos1 aKatsampiris, Spyridon  uhttp://telematics.upatras.gr/telematics/publications/guideme-complete-system-indoor-orientation-and-guidance?language=en01923nas a2200157   4500008004100000245007300041210006900114520131600183100002101499700001801520700002201538700002401560700002201584700002601606856013301632       2020                        eng d00aGuideMe: A Networked Application for Indoor Orientation and Guidance0 aGuideMe A Networked Application for Indoor Orientation and Guida3 aToday’s indoor navigational systems are more and more in demand, commonly used for applications such as smart cities, robots and visually impaired people. As far as outdoor navigation is concerned, the Global Positioning System (GPS) technology is still one of the most (if not the most) commonly used approaches. Even though it is still considered an ideal solution for navigating in outdoor areas, challenges and problems arise when GPS is considered for navigation inside buildings due to obstacles (e.g., shopping malls, hospitals, etc.) and because signals cannot be absorbed by the building walls. To tackle the aforementioned issue, other technologies have emerged aimed at indoor navigation, such as Wireless-Fidelity (Wi-Fi), Bluetooth and sensors. This paper’s contribution is towards indoor navigation and, more specifically, it targets designing and developing a tracking and navigation system aimed at people that experience difficulties in indoor orientation using a wearable device. The user takes direction from the wearable device for the indoor orientation through voice commands helping him to avoid obstacles. The central part of the system is a device that provides the ability to navigate and find a route by voice commands, based on the device's location and orientation capabilities.1 aBouras, Christos1 aBarri, Eirini1 aGkamas, Apostolos1 aKoulouri, Christina1 aMichos, Evangelos1 aKatsampiris, Spyridon  uhttp://telematics.upatras.gr/telematics/publications/guideme-networked-application-indoor-orientation-and-guidance-0?language=en01915nas a2200157   4500008004100000245007300041210006900114520131000183100001801493700002101511700002201532700002401554700002201578700002601600856013101626       2020                        eng d00aGuideMe: A Networked Application for Indoor Orientation and Guidance0 aGuideMe A Networked Application for Indoor Orientation and Guida3 aToday’s indoor navigational systems are more and more in demand, commonly used for applications such as smart cities, robots and visually impaired people. As far as outdoor navigation is consider, the Global Positioning System (GPS) technology is still one of the most (if not the most) commonly used approaches. Even though it is still considered an ideal solution for navigating in outdoor areas, challenges and problems arise when GPS is considered for navigation inside buildings due to obstacles (e.g., shopping malls, hospitals, etc.) and because signals cannot be absorbed by the building walls. To tackle the aforementioned issue, other technologies have emerged aimed at indoor navigation, such as Wireless-Fidelity (Wi-Fi), Bluetooth and sensors. This paper’s contribution is towards indoor navigation and more specifically, it targets at designing and developing a tracking and navigation system aimed at people that experience difficulties in indoor orientation using a wearable device. The user takes direction from the wearable device for the indoor orientation through voice commands helping him to avoid obstacles. The central part of the system is a device that provides the ability to navigate and route by voice commands, based on the device's location and orientation capabilities.1 aBarri, Eirini1 aBouras, Christos1 aGkamas, Apostolos1 aKoulouri, Christina1 aMichos, Evangelos1 aKatsampiris, Spyridon  uhttp://telematics.upatras.gr/telematics/publications/guideme-networked-application-indoor-orientation-and-guidance?language=en01073nas a2200133   4500008004100000245004600041210004600087520060100133100002100734700002200755700002400777700002700801856011100828       2020                        eng d00aIoT Geolocation Performance Using LoRaWAN0 aIoT Geolocation Performance Using LoRaWAN3 aLow Power Wide Area Network (LPWAN) technologies aiming to provide power-efficient solutions to the world of IoT. This paper describes a solution based on the Long Range Wide Area Network (LoRaWAN) technology to geolocalise IoT modules such as wearables used from vulnerable groups. Through estimation of the behavior of a LoRaWAN channel and using trilateration and RSSI information, the localization of an IoT wearable can be obtained within a small range. Routing people in need is one of the use cases the above mechanism could be integrated so as to be able to be tracked by familiar people.1 aBouras, Christos1 aGkamas, Apostolos1 aKokkinos, Vasileios1 aPapachristos, Nikolaos  uhttp://telematics.upatras.gr/telematics/publications/iot-geolocation-performance-using-lorawan?language=en01765nas a2200145   4500008004100000245010400041210006900145520113500214100001801349700002101367700002201388700002401410700002501434856016001459       2020                        eng d00aA Novel Approach for Handling Diverse Energy Consumption Issues in Large Passenger and Cruise Ships0 aNovel Approach for Handling Diverse Energy Consumption Issues in3 aThe prediction of energy consumption in large passenger and cruise ships is certainly a complex and challenging issue. Towards addressing it, this paper reports on the development of a novel approach that builds on a sophisticated agent-based simulation model, which takes into account diverse parameters such as the size, type and behavior of the different categories of passengers onboard, the energy consuming facilities and devices of a ship, spatial data concerning the layout of a ship’s decks, and alternative ship operation modes. Outputs obtained from multiple simulation runs are then exploited by prominent Machine Learning algorithms to extract meaningful patterns between the composition of passengers and the corresponding energy demands in a ship. In this way, our approach is able to predict alternative energy consumption scenarios and trigger meaningful insights concerning the overall energy management in a ship. Overall, the proposed approach may handle the underlying uncertainty by blending the process-centric character of a simulation model and the data-centric character of Machine Learning algorithms.1 aBarri, Eirini1 aBouras, Christos1 aGkamas, Apostolos1 aKournetas, Georgios1 aKaracapilidis, Nikos  uhttp://telematics.upatras.gr/telematics/publications/novel-approach-handling-diverse-energy-consumption-issues-large-passenger-and-cruise-ships?language=en01903nas a2200145   4500008004100000245005100041210004800092300001200140490001400152520141400166100002101580700002401601700002201625856011001647       2020                        eng d00aAn online tool on sustainable water management0 aonline tool on sustainable water management  a450-4650 v68, Νο43 aWater demand strains supply capacity in the Mediterranean coastal areas, affecting negatively the maintenance of natural and cultural heritage. Tackling this subject, the “Coastal areas sustainable tourism water management in the Mediterranean - CASTWATER” project aims to support sustainable tourism water management in Mediterranean (MED) coastal areas, by improving the monitoring and assessment of the water sustainability performance of tourism. To this end, the elaboration of an online tool to monitor and assess sustainable tourism water management was envisaged and developed, primarily addressed to tourism sector small and medium-sized enterprises (SMEs). The CASTWATER online tool was designed to so as to provide two different functionalities. On the one hand, SMEs can self-evaluate their performance in sustainable water management and efficiently acknowledge possible actions that promote water efficiency in their tourism establishments. On the other hand, the tool measures, at both regional and local level, the levels of good governance and the effectiveness of water-tourism policies in order to improve sustainable water management. The approach presented in this work is heavily based on the initial technical specifications and end-user feedback, aiding SMEs in understanding, comparing, assessing and rating their performance regarding water efficiency and sustainable water manag1 aBouras, Christos1 aKokkinos, Vasileios1 aMichos, Evangelos  uhttp://telematics.upatras.gr/telematics/publications/online-tool-sustainable-water-management?language=en01752nas a2200133   4500008004100000245007700041210006900118300000900187490000700196520123400203100002101437700002701458856013301485       2020                        eng d00aA QoS driven adaptive mechanism for Downlink and Uplink Decoupling in 5G0 aQoS driven adaptive mechanism for Downlink and Uplink Decoupling  a1-110 v113 aIn current cellular networks, cell association is heavily based on the Downlink signal power and all devices are associated with the same Base Station (BS) in Downlink (DL) and Uplink (UL). While as of now this technique has been proved adequate in homogeneous networks where all BSs have similar transmission levels, in increasingly dense heterogeneous networks (HetNets) rate is heavily dependent on the load, which can significantly vary from BS to BS. Due to increased demands for usage over several devices in HetNets, large disparities in the DL pose a threat to the quality of services (QoS) rendered by the network and this technique seems obsolete. Decoupling Uplink and Downlink is the proposed solution, where the UL cell association is not necessarily based on the same criteria as the DL association. We propose using Signal to Noise Ratio (SINR) and Path Loss with Range Extension (PLRE) as factors for choosing the appropriate BS for connection in DL and UL respectively for every user, taking into consideration the BS’s Resource Block availability, to avoid overloading BSs. We will use simulations to test our approach, with different Path Loss offsets for PLRE, to note the importance of adaptive mechanisms.1 aBouras, Christos1 aKalogeropoulos, Rafail  uhttp://telematics.upatras.gr/telematics/publications/qos-driven-adaptive-mechanism-downlink-and-uplink-decoupling-5g?language=en01700nas a2200121   4500008004100000245005100041210005100092520125400143100002101397700002401418700002401442856011201466       2020                        eng d00aResource Allocation Mechanism for Massive MIMO0 aResource Allocation Mechanism for Massive MIMO3 aNowadays, mobile users need faster data speeds and more reliable service. The next generation of wireless networks 5G pledges to commit that, and much more. Multiple-Input, Multiple-Output (ΜΙΜΟ) technology in 5G networks is studied in this paper, with emphasis on the achieved performance in terms of achieved Bandwidth. Multi-antenna technologies, such as MIMO, are anticipated to play a key role in 5G systems, as they will have to handle much higher speeds than today's cellular networks and greater network traffic. Specifically, we will refer to Massive MIMO (Ma-MIMO) technology. In this paper, a resource allocation mechanism is proposed from the Base Station (BS) to the available antennas, using the Knapsack Problem (KP) algorithm. Our goal is to evaluate user access throughput to the antennas and to study the case where the BS allocates resources, according to the channel rate it receives from each User Equipment (UE). The scenario executed is about serving the maximum number of UE connected to the BS, in high quality services. Finally, we simulate the results in MATLAB, in order to be able to evaluate the Quality of Service (QoS) that is provided to the UE by the BS, with the resource allocation technique that is proposed.1 aBouras, Christos1 aKokkinos, Vasileios1 aKoulouri, Christina  uhttp://telematics.upatras.gr/telematics/publications/resource-allocation-mechanism-massive-mimo?language=en01604nas a2200133   4500008004100000245010800041210006900149300001200218490000600230520102800236100002101264700002201285856016301307       2020                        eng d00aA Resource - efficient Approach on User Association in 5G Networks using Downlink and Uplink Decoupling0 aResource efficient Approach on User Association in 5G Networks u  a43 - 590 v93 aA user-centered network model can significantly optimize connectivity issues between a user and the corresponding Base Station (BS). This paper shall evaluate the User Centric (UC) model targeted for Fifth Generation telecommunication systems and will attempt to optimize communication between users and BSs. The authors suggest a resource-aware mechanism that targets at improving coverage through the network decoupling into two separate and independent uplink and downlink networks. Our mechanism shall fully respect each user’s initially requested throughput demands and aims to solve the network user – BS association problem with efficient resource management techniques. Simulations revealed that the mechanism perfectly preserves Quality of Service (QoS) and offers increased data rates in favor of ultimate user coverage, in both scenarios. Additionally, Frequency Range 2 offers an increased amount of resources, both increased data rates and higher amounts of devices that are covered by the overall network.1 aBouras, Christos1 aMichos, Evangelos  uhttp://telematics.upatras.gr/telematics/publications/resource-efficient-approach-user-association-5g-networks-using-downlink-and-uplink-decoupling?language=en01345nas a2200145   4500008004100000245006100041210006000102300001200162520080600174100002100980700002201001700002601023700002701049856012301076       2020                        eng d00aSearch and Rescue System Based on NB-IoT Wearable Device0 aSearch and Rescue System Based on NBIoT Wearable Device  a195-2223 aThis chapter presents the design and development of a search and rescue (SAR) system, for the location and provision of aid to people who are missing or in imminent danger, especially those belonging to population groups with a particularly high probability of getting lost. With the use of Low-Power Wide Area Network (LPWAN) technology, such as Narrow Band Internet of Things (NB-IoΤ), authors are able to provide search and rescue solutions for individuals, especially those belonging to groups of people who are more likely to get lost. The central part of the system is a modular “wearable (portable)” device, while in the framework of the implementation of this system authors have seriously taken into consideration the aspects of energy efficiency in order to provide better battery life.1 aBouras, Christos1 aGkamas, Apostolos1 aKatsampiris, Spyridon1 aPapachristos, Nikolaos  uhttp://telematics.upatras.gr/telematics/publications/search-and-rescue-system-based-nb-iot-wearable-device?language=en01187nas a2200109   4500008004100000245007900041210006900120520071100189100002100900700002200921856013400943       2020                        eng d00aTechno - economic analysis of MMWave vs Mid - Band Spectrum in 5G networks0 aTechno economic analysis of MMWave vs Mid Band Spectrum in 5G ne3 aNowadays, users rapidly augment and need more efficient and better-quality network coverage. Therefore, the available spectrum is not able to meet these excessive demands. Several novel technologies and approaches are introduced into the 5G networks. One of these is the MiliMeter Wave (MMWave) spectrum. In this paper, a techno-economic analysis of the MMWave compared to the Mid-Band Spectrum (MBS) is developed. The technologies are analyzed in a technical way. Mathematical models that help determining the models’ pricing are analyzed. What is more, several experiments are conducted using the Sensitivity Analysis (SA) technique determining if the advantages and profits outweigh the disadvantages.1 aBouras, Christos1 aKollia, Anastasia  uhttp://telematics.upatras.gr/telematics/publications/techno-economic-analysis-mmwave-vs-mid-band-spectrum-5g-networks?language=en01473nas a2200145   4500008004100000245011400041210006900155300001600224490000800240520084000248100002101088700002201109700002701131856016901158       2020                        eng d00aTechno - economic comparison of Cognitive Radio and Software Defined Network (SDN) cost models in 5G networks0 aTechno economic comparison of Cognitive Radio and Software Defin  a1403–14300 v1143 a5G is anticipated in 2020. In this generation of mobile networks, a great deal of requirements have been set. Although, there are many strong technologies in the telecommunications’ sector they do not respond to the 5G goals. On the other hand, telecommunication operators and providers do not want to invest in new equipment/architectures. Cognitive Radio (CR) and Software Defined Networking (SDN) are two technologies with special and vigorous advantages. In this paper, several technical and economic models are developed. The CR is combined with the Stackelberg game. A Sensitivity Analysis (SA) is implemented and the parameters that impact mostly on the model are pinpointed. It is shown that the CR technology could offer all its fundamental cognitive advantages and even financial profits to the telecommunication companies.1 aBouras, Christos1 aKollia, Anastasia1 aMaligianni, Eleftheria  uhttp://telematics.upatras.gr/telematics/publications/techno-economic-comparison-cognitive-radio-and-software-defined-network-sdn-cost-models-5g-networks?language=en01143nas a2200121   4500008004100000245007000041210006900111520064700180100002100827700002200848700002200870856012900892       2020                        eng d00aTechno-economic analysis of cognitive radio models in 5G networks0 aTechnoeconomic analysis of cognitive radio models in 5G networks3 aThe first commercial products of 5G will be released within 2020 and therefore, it becomes an absolute necessity to research whether the key enabling technologies are advantageous for the operators to invest in. One of the most fundamental technologies Cognitive Radio (CR), since there is not much research in the field. This paper develops a techno-economic framework for the CR technology and is contrasted with an already existing model for Software Defined Networks (SDN). A Sensitivity Analysis (SA) indicates the cost parameters that are the most expensive ones and should be reconsidered for the model’s wide adoption and viability.1 aBouras, Christos1 aKollia, Anastasia1 aPapazois, Andreas  uhttp://telematics.upatras.gr/telematics/publications/techno-economic-analysis-cognitive-radio-models-5g-networks?language=en01970nas a2200157   4500008004100000245007400041210006900115300000900184490000700193520139000200100002101590700002401611700002201635700002201657856013301679       2020                        eng d00aTechno-economic comparison of MIMO and DAS cost models in 5G networks0 aTechnoeconomic comparison of MIMO and DAS cost models in 5G netw  a1-150 v263 aHigh communicational standards have been set for the 5G mobile networks. Therefore, it is of great importance that technological solutions that include all the significant features, such as the high coverage and capacity and low round-trip delays, are adopted for the next generation of mobile networks. Except for their technical efficiency, these technologies should be profitable for providers as well. As a result, the need for limiting the costs spent for the development of these technologies emerges. In this papers, four models two for each one of the two solutions for 5G networks are developed, namely the Multiple Input Multiple Output (MIMO) and the Distributed Antenna System. The architectural models assumed for the techno-economic analyses are presented. The mathematical models for both technologies are developed. Experiments are conducted using prices of the Greek market and also Sensitivity Analysis (SA) is used to pinpoint, which cost parameters are the most expensive ones and therefore it is likely that they discourage providers to invest in them. To our knowledge there are not many studies comparing and contrasting these technologies and there is no SA for MIMO. Therefore, it is considered that research for these models is of vital importance for the next generation of mobile communication networks, as they are foundation stonesfor the formation of 5G.1 aBouras, Christos1 aKokkalis, Stylianos1 aKollia, Anastasia1 aPapazois, Andreas  uhttp://telematics.upatras.gr/telematics/publications/techno-economic-comparison-mimo-and-das-cost-models-5g-networks?language=en02032nas a2200157   4500008004100000245007800041210006900119520142200188100001801610700002101628700002201649700002401671700002201695700002601717856013101743       2020                        eng d00aText to Speech through Bluetooth for People with Special Needs Navigation0 aText to Speech through Bluetooth for People with Special Needs N3 aAs far as outdoor navigation is considered, the Global Positioning System (GPS) technology is still one of the most (if not the most) commonly used approaches. Even though it is still considered an ideal solution for navigating in outdoor areas, challenges and problems arise when GPS is considered for navigation inside buildings due to the fact that GPS signals cannot penetrate walls/ceilings (e.g., shopping malls, hospitals, etc.) and because signals can be absorbed by the building walls. This paper’s contribution is navigation system that assists people with special needs using an audio guidance system that incorporates input from a voice recognition system. The central part of the system is a device that is able to identify the position and orientation of the person that carries it and provide the ability to navigate and route by voice commands. The suggested voice synthesis system is used, so as to guide the user through obstacles in indoor locations. The information of the precise location and.orientation of the device is made available to the whole system, through the building’s network infrastructure, so that the user’s mobile phone, been connected to the same network and also to the user’s headset through BLE, is able to send audio commands. For the voice commands, Google Cloud Text-ToSpeech (TTS) will be used, supposed that an online connection is active on the user’s device.1 aBarri, Eirini1 aBouras, Christos1 aGkamas, Apostolos1 aKoulouri, Christina1 aMichos, Evangelos1 aKatsampiris, Spyridon  uhttp://telematics.upatras.gr/telematics/publications/text-speech-through-bluetooth-people-special-needs-navigation?language=en01462nas a2200133   4500008004100000245007900041210006900120520090800189100002101097700002201118700002401140700002701164856013701191       2020                        eng d00aTime Difference of Arrival Localization Study for SAR Systems over LoRaWAN0 aTime Difference of Arrival Localization Study for SAR Systems ov3 aOver the last years we have seen a rapid expansion within the area of Internet of Things (IoT) applications. For many applications’ use cases, such as rescue monitor systems, the problem of localization (i.e. determine the physical location of nodes) is critical. This paper studies and evaluates the usage of mathematical model of multilateration algorithms using Time Difference of Arrival (TDoA) as a solution for positioning over Long Range Wide Area Network (LoRaWAN). The research is carried out using simulations in Python by configuring the constant positions of the Gateways inside an outdoor area. The proposed algorithms can be integrated in application for tracking people at any time and especially routing people from vulnerable groups. Through multilateration and algorithm’s prediction, we can have an accuracy of 40-60m in location positioning ideal for search and rescue use cases.1 aBouras, Christos1 aGkamas, Apostolos1 aKokkinos, Vasileios1 aPapachristos, Nikolaos  uhttp://telematics.upatras.gr/telematics/publications/time-difference-arrival-localization-study-sar-systems-over-lorawan?language=en01447nas a2200169   4500008004100000245011000041210006900151520073500220100001800955700002100973700002200994700002501016700002401041700002401065700002301089856016501112       2020                        eng d00aTowards an informative simulation-based application for energy saving in large passenger and cruise ships0 aTowards an informative simulationbased application for energy sa3 aOver the years, the need to save energy and efficiently manage its consumption becomes increasingly imperative. This paper reports on the development of a novel application for handling diverse energy consumption issues in large passenger and cruise ships. Our overall approach is based on a comprehensive agent-based simulation model, which takes into account spatial data concerning a ship’s decks and position of energy consuming facilities, as well as data concerning the ship’s passengers and their behavior during the operation of the vessel. The proposed application may predict energy consumption for a particular vessel and passenger group and accordingly facilitate informed decision making on energy saving matters.1 aBarri, Eirini1 aBouras, Christos1 aGkamas, Apostolos1 aKaracapilidis, Nikos1 aKaradimas, Dimitris1 aKournetas, Georgios1 aPanaretou, Yiannis  uhttp://telematics.upatras.gr/telematics/publications/towards-informative-simulation-based-application-energy-saving-large-passenger-and-cruise-ships?language=en01048nas a2200145   4500008004100000245004500041210004400086260002100130300001000151520055700161100002100718700002800739700002200767856011300789       2019                        eng d00a5G Νetworks: Advancement and Challenges0 a5G Νetworks Advancement and Challenges  cJune 30 - July 4  a33-383 aNowadays, mobile networks consist an indispensable part of everyday life. Although, the advent of 5G is imminent, given that the 2020 is approaching, there are still a lot of addressable questions. It becomes of great significance that the Advancements and Challenges of the 5th generation of mobile networks are presented. The Strong points and the Weak parts should be indicated so that they will be treated. In this paper, a review of the current foundational stones of the 5G networks is completed. The state of all different technologies is noted.1 aBouras, Christos1 aFotakopoulou, Paraskevi1 aKollia, Anastasia  uhttp://telematics.upatras.gr/telematics/publications/5g-%CE%BDetworks-advancement-and-challenges?language=en01404nas a2200133   4500008004100000245006700041210006700108260001500175520088200190100002101072700002001093700002901113856012801142       2019                        eng d00aCapacity guaranteed sleep mode algorithm for 5G femtocell tier0 aCapacity guaranteed sleep mode algorithm for 5G femtocell tier  cJune 18-203 aThe upcoming 5G networks require an advanced planning in terms of coordinating various mechanisms to achieve the highly expected performance growths that they pledge. This coordination becomes more challenging due to the increased density in urban environments of the deployment of small radius base stations, such as femtocells. In this paper we test our proposed mechanism for sleep mode power control in femtocell networks, over a widely used simulated traffic model, adjusted to our scenario. Our sleep mode strategy has been developed for femtocell clusters with the goal of reducing the number of operating femtocells without compromising the data rate performance of their subscribers. Our simulations reaffirm the benefits of our algorithm, especially the reduced number of operating femtocells and the increased offered capacity, when tested in realistic environments.1 aBouras, Christos1 aDiles, Georgios1 aNikolareas, Konstantinos  uhttp://telematics.upatras.gr/telematics/publications/capacity-guaranteed-sleep-mode-algorithm-5g-femtocell-tier?language=en01219nas a2200157   4500008004100000245004700041210004700088260002100135300001000156520069600166100002100862700002000883700002200903700002700925856010900952       2019                        eng d00aComparison of 4G and 5G Network Simulators0 aComparison of 4G and 5G Network Simulators  cJune 30 - July 4  a13-183 aNetwork simulation is a technique of utmost importance to evaluate new network performance, verify new algorithms and analyze various network topologies. It is used to find results to be expected from a hardware setup without the need for actual implementation. For this reason, there is a plethora of Network Simulation Software applied to different scenarios to evaluate theories and hypotheses. The aim of this paper is to study the most common Simulators regarding the deployment of 5G networks, provide a detailed comparison featuring their main advantages and showcasing potential defects and support the academic community, offering the required data to help choose the necessary one.1 aBouras, Christos1 aDiles, Georgios1 aGkamas, Apostolos1 aZacharopoulos, Andreas  uhttp://telematics.upatras.gr/telematics/publications/comparison-4g-and-5g-network-simulators?language=en01487nas a2200157   4500008004100000245004700041210004700088260001900135300001200154520096100166100002101127700002201148700002601170700002401196856010901220       2019                        eng d00aComparison of LoRa Simulation Environments0 aComparison of LoRa Simulation Environments  cNovember 7 - 9  a374-3853 aInternet of Things (IoT) is used more and more in our everyday life, connecting different wireless devices, and their distance can vary from some centimeters to many kilometers. New IoT technologies such as Long Range (LoRa) are emerging enabling power efficient wireless communication over very long distances. Simulation of LoRa networks is quite important, because can be used for the design and the evaluation of LoRa based application without the need of costly implementations or before to proceed to the actual implementation of the system. Choosing the right parameters of the systems like spreading factor can improve the energy consumption of the wireless devices. This paper presents the most important LoRa simulation environments available in the literature and after that, we present a comparative evaluation of LoRa simulation environments. The benefits, the disadvantages and the highlights of each LoRa simulation environment is presented.1 aBouras, Christos1 aGkamas, Apostolos1 aKatsampiris, Spyridon1 aKokkinos, Vasileios  uhttp://telematics.upatras.gr/telematics/publications/comparison-lora-simulation-environments?language=en02016nas a2200145   4500008004100000245008900041210006900130260001900199300001200218520141900230100002101649700002401670700002201694856015401716       2019                        eng d00aEfficient 5G Network Decoupling using dynamic Modulation and Coding Scheme Selection0 aEfficient 5G Network Decoupling using dynamic Modulation and Cod  cNovember 7 - 9  a253-2653 aThe transmission power limitations in telecommunication systems are tackled by using low code rates and high order modulation schemes, thus achieving high spectral efficiency with lower costs per bit. This paper evaluates the User-Centric model for Fifth Generation wireless telecommunication systems, attempting to efficiently improve user terminal-Base Station communication aspects. We propose a resource-aware method of improving network coverage across all layers by choosing to decouple the overall network into two separate uplink and downlink networks. The algorithm fully respects each user’s throughput demands and solves the User Equipment – Base Station association problem efficiently by choosing the appropriate Modulation and Coding Scheme that maximizes spectral efficiency inside each macro cell coverage area. Results are evaluated for both acceptable frequency ranges defined in 5G New Radio protocol interfaces (namely, Frequency Range 1 and Frequency Range 2) and show that the proposed Modulation and Coding Scheme-based mechanism offers perfect Quality of Service preservation and augmented data rates in favor of ultimate user coverage, in both scenarios. Additionally, due to the extended resources Frequency Range 2 provides, the equivalent simulation not only offers increased data rates compared to Frequency Range 1, but also a lower number of devices unsupported by the mechanism.1 aBouras, Christos1 aKokkinos, Vasileios1 aMichos, Evangelos  uhttp://telematics.upatras.gr/telematics/publications/efficient-5g-network-decoupling-using-dynamic-modulation-and-coding-scheme-selection?language=en01721nas a2200145   4500008004100000245008400041210006900125260001900194300001200213520114300225100002101368700002001389700002701409856013901436       2019                        eng d00aAn Energy Efficient Mechanism for Downlink and Uplink Decoupling in 5G Networks0 aEnergy Efficient Mechanism for Downlink and Uplink Decoupling in  cNovember 7 - 9  a241-2523 aIn current cellular networks, cell association is heavily based on the Downlink signal power and all devices are associated with the same Base Station in Downlink and Uplink. While as of now this technique has been proved adequate in homogeneous networks where all BSs have similar transmission levels, in increasingly dense heterogeneous networks rate is heavily dependent on the load, which can significantly vary from Base Station to Base Station. Due to increased demands for usage over several devices in heterogenous networks, large disparities in the Downlink pose a threat to the quality of services rendered by the network and this tecnhique seems obsolete. Uplink and Downlink decoupling is the proposed solution, where the Downlink cell association is not necessarily based on the same criteria as Uplink . We propose using SINR and Path Loss with Range Extension as factors for choosing the appropriate Base Station for connection in Downlink and Uplink respectively, taking into consideration the Base Stations’ Resource Block availability, to avoid overloading Base Stations and we will use simulations to test our theory.1 aBouras, Christos1 aDiles, Georgios1 aKalogeropoulos, Rafail  uhttp://telematics.upatras.gr/telematics/publications/energy-efficient-mechanism-downlink-and-uplink-decoupling-5g-networks?language=en01753nas a2200133   4500008004100000245006100041210005900102260001500161520125300176100002101429700002401450700002201474856012301496       2019                        eng d00aResource-Efficient Decoupling in Ultra-Dense 5G Networks0 aResourceEfficient Decoupling in UltraDense 5G Networks  cJune 18-203 aThe evolution of 5G mobile networks is expected to be comprised of small cell deployments within spitting distance of existing macrocell infrastructures. The small cells adoption, which promises to offer an economical solution for improved coverage and data rate, appears to be the key factor at improving network cooperation and system performance. In this paper, we evaluate the User-Centric model for 5G networks, targeted at improving communication between user terminal and Base Stations across all layers. We suggest a cost-effective, resource-aware method for improved mobile outdoor coverage and overall network capacity while fully respecting the user’s Quality of Service, by decoupling the overall network into downlink and uplink networks. The proposed algorithm determines how the network users in both networks will efficiently connect to a Base Station. The network performances are evaluated in terms of data rates enhancements, association outcome and preservation of the Quality of Service for each user. Our low-complexity algorigthm ultimately manages to serve the vast majority of the users placed inside an ultra-dense network and achieve perfect preservation of Quality of Service, regardless of the number of active users.1 aBouras, Christos1 aKokkinos, Vasileios1 aMichos, Evangelos  uhttp://telematics.upatras.gr/telematics/publications/resource-efficient-decoupling-ultra-dense-5g-networks?language=en01983nas a2200109   4500008004100000245005700041210005500098520156100153100002101714700002201735856011601757       2019                        eng d00aTechno - economic analysis for programmable networks0 aTechno economic analysis for programmable networks3 aThe forthcoming advent of the fifth generation of mobile networks (5G) will boost technology, as new solutions are needed to meet the growing demands of 5G. These novelties are pinpointed both by scientists and elecommunication providers. Programmable logic solutions are going to be used, as they accumulate financial, performance and environmental benefits. The programmable logic nowadays is represented by the combination of the Software Defined Networking (SDN) technology with the Network Function Virtualization (NFV). This combination not only reduces hardware as most network components are replaced by Network Functions or Virtual Machines (VMs), but also offers better resource allocation and provides more bandwidth, CPU etc. to the parts of the network that become more congested. Solutions, such as SDN, may concentrate fundamental advantages and profits, but they appear to face basic problems and therefore, key questions are raised concerning their cost and safety. One of these issues contains all the expenses that need to be made for the acquisition of the technology and the adjustments that need to be incorporated into current infrastructure so that it is able to cover SDN networks as well. This paper analyses a programmable model of SDN combined with NFVs. A Sensitivity Analysis (SA) is held to enable determining the factors, that largely influence the pricing so as to propose ways to significantly reduce several types of costs and propose solutions or research directions to cut down on the expenses of these network factors.1 aBouras, Christos1 aKollia, Anastasia  uhttp://telematics.upatras.gr/telematics/publications/techno-economic-analysis-programmable-networks?language=en01249nas a2200133   4500008004100000245005200041210004700093260002100140520077800161100002100939700002200960700002700982856010601009       2019                        eng d00aThe techno-economic models for CR and SDN in 5G0 atechnoeconomic models for CR and SDN in 5G  cSeptember 11-13 3 a5G is closer than ever, considering that in 2020 it will have been released. Existing technologies do not adequately cover the 5G demands, therefore new or modified versions of the existing technologies should be introduced. Telecommunication operators remain skeptical about the costs induced by 5G technologies. In this context, it is fundamental that 5G enabling technologies are analyzed in a techno-economic way. In this paper, authors present models of Cognitive Radio (CR) and Software Defined Networking (SDN). They develop economic models based on the Stackelberg competition, opt for the experimentation parameters and conduct Sensitivity Analysis (SA) experiments that show which are the most influential factors for each technology proposing ways to limit them.1 aBouras, Christos1 aKollia, Anastasia1 aMaligianni, Eleftheria  uhttp://telematics.upatras.gr/telematics/publications/techno-economic-models-cr-and-sdn-5g?language=en01944nas a2200157   4500008004100000245005300041210005300094260001800147300001200165520140100177100002101578700002201599700002401621700002701645856011401672       2019                        eng d00aUsing LoRa Technology for IoT Monitoring Systems0 aUsing LoRa Technology for IoT Monitoring Systems  cOctober 1 - 3  a134-1373 aThis paper presents technology comparison scenarios for Internet of Things (IoT) concepts on rescue monitoring. The study starts by comparing WiFi & LoRa as wireless technologies able to be used by smart devices for data transmission. The IoT end-devices used in these concepts have high requirements in battery saving and for this reason the usage of low-power modules is advisable. This paper focus in rescue monitoring and the goal in the current study is the usage of the two wireless technologies used for data transmission from IoT devices: the already known WiFi and the upcoming LoRa technology. During rescue monitoring, important concepts are
the identification and individuals' rescue of particularly vulnerable groups or individuals belonging to population groups with a high probability of being lost. A LoRa based gateway and WiFi Router is used to connect the end-devices used in our scenarios to the Internet. The collected data on server application as captured from installed sensors on the IoT modules can be displayed to authorized users through a web or mobile application. The results through simulation and real time experiments indicate that LoRa could be an ideal candidate for rescue monitoring. This study is a first step in creating a more general ecosystem for rescue concepts including all the hardware and software using the LoRa technology as transmission method.1 aBouras, Christos1 aGkamas, Apostolos1 aKokkinos, Vasileios1 aPapachristos, Nikolaos  uhttp://telematics.upatras.gr/telematics/publications/using-lora-technology-iot-monitoring-systems?language=en01701nas a2200169   4500008004100000245007100041210006800112300000900180490000600189520109900195100001801294700002101312700002401333700002701357700001901384856012801403       2019                        eng d00aWiFiMon - A Tool for Wi-Fi Performance Monitoring and Verification0 aWiFiMon A Tool for WiFi Performance Monitoring and Verification  a1-180 v83 aMeasuring network quality of a wireless network as experienced by end-users is quite difficult, as there isn’t a single tool available that can record measurements on all sides of the system. The approach presented in this research work is based on the end-user feedback, giving the opportunity of visualization of network performance in real time. We initially present an overview of the developed tool, called WiFiMon, which has the ability to capture, record measurements and export statistics on the quality of Wi-Fi network as perceived by the end-users. The measurements are initiated by the end-users - without their intervention – after they visit a web page or use a mobile application. WiFiMon aims to give a clear understanding of the Wi-Fi network conditions by measuring specific parameters of the network, such as download/upload throughput, and correlate these measurements with raw data from various log files to obtain additional information regarding the performance of specific access points. The results reveal the functionality of the proposed tool and its scalability.1 aBaumann, Kurt1 aBouras, Christos1 aKokkinos, Vasileios1 aPapachristos, Nikolaos1 aStamos, Kostas  uhttp://telematics.upatras.gr/telematics/publications/wifimon-tool-wi-fi-performance-monitoring-and-verification?language=en02202nas a2200133   4500008004100000245006500041210006300106260001500169300001200184520170200196100002101898700002201919856012701941       2018                        eng d00aAL-FEC application on NGMN-Edge computing integrated systems0 aALFEC application on NGMNEdge computing integrated systems  cJuly 3 - 6  a364-3693 aEdge computing or edge networking is an architecture that uses one or more collaborative multitude of enduser clients or near-user edge devices to carry out a substantial amount of communication, control, management or other operations. Edge Computing for mobile networks is a new technology which is currently under standardization providing an IT service environment and cloud-computing capabilities at the edge of the mobile network in close proximity to the mobile end users. The aim of this technology is to reduce latency, ensure highly efficient network operation and service delivery, providing improved user experience. All of these can be translated into value and can create opportunities for operators, application and content providers enabling them to better utilize the mobile broadband capabilities. Furthermore, edge computing enables a new value chain for end users but also for industries allowing to efficient deliver their applications over the mobile network providing fresh business opportunities and new use cases. FEC is a feedback free error recovery method where the sender introduces redundant data in advance with the source data enabling the recipient to recover from different arbitrary packet losses. Recently, the adoption of FEC error control method has been boosted by the introduction of the powerful RaptorQ Application Layer FEC (AL-FEC) codes. In this work we propose the integration of AL-FEC error protection application at the edge layer. We propose a novel AL-FEC application architecture scheme based on RaptorQ codes and we analyze the performance enhancements such an error control architecture can introduce on NGMN-edge computing integrated systems.1 aBouras, Christos1 aKanakis, Nikolaos  uhttp://telematics.upatras.gr/telematics/publications/al-fec-application-ngmn-edge-computing-integrated-systems?language=en01390nas a2200145   4500008004100000245006000041210006000101260001700161300001700178520086600195100002101061700002201082700002201104856011801126       2018                        eng d00aDAS modifications for more efficient network cost in 5G0 aDAS modifications for more efficient network cost in 5G  cJune 25 - 29  a1110 - 1115 3 aDemanding goals have already been described concerning the next generation of mobile networks. In order to address these requirements, novel technologies are introduced or new concepts are integrated into conventional ones. In this paper, a modified Distributed Antenna System (DAS) architecture is described. Several hardware components are replaced with Network Function Virtualization (NFV) techniques, which are introduced in modern architectures so as to contribute in reducing capital and operational expenses. The model is described mathematically, is compared and contrasted with the conventional model proposed by authors in past research activity. Simulation scenarios help concluding into fundamental results concerning which are the most dissuasive cost factors e.g. bandwidth, frequency, capacity, coverage, etc. Several conclusions are summarized.1 aBouras, Christos1 aKollia, Anastasia1 aPapazois, Andreas  uhttp://telematics.upatras.gr/telematics/publications/das-modifications-more-efficient-network-cost-5g?language=en01820nas a2200133   4500008004100000245006600041210006400107300001200171490000600183520132600189100002101515700002201536856012801558       2018                        eng d00aEvolving AL-FEC application on 5G NGMN-Edge computing systems0 aEvolving ALFEC application on 5G NGMNEdge computing systems  a152-1600 v33 aFifth generation of mobile networks (5G) comes to cope with the context of the new mobile telecommunications era. Edge computing is a new collaborative technology under standardization utilizing end-user devices or near-end-user edge devices to operate processing, communication, or control operations. The achievement of efficient error control is a very critical aspect in the successful development of 5G Next Generation Mobile Networks (NGMN). Especially utilizing Forward Error Correction (FEC) codes on the application level is an efficient approach on improving error control on NGMN since it is adopted in several mobile multicast standards. FEC is a feedback free error control technique where redundant data are introduced with the source data to enable the recipient recovering from packet losses with an interesting approach on applying AL-FEC error protection introduces deterministic or randomized online algorithms. Based on this we present a novel online scheme on applying AL-FEC application on the context of the AL-FEC policy online problem. In this work we present an online algorithm based on feedback received from mobile end-users which adapts the introduced protection based on this. Another aspect of this work is the utilization of AL-FEC protection on the edge level based on RaptorQ FEC codes.1 aBouras, Christos1 aKanakis, Nikolaos  uhttp://telematics.upatras.gr/telematics/publications/evolving-al-fec-application-5g-ngmn-edge-computing-systems?language=en02110nas a2200133   4500008004100000245004800041210004700089260001900136300000900155520165600164100002101820700002201841856011301863       2018                        eng d00aEvolving AL-FEC application towards 5G NGMN0 aEvolving ALFEC application towards 5G NGMN  cFebruary 26-28  a1-153 aThe fifth generation of mobile technology (5G) is positioned to address the demands and business contexts of 2020 and beyond. Therefore, in 5G, there is a need to push the envelope of performance to provide, where needed, for example, much greater throughput, much lower latency, ultra-high reliability, much higher connectivity density, and higher mobility range. A crucial point in the effective provisioning of 5G Next Generation Mobile Networks (NGMN) lies in the efficient error control and in more details in the utilization of Forward Error Correction (FEC) codes on the application layer. FEC is a method for error control of data transmission adopted in several mobile multicast standards. FEC is a feedback free error recovery method where the sender introduces redundant data in advance with the source data enabling the recipient to recover from different arbitrary packet losses. Recently, the adoption of FEC error control method has been boosted by the introduction of powerful Application Layer FEC (AL-FEC) codes. Furthermore, several works have emerged aiming to address the efficient application of ALFEC protection introducing deterministic or randomized online algorithms. In this work we propose a novel AL-FEC scheme based on online algorithms forced by the well stated AL-FEC policy online problem. We present an algorithm which exploits feedback capabilities of the mobile users regarding the outcome of a transmission, and adapts the introduced protection respectively. Moreover, we provide an extensive analysis of the proposed ALFEC algorithm accompanied by a performance evaluation against common error protection schemes.1 aBouras, Christos1 aKanakis, Nikolaos  uhttp://telematics.upatras.gr/telematics/publications/evolving-al-fec-application-towards-5g-ngmn?language=en01488nas a2200145   4500008004100000245005900041210005500100300001000155490000700165520098800172100002101160700002201181700002201203856011701225       2018                        eng d00aExploring SDN & NFV in 5G Using ONOS & POX Controllers0 aExploring SDN NFV in 5G Using ONOS POX Controllers  a46-600 v103 aNovel functionalities will take advantage of the cloud networking and will gradually replace the existing infrastructure of mobile networks with a virtualized one. Two technologies, namely Software Defined Networking (SDN) and Network Function Virtualization (NFV), offer their important benefits and a combination of them is an answer to the demands raised, such as Central Office Re-architected as a Data Center (CORD). Open Network Operating System (ONOS) and POX are SDN controllers and offer an option to combine SDN and NFV addressing many ongoing problems in the field of mobile networks. In this paper, technologies and both controllers are compared and contrasted. Indicative cases of topologies are simulated and help evaluating both controllers. According to the experimental findings, ONOS is one of the most important controllers for practical, theoretical, research and educational purposes, while POX is a useful and simpler controller for other educative applications1 aBouras, Christos1 aKollia, Anastasia1 aPapazois, Andreas  uhttp://telematics.upatras.gr/telematics/publications/exploring-sdn-nfv-5g-using-onos-pox-controllers?language=en01702nas a2200157   4500008004100000245007900041210006900120490000700189520108500196100002101281700002201302700002401324700002701348700002801375856014101403       2018                        eng d00aMCS Selection Exploiting Femtocells Utilization in Multicast Transmissions0 aMCS Selection Exploiting Femtocells Utilization in Multicast Tra0 v313 aMulticast-Broadcast over Single Frequency Network (MBSFN) technology, as introduced by the Long Term Evolution Advanced (LTE-A) group, is expected to be part of the upcoming cellular systems offering resource efficiency to broadcast services. MBSFN transmission is suitable to serve multicast groups searching the same content. In addition, the fast emerging technology of femtocells networks and their hybrid nature can lead to efficient resource sharing between non-subscribed users when located inside their coverage. The focus of this manuscript is twofold; firstly, we have contacted simulation experiments to compare the MBSFN transmission with the traditional PTP transmission for various femtocell distributions and network topology changes; secondly, a novel multicast transmissions mechanism is proposed from non-subscribed users who exploit femtocells resources for broadcast services, without limiting user’s data requirements. The simulation results lead to a significant system’s performance in terms of average throughput, total capacity and energy consumption.1 aBouras, Christos1 aKanakis, Nikolaos1 aKokkinos, Vasileios1 aPapachristos, Nikolaos1 aVouyioukas, Demosthenes  uhttp://telematics.upatras.gr/telematics/publications/mcs-selection-exploiting-femtocells-utilization-multicast-transmissions?language=en01507nas a2200205   4500008004100000245009700041210006900138300001000207490000700217520076300224100001900987700002101006700002101027700001901048700002001067700002301087700002201110700001901132856015001151       2018                        eng d00aPeer-to-peer live video streaming with rateless codes for massively multiplayer online games0 aPeertopeer live video streaming with rateless codes for massivel  a44-620 v113 a<p class="rtejustify">We present a multi-level multi-overlay hybrid peer-to-peer live video system that enables players of Massively Multiplayer Online Games to simultaneously stream the video of their game and watch the game videos of other players. Each live video bitstream is encoded with rateless codes and multiple trees are used to transmit the encoded symbols. Trees are constructed dynamically with the aim to minimize the transmission rate at the source while maximizingthe number of served peers and guaranteeing on-time delivery and reliability. ns-2 simulations and real measurements on the Internet show competitive performance in terms of start-up delay, playback lag, rejection rate, used bandwidth, continuity index, and video quality.</p>
1 aAhmad, Shakeel1 aBouras, Christos1 aBuyukkaya, Eliya1 aDawood, Muneeb1 aHamzaoui, Raouf1 aKapoulas, Vaggelis1 aPapazois, Andreas1 aSimon, Gwendal  uhttp://telematics.upatras.gr/telematics/publications/peer-peer-live-video-streaming-rateless-codes-massively-multiplayer-online-games?language=en01530nas a2200121   4500008004100000245008000041210006900121520100700190100002101197700002401218700002701242856013901269       2018                        eng d00aPerformance evaluation of LoraWan physical layer integration on IoT devices0 aPerformance evaluation of LoraWan physical layer integration on 3 aDue to the constant motion of wireless devices in the Internet of Things (IoT), infrastructure wireless networks cannot provide connectivity at all times, in comparison with ad hoc networks, which are more easy to use and are based on abstract and continuously altering topologies. LoraWan, as a Long Range Wide Area Network specification recommended by the LoRa Alliance, is a low power and long distance communication protocol suitable for IoT environments and applications to different domains such as healthcare and smart farming. This IoT concept is gaining a rapid growth on the IoT market and is simultaneously improving our living environment. In this paper, we first briefly introduce LoRa as an efficient solution of physical layer integration on the IoT devices. We then conduct a performance evaluation taking into consideration metrics such as bit error rate, time on air transmission based on Signal to Noise Ratio (SNR) and Spreading Factors modifications for different bandwidth values.1 aBouras, Christos1 aKokkinos, Vasileios1 aPapachristos, Nikolaos  uhttp://telematics.upatras.gr/telematics/publications/performance-evaluation-lorawan-physical-layer-integration-iot-devices?language=en01282nas a2200133   4500008004100000245005900041210005900100300001200159520079200171100002100963700002000984700002401004856012001028       2018                        eng d00aSleep mode strategies for dense small cell 5G networks0 aSleep mode strategies for dense small cell 5G networks  a28 - 333 aThe evolution of the fifth generation (5G) of mobile networks tends towards the prevalence of dense femtocell deployments, which offer improvements in data rate and overall network’s capacity. Small cell deployments and particularly femtocells provide an attractive, cheap and flexible solution for the increased traffic demand. However, the resulting dense networks are characterized by challenges, too, such as increased interference and resource allocation. In this paper, we propose ways to address these difficulties by combining hybrid access, sleep mode and a power control mechanism. Simulations show that the above mechanism leads to improved capacity and throughput for subscribers, along with improved energy efficiency, without compromising the non-subscribers performance.1 aBouras, Christos1 aDiles, Georgios1 aNtoutsos, Dimitrios  uhttp://telematics.upatras.gr/telematics/publications/sleep-mode-strategies-dense-small-cell-5g-networks?language=en01321nas a2200145   4500008004100000245004900041210004600090300001000136520083400146100002100980700002401001700002201025700002201047856010601069       2018                        eng d00aTechno-economic analysis of MIMO & DAS in 5G0 aTechnoeconomic analysis of MIMO DAS in 5G  a73-803 a2020 will be the year, in which 5G is going to be put into operation, therefore, it is fundamental that all enabling technologies are analyzed in a technical and economic way. The business sector is not very favorable in investing into novel technologies. In this paper, authors propose a techno-economic model for the Multiple Input Multiple Output (MIMO) tech- nology and compare it to the previously developed model for the Distributed Antenna Systems (DAS). Firstly, the experimentation models are analyzed. Secondly, the mathematical models are presented and the specific parameters are opted. Several experiments help comparing and contrasting the two different technologies. There are not many works concerning the technoeconomic perspectives of MIMO comparing it with the DAS, this research contributes in this direction.1 aBouras, Christos1 aKokkalis, Stylianos1 aKollia, Anastasia1 aPapazois, Andreas  uhttp://telematics.upatras.gr/telematics/publications/techno-economic-analysis-mimo-das-5g?language=en04111nas a2200157   4500008004100000245009500041210006900136300001000205490000600215520349200221100002103713700002403734700002203758700002203780856015103802       2017                        eng d00aAnalyzing Small - cells and Distributed Antenna Systems from Techno - economic Perspective0 aAnalyzing Small cells and Distributed Antenna Systems from Techn  a45-640 v63 a<p class="rtejustify">Next-generation of mobile technologies is expected to largely augment the system's peak data rates and cut down on the round-trip delays. The main idea of using ultra-density or DAS (Distributed Antenna Systems) based on their properties, is that they are able to increase efficiency and expand network capacity without the need for more spectrum resources by redistributing the existing ones, depict them as the key solutions for the future mobile networks. Small cells and DAS were launched mainly for addressing the issue of limited connectivity indoors.<br />
There are several other important benefits of these technologies, which constitute them as bases for future generations of mobile networks, such as 5G (5G-PPP, 2014). Femtocells' benefit is that they provide ultra-density, which is expected to be one of the essential features of 5G. Ultra-dense networks coexist with the existing macrocellular ones forming altogether heterogeneous networks and fulfill the requirements and the network's future demands. Scientists and researchers have decided to move towards this direction by conducing several research activity in the area (Networld2020 ETP, 2014; IWPC, 2014).<br />
The future mobile networks are going to demand a large network coverage. DAS would be an ideal solution to deal with the limited spectrum, because it provides repeaters, that are connected to the antenna system. It also serves the augmenting numbers of the smart devices, that in the future will be connected to the Internet or the smart home devices of the owner's home network as we move dynamically to the Internet of Things.<br />
This paper studies the techno-economic aspects of ultra-dense and DAS deployments. It presents the characteristics and advantages for all their parts, as well as a techno-economic modeling of these deployment types. The defined models are used for the investigation of the upper technologies from an economic point of view. They provide an insight in the future financial and pricing aspects of these solutions and consist a useful tool for the definition of financing and pricing policies towards economically viable deployments. The authors define models for selecting the most appropriate network architectural solution for public buildings' indoor coverage. Cost, investment, materials, coverage and capacity are the parameters that are taken into account for the definition of their models. The main scientific contribution of this paper is that it includes multiple case-study examples of the techno-economic models as well as results of conducted experiments. It also analyzes and presents a techno-economic model and summarizes the main research activity in the particular field.<br />
The remaining part of this paper is structured as follows: the second section refers to the related research that has been conducted so far. The third section presents the architectures of ultra-dense and DAS deployments used in the models. In the following section we describe cost models for ultra-dense and DAS deployments. In the next section we define the parameterization of the cost models. In the sixth section we conduce some experimental scenarios and analyze the corresponding results. Finally, in the seventh section we conclude our paper with the most fundamental conclusions realized in the experimental procedure and in the final section we list some ideas for future research work in the field of mobile network technologies.</p>
1 aBouras, Christos1 aKokkinos, Vasileios1 aKollia, Anastasia1 aPapazois, Andreas  uhttp://telematics.upatras.gr/telematics/publications/analyzing-small-cells-and-distributed-antenna-systems-techno-economic-perspective?language=en02169nas a2200145   4500008004100000245006600041210006400107260001400171490000700185520164100192100002101833700002201854700002201876856012501898       2017                        eng d00aDense deployments and DAS in 5G: a techno-economic comparison0 aDense deployments and DAS in 5G a technoeconomic comparison  c1777-17970 v193 a<p class="rtejustify">5G wireless telecommunications require rapid data traffic and high network speed. Thus, it is important to focus on technologies that are capable of meeting these high demands. On the other hand, the cost calculation of installing, maintaining and operating a network deployment, plays an important role for its adoption by an enterprise or a network provider. In this paper, there is a presentation of cost models for Distributed Antenna Systems (DAS) and small cells, because these two technologies offer significant benefits and meet the needs of the next generation of mobile networking. A Sensitivity Analysis (SA) of several network components, such as the allocated bandwidth, the running costs, the periodical interest rate, the base station, the equipment, the power consumption, the backhauling, the implementation costs and throughput density is analyzed. Throughput density and several important information are listed and calculated, according to public data. All these components are tested, using parameters and variables to represent them in mathematical equations model resulting in a cost provision for the next five years. Then, the overall and the individual costs are computed, namely the Total Cost of Ownership (TCO), the Capital (CAPEX) and the Operational (OPEX) expenditures for several throughput density prices according to the suggested pricing models. The paper concludes by drawing fundamental conclusions for the expenses and as a result, for the viability of each technological suggestion and it ends up offering ideas for future research activity in the field.<br />
&nbsp;</p>
1 aBouras, Christos1 aKollia, Anastasia1 aPapazois, Andreas  uhttp://telematics.upatras.gr/telematics/publications/dense-deployments-and-das-5g-techno-economic-comparison?language=en01227nas a2200133   4500008004100000245006800041210006800109260001700177300001000194520071800204100002100922700002000943856013000963       2017                        eng d00aDistributed Sleep Mode Power Control in 5G Ultra Dense Networks0 aDistributed Sleep Mode Power Control in 5G Ultra Dense Networks  cJune 21 - 23  a65-763 a<p class="rtejustify">The upcoming 5G networks are characterized by ultra dense deployments of small cells. These structures are capable of providing the much desired increase in capacity and data rates. The limited resources though present challenges on how they will be shared among the high number of base stations. Distributed coordination will play a big part in resource allocation. In this paper, we present a power control mechanism for dense femtocell deployments which utilizes sleep mode strategies and spectrum sharing among users. The mechanism exhibits increased throughput for the femtocell subscribers, preserving non-subscribers performance and increasing the network’s energy efficiency.</p>
1 aBouras, Christos1 aDiles, Georgios  uhttp://telematics.upatras.gr/telematics/publications/distributed-sleep-mode-power-control-5g-ultra-dense-networks?language=en01249nas a2200133   4500008004100000245005400041210005400095260001800149300001200167520078300179100002100962700002000983856011201003       2017                        eng d00aEnergy efficiency in sleep mode for 5G femtocells0 aEnergy efficiency in sleep mode for 5G femtocells  cMarch 29 - 31  a143-1453 a<p class="rtejustify">Energy efficiency is a major requirement for next generation mobile networks both as an end to reduce operational expenses and to increase the systems’ ecological friendliness. Another integral part of 5G networks is the increased density of the deployment of small radius base stations, such as femtocells. Based on the design principle that demands a system to be active and transmitting only when and where it is needed, we evaluatethe energy savings harvested when sleep mode techniques are enforced in dense femtocell deployments. We present our novel variations of sleep mode combined with hybrid access strategies and we estimate capacity and energy benefits. Our simulations show significant advantages in performance and energy efficiency.</p>
1 aBouras, Christos1 aDiles, Georgios  uhttp://telematics.upatras.gr/telematics/publications/energy-efficiency-sleep-mode-5g-femtocells?language=en01431nas a2200145   4500008004100000245006000041210006000101260001800161300001200179520090800191100002101099700002001120700002301140856012201163       2017                        eng d00aEnergy savings in power control fro 5G dense femtocells0 aEnergy savings in power control fro 5G dense femtocells  cNovember 8-10  a299-3083 aThe dramatic increase in traffic observed in the recent years in mobile networks is not expected to slow down. Increasing the number of deployed base stations of different range and capabilities creating ultra dense networks is one of the solutions that will be adapted in order to cover the demand. Energy efficiency schemes are needed in order to keep the energy impact of such an approach limited. In this paper we focus on densely deployed femtocells (clusters) evaluating the power savings resulted from a power controlled sleep mode mechanism. The mechanism tries to reduce the number of operating closed access femtocells, by providing perfofmance incentives to the clusters subscribers to coordinate reducing energy consumption without compromising their throughput. Simulations investigate the different levels of power savings depending on the chosen configuration
and the deployment density.1 aBouras, Christos1 aDiles, Georgios1 aMoulias, Theodoros  uhttp://telematics.upatras.gr/telematics/publications/energy-savings-power-control-fro-5g-dense-femtocells?language=en01371nas a2200169   4500008004100000245007900041210006900120260001800189520072700207100002100934700002300955700002400978700002401002700002001026700002701046856012801073       2017                        eng d00aExtension to Middleware for IoT Devices, with Applications in Smart Cities0 aExtension to Middleware for IoT Devices with Applications in Sma  cApril 20 - 213 a<p class="rtejustify">This work proposes extensions toWubby (a device-level software platform for IoT devices, a technology developed by Econais A.E.) to support wireless modules for mobile networks (4G / LTE-A, and also supporting the forthcoming 5G). The proposed extension leverages the use of such modules, as it allows easy programming and existing code re-use. It thus adds a compatibility layer across the di erent modules as it a common set of classes for the wireless modules. The system can be used to support the networking aspects of a variety of IoT applications, including applications for Smart Cities, using a variety of IoT devices. This work suggests such a case focusing on air quality monitoring.</p>
1 aBouras, Christos1 aKapoulas, Vaggelis1 aKokkinos, Vasileios1 aLeonardos, Dimitris1 aPipilas, Costas1 aPapachristos, Nikolaos  uhttp://telematics.upatras.gr/telematics/publications/extension-middleware-iot-devices-applications-smart-cities?language=en01665nas a2200133   4500008004100000245006400041210006400105300001200169490000600181520117600187100002101363700002201384856012501406       2017                        eng d00aImproving news articles recommendations via user clustering0 aImproving news articles recommendations via user clustering  a223-2370 v83 a<p>Although commonly only item clustering is suggested by Web mining techniques for news articles recommendation systems, one of the various tasks of personalized recommendation is categorization of Web users. With the rapid explosion of online news articles, predicting<br />
user-browsing behavior using collaborative filtering (CF) techniques has gained much attention in the web personalization area. However common CF techniques suffer from problems like low accuracy and performance. This research proposes a new personalized recommendation approach that integrates both user and text clustering based on our developed algorithm, W-kmeans, with other information retrieval (IR) techniques, like text categorization and summarization in order to provide users with the articles that match their profiles. Our system can easily adapt over time to divertive user preferences. Furthermore, experimental results show that by aggregating item and<br />
user clustering with multiple IR techniques like categorization and summarization, our recommender generates results that outperform the cases where each or both of them are used, but clustering is not applied.</p>
1 aBouras, Christos1 aTsogkas, Vassilis  uhttp://telematics.upatras.gr/telematics/publications/improving-news-articles-recommendations-user-clustering?language=en01805nas a2200133   4500008004100000245006300041210006300104300001200167490000700179520132000186100002101506700002001527856012401547       2017                        eng d00aInterference Management Strategy for 5G Femtocell Clusters0 aInterference Management Strategy for 5G Femtocell Clusters  a323-3390 v963 a<p class="rtejustify">With the next generation of mobile networks closing in, its main characteristics have already been proposed and adapted. Ultra-dense heterogeneous networks seem to be one of the main drivers to answer the need for larger device connectivity and increased data rate. Multiple Base Stations with different specifications will be deployed to achieve these targets. Femtocells are a type of Base Station that is expected to dominate, due to their low cost and easy deployment and maintenance. However, trying to increase spectral efficiency with the use of femtocells, by multiple base stations utilizing the same spectrum will lead to severe interference phenomena. This can be tackled by sharing spectrum strategies and power control techniques. In this manuscript, we propose a full scheme of resource management that can be applied in instances of femtocell deployments of increased density. The mechanism is based on coordination among the femtocells to achieve better spectrum usage, on power control and on hybrid access configuration aiming to fairness in resource allocation and to the improvement of overall capacity. Conducted simulations showed that our algorithm increases the overall capacity, protects non-subscribed users and balances the hybrid access effect on subscribers.</p>
1 aBouras, Christos1 aDiles, Georgios  uhttp://telematics.upatras.gr/telematics/publications/interference-management-strategy-5g-femtocell-clusters?language=en01764nas a2200133   4500008004100000245006200041210006000103300001100163490000700174520128200181100002101463700002201484856012401506       2017                        eng d00aOnline AL - FEC Policy Problem on Mobile Unicast Services0 aOnline AL FEC Policy Problem on Mobile Unicast Services  a95-1020 v233 a<p class="rtejustify">Forward error correction (FEC) is a method for error control of data transmission adopted in several mobile multicast standards. FEC is a feedback free error recovery method where the sender introduces redundant data in advance with the source data enabling the recipient to recover from different arbitrary packet losses. Recently, the adoption of FEC error control method has been boosted by the introduction of powerful Application Layer FEC (AL-FEC) codes, e.g. RaptorQ codes. Furthermore, several works have emerged aiming to address the shortcomings of AL-FEC protection application utilizing deterministic or randomized online algorithms to enhance the efficiency of AL-FEC error control method. In this work, since the investigation of AL-FEC application as primary or auxiliary error protection method over mobile multicast environments is a well investigated field but the opportunity of utilizing the AL-FEC over mobile unicast services as the only method for error control replacing common feedback based methods that are now considered to be obsolete, we provide an analysis on the feasibility of AL-FEC protection over unicast delivery utilizing online algorithms in conjunction with AL-FEC codes with exceptional recovery performance.</p>
1 aBouras, Christos1 aKanakis, Nikolaos  uhttp://telematics.upatras.gr/telematics/publications/online-al-fec-policy-problem-mobile-unicast-services-0?language=en01455nas a2200145   4500008004100000245004900041210004600090260001600136300001200152520097200164100002101136700002201157700002201179856010801201       2017                        eng d00aSDN & NFV in 5G: Advancements and Challenges0 aSDN NFV in 5G Advancements and Challenges  cMarch 7 - 9  a107-1113 a<p class="rtejustify">The next generation of mobile networks has risen the expectations and has induced a whole new approach in the networking future. This study summarizes solutions, that meet all the existing requirements integrating Software Defined Network (SDN) and Network Function Virtualization (NFV) in mobile networking. The main contribution of this research activity is that it is a tool for literature reference for scientists and engineers, because it presents and compares the most fundamental existing solutions and the future directions. In this paper, the main characteristics of SDN and NFV are summarized as fundamental alternatives contributing to succeed the goals set by 5G. The main demands and challenges faced by these solutions and the most beneficial applications of the combination of SDN with NFV are described. Finally, the main conclusions of this research and suggestions for possible future activity in the field are described.</p>
1 aBouras, Christos1 aKollia, Anastasia1 aPapazois, Andreas  uhttp://telematics.upatras.gr/telematics/publications/sdn-nfv-5g-advancements-and-challenges?language=en01616nas a2200145   4500008004100000245005500041210005500096260001500151300001200166520111100178100002101289700002201310700002201332856011601354       2017                        eng d00aTeaching 5G Networks Using the ONOS SDN Controller0 aTeaching 5G Networks Using the ONOS SDN Controller  cJuly 4 - 7  a312-3173 a<p class="rtejustify">Software Defined Networks (SDN) and Network Functions Virtualization (NFV) are two significant answers to the demands raised by the next generation of mobile networks. Teaching 5G, wireless and mobile networking is becoming an absolute necessity as virtualization and SDN generate a whole new approach for these types of networks and are candidate solutions for the fifth generation. We present several ideas for teaching the combination of SDN and NFV in future mobile networks using the Open Network Operating System (ONOS) and its use cases. The architectural scheme which is experimentedis thoroughly explained. There are several network simulations using the use cases vRouter (Virtual Router), IPRAN (InternetProtocol Radio Access Network) and MCORD&nbsp; (Mobile Central Office Re-architected as a data center) of the ONOS controller, which show how important the ONOS is and how it contributes in explaining 5G and SDN in the teaching process. Finally, experiments indicate that ONOS is suitable for teaching SDN and NFV in 5G. Future activity in the field is suggested.</p>
1 aBouras, Christos1 aKollia, Anastasia1 aPapazois, Andreas  uhttp://telematics.upatras.gr/telematics/publications/teaching-5g-networks-using-onos-sdn-controller?language=en01742nas a2200145   4500008004100000245007300041210006900114260001500183300001200198520119000210100002101400700002201421700002201443856013101465       2017                        eng d00aTeaching network security in mobile 5G Using the ONOS SDN controller0 aTeaching network security in mobile 5G Using the ONOS SDN contro  cJuly 4 - 7  a465-4703 a<p class="rtejustify">Software Defined Networking (SDN) constitutes a fundamental technological solution which responds to the most essential challenges in 5G and beyond networks. Security still remains one of its most controversial issues. Security should be ensured in order to create reliable and consistent networks and on line applications and satisfy the demands of Service Level Agreements (SLAs). Therefore, teaching security of SDN and NFV is fundamental for academia these days. In this paper, we are going to summarize the most fundamental issues related to SDN security challenges and problems appearing alongside with the key back-doors in future SDN mobile networks. Several solutions utilizing SDN capabilities are suggested to avoid SDN security issues. We are also presenting experiments of network topologies using well-known network attack scenarios performed to showcase how networks’ security could be taught using SDN controllers. Experiments are conducted using the Open Network Operating System (ONOS) controller indicating that security teaching using ONOS controller is easy and offers many benefits. Future research activity in the field is proposed.</p>
1 aBouras, Christos1 aKollia, Anastasia1 aPapazois, Andreas  uhttp://telematics.upatras.gr/telematics/publications/teaching-network-security-mobile-5g-using-onos-sdn-controller?language=en02755nas a2200181   4500008004100000245009700041210006900138260001300207300000900220490000600229520207400235100002102309700002202330700002302352700002202375700001702397856015902414       2017                        eng d00aVideo transmission in mobile ad hoc networks using multiple interfaces and multiple channels0 aVideo transmission in mobile ad hoc networks using multiple inte  cMay 2017  a1-280 v83 a<p class="rtejustify">Mobile Ad hoc NETworks (MANETs) are an important part of wireless communications and the increasing use of mobile devices is confirming that. MANETs can be of great value in Emergency Response situations where communication between mobile deployed units is critical and wired or wireless infrastructures may not be present or functional. In emergency scenarios, multimedia communication is very important for decision making and situation assessment. This requires up-to-date (on-line) information feed on the situation, including voice and video from the affected zone. However, MANETs do not seem to efficiently support multimedia applications, and this is quite evident in video transmission. One way to remedy this is to use more (wireless) interfaces per mobile node and consequently more communication channels. In this work, we perform an analytical study on the use of multiple interfaces and multiple channels (MIMC) in video transmission with respect to the requirements of Emergency Response Ad hoc Networks. More specifically, we examine and present the impact of using MIMC on MANETs during video transmission applications, we evaluate the performance of three basic routing protocols in MANETs, and we propose a channel selection mechanism in MANET nodes with MIMC for enhanced video transmission. In addition, we evaluate video transmission streams with rate adaptation and present comparative results. The proposed mechanism is evaluated using the ns-2 network simulator and the simulations are performed for a variety of topologies. Simulation results show that the different routing protocols respond differently when MIMC is introduced. The Ad hoc On-Demand Multipath Distance Vector and (especially) the Ad hoc On-Demand Distance Vector routing protocols benefit significantly, while the Destination Sequenced Distance Vector shows fewer improvements. The proposed mechanism is shown to be beneficial for transmitting video streams and enhances the network’s ability to accommodate more streams and reduce packet delay.</p>
1 aBouras, Christos1 aGkamas, Apostolos1 aKapoulas, Vaggelis1 aPolitaki, Dimitra1 aTsanai, Enea  uhttp://telematics.upatras.gr/telematics/publications/video-transmission-mobile-ad-hoc-networks-using-multiple-interfaces-and-multiple-channels?language=en01587nas a2200157   4500008004100000245007400041210006900115260001400184520099100198100001801189700002101207700002401228700002701252700001901279856013101298       2017                        eng d00aWiFiMon App Measuring Wi-Fi Performance as Experienced by End - Users0 aWiFiMon App Measuring WiFi Performance as Experienced by End Use  cMay 3 - 53 a<p class="rtejustify">The measurement of quality and efficiency of a wireless Wi-Fi network is particularly difficult, as there is not a single tool that can record measurements from all sides of the system, i.e. from both the access point and the end-user. Existing tools are able to monitor the overall quality of the wireless network; although they cannot determine how end-users experience the quality of Wi-Fi in a particular part of the network at a given time. In this paper we present a novel tool, named WiFiMon, which enables measuring, recording and exporting statistics regarding the quality of a Wi-Fi network as experienced by the end-users. The measurements are triggered by the end-users when they visit WiFiMon-enabled websites and/or run WiFiMon-enabled mobile applications and are recorded without users’ intervention. Main goal of WiFiMon is to give network administrators a better overview on how the endusers experience the conditions of the Wi-Fi network.</p>
1 aBaumann, Kurt1 aBouras, Christos1 aKokkinos, Vasileios1 aPapachristos, Nikolaos1 aStamos, Kostas  uhttp://telematics.upatras.gr/telematics/publications/wifimon-app-measuring-wi-fi-performance-experienced-end-users?language=en01901nas a2200133   4500008004100000245010300041210006900144300001200213490000600225520134600231100002101577700002201598856014701620       2016                        eng d00aAssisting cluster coherency via N-grams and clustering as a tool to deal with the new user problem0 aAssisting cluster coherency via Ngrams and clustering as a tool   a171-1840 v73 a<p class="rtejustify">Collaborative filtering systems typically need to acquire some data about the new user in order to start making personalized suggestions, a situation commonly referred to as the “new user problem”. In this work we attempt to address the new user problem via a unique personalized strategy for prompting the user with articles to rate. Our approach makes use of hypernyms extracted from the WordNet database and proves to be converging fast to the actual user interests based on minimal user ratings, which are provided during the registration process. In addition, we explore the possible enhancement of the document clustering results, and in particular clustering of news articles from the web, when using word-based n-grams during the keyword extraction phase. We present and evaluate a weighting approach that combines clustering of news articles derived from the web, using n-grams that are extracted from the articles at an offline stage. This technique is then compared with the single minded “bag-of-words” representation that our clustering algorithm, W-kmeans, previously used. Our experimentation reveals that via fine tuning the weighting parameters between keyword and n-grams, as well as the n value itself, a significant improvement regarding the clustering results metrics can be achieved.</p>
1 aBouras, Christos1 aTsogkas, Vassilis  uhttp://telematics.upatras.gr/telematics/publications/assisting-cluster-coherency-n-grams-and-clustering-tool-deal-new-user-problem?language=en01421nas a2200169   4500008004100000245009200041210006900133260002100202300001200223520074900235100002100984700001901005700002401024700002701048700002801075856014801103       2016                        eng d00aComparison of Point to Point and MBSFN transmissions in Next Generation Mobile Networks0 aComparison of Point to Point and MBSFN transmissions in Next Gen  cNovember 13 - 17  a169-1723 a<p class="rtejustify">Multicast/Broadcast Multicast Service over Single Frequency Network (MBSFN) technology has introduced advanced broadcast capabilities to cellular systems. In Long Term Evolution Advanced (LTE-A) systems, MBSFN transmission accommodates multicast groups in search of the same data. In this paper we compare the traditional Point-to-Point (PTP) communication with the MBSFN services through simulation experiments for various femtocell distributions and network configurations. The comparison takes into account the average throughput, overhead cost, energy consumption and capacity gain, concluding that MBSFN through multicast transmission may guarantee performance improvement even for users in the cell boundaries.</p>
1 aBouras, Christos1 aKanakis, Nikos1 aKokkinos, Vasileios1 aPapachristos, Nikolaos1 aVouyioukas, Demosthenes  uhttp://telematics.upatras.gr/telematics/publications/comparison-point-point-and-mbsfn-transmissions-next-generation-mobile-networks?language=en01364nas a2200121   4500008004100000245006100041210006100102260003600163520088000199100002101079700002001100856012201120       2016                        eng d00aCoordination strategy for dense 5G femtocell deployments0 aCoordination strategy for dense 5G femtocell deployments  aLarnaca, CypruscNovember 21-233 a<p>The demand of next generation mobile networks for high connectivity for multiple devices with tenfold data rate<br />
requires the deployment of multiple base stations of different range and capacity and their optimal management. Femtocells will play a major role in these heterogeneous networks, being a low-cost and effective solution. In this paper we propose a mechanism on management of femtocells’ resources, based on spectrum allocation policies, power control and user classification. We combine hybrid access operation with user redistribution to provide a complete mechanism for resource allocation in dense femtocell deployments. Simulations show that the proposed scheme increases the capacity provided by the involved femtocells, it guarantees service to non-subscribers and balances the performance of the subscribed users improving the worst cases.</p>
1 aBouras, Christos1 aDiles, Georgios  uhttp://telematics.upatras.gr/telematics/publications/coordination-strategy-dense-5g-femtocell-deployments?language=en01573nas a2200145   4500008004100000245005500041210005400096260002000150300001000170520106300180100002101243700002601264700002201290856011501312       2016                        eng d00aCost Modeling for SDN/NFV Based Mobile 5G Networks0 aCost Modeling for SDNNFV Based Mobile 5G Networks  cOctober 18 - 20  a87-923 a<p class="rtejustify">This paper presents a techno-economic analysis on the integration of new technologies in 5G mobile networks, in order to fulfil the requirements provided by ETSI organization. Therefore “softwarization” of 5G networks is imperative and becomes a reality through new technologies, such as Software Defined Networking (SDN), Network Function Virtualization (NFV) and Cloud Computing. In this context, this paper provides a cost model in order to estimate the Capital Expenditure (CAPEX), the Operational Expenditure (OPEX) and the Total Cost of Ownership (TCO) for the proposed architecture. Furthermore, the proposed techno- economic model is used in order to estimate the above-mentioned network costs for the proposed network architecture and these costs are compared with the corresponding costs of a traditional network architecture. The experimental results verify and even exceed the ambitious predictions for cost reduction, due to the integration of those state of the art technologies in next-generation architectures.</p>
1 aBouras, Christos1 aNtarzanos, Panagiotis1 aPapazois, Andreas  uhttp://telematics.upatras.gr/telematics/publications/cost-modeling-sdnnfv-based-mobile-5g-networks?language=en01799nas a2200145   4500008004100000245010600041210006900147300001000216490000600226520120100232100002101433700002301454700001701477856015901494       2016                        eng d00aEfficient Mechanism and Performance Analysis of Routing   Protocols in VANETs for Realistic Scenarios0 aEfficient Mechanism and Performance Analysis of Routing Protocol  a20-490 v83 a<p class="rtejustify">Vehicular Ad Hoc Networks (VANETs) are considered as a special case of mobile Ad Hoc Networks (MANETs) and are recently gaining a great attention from the research community. The need for improved road safety, traffic efficiency and direct communi-cation along with the great complexity in routing, makes VANETs a highly challeng-ing field. Routing in VANETs has to adapt to special characteristics such as high speed and road pattern movement as well as high linkage break probability. In this work, we show that traditional MANET routing protocols cannot efficiently handle the challeng-es in a VANET environment and thus need further modifications. For this reason, we propose and implement an enhancement mechanism, applied to the GPSR routing pro-tocol that adapts to the needs of a VANET. The proposed mechanism’s performance is evaluated through simulation sets for urban and highway scenarios and compared to the performance of the most common MANET routing protocols adopted in VANETs. The proposed enhancement is shown to be considerably beneficial and it significantly outperforms the rest of the tested routing protocols for almost every topology setting</p>
1 aBouras, Christos1 aKapoulas, Vaggelis1 aTsanai, Enea  uhttp://telematics.upatras.gr/telematics/publications/efficient-mechanism-and-performance-analysis-routing-protocols-vanets-realistic-scenarios?language=en01786nas a2200157   4500008004100000245006700041210006700108260001800175300001400193520120800207100002101415700002301436700001901459700002401478856012601502       2016                        eng d00aEvaluation of Power Control Mechanism on OLSR Routing Protocol0 aEvaluation of Power Control Mechanism on OLSR Routing Protocol  cMarch 23 - 25  a766 - 7713 a<p class="rtejustify">The mobility that characterizes the wireless networks, is leading to the use of ad hoc networks for wireless communications. Due to the constant motion of wireless devices, infrastructure wireless networks cannot provide connectivity at all times, in comparison with ad hoc networks, which are more easy to use and are based on abstract and continuously altering topologies. The use of specialized routing protocols is improving the performance of these networks, concluding to lower power consumption and faster communication. However, routing is not enough to preserve the battery power of the mobile devices. By using a power control mechanism on top of the routing protocols, further power savings can be achieved. In this paper, we present a power control mechanism which relies on the routing protocol in<br />
order to make decisions about power management and the behavior and the performance of the network. The mechanism is based on using SNR (Signal-to-Noise Ratio) as a metric for adjusting the transmission power accordingly and eventually saving a respectable amount of energy to prolong life time of mobile devices and benefit the performance ad hoc networks.</p>
1 aBouras, Christos1 aKapoulas, Vaggelis1 aStamos, Kostas1 aStathopoulos, Nikos  uhttp://telematics.upatras.gr/telematics/publications/evaluation-power-control-mechanism-olsr-routing-protocol?language=en01718nas a2200157   4500008004100000245007600041210006900117260002100186300001000207520112600217100002101343700002301364700002401387700002201411856012701433       2016                        eng d00aMechanisms for enhancing the performance of routing protocols in VANETs0 aMechanisms for enhancing the performance of routing protocols in  cNovember 13 - 17  a11-183 a<p class="rtejustify">Vehicular Ad Hoc Networks (VANETs) are considered as a special case of Mobile Ad Hoc Networks (MANETs) and are recently gaining a great attention from the research community. Routing in VANETs has to adapt to special characteristics such as high speed and road pattern movement as well as high linkage break probability. In an urban setting the problem becomes more difficult as the existence of buildings blocks the wireless signal and hinders communication, resulting in only few nodes with increased connectivity (mostly in the intersections) that can act as true routing nodes rather than just forwarding nodes. In this paper, we compare the performance of GPCR (Greedy Perimeter Coordinator Routing), GPSR (Greedy Perimeter Stateless Routing) as well as the modified GPSR (GPSR-M) routing protocols. GPSR-M is an enhancement for the GPSR protocol that focuses on routing a message to an intermediate vehicle moving in the line of movement of the final destination, as soon as possible. Based on the performance evaluation we propose enhancements to GPSR-M in order to improve performance.</p>
1 aBouras, Christos1 aKapoulas, Vaggelis1 aStathopoulos, Nikos1 aGkamas, Apostolos  uhttp://telematics.upatras.gr/telematics/publications/mechanisms-enhancing-performance-routing-protocols-vanets?language=en01919nas a2200157   4500008004100000245004400041210004200085300001000127490000700137520141900144100002701563700002101590700002401611700002201635856010401657       2016                        eng d00aMobility - aware Power Control in MBSFN0 aMobility aware Power Control in MBSFN  a77-910 v613 a<p class="rtejustify">Multimedia Broadcast/Multicast Service (MBMS) over a Single&nbsp;Frequency Network (MBSFN) within LTE systems is a feature that allows&nbsp;synchronous broadcasting of common data among neighboring cells. With&nbsp;MBSFN operation, mobile broadcast/multicast users are able to use inter-cell&nbsp;interference in a constructive way and to achieve increased bit-rates compared&nbsp;to when conventional broadcasting is used. In this manuscript, we present our&nbsp;work on the optimization of the power control for future mobile networks that&nbsp;employ MBSFN transmission. We propose a novel simulator and system optimizer&nbsp;that can minimize the individual cell's transmission power by taking&nbsp;into account the changing positions of users. The system optimizer is based&nbsp;on a novel genetic algorithm, which is resistant to entrapment in local optima&nbsp;and makes use of mutations over the previous solutions in order to optimize<br />
the power consumption given the new users' positions. The optimizer's engine&nbsp;can be used in conjunction with the simulator or can be easily modied to&nbsp;receive real-time measurements from a real LTE network as an input. In order<br />
to read descriptions of the various scenarios, the simulator uses the eXtendable&nbsp;Temporal Network Description Language (XTNDL), a language that is also&nbsp;specied in this manuscript.</p>
1 aAsimakis, Konstantinos1 aBouras, Christos1 aKokkinos, Vasileios1 aPapazois, Andreas  uhttp://telematics.upatras.gr/telematics/publications/mobility-aware-power-control-mbsfn?language=en01752nas a2200157   4500008004100000245009300041210006900134300001000203490000600213520113300219100002201352700002201374700002201396700002101418856015501439       2016                        eng d00aPower-Aware and QoS Provisioned Real Time Multimedia Transmission in Small Cell Networks0 aPowerAware and QoS Provisioned Real Time Multimedia Transmission  a24-450 v53 a<p class="rtejustify">The recent emergence of ultra-high-speed and high-definition data and video services has pushed wireless network capacity to its limits. Cellular network capacity is therefore a valuable resource, whereas indoor coverage poses itself as a challenging issue. At the same time, real-world paradigms of multimedia transmission require effective Quality-of-Service (QoS) provisioning as well as power admission. To confront issues like delay-sensitive QoS requirements and traffic provisioning, as well as meet the mobile customer needs, this paper presents a traffic-aware Orthogonal Frequency-Division Multiple-Access (OFDMA) hybrid small-cell deployment for QoS provisioning and an optimal admission control strategy for 4G cellular systems. The traffic awareness in the proposed framework is provided by a utility function, which differentiates the traffic QoS levels with the user’s grouping priority indexes, channel conditions, and traffic characteristics. To further enhance the proposed framework, an admission power control algorithm based on an efficient algorithm handover is also proposed.</p>
1 aAlexiou, Antonios1 aBikos, Anastasios1 aBilios, Dimitrios1 aBouras, Christos  uhttp://telematics.upatras.gr/telematics/publications/power-aware-and-qos-provisioned-real-time-multimedia-transmission-small-cell-networks?language=en02252nas a2200169   4500008004100000245009200041210006900133260001600202300001200218490000700230520160900237100001901846700002401865700002101889700002201910856015001932       2016                        eng d00aScience parks and regional innovation performance in fiscal austerity era: Less in more0 aScience parks and regional innovation performance in fiscal aust  cAugust 2016  a313-3300 v473 a<p class="rtejustify">European financial crisis has raised questions about the sustainability and the contribution of innovation anchors especially in Southern European countries such as Greece. This paper utilizes the concept of regional innovation systems (RISs) and introduces a methodological approach that allows for evaluating an Science and Technology Park’s (STP) contribution into the corresponding RIS performance, taking into consideration (1) the RIS idiosyncrasies, (2) the dominant role of government expenditures on R&amp;D and (3) the underlying complexity of knowledge production and management, under alternative sets of restrictions imposed by fiscal consolidation on the preferences of authorities which design and implement Science, Technology and Innovation (STI) policies. Our framework relies on the estimation of a multi-input–multi-output latent knowledge production function approach and the corresponding efficiency indices. Data requirements are sourced from the Regional Innovation Scoreboard, for the four Greek regions and from a small-scale case study, with respect to the examined regional STP covering the period from 2000 to 2012. The main empirical findings highlight that the contribution of the examined STP in the corresponding RIS performance diminishes alongside with the decrease in GERD investment levels, with respect to all the efficiency indices. These findings are attributed to the structural characteristics of both the RIS and the STP under investigation, and capture their dependence on managing public financial resources for STI activities.</p>
1 aGkypali, Areti1 aKokkinos, Vasileios1 aBouras, Christos1 aTsekouras, Kostas  uhttp://telematics.upatras.gr/telematics/publications/science-parks-and-regional-innovation-performance-fiscal-austerity-era-less-more?language=en01829nas a2200145   4500008004100000245008400041210006900125260001600194300001600210520124900226100002101475700002201496700002201518856014301540       2016                        eng d00aSensitivity Analysis of Small Cells and DAS Techno-economic Models in Mobile 5G0 aSensitivity Analysis of Small Cells and DAS Technoeconomic Model  cApril 3 - 6  a2742 - 27473 a<p class="rtejustify">Next generation of mobile technologies demands high date rates and low round trip times. Therefore, we analyze deployments that offer these performance capabilities. We consider the fundamental issue of the expenses of the network’s installation, maintenance and operation. We calculate the costs of Distributed Antenna Systems (DAS) and small cells by describing updated cost models for each one. We present a Sensitivity Analysis of certain types of cost variables and parameters including the existing bandwidth, the running costs, the interest rate, the base station, the equipment, the power consumption, the backhaul, the implementation costs and Throughput Density. We include a variable cost provision for the year 2016 and beyond, and conduce several experiments, based on the upper analysis, by considering many different parameter prices and introducing the Throughput Density. We calculate the Total Cost of Ownership (TCO), the Capital (CAPEX) and the Operational (OPEX) expenditures. Finally, we are led to important conclusions by comparing the two main technologies costs and evaluating the cost parameters and variables that will lead future researchers to suggest ways to reduce the higher costs.</p>
1 aBouras, Christos1 aKollia, Anastasia1 aPapazois, Andreas  uhttp://telematics.upatras.gr/telematics/publications/sensitivity-analysis-small-cells-and-das-techno-economic-models-mobile-5g?language=en01502nas a2200133   4500008004100000245005800041210005800099260002000157300001200177520101800189100002101207700002001228856012001248       2016                        eng d00aSleep Mode Performance Gains In 5G Femtocell Clusters0 aSleep Mode Performance Gains In 5G Femtocell Clusters  cOctober 18 - 20  a106-1113 a<p class="rtejustify">Femtocells present an efficient, low cost solution to help reach the traffic and data rate targets of 5G mobile networks. However, their ad-hoc nature, the expected great density of deployment and their closed&nbsp; registration policy may result in multi-layered networks with base stations’ ranges constantly overlapping and non-registered users struggling from the accumulative interference. In this paper, we propose a mechanism where femtocells operate in clusters, and may decide to turn to sleep mode if capacity demand of its users is met adequately by the remaining awake femtocells. We propose a special version of hybrid access targeting only users of neighboring femtocells, in order to reduce the number of active base stations and thus, to reduce interference. We enforce sleep mode under conditions that ensure the increased throughput of each involved registered user and the increased capacity provided by the entire cluster with the extra benefit of reduced energy.</p>
1 aBouras, Christos1 aDiles, Georgios  uhttp://telematics.upatras.gr/telematics/publications/sleep-mode-performance-gains-5g-femtocell-clusters?language=en02212nas a2200157   4500008004100000245006500041210006500106300001600171490000700187520164900194100002101843700002001864700002401884700002201908856012401930       2016                        eng d00aTransmission optimizing on dense femtocell deployments in 5G0 aTransmission optimizing on dense femtocell deployments in 5G  a2325 - 24380 v293 a<p class="rtejustify">In the upcoming generation of mobile networks, femtocells will play a major role because they provide cost-efficient improvement in data rates and coverage. High penetration is expected in the upcoming ultradense 5G networks, increasing the probability of femtocells’ clusters. This, in turn, will require interference mitigation techniques to protect nearby non-subscribed users, especially in weak macrocell signal areas. In this paper, we present a mechanism where multiple femtocells coordinate their transmission to serve multiple non-subscribed users through hybrid access. First, we introduce an algorithm that determines the spectrum allocation of femtocells’ hybrid access. The algorithm aims to compensate for the performance reduction of subscribed users, due to reduced spectrum. For the second step of the mechanism, we introduce a power control algorithm that balances the impact of hybrid access among all the members of the femtocell cluster. First, we investigate the case where only one femtocell operates in hybrid access, and then we refine the power control algorithm by allowing multiple femtocells in the same cluster to operate in hybrid mode and by taking into account the effect that any change in power transmission will have on neighbouring femtocells. Simulations for the evaluation of the hybrid access algorithm compared with closed and other hybrid access schemes show improvement in the throughput of the non-subscribed users connected to femtocell and the most impacted subscribed users at weak macrocell signal areas and in the fairness of the hybrid access application scheme.</p>
1 aBouras, Christos1 aDiles, Georgios1 aKokkinos, Vasileios1 aPapazois, Andreas  uhttp://telematics.upatras.gr/telematics/publications/transmission-optimizing-dense-femtocell-deployments-5g?language=en01735nas a2200169   4500008004100000245009400041210006900135260001700204300001200221520105700233100002101290700002201311700002401333700002701357700002801384856015301412       2016                        eng d00aUtilization of Hybrid Access Femtocells During Multicast Transmissions in Mobile Networks0 aUtilization of Hybrid Access Femtocells During Multicast Transmi  cJune 27 - 30  a190-1943 a<p class="rtejustify">Femtocells enhance indoor coverage of mobile services using the owner’s broadband connection. They were initially designed to serve a number of subscribed User Equipments within their range. This design however, resulted in underutilization of the femtocells resources, and simultaneously in high interference levels for nearby non-subscribed users. Nowadays, femtocells can support multicast transmissions, while their hybrid operation allows non-subscribed users to use a portion of their resources. In this paper we propose a novel mechanism that is based on the selection of the appropriate Modulation and Coding Scheme. The mechanism allows non-subscribed users to utilize a portion of the femtocells’ resources for multicast transmissions when located inside their coverage, without affecting the owners’ satisfaction. The simulation results show that depending on the portion of the femtocells’ resources allocated to non-subscribed users, the mechanism may significantly increase the average user throughput.</p>
1 aBouras, Christos1 aKanakis, Nikolaos1 aKokkinos, Vasileios1 aPapachristos, Nikolaos1 aVouyioukas, Demosthenes  uhttp://telematics.upatras.gr/telematics/publications/utilization-hybrid-access-femtocells-during-multicast-transmissions-mobile-networks?language=en01779nas a2200193   4500008004100000245012200041210006900163300001000232490000600242520101300248100002601261700002101287700002301308700002601331700002001357700002401377700002201401856016201423       2015                        eng d00aBroadband and e - Government Services in South East Europe:   Comparative Analysis, Impact and Policy Recommendations0 aBroadband and e Government Services in South East Europe Compara  a39-560 v63 a<p>The European Commission acknowledging the significance of broadband for the improvement of citizen welfare and its economic benefits, has put in place targets for the diffusion of broadband to all citizens and businesses in the European Union. This manuscript comparatively assesses the current state of affairs in broadband and digital public services in selected South East Europe (SEE) countries in order to identify weaknesses and highlight strengths, and attempts to measure the impact and effectiveness of broadband on the economy. To this direction, the authors focus on evaluating the correlation between broadband and growth and employment. They also estimate the savings achieved by the usage of e-services and the potential savings that will follow their increased utilization over the next years. The analysis is followed by a number of recommendations that aim to support informed decision making. The manuscript builds on four surveys that took place during the second quarter of 2013.</p>
1 aAntonis, Konstantinos1 aBouras, Christos1 aD’Elia, Fabrizio1 aDi Vincenzo, Annalisa1 aDiles, Georgios1 aKokkinos, Vasileios1 aKoskeris, Andreas  uhttp://telematics.upatras.gr/telematics/publications/broadband-and-e-government-services-south-east-europe-comparative-analysis-impact-and-policy?language=en01792nas a2200145   4500008004100000245006100041210006000102300001200162490000600174520127900180100002101459700002201480700002301502856012101525       2015                        eng d00aCross-platform Mobile Applications with Web Technologies0 aCrossplatform Mobile Applications with Web Technologies  a153-1630 v43 a<p class="rtejustify">The extended use of smart mobile devices has become an integral part of daily life leading to the expansion of mobile application development. Currently, the majority of mobile applications are native applications that need an initial installation prior to being utilized. In addition, for a given application, a separate software development process could be required for each mobile platform, which subsequently increases dramatically the corresponding effort and cost. With the emergence of HTML5 these issues can be addressed efficiently, since web technologies allow the application development in a cross-platform manner. An important benefit is that users can have easy and immediate access the application without any need for downloading and installation. In this manuscript, we investigate the potentials of mobile application development with web technologies and we present a development framework that we have designed and implemented. This framework utilizes the most important state-of-art web technologies for the support of mobile devices. It can be used for the implementation of mobile web applications and also for the investigation and experimentation on the main features that HTML5 offers for this specific type of devices.</p>
1 aBouras, Christos1 aPapazois, Andreas1 aStasinos, Nikolaos  uhttp://telematics.upatras.gr/telematics/publications/cross-platform-mobile-applications-web-technologies?language=en01876nas a2200157   4500008004100000245010100041210006900142300001400211490000700225520124300232100002101475700001901496700002401515700002201539856015701561       2015                        eng d00aDeploying AL-FEC Protection with Online Algorithms for Multicast Services over Cellular Networks0 aDeploying ALFEC Protection with Online Algorithms for Multicast   a2109-21220 v203 a<p class="rtejustify">Reliability control is a key concern on the evolution of mobile multicast services. To this direction, the use of forward error correction (FEC)&nbsp;on the application layer is widely adopted in several mobile multicast standards. FEC is a feedback free error control method, where the transmitter&nbsp;introduces in advance redundant information within the source data to enable receivers recovering arbitrary data erasures. On multicast delivery where&nbsp;retransmission-based error recovery methods are not ecient, the most suitable error control method is the use of application layer forward error correction (AL-FEC) codes. In this work, we introduce novel AL-FEC deployment&nbsp;policies over mobile multicast environments utilizing online algorithms. We&nbsp;aim at the ecient application of AL-FEC protection with RaptorQ codes over multicast delivery in the context of competitive analysis. We provide a&nbsp;competitiveness analysis model of AL-FEC application over mobile multicast&nbsp;environments. Furthermore, we propose two online algorithms adjusting the introduced redundancy of AL-FEC protection according to several FEC encoding parameters and constraints of mobile multicast delivery.</p>
1 aBouras, Christos1 aKanakis, Nikos1 aKokkinos, Vasileios1 aPapazois, Andreas  uhttp://telematics.upatras.gr/telematics/publications/deploying-al-fec-protection-online-algorithms-multicast-services-over-cellular-networks?language=en01395nas a2200145   4500008004100000245005500041210005300096260001400149300001400163520090000177100002101077700002301098700001701121856011101138       2015                        eng d00aA GPSR Enhancement Mechanism for Routing in VANETs0 aGPSR Enhancement Mechanism for Routing in VANETs  cMay 25-27  a94 - 107 3 a<p class="rtejustify">Vehicular Ad Hoc Networks (VANETs) are considered as a special case of mobile Ad Hoc Networks (MANETs) and are recently gaining a great attention from the research community. The need for improved road safety, traf-fic efficiency and direct communication along with the great complexity in rout-ing, makes VANETs a highly challenging field.. Routing in VANETs has to adapt to special characteristics such as high speed and road pattern movement as well as high linkage break probability. In this paper, we propose an enhancement mechanism for the GPSR routing protocol and present its performance for urban and highway scenarios. Its performance is compared to the performance of the most common MANET routing protocols adopted in VANETs. The proposed enhancement is shown to be beneficial in most occasions as it outperforms the rest of the tested routing protocols.</p>
1 aBouras, Christos1 aKapoulas, Vaggelis1 aTsanai, Enea  uhttp://telematics.upatras.gr/telematics/publications/gpsr-enhancement-mechanism-routing-vanets?language=en02247nas a2200169   4500008003900000245006400039210006200103250000800165260007700173300001400250490000600264520162100270100002201891700002101913700002001934856012301954       2015                          d00aMobile Ad hoc networks (MANETs) for multimedia transmission0 aMobile Ad hoc networks MANETs for multimedia transmission  a3rd  bEncyclopedia of Information Science and Technology (3rd Ed.), IGI Global  a6239-62480 v93 a<p class="rtejustify">Mobile Ad hoc Networks (MANETs) are becoming more essential to wireless communications due to growing popularity of mobile devices. A node in MANETs could act as a router while having also the possibility of being the sender or receiver of information. MANETs offer the freedom to use mobile devices and move independently of the location of base stations (and outside their coverage) with the help of other network devices. The ability of MANETs to be self-configured and form a mobile mesh network, by using wireless links, make them very suitable for a number of cases that other type of networks cannot operate. In addition, MANETs do not require vast technological investments.&nbsp;An ideal application area for the utilization of MANET technology is for instance any disaster scenario in which the fixed infrastructure is incapacitated or non-existent. In this case it is important to ensure that a suitable communication solution is established within the very first critical hours of an incident, considering national or cross-border emergency incidents.&nbsp;What is missing, however, from this type of networks is the so called a “killer application” that could boost its utilizations in the real world. Real time multimedia applications have the potential to turn MANETs into a very attractive solution in wireless networks taking into account its unique characteristics.&nbsp;Our motivation for this article is to present the shortcomings and the current state of the art in MANETs in regards to the transmission of multimedia data, which is a promising application area.</p>
1 aGkamas, Apostolos1 aBouras, Christos1 aKioumourtzis, G  uhttp://telematics.upatras.gr/telematics/publications/mobile-ad-hoc-networks-manets-multimedia-transmission?language=en01371nas a2200169   4500008004100000245007600041210006900117260002100186300001200207520073500219100002100954700002300975700002500998700002401023700002201047856013201069       2015                        eng d00aA Mobile Learning Application for Self-Management of Health and Disease0 aMobile Learning Application for SelfManagement of Health and Dis  cNovember 19 - 20  a101-1053 a<p class="rtejustify">Supporting self-management of patients is a highly challenging task, which needs to meaningfully exploit and interrelate approaches and technologies concerning interactive communication, personalized health and mobile learning. In line with these remarks, this paper reports on the development of an innovative clinical decision support platform for selfmanagement of health and disease purposes. Work presented focuses on two basic components of the platform, namely a webbased collaboration support tool and a mobile application, both aiming to augment the interaction of all types of stakeholders with the platform. The functionality of the above components is sketched through a realistic use case.</p>
1 aBouras, Christos1 aKapoulas, Vaggelis1 aKaracapilidis, Nikos1 aKokkinos, Vasileios1 aPapazois, Andreas  uhttp://telematics.upatras.gr/telematics/publications/mobile-learning-application-self-management-health-and-disease?language=en01664nas a2200169   4500008004100000245008900041210006900130260001300199300001200212520100500224100002101229700002001250700002401270700002601294700002601320856014801346       2015                        eng d00aA Novel Tool for Cost-Efficient Broadband Development through Infrastructure Sharing0 aNovel Tool for CostEfficient Broadband Development through Infra  cJuly 6-9  a323-3283 a<p class="rtejustify">Broadband is a public utility with positive effects on competitiveness, employment and growth. Although evidence shows that broadband development is increasing, this increment is not homogeneous between urban and rural areas. The main cause is the high cost for deploying next generation networks in rural areas, and especially the cost linked to civil engineering works. In order to overcome the investment challenges arising in the context of broadband deployment, the European Commission made mandatory the sharing of existing telecommunication and non-telecommunication infrastructures and facilities. This paper proposes and presents a novel tool that enables the estimation of the expected savings from exploiting existing infrastructures when deploying a broadband network. This is followed by a number of general principles and recommendations that policy makers and national authorities could embrace to diminish deployment costs and promote broadband deployment.</p>
1 aBouras, Christos1 aDiles, Georgios1 aKokkinos, Vasileios1 aAntonis, Konstantinos1 aLoukopoulos, Leonidas  uhttp://telematics.upatras.gr/telematics/publications/novel-tool-cost-efficient-broadband-development-through-infrastructure-sharing?language=en01735nas a2200133   4500008004100000245005800041210005700099260002100156300001200177520124600189100002101435700002201456856012301478       2015                        eng d00aOnline AL-FEC protection over Mobile Unicast Services0 aOnline ALFEC protection over Mobile Unicast Services  cJune 29 - July 2  a234-2383 a<p class="rtejustify">Forward error correction (FEC) is a method for error control of data transmission adopted in several mobile multicast standards. FEC is a feedback free error recovery method where the sender introduces redundant data in advance with the source data enabling the recipient to recover from different arbitrary packet losses. Recently, the adoption of FEC error control method has been boosted by the introduction of powerful Application Layer FEC (AL-FEC) codes i.e., RaptorQ codes. Furthermore, several works have emerged aiming to address the efficient application of AL-FEC protection introducing deterministic or randomized online algorithms. The investigation of ALFEC application as primary or auxiliary error protection method over mobile multicast environments is a well investigated field. However, the opportunity of utilizing the AL-FEC over mobile unicast services as the only method for error control, replacing common feedback based methods that are now considered to be obsolete, is not yet examined. In this work we provide an analysis on the feasibility of AL-FEC protection over unicast delivery utilizing online algorithms on the application of AL-FEC codes with exceptional recovery performance.</p>
1 aBouras, Christos1 aKanakis, Nikolaos  uhttp://telematics.upatras.gr/telematics/publications/online-al-fec-protection-over-mobile-unicast-services?language=en01553nas a2200157   4500008004100000245006300041210006300104260001900167300001200186520098500198100002101183700002001204700002401224700002201248856012501270       2015                        eng d00aOptimizing hybrid access femtocell clusters in 5G networks0 aOptimizing hybrid access femtocell clusters in 5G networks  cNovember 4 - 6  a220-2263 a<p class="rtejustify">Femtocells are an efficient way of reducing infrastructure costs while providing better data rates and coverage. High penetration is expected in the upcoming ultra dense 5G networks, increasing the probability of femtocells’ clusters. Strong resulting interference for nearby non-subscribed users will require interference mitigation techniques. In this paper we present a mechanism where multiple femtocells coordinate their transmission to serve multiple non-subscribed users through hybrid access. First, the spectrum allocation of non-subscribed users by femtocells is determined. Then, we introduce a power control algorithm that is based on two factors. The need for compensation for the subscribed users, due to reduced spectrum, and the effect that any change in power transmission will have on neighbouring femtocells. We evaluate the effectiveness of the algorithm through simulations on individual throughput and overall achieved capacity.</p>
1 aBouras, Christos1 aDiles, Georgios1 aKokkinos, Vasileios1 aPapazois, Andreas  uhttp://telematics.upatras.gr/telematics/publications/optimizing-hybrid-access-femtocell-clusters-5g-networks?language=en01515nas a2200133   4500008004100000245007500041210006900116300001200185520099300197100002101190700002301211700001701234856013001251       2015                        eng d00aPerformance Evaluation of Routing Mechanisms for VANETs in Urban Areas0 aPerformance Evaluation of Routing Mechanisms for VANETs in Urban  a133-1353 a<p class="rtejustify">Mobile Ad hoc Networks (MANETs) and especially Vehicular Ad hoc Networks (VANETs) have recently gained large interest and their performance is heavily studied. A great challenge in VANETs, especially in an urban setting, is the routing scheme used and the subsequent performance obtained. This work presents an experimental performance evaluation of routing mechanisms in VANETs, using simulation, within<br />
an urban Manhattan grid like environment. It also describes and evaluates an enhancement of the Greedy Perimeter Stateless Routing (GPSR) protocol that takes into account the motion of the vehicles and the nature of the urban environment. The simulation results demonstrate that the proposed enhancement to the GPSR protocol manages to significantly increase the delivery ratio without increasing the power consumption; nevertheless, in some cases the improvement on delivery ratio is achieved at the expense of slightly increased end-to-end delay.</p>
1 aBouras, Christos1 aKapoulas, Vaggelis1 aTsanai, Enea  uhttp://telematics.upatras.gr/telematics/publications/performance-evaluation-routing-mechanisms-vanets-urban-areas?language=en01508nas a2200169   4500008004100000245008200041210006900123260002000192300001200212520085900224100002101083700002301104700001901127700002401146700002501170856014301195       2015                        eng d00aPower Management and Rate Control Mechanism for Wi-Fi Infrastructure Networks0 aPower Management and Rate Control Mechanism for WiFi Infrastruct  cOctober 26 - 28  a731-7363 a<p class="rtejustify">The advances in wireless networks have encouraged the use of mobile devices in everyday life. However, one of the main problems of these devices is the limited amount of energy they have available to use in order to function and the extended energy consumption of wireless adapters. A lot of research has been done to reduce the amount of energy spent on wireless communications. On the other hand, the extended use of wireless networks causes interference problems in communications, which affect the overall performance of each network. The purpose of this work is to provide a mechanism, which can reduce the power consumption on the station side and increase the mobile devices’ operation time, and in combination with a rate adaptation mechanism on the access point side, improve the overall performance of the network.</p>
1 aBouras, Christos1 aKapoulas, Vaggelis1 aStamos, Kostas1 aStathopoulos, Nikos1 aTavoularis, Nikolaos  uhttp://telematics.upatras.gr/telematics/publications/power-management-and-rate-control-mechanism-wi-fi-infrastructure-networks?language=en01474nas a2200145   4500008004100000245006200041210006100103260002000164300001200184520094300196100002101139700002201160700002201182856012401204       2015                        eng d00aPower-Aware QoS Provisioning in OFDMA Small Cell Networks0 aPowerAware QoS Provisioning in OFDMA Small Cell Networks  cOctober 26 - 28  a725-7303 a<p class="rtejustify">Orthogonal frequency-division multiple-access (OFDMA) small-cell networks of next-generation Long-Term Evolution (LTE-Advanced) standard, is perhaps a key factor to efficiently provide beneficial usage of expensive radio resources, while maintaining adequate network capacity. Network capacity is without doubt a critical resource for LTE networks. At the same time, real-time multimedia transmission requires effective quality-of-service (QoS) provisioning, as well as power admission. This paper proposes a traffic-aware OFDMA hybrid small-cell deployment for QoS provisioning and an optimal power admission control strategy for 4G cellular systems. By performing real-case scenario simulations of user-type multimedia transmission, we show that the implemented framework achieves high QoS levels of performance, increased<br />
throughput capacity, lower delay levels and optimally adapted network traffic.</p>
1 aBouras, Christos1 aAlexiou, Antonios1 aBikos, Anastasios  uhttp://telematics.upatras.gr/telematics/publications/power-aware-qos-provisioning-ofdma-small-cell-networks?language=en01378nas a2200133   4500008004100000245004900041210004900090260001900139300001200158520092200170100002101092700002001113856011101133       2015                        eng d00aResource management in 5G femtocell networks0 aResource management in 5G femtocell networks  cNovember 4 - 6  a353-3583 a<p class="rtejustify">Small cells are expected to contribute to the targets of next generation mobile networks. Ultra dense networks through the form of heterogeneous structures of multiple RAT technologies and small cells present a flexible, economical way for better coverage and data rates. In this paper, we investigate particularly how femtocells may best utilize their available resources in order to increase their provided capacity when neighbouring femtocells are present. We propose a spectrum policy, according to which femtocell deployments are forming clusters and the femtocells adopt hybrid access policy versus users subscribed to other femtocells members of the same cluster. We also determine the spectrum allocation for non-subscribed users in the range of the femtocell. We evaluate the performance of the set up through simulations showing that the mechanism offers better overall capacity.</p>
1 aBouras, Christos1 aDiles, Georgios  uhttp://telematics.upatras.gr/telematics/publications/resource-management-5g-femtocell-networks?language=en01723nas a2200181   4500008004100000245007800041210006900119300001000188490000900198520106100207100002101268700002301289700002701312700001901339700002401358700002501382856013401407       2015                        eng d00aA Signal Adaptation Mechanism for power optimization of wireless adapters0 aSignal Adaptation Mechanism for power optimization of wireless a  a48-720 v4(3)3 a<p class="rtejustify">This manuscript introduces, implements and evaluates a feedback-based adaptation mechanism that adjusts the transmission power of a wireless card on commodity mobile devices. Main focus of this work is to minimize the power consumption by adjusting the transmission power of the wireless card, thus extending the battery life, while negative effects on connection quality are avoided. To achieve that, a mechanism that optimizes the power depending on the quality of the connection is presented, which measures the quality of the transmission and adjusts the transmission power, by utilizing an expanded array of metrics, for more accurate estimation. The mechanism has been implemented and tested on actual wireless adapters. In order to evaluate, fine-tune and improve the mechanism, a list of real environment experiments has been performed. The results indicate that power consumption can be significantly reduced for nodes that are either almost stationary or slowly moving, without any significant increase in packet loss.</p>
1 aBouras, Christos1 aKapoulas, Vaggelis1 aKioumourtzis, Georgios1 aStamos, Kostas1 aStathopoulos, Nikos1 aTavoularis, Nikolaos  uhttp://telematics.upatras.gr/telematics/publications/signal-adaptation-mechanism-power-optimization-wireless-adapters?language=en01650nas a2200157   4500008004100000245007700041210006900118260001900187300001200206520104900218100002101267700002401288700002201312700002201334856013601356       2015                        eng d00aTechno-economic Analysis of Ultra-dense and DAS Deployments in Mobile 5G0 aTechnoeconomic Analysis of Ultradense and DAS Deployments in Mob  cAugust 25 - 28  a241-2453 a<p class="rtejustify">Ultra-dense and Distributed Antenna Systems (DAS) technology consist fundamental means for achieving the data rates and round-trip times promised by future mobile networks, because they promise to assure excellent indoor coverage and offer the potential to meet the target key performance indicators at a lower cost. In this paper, we study the techno-economic aspects of ultra-dense and DAS deployments. Apart from the presentation of their architectures and advantages, we present a techno-economic modeling of these deployment types. The defined models are used for the investigation of the upper technologies from an economic perspective and therefore, they provide an insight in the future financial and price aspects of these technologies by consisting a useful tool for the definition of financing and pricing policies towards an economically viable ultra-dense femtocell-based or DAS deployment. Finally, it is confirmed that the Total Cost of Ownership (TCO) is lower for the femtocells compared to the DAS.</p>
1 aBouras, Christos1 aKokkinos, Vasileios1 aKollia, Anastasia1 aPapazois, Andreas  uhttp://telematics.upatras.gr/telematics/publications/techno-economic-analysis-ultra-dense-and-das-deployments-mobile-5g?language=en02125nas a2200133   4500008004100000245008000041210006900121260001600190300001400206520159000220100002101810700001901831856014101850       2014                        eng d00aAn Adaptive Weighted Online AL -FEC Algorithm over Mobile Multicas Networks0 aAdaptive Weighted Online AL FEC Algorithm over Mobile Multicas N  cApril 6 - 9  a1602-16073 a<p class="rtejustify">A crucial point on the delivery of multicast content&nbsp;over mobile multicast networks is the utilization of Forward Error Correction (FEC) codes on the application layer (AL-FEC) so as to introduce robustness against arbitrary erasures on different recipients without the need of inefficient common error control&nbsp;methods based on data retransmission. FEC is a feedback free error recovery method where the sender introduces redundant data in advance with the source data enabling the recipients to recover from different arbitrary packet losses. The main issue on the efficient application of AL-FEC protection is the adaptation&nbsp;of the introduced redundancy to the current network conditions, in order to avoid network resources wastage ensuring at the same time sufficient transmission robustness. Based on this, in this work we present an adaptive weighted online algorithm aiming at the efficient application of RaptorQ AL-FEC codes over mobile multicast services. The proposed algorithm adapts the introduced AL-FEC transmission overhead exploiting at first the reception reports ability defined by several mobile multicast standards and thereafter the performance properties of the newly introduced RaptorQ FEC codes. We introduce the competitive&nbsp;framework of the efficient application of AL-FEC protection over mobile multicast networks, in the context of which, we design and analyze the adaptive online weighted algorithm and we further&nbsp;provide a series of simulation results to analyze the performance of the proposed scheme.</p>
1 aBouras, Christos1 aKanakis, Nikos  uhttp://telematics.upatras.gr/telematics/publications/adaptive-weighted-online-al-fec-algorithm-over-mobile-multicas-networks?language=en01641nas a2200181   4500008004100000245009200041210006900133260001500202520096200217100001501179700002101194700001201215700002001227700002001247700002401267700001701291856015101308       2014                        eng d00aComperative analysis of broadband penetration and digital services in South East Europe0 aComperative analysis of broadband penetration and digital servic  cJune 23-263 a<p class="rtejustify">Broadband is starting to be deemed by many as a&nbsp;public utility and several countries have already recognized it as<br />
a civil right. The European Commission (EC) acknowledging the&nbsp;significance of broadband services for the improvement of citizen&nbsp;welfare and its economic benefits, has put in place targets for the&nbsp;diffusion of broadband to all citizens and businesses in the&nbsp;European Union. This paper, comparatively assesses the current&nbsp;state of affairs in broadband and digital public services in&nbsp;selected South East Europe countries in order to identify&nbsp;weaknesses and highlight strengths and to produce knowledge&nbsp;resources and provide insights that will support informed&nbsp;decision making including strategy and policy planning. It builds&nbsp;on three surveys that took place in the second quarter of 2013&nbsp;and evidence gathered from seven South East Europe countries.</p>
1 aAntonis, K1 aBouras, Christos1 aElia, D1 aDi Vincenzo, A.1 aDiles, Georgios1 aKokkinos, Vasileios1 aKoskeris, A.  uhttp://telematics.upatras.gr/telematics/publications/comperative-analysis-broadband-penetration-and-digital-services-south-east-europe?language=en01506nas a2200169   4500008004100000245005300041210005300094300001200147490001300159520095000172100001701122700002101139700002201160700002301182700002001205856011101225       2014                        eng d00aCross Layer Design for Video Streaming in MANETs0 aCross Layer Design for Video Streaming in MANETs  a328-3380 v9, No. 23 a<p class="rtejustify">Mobile Ad hoc NETworks (MANETs) are&nbsp;becoming more essential to wireless communications due to<br />
growing popularity of mobile devices. However, MANETs&nbsp;do not seem to effectively support multimedia applications<br />
and especially video transmission. In this work, we propose&nbsp;a cross-layer design that aims to improve the performance&nbsp;of video transmission using TCP Friendly Rate Control&nbsp;(TFRC). Our design provides priority to video packets and&nbsp;exploits information from the MAC layer in order to&nbsp;improve TFRC?s performance. The proposed cross-layer&nbsp;design utilizes SNR measurements along the routing path, in&nbsp;order to make the route reconstruction procedure more&nbsp;efficient. Simulation results show that both the use of traffic&nbsp;classification and the SNR utilization lead to important&nbsp;improvements in terms of end-to-end Quality of Service&nbsp;(QoS).</p>
1 aAdam, George1 aBouras, Christos1 aGkamas, Apostolos1 aKapoulas, Vaggelis1 aKioumourtzis, G  uhttp://telematics.upatras.gr/telematics/publications/cross-layer-design-video-streaming-manets?language=en01619nas a2200169   4500008004100000245006600041210006600107300001000173490000700183520101100190100002101201700002601222700002001248700002401268700002601292856013101318       2014                        eng d00aEconomic Broadband Development through Infrastructure Sharing0 aEconomic Broadband Development through Infrastructure Sharing  a21-420 v103 a<p class="rtejustify">Broadband is a public utility with positive effects on competitiveness, employment and growth. Although evidence shows that broadband development is increasing, this increment is not homogeneous between urban and rural areas. The main factor is the high cost for deploying next generation networks in rural areas, and especially the cost linked to civil engineering works. In order to overcome the investment challenges arising in the context of broadband deployment, the European Commission made mandatory the sharing of existing telecommunication and non-telecommunication infrastructures and facilities. This manuscript proposes and presents a novel tool that enables the estimation of the expected savings from exploiting existing infrastructures when deploying a broadband network. This is followed by a number of general principles and recommendations that policy makers and national authorities could embrace to diminish deployment costs and promote broadband deployment.</p>
1 aBouras, Christos1 aAntonis, Konstantinos1 aDiles, Georgios1 aKokkinos, Vasileios1 aLoukopoulos, Leonidas  uhttp://telematics.upatras.gr/telematics/publications/economic-broadband-development-through-infrastructure-sharing?language=en01398nas a2200169   4500008004100000245004900041210004900090260001400139300001200153520084200165100002101007700002601028700002601054700002001080700001901100856010901119       2014                        eng d00aEnhancing simulation environment with TRAFIL0 aEnhancing simulation environment with TRAFIL  bCRC Press  a391-4153 a<p>This chapter presents TRAFIL, a comprehensive tool for enhancing execution of simulations. It provides an overview of the tool, its architecture and its functionalities. It explains how TRAFIL en-hances the entire simulation procedure including graphical setup of simulation scenarios, automated execution of simulations, flexible handling and storage of simulation trace files and presentation of plots based on processing of simulation results. It presents the concept of metafiles that provides TRAFIL with the flexibility to handle heterogeneous simulation environments. The chapter also compares TRAFIL performance with other similar tools and finds that it offers significantly im-proved performance. It therefore concludes that TRAFIL offers both a rich set of simulation en-hancement functionalities and top performance.</p>
1 aBouras, Christos1 aCharalambides, Savvas1 aDrakoulelis, Michalis1 aKioumourtzis, G1 aStamos, Kostas  uhttp://telematics.upatras.gr/telematics/publications/enhancing-simulation-environment-trafil?language=en01502nas a2200133   4500008004100000245010500041210006900146260001700215300001000232520092700242100002101169700002201190856015601212       2014                        eng d00aEvaluating the Unification of Multiple Information Retrieval Techniques into a News Indexing Service0 aEvaluating the Unification of Multiple Information Retrieval Tec  c29-31 August  a33-403 a<p>While online information sources are rapidly increasing in amount, so does the daily available online news content. Several approaches have being proposed for organizing this immense amount of data. In this work we explore the integration of multiple information retrieval techniques, like text preprocessing, n-grams expansion, summarization, categorization and item/user clustering into a single mechanism designed to consolidate and index news articles from major news portals from around the web. Our goal is to allow users to seamlessly and quickly get the news of the day that are of appeal to them via our system. We show how, the application of each one of the proposed techniques gradually improves the precision results in terms of the suggested news articles for a number of registered system users and how, aggregately, these<br />
techniques provide a unified solution to the recommendation problem.</p>
1 aBouras, Christos1 aTsogkas, Vassilis  uhttp://telematics.upatras.gr/telematics/publications/evaluating-unification-multiple-information-retrieval-techniques-news-indexing-service?language=en01431nas a2200157   4500008004100000245006500041210006500106260001700171300001200188520085900200100002101059700002001080700002401100700002201124856012701146       2014                        eng d00aFemtocells Coordination in Future Hybrid Accesss Deployments0 aFemtocells Coordination in Future Hybrid Accesss Deployments  c26-29 August  a313-3173 a<p>Femtocells provide an attractive solution to locally improve the data rates and the coverage of future mobile networks including 5G. However, nearby non-subscribed users may experience severe interference. Hybrid access operation allows femtocells to serve non-subscribers by allowing them access to part of the spectrum. In this work, we propose a distributed process that allows the hybrid femtocell to defines the<br />
spectrum access for the two types of users. The mechanism takes into account the prior condition of the users and tries to minimize the femtocell’s impact to the rest of the network. We also introduce a power control mechanism within clusters of femtocells. The mechanism relieves the femtocell operating in hybrid access mode and its subscribed users, by coordinating accordingly the nearby femtocells’ transmission.</p>
1 aBouras, Christos1 aDiles, Georgios1 aKokkinos, Vasileios1 aPapazois, Andreas  uhttp://telematics.upatras.gr/telematics/publications/femtocells-coordination-future-hybrid-accesss-deployments?language=en02674nas a2200145   4500008004100000245007500041210006900116260001400185300001000199520211700209100002102326700002402347700002202371856013502393       2014                        eng d00aFinancing and Pricing Small Cells in Next - Generation Mobile Networks0 aFinancing and Pricing Small Cells in Next Generation Mobile Netw  cMay 26-28  a41-543 a<p class="rtejustify"><span style="color:rgb(0, 0, 0); font-family:times new roman; font-size:medium">Small cells technology has also strong potentials for enhancing cell coverage and network capacity of next-generation cellular net</span><span style="color:rgb(0, 0, 0); font-family:times new roman; font-size:medium">works including 5G. From mobile network operators' perspective, small&nbsp;</span><span style="color:rgb(0, 0, 0); font-family:times new roman; font-size:medium">cell deployment will additionally achieve large reduction to the network&nbsp;</span><span style="color:rgb(0, 0, 0); font-family:times new roman; font-size:medium">costs in both elds of capital expenditure and operational expenditure.&nbsp;</span><span style="color:rgb(0, 0, 0); font-family:times new roman; font-size:medium">In this study, we analyze the benets of small cells' deployment for oper</span><span style="color:rgb(0, 0, 0); font-family:times new roman; font-size:medium">ators and we list the subscriber incentives for choosing small cells instead&nbsp;</span><span style="color:rgb(0, 0, 0); font-family:times new roman; font-size:medium">of other access types, such as WiFi, for indoor deployment. Furthermore,&nbsp;</span><span style="color:rgb(0, 0, 0); font-family:times new roman; font-size:medium">we provide a nancial analysis of the small cell costs for deployment and&nbsp;</span><span style="color:rgb(0, 0, 0); font-family:times new roman; font-size:medium">operation against the corresponding macrocellular costs. We also exam</span><span style="color:rgb(0, 0, 0); font-family:times new roman; font-size:medium">ine pricing models that could be used to incentivize subscribers and to&nbsp;</span><span style="color:rgb(0, 0, 0); font-family:times new roman; font-size:medium">expedite the small cells' penetration into the market so as to become an&nbsp;</span><span style="color:rgb(0, 0, 0); font-family:times new roman; font-size:medium">economically viable solution. Finally, we present our experimental results&nbsp;demonstrating possible use cases of our cost and pricing models.</span></p>
1 aBouras, Christos1 aKokkinos, Vasileios1 aPapazois, Andreas  uhttp://telematics.upatras.gr/telematics/publications/financing-and-pricing-small-cells-next-generation-mobile-networks?language=en01670nas a2200145   4500008004100000245007300041210006900114260001700183300001200200520111900212100002101331700002201352700002001374856013001394       2014                        eng d00aA Framework for Cross - platform Mobile Web Applications Using HTML50 aFramework for Cross platform Mobile Web Applications Using HTML5  cAugust 27-29  a420-4243 a<p class="rtejustify">In recent years the use of smart mobile devices has become&nbsp;an integral part of everyday life leading to the expansion of applications&nbsp;development for the various mobile platforms. Each of these platforms&nbsp;requires separate software development process, which subsequently increases&nbsp;dramatically the corresponding eort. With the emergence of<br />
HTML5 these issues can be addressed eciently since application development&nbsp;is allowed in a cross-platform manner. An additional important&nbsp;benet is that users can access the application immediately without&nbsp;any need for installation. In this paper, we investigate the potentials of&nbsp;mobile application development with web technologies and we present<br />
a development framework that utilizes the most important state-of-art&nbsp;web technologies for the support of mobile devices. This framework can&nbsp;be used for the implementation of mobile web applications and also for&nbsp;the investigation and experimentation on the main features that HTML5&nbsp;oers for this specic type of devices.</p>
1 aBouras, Christos1 aPapazois, Andreas1 aStasinos, Nikos  uhttp://telematics.upatras.gr/telematics/publications/framework-cross-platform-mobile-web-applications-using-html5?language=en01559nas a2200181   4500008004100000245003500041210003500076300001000111520101700121100002101138700002401159700002001183700002501203700002101228700001601249700001801265856009401283       2014                        eng d00aIMPACT OF BROADBAND ON ECONOMY0 aIMPACT OF BROADBAND ON ECONOMY  a28-423 a<p>In this chapter, we investigate the impact of broadband on the growth and employment in SEE countries, namely Austria, Bulgaria, the former Yugoslav Republic of Macedonia (FYROM), Greece, Montenegro, Slovenia. Specifically, we define the macroeconomic evidence required for the analysis. We then enforce regression analysis on data collected by the respective countries in order to find the correlation between broadband, growth and employment. The period of the examination was set to be the last decade in order to obtain an extended amount of data, and take into account possible influences on the results by the economic crisis and the subsequent recession of the last years in the area. We also estimate the cost savings to companies and the state by the usage of broadband-based e-government services. We then forecast these benefits to 2015 when the respective countries are expected to have reached the e-government usage level which is set by the European digital agenda (Digital agenda, 2013).</p>
1 aBouras, Christos1 aKokkinos, Vasileios1 aDiles, Georgios1 aTopaloglou, Lefteris1 aBouras, Christos1 aKos, Andrej1 aFrank, Andrew  uhttp://telematics.upatras.gr/telematics/publications/impact-broadband-economy?language=en01684nas a2200145   4500008004100000245013800041210006900179300001000248490000700258520104200265100002101307700002701328700002601355856015701381       2014                        eng d00aImplementing Advanced Characteristics of X3D Collaborative Virtual Environments for supporting e - Learning: The Case of EVE Platform0 aImplementing Advanced Characteristics of X3D Collaborative Virtu  a13-370 v123 a<p>Three dimensional Collaborative Virtual Environments are a powerful form of collaborative telecommunication applications, enabling the users to share a common three-dimensional space and interact with each other as well as with the environment surrounding them, in order to collaboratively solve problems or aid learning processes. Such an environment is “EVE Training Area tool” which is supported by “EVE platform”. This tool is a three-dimensional space where participants, represented by three-dimensional humanoid avatars, can use a variety of e-collaboration tools. This paper presents advanced functionality that has been integrated on “EVE Training Area tool” in order to support: (a) multiple collaborative learning techniques (b) Spatial audio conferencing, which is targeted to support principle 3 (augmenting user?s representation and awareness). Furthermore the paper presents technological and implementation issues concerning the evolution of “EVE platform” in order to support this functionality.</p>
1 aBouras, Christos1 aTsiatsos, Thrasivoulos1 aTriglianos, Vasileios  uhttp://telematics.upatras.gr/telematics/publications/implementing-advanced-characteristics-x3d-collaborative-virtual-environments-supporting?language=en02016nas a2200169   4500008004100000245007000041210006800111300001400179490001300193520140100206100001701607700002101624700003601645700001901681700002101700856012501721       2014                        eng d00aMulti - domain Information Exchange in a Bandwidth on Demand Tool0 aMulti domain Information Exchange in a Bandwidth on Demand Tool  a1075-10850 v9, No. 53 a<p class="rtejustify">Abstract—In this paper we describe the multi-domain&nbsp;information exchange aspects of the AutoBAHN tool, which<br />
is used for implementing a Bandwidth on Demand service as&nbsp;part of the GEANT project. This project was driven by the&nbsp;increasing demand for reliable and guaranteed data&nbsp;transportation for scientific purposes. In order to&nbsp;implement the process of information exchange in a multidomain&nbsp;heterogeneous environment several design decisions&nbsp;have to take place, in order to balance and satisfy by the&nbsp;needs of information security, fast information&nbsp;dissemination, efficient request processing, reliability and&nbsp;robustness. The paper describes how AutoBAHN&nbsp;implements a flexible AAI in a distributed environment,&nbsp;how it exchanges and updates information and how it&nbsp;handles incoming requests in an efficient and timely manner.&nbsp;The multi-domain aspect of this effort stems from the fact&nbsp;that the tool is used in the production environment of&nbsp;several cooperating National Research and Educational&nbsp;Networks (NRENs) across Europe. Each NREN may have&nbsp;different underlying technologies, different policies and&nbsp;different use cases, but they all have to coordinate through&nbsp;usage of the AutoBAHN tool in order to produce a multidomain&nbsp;service of circuit reservation.</p>
1 aAdam, George1 aBouras, Christos1 aKalligeros, Ioannis, - Christos1 aStamos, Kostas1 aZaoudis, Giannis  uhttp://telematics.upatras.gr/telematics/publications/multi-domain-information-exchange-bandwidth-demand-tool?language=en01246nam a2200133   4500008004100000245006900041210006900110520071500179100002500894700002100919700001600940700002900956856012700985       2014                        eng d00aPolicies and Tools for Efficient Design of Broadband Development0 aPolicies and Tools for Efficient Design of Broadband Development3 a<p>Broadband is the fourth strategic pillar of the Digital Agenda for Europe. The connectivity and internet access it provides is a key enabler for a number of important services for citizens, businesses and the public sector. The ambitious targets set in the Digital Agenda indicate the importance of broadband for the economy of the EU and citizen welfare.</p>

<p>The SIVA project supports the goals of EU's strategy on digital technologies (namely the Digital Agenda for Europe) and aims to contribute to the improvement of virtual accessibility in South East Europe through the promotion of broadband access, supplementing physical accessibility and thus narrowing the digital gap in the SEE area.</p>
1 aTopaloglou, Lefteris1 aBouras, Christos1 aKos, Andrej1 aFrank, Andrew, (editors)  uhttp://telematics.upatras.gr/telematics/publications/policies-and-tools-efficient-design-broadband-development?language=en01983nas a2200169   4500008004100000245009200041210006900133490000700202520131000209100002101519700002401540700002401564700002701588700002701615700002101642856015001663       2014                        eng d00aPolicy recommendations for public administrators on free and open source software usage0 aPolicy recommendations for public administrators on free and ope0 v313 a<div>&nbsp;</div>

<div>
<p>Free and open source software, holding a strategic position in knowledge economy, reaffirms&nbsp;the critical role of governments and regional authorities in establishing strategies for integrating&nbsp;effective and sustainable Information Technology solutions in the public sector&nbsp;towards economic growth and social welfare. Moreover, public services, organisations and&nbsp;territorial administrations collectively represent a major software user with great impact&nbsp;on the software market. In this sense, software selection in the public sector is a highly political&nbsp;and strategic process; various collateral implications and policy aspects should be considered&nbsp;in order to reach the best possible decisions. Within this context, this manuscript&nbsp;provides policy recommendations on issues and challenges pertaining to the use of free&nbsp;and open source software by European public administrations. The recommended policy&nbsp;actions are mainly based on review of the current policy framework. The main goal of this&nbsp;manuscript is to contribute in providing policy orientations and proposing actions that can&nbsp;help governments, public administrations and European institutions fully harvest the benefits&nbsp;of open source.</p>
</div>
1 aBouras, Christos1 aFilopoulos, Anestis1 aKokkinos, Vasileios1 aMichalopoulos, Sotiris1 aPapadopoulos, Dimitris1 aTseliou, Georgia  uhttp://telematics.upatras.gr/telematics/publications/policy-recommendations-public-administrators-free-and-open-source-software-usage?language=en01397nas a2200145   4500008004100000245006300041210006300104260001900167300001200186520086200198100002101060700002201081700002301103856012501126       2014                        eng d00aPower Efficient Group Communication in Small Cell Networks0 aPower Efficient Group Communication in Small Cell Networks  c8-10 September  a102-1093 a<p>Small Cell Networks (SCNs) constitute a new promising way for increasing coverage, boosting data rates and lowering capital and operating expenditures (CAPEX and OPEX) of today’s mobile networks. In this paper, we deal with the problem of efficient power control in SCNs. We propose and evaluate an efficient power control mechanism for SCNs, which efficiently controls the available power resources of the network, while on the other hand guarantees home users’ Quality of Service. We introduce the methodology of Priority Grouping, in which home users in the topology, are assigned to one of a number of predefined groups, with different priorities, in terms of traffic requirements. Furthermore, the<br />
mechanism dynamically updates the power setting of home base stations, based on the topology of the macro and home users in real time.</p>
1 aBouras, Christos1 aAlexiou, Antonios1 aBillios, Dimitrios  uhttp://telematics.upatras.gr/telematics/publications/power-efficient-group-communication-small-cell-networks?language=en01626nas a2200169   4500008004100000245007500041210006900116260001500185300001200200520099900212100002101211700002301232700001901255700002401274700002201298856013601320       2014                        eng d00aPower management for wireless adapters using multiple feedback metrics0 aPower management for wireless adapters using multiple feedback m  c4-8 August  a262-2673 a<p class="rtejustify">The main focus of this work is the effort to minimize the power consumption on mobile devices such as notebooks, netbooks, tablets, tablets, smartphones, etc. by adjusting the transmission power of the wireless card, thus extending the battery life. In order to achieve that, we provide a mechanism (which we call Signal Adaptation Mechanism – SAM) that optimizes the power depending on the quality of the connection. This mechanism measures the quality of the transmission and adjusts the transmission power accordingly, by utilizing an expanded array of metrics along the Received Signal Strength Indicator (RSSI), for more accurate estimation. It also aims at easy implementation on various wireless adapters. In order to evaluate, fine-tune and improve the mechanism, a list of experiments has been performed. These experiments were conducted on a real (as opposed to simulated) ad-hoc network, where the nodes of the networks followed varying moving patterns.</p>
1 aBouras, Christos1 aKapoulas, Vaggelis1 aStamos, Kostas1 aStathopoulos, Nikos1 aTavoularis, Nikos  uhttp://telematics.upatras.gr/telematics/publications/power-management-wireless-adapters-using-multiple-feedback-metrics?language=en01585nas a2200157   4500008004100000245009400041210006900135260001800204300000900222520096800231100002101199700002201220700002401242700001901266856014201285       2014                        eng d00aRevisiting the role of Incubators during Fiscal Austerity Times: The Case of PSP, Greece.0 aRevisiting the role of Incubators during Fiscal Austerity Times   c18 - 20 June   a1-443 a<p class="rtejustify">European financial crisis has raised questions about the sustainability and the contribution of Innovation anchors especially in Southern European countries such as Greece. Based on the concept of Regional Innovation Systems we introduce a methodological approach which allows for the evaluation of the performance of Science and Technology Parks performance under different intensity levels of Government Expenditures on R&amp;D which is considered as the dominant a policy instrument. Our framework relies on the estimation of efficiency indices which come out of a multi input - multi output knowledge production function approach. The region under scrutiny is Western Greece and its corresponding Science Park for the period from 2000-2009. The main empirical finding suggests that, due to institutional and other factors, the contribution of PSP, as it has been formed in last decade, is negative in fostering innovation activitie</p>
1 aBouras, Christos1 aTsekouras, Kostas1 aKokkinos, Vasileios1 aGkypali, Areti  uhttp://telematics.upatras.gr/telematics/publications/revisiting-role-incubators-during-fiscal-austerity-times-case-psp-greece?language=en02309nas a2200169   4500008004100000245011600041210006900157300001400226490000700240520162600247100002101873700002001894700002401914700002901938700002201967856015001989       2014                        eng d00aA Simulation Framework for Evaluating Interference Mitigation Techniques in Heterogeneous Cellurar Environments0 aSimulation Framework for Evaluating Interference Mitigation Tech  a1213-12370 v773 a<p class="rtejustify">Femtocells present an attractive solution for the improvement of a mobile network?s&nbsp;services providing better data rates and coverage. Since their deployment results to a&nbsp;heterogeneous network where two layers must utilize the available spectrum, issues of interference&nbsp;arise. A method to address this challenge, is investigating the locations of the newly&nbsp;installed FBS, and enforcing a power controlled transmission of all FBSs that achieves optimal&nbsp;and fair overall performance. Another option that becomes available in inter-cell interference&nbsp;cancellation (ICIC) macrocell environments, is utilizing the available spectrum to complete&nbsp;or partly avoid co-channel operation. In this work, we provide a simulation framework that&nbsp;allows the creation of custom, high configurable, user defined topologies of femtocells with&nbsp;power control and frequency allocation capabilities. It allows the investigation of the margin&nbsp;of improvement in interference when these methods are applied and may work as a decision&nbsp;tool for planning and evaluating heterogeneous networks. To showcase the framework?s&nbsp;capabilities, we evaluate and study the behaviour of custom deployed femtocells/macrocells&nbsp;networks and examine the cross-tier interference issues. Facilitated by the framework, we&nbsp;enforce and evaluate each interference mitigation technique for different femtocells? deployment<br />
densities. Finally, we compare the results of each method in terms of total throughput,&nbsp;spectral efficiency and cell-edge users? performance.</p>
1 aBouras, Christos1 aDiles, Georgios1 aKokkinos, Vasileios1 aKontodimas, Konstantinos1 aPapazois, Andreas  uhttp://telematics.upatras.gr/telematics/publications/simulation-framework-evaluating-interference-mitigation-techniques-heterogeneous?language=en02006nas a2200181   4500008004100000245008400041210006900125300001000194490000600204520135500210100002201565700002101587700002001608700002401628700002201652700002101674856012901695       2014                        eng d00aA Simulation Framework for the Evaluation of Frequency Reuse in LTE - A Systems0 aSimulation Framework for the Evaluation of Frequency Reuse in LT  a56-830 v33 a<p class="rtejustify">Long Term Evolution Advanced (LTE-A) technology is considered as the most possible candidate for next generation mobile communications. LTE-A networks offer high capacity and are specified and designed to accommodate small, high performance, power-efficient end-user devices. Similarly to its predecessor LTE, LTE-A incorporates inter-cell interference mitigation methods in order to mitigate interference and to enhance efficiency in bandwidth usage. These methods include power and frequency allocation schemes that allow neighbouring cells and femtocells in heterogeneous networks to co-ordinately share and reuse available spectral resources, in order to avoid performance degradation for interference suffering cell-edge users. In this paper, we study the LTE-A multi-cell systems? performance using a simulation framework, which integrates several frequency reuse techniques and provides a user-friendly graphical presentation of the evaluation results. The optimal Fractional Frequency Reuse (FFR) configuration for the user-defined network instance is also determined, based on overall performance and fairness index metrics. Finally, we examine FFR techniques in two-tier femtocell/macrocell environments and evaluate them based on the optimization of different metrics, depending on the network operator?s needs.</p>
1 aBilios, Dimitrios1 aBouras, Christos1 aDiles, Georgios1 aKokkinos, Vasileios1 aPapazois, Andreas1 aTseliou, Georgia  uhttp://telematics.upatras.gr/telematics/publications/simulation-framework-evaluation-frequency-reuse-lte-systems?language=en01909nas a2200193   4500008004100000245008900041210006900130300001400199490000700213520123400220653000801454653000801462653000901470100002101479700002201500700002401522700001901546856015001565       2013                        eng d00aApplication Layer Forward Error Correction for Multicast Streaming over LTE Networks0 aApplication Layer Forward Error Correction for Multicast Streami  a1459-15740 v263 a<p>The next step beyond third generation (3G) mobile networks is the Third Generation Partnership Project (3GPP) standard, named Long Term Evolution (LTE). A key feature of LTE is the enhancement of Multimedia Broadcast/Multicast Services (MBMS), where the same content is transmitted to multiple users located in a specific service area. To support efficient download and streaming delivery, 3GPP included an application layer Forward Error Correction (AL-FEC) technique based on the systematic fountain Raptor code, in the MBMS standard. In order to achieve protection against packet losses, Raptor codes introduce redundant packets to the transmission, i.e., the FEC overhead. In this work, we investigate the application of AL-FEC over MBMS streaming services. We consider the benefits of AL-FEC for a continuous multimedia stream transmission to multiple users and we examine how the amount of FEC redundancy can be adjusted under different packet loss conditions. For this purpose, we present a variety of realistic simulation scenarios for the application of AL-FEC and furthermore we provide an in-depth analysis of Raptor codes performance introducing valuable suggestions to achieve efficient use of Raptor codes.</p>
10aFEC10aLTE10aMBMS1 aBouras, Christos1 aPapazois, Andreas1 aKokkinos, Vasileios1 aKanakis, Nikos  uhttp://telematics.upatras.gr/telematics/publications/application-layer-forward-error-correction-multicast-streaming-over-lte-networks?language=en01360nas a2200145   4500008004100000245006200041210006200103260002800165300001600193520080800209100002101017700001901038700003301057856012401090       2013                        eng d00aBandwidth on Demand over Carrier Grade Ethernet Equipment0 aBandwidth on Demand over Carrier Grade Ethernet Equipment  cJanuary 27 - February 1  a 204 - 208 3 aThis paper presents the prototype implementation of
a Bandwidth on Demand (BoD) service over equipment using
Carrier Grade Ethernet. The BoD multi-domain service is
based on AutoBAHN (Automated Bandwidth Allocation across
Heterogeneous Networks) software. The paper describes the
steps that have taken place for designing and implementing a
prototype technology proxy that is able to match the Carrier
Grade Ethernet equipment with AutoBAHN, based on the
implementations of the relevant standards and technologies by
Extreme Networks. The equipment in particular is comprised
of BlackDiamond 12804 switches, running ExtremeXOS
version 12. The paper demonstrates how a suitable testbed can
be created and utilized and how a new technology at the data
plane can be supported by a Bandwidth on Demand tool.1 aBouras, Christos1 aStamos, Kostas1 aSpuropoulou, Theoni-Katerina  uhttp://telematics.upatras.gr/telematics/publications/bandwidth-demand-over-carrier-grade-ethernet-equipment?language=en01794nas a2200145   4500008004100000245006600041210006300107260001500170300001200185520127400197653000801471100002101479700001901500856012901519       2013                        eng d00aA Competitive AL-FEC Framework over Mobile Multicast Delivery0 aCompetitive ALFEC Framework over Mobile Multicast Delivery  cJuly 1 - 5  a305-3103 a<p>Reliability control is a key concern on the evolution of real-time mobile multicast services. To this direction the use of forward error correction (FEC) on the application layer is widely adopted in several mobile multicast standards. FEC is a feedback free error control method where the transmitter introduces in advance redundant information to enable receivers recovering data erasures. On multicast delivery and especially on the time constrained streaming delivery where retransmission-based error recovery methods are not feasible, the most suitable error control method is the use of application layer forward error correction (AL-FEC) codes. In this work, we introduce a novel AL-FEC deployment policy over mobile multicast standards utilizing online algorithms. We aim on the efficient application of ALFEC protection with RaptorQ codes over multicast streaming delivery in the context of competitive analysis. We provide a competitiveness analysis model of AL-FEC application over mobile multicast real-time environments and we introduce an innovative online algorithm adjusting the introduced redundancy of AL-FEC protection according to the FEC encoding parameters in order to satisfy the individual constraints of a multicast streaming delivery.</p>
10aFEC1 aBouras, Christos1 aKanakis, Nikos  uhttp://telematics.upatras.gr/telematics/publications/competitive-al-fec-framework-over-mobile-multicast-delivery?language=en01839nas a2200157   4500008004100000245004600041210004400087260002000131300001200151520132800163100002101491700001901512700002401531700002201555856010401577       2013                        eng d00aDeploying AL - FEC with Online Algorithms0 aDeploying AL FEC with Online Algorithms  cSeptember 25-27  a175-1803 a<p class="rtejustify">Application Layer Forward Error Correction (ALFEC)&nbsp;schemes are the most suitable mechanism for error control in mobile multicast services. AL-FEC introduces redundant information in advance with the source data to provide reliability control in the multicast transmission. Due to this fact the introduced&nbsp;redundancy must be carefully selected with respect to the current network conditions to avoid channel bandwidth wastage and achieve an efficient and reliable multicast delivery. However, the efficient selection of the introduced redundancy is not a trivial issue for the multicast source, due to the individual constraints&nbsp;of a multicast environment. In this work, we present a novel way to face the AL-FEC deployment utilizing online algorithms for selecting the appropriate amount of redundancy introduced in the multicast transmission. We provide an efficient way to apply AL-FEC protection on mobile multicast environments with randomized online algorithms eliminating the need for prior&nbsp;knowledge of the network conditions. To this direction, we present a competitive framework under which, we state the problem of the efficient deployment of AL-FEC protection and provide a randomized online algorithm for the AL-FEC application over mobile multicast environments.</p>
1 aBouras, Christos1 aKanakis, Nikos1 aKokkinos, Vasileios1 aPapazois, Andreas  uhttp://telematics.upatras.gr/telematics/publications/deploying-al-fec-online-algorithms?language=en02103nas a2200181   4500008004100000245005300041210005300094300001400147490000700161520153500168653000801703653000901711100002101720700002201741700002401763700001901787856011501806       2013                        eng d00aEmbracing RaptorQ FEC in 3GPP multicast services0 aEmbracing RaptorQ FEC in 3GPP multicast services  a1023-10350 v193 a<p>Multimedia Broadcast/Multicast Services (MBMS) have been introduced by Third Generation Partnership Project (3GPP) aiming to efficiently deliver data to mobile users in a one-to-many way. In order to provide reliable multicast transmission, 3GPP recommends exclusively for MBMS the use of a Forward Error Correction (FEC) mechanism on the application layer. Raptor codes are standardized as the Application Layer FEC (AL-FEC) scheme over 3GPP MBMS. However, the 3GPP standardized systematic fountain Raptor code is nowadays considered obsolete, since a new variation of the Raptor codes has emerged. This enhanced AL-FEC scheme, named RaptorQ, promises higher protection efficiency and superior flexibility on the provision of demanding mobile multicast services. In this work, we provide an extensive performance evaluation presenting at first a theoretical performance comparison of the newly introduced RaptorQ FEC scheme with its predecessor Raptor code, examining the enhancements that RaptorQ introduces on the AL-FEC protection robustness. Thereafter, to verify the enhanced performance of RaptorQ, we present several simulation results considering the modeling of the AL-FEC protection over multicast services for next generation mobile networks, utilizing the ns-3 simulation environment. Investigating several mobile system parameters in conjunction with FEC encoding parameters, we provide valuable results regarding the impacts of the examined AL-FEC schemes application on the multicast services performance.</p>
10aFEC10aMBMS1 aBouras, Christos1 aPapazois, Andreas1 aKokkinos, Vasileios1 aKanakis, Nikos  uhttp://telematics.upatras.gr/telematics/publications/embracing-raptorq-fec-3gpp-multicast-services?language=en01314nas a2200133   4500008004100000245006000041210005800101260001700159300001000176520082800186100002101014700002201035856012301057       2013                        eng d00aEnhancing news articles clustering using word n - grams0 aEnhancing news articles clustering using word n grams  cJuly 29 - 31  a53-603 a<p>In this work we explore the possible enhancement of the document clustering results, and in particular clus-tering of news articles from the web, when using word-based n-grams during the keyword extraction phase. We present and evaluate a weighting approach that combines clustering of news articles derived from the web using n-grams, extracted from the articles at an offline stage. We compared this technique with the sin-gle minded bag-of-words representation that our clustering algorithm, W-kmeans, previously used. Our ex-perimentation revealed that via tuning of the weighting parameters between keyword and n-grams, as well as the n itself, a significant improvement regarding the clustering results metrics can be achieved. This re-flects more coherent clusters and better overall clustering performance.</p>
1 aBouras, Christos1 aTsogkas, Vassilis  uhttp://telematics.upatras.gr/telematics/publications/enhancing-news-articles-clustering-using-word-n-grams?language=en01578nas a2200157   4500008004100000245010400041210006900145260002100214520092300235100002101158700002201179700002301201700002201224700001701246856015701263       2013                        eng d00aEnhancing video transmission in MANETs utilizing multiple interfaces and multiple channels per node0 aEnhancing video transmission in MANETs utilizing multiple interf  cOctober 16 - 18 3 a<p>Mobile Ad hoc NETworks (MANETs) are becoming more essential to wireless communications due to growing popularity of mobile devices. MANETs are also essential in Emergency Response situation where network information flow between deployed units is vital. In such cases voice and video transmission is essential to form a global view of the situation and decide on action. However, MANETs do not seem to effectively support multimedia applications and especially video transmission. In this work we propose a simple and efficient channel selection mechanism for enhancing Video Transmission in MANETS that have nodes with multiple interfaces, and can utilize multiple channels at the same time. The mechanism is implemented and tested in the ns-2 network simulator. Simulation results indicate that the mechanism improves the networks capacity for video transmission and reduces the video streams? packet delay.</p>
1 aBouras, Christos1 aGkamas, Apostolos1 aKapoulas, Vaggelis1 aPolitaki, Dimitra1 aTsanai, Enea  uhttp://telematics.upatras.gr/telematics/publications/enhancing-video-transmission-manets-utilizing-multiple-interfaces-and-multiple-channels?language=en01399nas a2200169   4500008004100000245005100041210004900092260001900141300001200160520083900172100002201011700002101033700002001054700002401074700002201098856010901120       2013                        eng d00aEvaluating ICIC Performance in LTE - A Systems0 aEvaluating ICIC Performance in LTE A Systems  cAugust 27 - 30  a400-4043 a<p class="rtejustify">LTE-A technology incorporates Inter-Cell Interference Coordination (ICIC) methods in order to enhance performance and mitigate interference. These methods include frequency allocation techniques that allow neighboring cells and femtocells in heterogeneous networks, to coordinately share and reuse available spectral resources, in order to avoid performance degradation for interference suffering cell-edge users. In this paper we evaluate the performance of the ICIC methods in LTE-A multi-cell systems using a simulation framework integrating several frequency reuse techniques and providing a user-friendly graphical presentation of the results. The optimal frequency&nbsp;reuse configuration for the examined network instance is also determined, based on overall performance and fairness index metrics.</p>
1 aBilios, Dimitrios1 aBouras, Christos1 aDiles, Georgios1 aKokkinos, Vasileios1 aPapazois, Andreas  uhttp://telematics.upatras.gr/telematics/publications/evaluating-icic-performance-lte-systems?language=en01333nas a2200145   4500008004100000245010300041210006900144260002100213520071400234100002100948700002000969700002400989700002201013856015201035       2013                        eng d00aEvaluation of Femtocells Interference Mitigation Techniques over ICIC Coordinated LTE - A Networks0 aEvaluation of Femtocells Interference Mitigation Techniques over  cNovember 13 - 153 a<p class="rtejustify">Abstract—Femtocells offer an attractive solution to locally&nbsp;improve the data rates and coverage of mobile networks, however interference issues may rise when they are deployed to nearby non-subscribed macro users. Power control and radio management are the most prominent ways to tackle the problem. In this work, we provide a simulation framework that is capable to simulate the behaviour of femtocells deployment over Long&nbsp;Term Evolution Advanced (LTE-A) macrocells networks. With the help of the tool, we evaluate several available interference mitigation techniques for femtocells, when applied in Inter-Cell Interference Cancellation (ICIC) macrocell environments.</p>
1 aBouras, Christos1 aDiles, Georgios1 aKokkinos, Vasileios1 aPapazois, Andreas  uhttp://telematics.upatras.gr/telematics/publications/evaluation-femtocells-interference-mitigation-techniques-over-icic-coordinated-lte?language=en01427nas a2200157   4500008004100000245013100041210006900172260002100241520074500262100002101007700002201028700002301050700002201073700001701095856015701112       2013                        eng d00aEvaluation of Routing Protocols for Video Transmission over MANETs that use Multiple Interfaces and Multiple Channels per node0 aEvaluation of Routing Protocols for Video Transmission over MANE  cDecember 11 - 133 a<p class="rtejustify">Mobile Ad hoc NETworks (MANETs) are becoming&nbsp;more essential to wireless communications due to growing popularity of mobile devices. Many researchers have committed effort to enhance the Multimedia (video) transmission over MANETs. Various algorithms and mechanisms concerning the optimization of multimedia transmission have been presented. In&nbsp;this work we evaluate the effect of using multiple interfaces and multiple channels per node in the performance of already existing MANET routing protocols during video transmission. The&nbsp;evaluation shows that all routing protocols benefit from using multiple interfaces and multiple channels per node, and the video transmission over MANETs is improved.</p>
1 aBouras, Christos1 aGkamas, Apostolos1 aKapoulas, Vaggelis1 aPolitaki, Dimitra1 aTsanai, Enea  uhttp://telematics.upatras.gr/telematics/publications/evaluation-routing-protocols-video-transmission-over-manets-use-multiple-interfaces-and?language=en01946nas a2200181   4500008004100000245007700041210006900118260001700187300001000204520129100214100002101505700002001526700002201546700002301568700002201591700001701613856013401630       2013                        eng d00aEvaluation of video transmission in emergency response ad - hoc networks0 aEvaluation of video transmission in emergency response ad hoc ne  cJuly 29 - 31  a27-353 a<p class="rtejustify">Mobile Ad hoc NETworks (MANETs) are becoming more essential to wireless communications due to&nbsp;growing popularity of mobile devices. MANETs are also essential in Emergency Response situation where&nbsp;network information flow between deployed units is vital. In such cases voice and video transmission is&nbsp;essential to form a global view of the situation and decide on action. However, MANETs do not seem to&nbsp;effectively support multimedia applications and especially video transmission. In this work we evaluate the&nbsp;use of multiple interfaces and multiple channels for Video Transmission in Emergency Response Ad hoc&nbsp;Networks. We also evaluate the video transmission with rate adaptation. Aim of this paper is to tune multiinterfaces&nbsp;and multi-channels video transmission mechanisms in order to support better emerging situations&nbsp;and offer a solution to have acceptable transmission of the necessary video streams so that the control can&nbsp;get a complete overall picture of the situation and decide on the action to be taken. The simulation&nbsp;evaluation performed shows that multi-interfaces and multi-channels video transmission offers many&nbsp;advantages in Video Transmission in Emergency Response Ad hoc Networks.</p>
1 aBouras, Christos1 aKioumourtzis, G1 aGkamas, Apostolos1 aKapoulas, Vaggelis1 aPolitaki, Dimitra1 aTsanai, Enea  uhttp://telematics.upatras.gr/telematics/publications/evaluation-video-transmission-emergency-response-ad-hoc-networks?language=en02075nas a2200181   4500008004100000245006100041210006000102260001800162300001600180520144600196100002101642700002301663700001901686700002001705700002201725700002401747856012201771       2013                        eng d00aFeedback-based Adaptation for Improved Power Consumption0 aFeedbackbased Adaptation for Improved Power Consumption  cMarch 25 - 28  a 562 - 568 3 aIn this paper we present a feedback-based
adaptation mechanism that adjusts the transmission power of
a wireless card on commodity PCs depending on the quality of
the connection. Our purpose is to manage the available power
in order to achieve lower power consumption without
negatively affecting the user?s perception of connection quality.
We based our implementation on an existing theoretical model
and focused on resolving problems and removing assumptions
which made it inefficient in real life implementation. The initial
model manages to minimize the power consumption in
networks with exactly two nodes. In this paper, we extend the
model to consider the possibility of the existence of a base
station, where any number of nodes can be connected. Our
objectives for the base station are to minimize the power
consumption and guarantee continuous connectivity for all
mobile nodes. We implement the adaptation mechanism for a
specific adapter with open sources drivers thus allowing
necessary modifications. We conduct a number of real world
experiments. The results indicate that power consumption can
be significantly reduced for nodes that are either almost
stationary or slowly moving (e.g. at walking speed), without
any significant increase in packet loss. The results are quite
important as nowadays mobile devices with limited battery life
time use tethering to become base stations for other devices
like in ad-hoc networks.1 aBouras, Christos1 aKapoulas, Vaggelis1 aStamos, Kostas1 aKioumourtzis, G1 aTavoularis, Nikos1 aStathopoulos, Nikos  uhttp://telematics.upatras.gr/telematics/publications/feedback-based-adaptation-improved-power-consumption?language=en01434nas a2200169   4500008004100000245007800041210006900119260001300188300001500201520081300216653000801029100002101037700002201058700002401080700002101104856013901125       2013                        eng d00aFractional Frequency Reuse in Integrated Femtocell/Macrocell Environments0 aFractional Frequency Reuse in Integrated FemtocellMacrocell Envi  cJune 5-7  a 229 - 2403 a<p>Femtocells have a strong potential for increasing the efficiency, cell coverage and network capacity of next-generation mobile networks. In Long Term Evolution technology, the adaptation of Fractional Frequency Reuse techniques has been proposed in order to overcome the co-channel interference and augment the total throughput of the network. In this work, we propose a Fractional Frequency Reuse method that on the one hand calculates the optimal inner region radius and frequency allocation of a macrocell and on the other hand assigns frequency resources to the femtocells in order to mitigate the co-channel interference. We apply this method in an integrated femtocell/macrocell environment and evaluate it based on the optimization of three metrics, depending on the network operator?s needs.</p>
10aFFR1 aBouras, Christos1 aPapazois, Andreas1 aKokkinos, Vasileios1 aTseliou, Georgia  uhttp://telematics.upatras.gr/telematics/publications/fractional-frequency-reuse-integrated-femtocellmacrocell-environments?language=en01577nas a2200145   4500008004100000245009100041210006900132260001800201300001200219520098300231100002101214700001901235700003601254856014101290       2013                        eng d00aHandling Topology Updates in a Dynamic Tool for Support of Bandwidth on Demand Service0 aHandling Topology Updates in a Dynamic Tool for Support of Bandw  cJune 23 ?- 28  a161-1653 a<p>Automated Bandwidth Allocation across Heterogeneous Networks (AutoBAHN) is a tool under active development that supports a Bandwidth on Demand (BoD) service, intended to operate in a multi-domain environment using heterogeneous transmission technologies. The AutoBAHN system aims at providing a guaranteed capacity, connection-oriented service between two end points. Due to the distributed nature of the system and the fact that AutoBAHN has access to critical parts of the network, the importance of a robust, secure and dynamic mechanism for handling and distributing topology information cannot be underestimated. We will present how AutoBAHN manages to create an abstract representation of the physical network topology by hiding information such as IP addresses, port values, VLAN, MTU, link capacities etc., how this abstract topology is merged among domains and how AutoBAHN system handles topology changes in terms of their influence on reservation processing.</p>
1 aBouras, Christos1 aStamos, Kostas1 aKalligeros, Ioannis, - Christos  uhttp://telematics.upatras.gr/telematics/publications/handling-topology-updates-dynamic-tool-support-bandwidth-demand-service?language=en01320nas a2200133   4500008004100000245008600041210006900127260002000196520076100216100002100977700002000998700002401018856014401042       2013                        eng d00aImpact of broadband public infrastructures and services on SEE countries' economy0 aImpact of broadband public infrastructures and services on SEE c  cOctober 28 - 313 a<p class="rtejustify">Broadband is an important tool for increasing&nbsp;productivity and competitiveness. This paper attempts to measure the accumulative impact and effectiveness of broadband public infrastructures and services on the economy of South East Europe (SEE) areas. To this direction, we focus on evaluating the correlation between broadband and each country?s growth and&nbsp;employment. Moreover, we estimate the cost savings achieved by the extended usage of e-services, and we evaluate the potential cost savings that will follow the increase of e-services utilization the next years. The results of our analysis show that broadband&nbsp;may have positive impact on growth and employment and that the possible savings are substantial.</p>
1 aBouras, Christos1 aDiles, Georgios1 aKokkinos, Vasileios  uhttp://telematics.upatras.gr/telematics/publications/impact-broadband-public-infrastructures-and-services-see-countries-economy?language=en02009nas a2200133   4500008004100000245010100041210006900142300001600211520143300227100002101660700002401681700002101705856014901726       2013                        eng d00aMethodology for Public Administrators for Selecting between Open Source and Proprietary Software0 aMethodology for Public Administrators for Selecting between Open  a  100 - 1103 aThe public sector needs to change over to communicating digitally. This development makes great demands both on work processes in the public sector and on the Information Technology systems, on which e-government is based. From the economic perspective, the change-over poses great challenges, as huge investments will have to be made in Information Technology in the public sector. It is therefore natural, in connection with these investments, for a detailed assessment to be made of what forms of technology it is anticipated to be used, and who controls the development and ownership of this technology. The question is: to what extent Free and Open Source Software can supplement or completely replace proprietary software? This work constitutes a review of literature on pre-existing comparative studies regarding the technical, social, economic and organizational factors on Free and Open Source Software usage. Furthermore, this work includes guidelines that Public Administrations should follow for the selection between open source and proprietary software. Our goal is to help public stakeholders understand the technical/social/economic/organizational environment and therefore reach informed decisions when selecting the appropriate software. The manuscript can also be useful for Free and Open Source Software developers, users and communities who are either directly or indirectly involved in the software market.1 aBouras, Christos1 aKokkinos, Vasileios1 aTseliou, Georgia  uhttp://telematics.upatras.gr/telematics/publications/methodology-public-administrators-selecting-between-open-source-and-proprietary?language=en01850nas a2200145   4500008004100000245007300041210006900114260001900183520129100202653000801493100002101501700002401522700002401546856013401570       2013                        eng d00aMobility MCS Selection Mechanisms for Multicasting over LTE Networks0 aMobility MCS Selection Mechanisms for Multicasting over LTE Netw  cApril 23 -? 253 a<p>In Long Term Evolution (LTE) networks, the Multimedia Broadcast/Multicast Services over Single Frequency Network (MBSFN) operation enables the delivery of the same multimedia content to a set or all the users in a cell, leading in this way to efficient utilization of the network resources. This is achieved through a time-synchronized common waveform that is transmitted from multiple cells for a given duration, which enables over-the-air combining, and therefore significantly improves the spectral efficiency. However, the performance of MBSFN is directly connected to the Modulation and Coding Scheme (MCS) and the transmission mode that will be selected for the delivery of the multimedia data. This paper proposes three different approaches for the selection of the MCS during MBSFN transmissions. Main target is to determine the most efficient approach depending on the target that the operator may set, i.e. the approach that either maximizes the spectral efficiency or achieves a target spectral efficiency for various user distributions. The performance of the approaches is evaluated for scenarios that include users? mobility and for three different transmission modes in order to also examine the effectiveness of Multiple Input Multiple Output (MIMO) techniques.</p>
10aMCS1 aBouras, Christos1 aKokkinos, Vasileios1 aBochrini, Stavroula  uhttp://telematics.upatras.gr/telematics/publications/mobility-mcs-selection-mechanisms-multicasting-over-lte-networks?language=en01497nas a2200169   4500008004100000245006500041210006400106260001800170300001600188520088500204653001801089100002101107700002201128700002401150700002701174856012601201       2013                        eng d00aMobility-Sensitive Power Control for MBSFN Cellular Networks0 aMobilitySensitive Power Control for MBSFN Cellular Networks  cMarch 25 - 28  a 483 - 487 3 aCellular networks? Multimedia Broadcast/Multicast
Service (MBMS) over a Single Frequency Network (MBSFN)
allows broadcasting cell signals to constructively interfere and
users to take advantage of increased bitrates compared to other
broadcasting technologies. In this paper, we present our work on
the optimization of the power control for future cellular networks
that employ MBSFN transmission scheme. We propose a novel
simulator and optimizer that can minimize the transmission
power of individual cells taking into account the changing
positions of users. In order to read descriptions of the various
scenarios, the simulator uses the eXtendable Temporal Network
Description Language (XTNDL), a language that is defined in this
paper. The optimizer?s engine can be used in conjunction with
the simulator or can be modified to read real time measurements
from a real network.10aPower Control1 aBouras, Christos1 aPapazois, Andreas1 aKokkinos, Vasileios1 aAsimakis, Konstantinos  uhttp://telematics.upatras.gr/telematics/publications/mobility-sensitive-power-control-mbsfn-cellular-networks?language=en01999nas a2200205   4500008004100000245013600041210006900177300001400246490000700260520122000267653000801487653001001495653000801505100002101513700002201534700002201556700002401578700002401602856016701626       2013                        eng d00aModulation and coding scheme selection in multimedia broadcast over a single frequency network-enabled long-term evolution networks0 aModulation and coding scheme selection in multimedia broadcast o  a1603-16190 v253 a<p>Long term evolution constitutes the next generation cellular network beyond 3G that is designed to support the explosion in demand for bandwidth-hungry multimedia services in wireless networks by providing an extremely high performance radio access technology. To support multimedia broadcast/multicast services (MBMS), long term evolution offers the functionality to transmit MBMS over a single frequency network, where a time-synchronized common waveform is transmitted from multiple cells for a given duration. This enables over-the-air combining, thus significantly improving the spectral efficiency (SE) compared with conventional MBMS operations. In MBMS over a single frequency network transmissions, the achieved SE is mainly determined by the modulation and coding scheme selected. This study proposes and evaluates four approaches for the selection of the modulation and coding scheme. Each approach corresponds to different users? distribution and multimedia traffic conditions. On the basis of SE measurements, we determine the approach that either maximizes or achieves a target SE for the corresponding users? distribution and traffic conditions. Copyright © 2011 John Wiley &amp; Sons, Ltd.</p>
10aLTE10aMBSFN10aMCS1 aBouras, Christos1 aAlexiou, Antonios1 aPapazois, Andreas1 aKokkinos, Vasileios1 aTsichritzis, George  uhttp://telematics.upatras.gr/telematics/publications/modulation-and-coding-scheme-selection-multimedia-broadcast-over-single-frequency-network-enabled?language=en01814nas a2200145   4500008004100000245008100041210006900122260002000191300001200211520124300223100002201466700002201488700002101510856013701531       2013                        eng d00aA Power Control Mechanism Based on Priority Grouping for Small Cell Networks0 aPower Control Mechanism Based on Priority Grouping for Small Cel  cOctober 28 - 30  a170-1763 a<p class="rtejustify">Future mobile networks following Long Term Evolution (LTE) will be characterized by demanding services, in terms of bandwidth and delay, already dominant in wired networks, such as cloud-computing, High Definition of anything (HDOA) and highly-interactive online games. Small Cell technology is one of the key-technologies aiming to address the need for ultra-high performance in future mobile networks. This paper is focused on efficient power control in Small Cell Networks (SCNs). In particular, we propose a power control mechanism for efficient power allocation in SCNs. The proposed mechanism efficiently controls systems? interference while on the other hand guarantees home user QoS. We introduce the methodology of Priority Grouping, in which home users in the topology is assigned to one of the available groups with different priorities in terms of power requirements and requested traffic load. The mechanism dynamically updates the Home evolved Node B power setting based on the topology of the macro and home users in real time. Additionally, depending on the examined traffic scenario the mechanism can provide better protection (in terms of interference) either on macro users or on home users.</p>
1 aAlexiou, Antonios1 aBilios, Dimitrios1 aBouras, Christos  uhttp://telematics.upatras.gr/telematics/publications/power-control-mechanism-based-priority-grouping-small-cell-networks?language=en01746nas a2200157   4500008004100000245009100041210006900132300001300201520110700214100002101321700001901342700002101361700002401382700002601406856015601432       2013                        eng d00aPower Management Mechanism Exploring Network and Video Information over Wireless Links0 aPower Management Mechanism Exploring Network and Video Informati  a 15 - 253 aThis article examines the ways in which crosslayer
information from higher network layers may be
utilized for more efficient power management in wireless
networks and energy constrained mobile devices. In
particular, we present and evaluate mechanisms that finetune
transmission power according to information received
from the transport (feedback reports from TFRC) and
application (type of the video frame encoded) layers.
Further improvements may be applied if the video encoding
is done using capabilities of the SVC standard. We also
describe power management adaptation techniques for
wireless video transmission using the TFRC protocol that
take into account feedback about the received video quality
and try to adapt transmitting power accordingly. The
purpose of the mechanisms is to utilize TFRC feedback and
thus achieve a beneficial balance between the power
consumption and the received video quality. The
mechanisms proposed, offer significant improvements when
used in terms of both power consumption and received
video quality. All proposals are compared and evaluated
using simulation.1 aBouras, Christos1 aStamos, Kostas1 aZaoudis, Giannis1 aStroumpis, Stamatis1 aCharalambides, Savvas  uhttp://telematics.upatras.gr/telematics/publications/power-management-mechanism-exploring-network-and-video-information-over-wireless-links?language=en01906nas a2200181   4500008004100000245009200041210006900133300001400202490000700216520123300223653000801456100002101464700002201485700002401507700002101531700002201552856015001574       2013                        eng d00aSelecting the Optimal Fractional Frequency Reuse Scheme in Long Term Evolution Networks0 aSelecting the Optimal Fractional Frequency Reuse Scheme in Long   a2693-27120 v713 a<p>Long Term Evolution (LTE) networks offer high capacity and are specified and designed to accommodate small, high performance, power-efficient end-user devices. One limiting factor that influences LTE performance is the interference from neighbouring cells, the so called Inter-Cell Interference (ICI). The investigation of ICI mitigation techniques has become a key focus area in achieving dense spectrum reuse in next generation cellular systems. Fractional Frequency Reuse (FFR) has been proposed as a technique to overcome this problem, since it can efficiently utilize the available frequency spectrum. This manuscript proposes a dynamic mechanism that selects the optimal FFR scheme based on a custom metric, which is called user satisfaction. In detail, the proposed mechanism divides the cell into two regions, the inner and outer region, and selects the optimal size as well as the optimal frequency allocation between these regions with main target to maximize the user satisfaction metric. The proposed mechanism is evaluated through several simulation scenarios that incorporate users? mobility and its selected FFR scheme is compared with other frequency reuse schemes in order to highlight its performance.</p>
10aFFR1 aBouras, Christos1 aPapazois, Andreas1 aKokkinos, Vasileios1 aTseliou, Georgia1 aBilios, Dimitrios  uhttp://telematics.upatras.gr/telematics/publications/selecting-optimal-fractional-frequency-reuse-scheme-long-term-evolution-networks?language=en01717nas a2200169   4500008004100000245005600041210005500097260001600152300001000168520114400178100002101322700001901343700002001362700002601382700002601408856011301434       2013                        eng d00aSimulation design and execution: The case of TRAFIL0 aSimulation design and execution The case of TRAFIL  c29-31 July   a27-343 a<p>This paper presents the enhancements that we have done on the TRAFIL (TRAce FILe) framework, which significantly extend its capabilities in the areas of simulation design and execution. In particular, TRAFIL now offers the possibility to design, create, execute and review NS-2 simulation scenarios, on top of its ex-isting post-simulation trace analysis functionalities. The enhancements make TRAFIL a complete wrapper around the NS-2 simulator, allowing the user to perform all steps from pre-simulation design to actual simu-lation execution in an automated way and fast and convenient post-simulation analysis of potentially large amount of data. The paper describes the new TRAFIL architecture and how these enhancements were im-plemented with the goal of relieving NS-2 users from the often cumbersome tasks of script writing and vali-dating, while also enabling them at to go behind the TRAFIL environment and into the simulator internals at any time. The paper presents the new GUI functionalities developed for that purpose, the approach that we took for their design and how these fit in the overall TRAFIL architecture.</p>
1 aBouras, Christos1 aStamos, Kostas1 aKioumourtzis, G1 aCharalambides, Savvas1 aDrakoulelis, Michalis  uhttp://telematics.upatras.gr/telematics/publications/simulation-design-and-execution-case-trafil?language=en02674nas a2200157   4500008004100000245007800041210006900119300001400188520206500202100002102267700001902288700002002307700002602327700002602353856013702379       2013                        eng d00aA tool for automatic network simulation and processing tracing data files0 atool for automatic network simulation and processing tracing dat  a 90 - 1103 a<p class="rtejustify">One of the most highly regarded discrete event simulators used for network simulation is NS-2 (Network Simulator). NS-2 executes simulation scenarios producing various data of which trace files are considered the most beneficial for evaluating a simulation. In this paper we present the design considerations and implementation of a new tool that can be used both in TRAce FILe analysis and execution of simulations using NS-2. Although TRAFIL is primarily based on NS-2 trace files it can be extended to support a number of different other simulation trace file formats. It aims to make the execution of a great number of network simulations quicker, and the extraction of results from a large amount of data more flexible and productive. In order to accomplish the above tasks TRAFIL presents a novel way of interpreting, parsing, reading and eventually using NS-2 trace files. It introduces the notion of ??metafiles?? and ??sub metafiles?? throughout the procedures of trace file recognition and parsing, making the overall analysis operation substantially efficient and faster than alternative approaches. Metafiles and sub metafiles are used to encode NS-2 trace file structures enabling a more abstract approach to the trace file processing operation. Furthermore, TRAFIL facilitates the overall trace file analysis task by offering the opportunity to store each trace file as well as every Quality of Service (QoS) measurement produced for each trace file. Following the trace file recognition and processing operations, the information contained in a trace file is presented through a Graphical User Interface (GUI) offered by TRAFIL along with a variety of data, metrics and statistics related to simulation results. Finally, the tool offers the opportunity to execute custom Structured Query Language (SQL) queries to the local database and to completely automate the simulation procedure by enabling the user to execute NS-2 scripts as well as perform a simulation of a video transmission using the Evalvid-RA framework.</p>
1 aBouras, Christos1 aStamos, Kostas1 aKioumourtzis, G1 aCharalambides, Savvas1 aDrakoulelis, Michalis  uhttp://telematics.upatras.gr/telematics/publications/tool-automatic-network-simulation-and-processing-tracing-data-files?language=en01869nas a2200133   4500008004100000245006400041210006400105520135800169100002101527700002301548700002201571700001701593856012501610       2012                        eng d00aBuilding community and collaboration applications for MMOGs0 aBuilding community and collaboration applications for MMOGs3 aSupporting collaborative activities among the online players are one of the major challenges in the area of Massively  multiplayer Online Games (MMOG), since they increase the richness of gaming experience and create more engaged communities. To this direction, our study has focused on the provision of services supporting and enhancing the players' in-game community and collaboration activities. We have designed and implemented innovative tools exploiting a game adaptation technology, namely the In-game Graphical Insertion Technology (IGIT), which permits the addition of web-based applications without any need from the game developers to modify the game at all, nor from the game players to change their game installation. The developed tools follow a design adapted to the MMOG players' needs and are based on the latest advances on Web 2.0 technology. Their provision is performed through the core element of our system, which is the so-called Community Network Game (CNG) Server. One of the important features provided by the implemented system's underlying framework is the utilization of enhanced Peer-to-Peer (P2P) technology for the distribution of user-generated live video streams. In this paper, we focus on the architecture of the CNG Server as well as on the design and implementation of the online community and collaboration tools.1 aBouras, Christos1 aKapoulas, Vaggelis1 aPapazois, Andreas1 aAdam, George  uhttp://telematics.upatras.gr/telematics/publications/building-community-and-collaboration-applications-mmogs?language=en01968nas a2200121   4500008004100000245005900041210005700100300001500157520151300172100002101685700002201706856011801728       2012                        eng d00aA clustering technique for news articles using WordNet0 aclustering technique for news articles using WordNet  a115 - 128 3 aThe Web is overcrowded with news articles, an overwhelming information source both with its amount and diversity. Document clustering is a powerful technique that has been widely used for organizing data into smaller and manageable information kernels. Several approaches have been proposed which, however, suffer from problems like synonymy, ambiguity and lack of a descriptive content marking of the generated clusters. In this work, we are investigating the application of a great spectrum of clustering algorithms, as well as similarity measures, to news articles that originate from the Web. Also, we are proposing the enhancement of standard k-means algorithm using the external knowledge from WordNet hypernyms in a twofold manner: enriching the ??bag of words?? used prior to the clustering process and assisting the label generation procedure following it. Furthermore, we are examining the effect that text preprocessing has on clustering. Operating on a corpus of news articles derived from major news portals, our comparison of the existing clustering methodologies revealed that k-means, gives better aggregate results when it comes to efficiency. This is amplified when the algorithm is accompanied with preliminary steps for data cleaning and normalizing, despite its simple nature. Moreover, the proposed WordNetenabled W-k means clustering algorithm significantly improves standard k-means generating also useful and high quality cluster tags by using the presented cluster labeling process.1 aBouras, Christos1 aTsogkas, Vassilis  uhttp://telematics.upatras.gr/telematics/publications/clustering-technique-news-articles-using-wordnet?language=en01534nas a2200133   4500008004100000245004900041210004900090260001900139300001300158520108400171100002101255700002201276856010201298       2012                        eng d00aClustering to Deal with the New User Problem0 aClustering to Deal with the New User Problem  c5 - 7 December  a 58 - 653 aCollaborative filtering (CF) techniques attempt to alleviate information overload by identifying which items a user will find interesting to browse. It focuses on identification of other users with similar tastes and usage of their opinions in order to recommend items. Commonly, however, CF suffers from the so-called new user problem which occurs when a new user is added to the system and there is not enough information to make a good suggestion. The system has to acquire some data about the new user in order to start making personalized recommendations. In this paper, we present a novel algorithm that combines previously acquired knowledge from article and user clustering in order to quickly determine the new user's interests. We attempt to address the new user problem by providing a personalized strategy for prompting the user with articles to rate. Our approach makes use of hypernyms extracted from the WordNet database and proves to be converging fast to the actual user interests based on minimal user ratings which are provided during the registration process.1 aBouras, Christos1 aTsogkas, Vassilis  uhttp://telematics.upatras.gr/telematics/publications/clustering-deal-new-user-problem?language=en02382nas a2200205   4500008004100000245009500041210006900136300001200205520163600217653001801853653000801871653001001879100002101889700002201910700002201932700002401954700002701978700002102005856015002026       2012                        eng d00aCost Optimization of MBSFN and PTM Transmissions for Reliable Multicasting in LTE Networks0 aCost Optimization of MBSFN and PTM Transmissions for Reliable Mu  a277-2933 aLong Term Evolution (LTE) systems have been specified and designed to accommodate small, high performance, power-efficient, end-user devices. The evolved Multimedia Broadcast/Multicast Service (e-MBMS) feature is introduced by the 3rd Generation Partnership Project (3GPP) as a complement to the existing MBMS service in order to accommodate multicast groups that are interested in receiving the same data. MBMS service is provided by MBMS over a Single Frequency Network (MBSFN) and/or Point-To-Multipoint (PTM) transmission methods. One of the challenges of MBMS is the complete error recovery of the transmitted files, a matter of great importance since the distribution of binary data must result in 100% error-free download. To fulfill this tight requirement, Forward Error Correction (FEC) mechanism has been proposed by 3GPP. In this work, we investigate the reliable multicasting by introducing a transmission method that combines the advantages of MBSFN and PTM transmission methods. We compare several FEC-based file recovery methods and evaluate them against various network parameters in a realistic simulation environment. The comparison is based on a cost-oriented analysis of MBMS service that takes into account the transmission cost over all the interfaces and nodes of the LTE architecture. The simulation results are performed with the aid of a new simulation tool and show that the performance of the file repair schemes depend on the network configuration.
KEYWORDS: multimedia multicasting; cellular networks; forward error correction; reliability; single frequency network; optimization; point to multipoint;10aCost analysis10aLTE10aMBSFN1 aBouras, Christos1 aAlexiou, Antonios1 aPapazois, Andreas1 aKokkinos, Vasileios1 aAsimakis, Konstantinos1 aTseliou, Georgia  uhttp://telematics.upatras.gr/telematics/publications/cost-optimization-mbsfn-and-ptm-transmissions-reliable-multicasting-lte-networks?language=en01687nas a2200169   4500008004100000245007000041210006600111260001500177300000900192520109400201100002101295700002301316700002201339700002001361700001701381856011901398       2012                        eng d00aA cross - layer design for video transmission with TFRC in MANETS0 across layer design for video transmission with TFRC in MANETS  c24-27 July  a5-123 a<p>Mobile Ad hoc NETworks (MANETs) are becoming more essential to wireless communications due to growing popularity of mobile devices. However, MANETs do not seem to effectively support multimedia applications and especially video transmission. In this work, we propose a cross-layer design that aims to improve the performance of video transmission using TCP Friendly Rate Control (TFRC). Our design provides priority to video packets and exploits information from the MAC layer in order to improve TFRC?s performance. The proposed cross-layer mechanism utilizes Signal to Noise Ratio (SNR) measurements along the routing path, in order to make the route reconstruction procedure more efficient. Simulation results show that both the use of traffic categorization and the SNR utilization lead to important improvements of video transmission over the mobile Ad hoc network. More specifically, simulations indicate increased average Peak Signal to Noise Ratio (PSNR) for the received video, increased throughput and packet delivery ration, as well as reduced average end-to-end delay.</p>
1 aBouras, Christos1 aKapoulas, Vaggelis1 aGkamas, Apostolos1 aKioumourtzis, G1 aAdam, George  uhttp://telematics.upatras.gr/telematics/publications/cross-layer-design-video-transmission-tfrc-manets?language=en01993nas a2200121   4500008004100000245008300041210006900124300001400193520147100207100002101678700002601699856014601725       2012                        eng d00aEnhancing Meta   Portals using Dynamic User Context Personalization Techniques0 aEnhancing Meta Portals using Dynamic User Context Personalizatio  a1446-14533 aThe Internet is 
ooded with Information and the last decade its size has
grown so many times that information search and presentation have become
tedious tasks even for experienced users. Minor changes to existing resources
can alter the situation and lead to major changes to the end user experi-
ence. In this manuscript we present the dynamic web personalization and
document grouping infrastructure for meta-portals and the evaluation of our
mechanism on a meta-portal. A meta-portal is an informational node where
articles from dierent sources are collected and presented in a categorized
and personalized manner. The web personalization mechanism is based on
dynamic creation and update of user proles according to the users prefer-
ences when browsing. In parallel a user's prole is aected by user grouping
details, which are constructed by users with similar proles. Assuming that
required information, such as article tagging, keywords to categories match-
ing and articles to categories relation is already part of the meta-portal we present a novel mechanism that can build and maintain a user prole which is
formed without disturbing the user. Furthermore, we describe the real-time
user-centred document grouping mechanism that is implemented to support
the web personalization system and present the experimental evaluation of
the whole system.
Keywords: personalization, web personalization, on-line document
grouping, user proling, meta-portal1 aBouras, Christos1 aPoulopoulos, Vassilis  uhttp://telematics.upatras.gr/telematics/publications/enhancing-meta-portals-using-dynamic-user-context-personalization-techniques?language=en01824nas a2200193   4500008004100000245005900041210005900100260001300159300001000172520121800182653000801400653000801408653000901416100002101425700002201446700002401468700001901492856011901511       2012                        eng d00aEnhaning Reliable Mobile Multicasting with RaptorQ FEC0 aEnhaning Reliable Mobile Multicasting with RaptorQ FEC  c1-4 July  a82-873 aA crucial point on the successful deployment of
multicast services is the enhanced reliability by means of advanced
error control schemes. To this direction Third Generation
Partnership Project (3GPP) has standardized exclusively for
Multimedia Broadcast/Multicast Services (MBMS) the use of a
Forward Error Correction (FEC) mechanism on the application
layer based on Raptor codes. Since the standardized systematic,
fountain Raptor code is now considered obsolete, the emergence
of a new variant of Raptor codes, named RaptorQ, provides
enhanced capabilities for mobile multicast services. In this paper,
we provide a performance comparison of the standardized
Raptor Application Layer FEC (AL-FEC) scheme with the very
promising RaptorQ FEC code. We examine the enhancements
that RaptorQ introduces on the AL-FEC protection robustness,
providing a thorough performance analysis in comparison with
the current Raptor FEC scheme. Furthermore, in order to
verify the improved performance of RaptorQ, we provide several
simulation results utilizing the ns-3 environment, considering the
application of both the examined AL-FEC schemes over multicast
services for next generation mobile networks.10aFEC10aLTE10aMBMS1 aBouras, Christos1 aPapazois, Andreas1 aKokkinos, Vasileios1 aKanakis, Nikos  uhttp://telematics.upatras.gr/telematics/publications/enhaning-reliable-mobile-multicasting-raptorq-fec?language=en01601nas a2200193   4500008004100000245005600041210005600097260001700153300001400170520099100184653000801175653000801183653000901191100002101200700002201221700002401243700001901267856012101286       2012                        eng d00aEvaluating RaptorQ FEC over 3GPP Multicast Services0 aEvaluating RaptorQ FEC over 3GPP Multicast Services  cAugust 27-31  a257 - 2623 aThird Generation Partnership Project (3GPP) introduced
Multimedia Broadcast/Multicast Services (MBMS), in
order to efficiently deliver the same content to multiple users over
mobile cellular networks. To enhance the download and streaming
delivery robustness against packet losses, 3GPP proposes
the use of Forward Error Correction (FEC) on the application
layer. The Application Layer FEC (AL-FEC) scheme that 3GPP
standardized is based on the systematic, fountain Raptor code.
In this work, in response to the emergence of an enhanced
FEC scheme, we provide a performance evaluation of the
existing standardized AL-FEC scheme with the newly introduced
RaptorQ code. Introducing a variety of simulation experiments,
we analyze the performance behavior of each AL-FEC scheme
considering several FEC encoding parameters. Furthermore, we
try to verify the improvements that have emerged in AL-FEC
providing enhanced capabilities in multicast services over next
generation mobile networks.10aFEC10aLTE10aMBMS1 aBouras, Christos1 aPapazois, Andreas1 aKokkinos, Vasileios1 aKanakis, Nikos  uhttp://telematics.upatras.gr/telematics/publications/evaluating-raptorq-fec-over-3gpp-multicast-services?language=en01459nas a2200193   4500008004100000245007600041210006900117260002000186300001000206520079400216653000801010653000901018653001001027100002101037700002201058700002401080700002701104856013401131       2012                        eng d00aGenetic Optimization for Spectral Efficient Multicasting in LTE Systems0 aGenetic Optimization for Spectral Efficient Multicasting in LTE   c19-21 September  a54-593 a<p>Past research has proposed the usage of assisting cells with Multimedia Broadcast/Multicast Service (MBMS) over a Single Frequency Network (MBSFN) to increase the Spectral Efficiency (SE) of LTE. In this paper we propose and investigate a method for optimizing the power consumption of the network while retaining an acceptable SE for most users. We design an algorithm that makes use of genetic optimization and analytical estimation of the SE. The algorithm is implemented in a novel simulation tool that allows experimentation over various user distributions and LTE deployments similar to the real-world ones. This simulation tool estimates the SE of each user and is able to optimize the network deployment by adjusting the individual transmission power levels for each cell.</p>
10aLTE10aMBMS10aMBSFN1 aBouras, Christos1 aPapazois, Andreas1 aKokkinos, Vasileios1 aAsimakis, Konstantinos  uhttp://telematics.upatras.gr/telematics/publications/genetic-optimization-spectral-efficient-multicasting-lte-systems?language=en01975nas a2200181   4500008004100000245009300041210006900134260001500203300001000218520127700228100002101505700002401526700002101550700002401571700002701595700002701622856014401649       2012                        eng d00aGuidelines for the procurement of free and open source software in public administrators0 aGuidelines for the procurement of free and open source software   c17-19 July  a29-363 a<p>This paper provides a concise guide on Free and Open Source Software procurement for European Public Administrations to be used by elected representatives and decision makers, procurement and Information Technology managers and staff in addition to any existing national or European Union guidelines and regulations. This work provides definitions of basic terms, outlines the legal context and the main principles of software procurement and highlights good practices and recommended actions for Public Administrations. Although the adoption of Free and Open Source Software as a strategic choice has certain advantages for public organisations, the guidelines and resources provided in this paper also apply to both open source and proprietary software procurement procedures and scenarios, such as downloading and purchasing, in-house development and outsourcing. The main aspects addressed and guidelines provided include: planning and defining a procurement method, estimating costs and benefits, setting interoperability and the use of open standards as a priority, avoiding discriminating practices such as naming trademarks, understanding and assessing licensing schemes, software provision models and suppliers, and establishing fair tendering processes.</p>
1 aBouras, Christos1 aKokkinos, Vasileios1 aTseliou, Georgia1 aFilopoulos, Anestis1 aMichalopoulos, Sotiris1 aPapadopoulos, Dimitris  uhttp://telematics.upatras.gr/telematics/publications/guidelines-procurement-free-and-open-source-software-public-administrators?language=en01502nas a2200181   4500008004100000245009400041210006900135260001600204520082500220653001401045653000801059653000801067100002101075700002201096700002401118700002501142856015301167       2012                        eng d00aInterference Management in LTE Femtocell Systems Using an Adaptive Frequency Reuse Scheme0 aInterference Management in LTE Femtocell Systems Using an Adapti  c18-20 April3 aLong Term Evolution (LTE) has developed a new
technology in order to enhance indoor coverage. This new
technology is called femtocells and is achieved with the use of
access points installed by home users. However, interference
problem between the femtocell and the macrocell decreases the
system's capacity and as a result users' throughput. In this paper
we study the interference mitigation techniques in
femtocell/macrocell networks and we propose a frequency reuse
mechanism that leads to increased overall system performance.
In particular, the mechanism aims to maximize throughput via a
variety of combinations between inner cell radius and frequency
allocation to the macrocell. Additionally, a position minded
frequency allocation to the femtocells targets to further optimize
the total throughput of the cell.10aFemtocell10aFFR10aLTE1 aBouras, Christos1 aPapazois, Andreas1 aKokkinos, Vasileios1 aKavourgias, Georgios  uhttp://telematics.upatras.gr/telematics/publications/interference-management-lte-femtocell-systems-using-adaptive-frequency-reuse-scheme?language=en01544nas a2200193   4500008004100000245004400041210004400085260001500129300001200144520095800156653000801114653000901122100002101131700002201152700002201174700002401196700002401220856010601244       2012                        eng d00aMultimedia Broadcasting in LTE Networks0 aMultimedia Broadcasting in LTE Networks  bIGI Global  a269-2893 a<p>Long Term Evolution (LTE) constitutes the latest step before the 4th generation (4G) of radio technologies designed to increase the capacity and speed of mobile communications. To support Multimedia Broadcast/Multicast Services (MBMS), LTE offers the functionality to transmit MBMS over Single Frequency Network (MBSFN), where a time-synchronized common waveform is transmitted from multiple cells for a given duration. In MBSFN transmissions, the achieved Spectral Efficiency (SE) is mainly determined by the Modulation and Coding Scheme (MCS) selected. This study proposes and evaluates four approaches for the selection of the MCS that will be utilized for the transmission of the MBSFN data. The evaluation of the approaches is performed for different users? distribution and from SE perspective. Based on the SE measurement, we determine the approach that either maximizes or achieves a target SE for the corresponding users? distribution.</p>
10aLTE10aMBMS1 aBouras, Christos1 aAlexiou, Antonios1 aPapazois, Andreas1 aKokkinos, Vasileios1 aTsichritzis, George  uhttp://telematics.upatras.gr/telematics/publications/multimedia-broadcasting-lte-networks?language=en01536nas a2200193   4500008004100000245007900041210006900120260001400189300001400203520086100217653000801078653000801086100002101094700002201115700002401137700002101161700002201182856013801204       2012                        eng d00aOptimization of Fractional Frequency Reuse in Long Term Evolution Networks0 aOptimization of Fractional Frequency Reuse in Long Term Evolutio  c1-4 April  a1875-18793 aIn cellular systems, Fractional Frequency Reuse (FFR)
partitions each cell into two regions; inner region and outer
region and allocates different frequency band to each region.
Since the users at the inner region are less exposed to inter-cell
interference, the frequency resources in each inner region can be
universally used. Based on this frequency band allocation, FFR
may reduce channel interference and offer large system capacity.
This paper proposes a mechanism that selects the optimal FFR
scheme based on the user throughput and user satisfaction. In
detail, the mechanism selects the optimal size of the inner and
outer region for each cell as well as the optimal frequency
allocation between these regions that either maximizes the mean
user throughput or the user satisfaction. The mechanism is
evaluated through several simulation scenarios.10aFFR10aLTE1 aBouras, Christos1 aPapazois, Andreas1 aKokkinos, Vasileios1 aTseliou, Georgia1 aBilios, Dimitrios  uhttp://telematics.upatras.gr/telematics/publications/optimization-fractional-frequency-reuse-long-term-evolution-networks?language=en01289nas a2200205   4500008004100000245007100041210006900112260002000181300001200201520061000213100002100823700001300844700002200857700001300879700001600892700001300908700002100921700001200942856012900954       2012                        eng d00aPeer-to-peer live streaming for massively multiplayer online games0 aPeertopeer live streaming for massively multiplayer online games  c3 - 5 September  a67 - 683 aOne of the most attractive features of Massively Multiplayer Online Games (MMOGs) is the possibility for users to interact with a large number of other users in a variety of collaborative and competitive situations. Gamers within an MMOG typically become members of active communities with mutual interests, shared adventures, and common objectives. This demonstration presents a peer-to-peer live video system that enables MMOG players to stream screen-captured video of their game. Players can use the system to show their skills, share experience with friends, or coordinate missions in strategy games.1 aBouras, Christos1 aShani, A1 aPapazois, Andreas1 aAhmad, S1 aHamzaoui, R1 aSimon, G1 aBuyukkaya, Elyia1 aZhou, F  uhttp://telematics.upatras.gr/telematics/publications/peer-peer-live-streaming-massively-multiplayer-online-games?language=en02232nas a2200133   4500008004100000245008300041210006900124300001400193520168700207100002101894700002201915700002001937856014101957       2012                        eng d00aPerformance Evaluation of Ad Hoc Routing Protocols for Military Communications0 aPerformance Evaluation of Ad Hoc Routing Protocols for Military   a216 - 2343 aMobile Ad hoc networks (MANETs) are of much interest to both the research community and the military because of the potential to establish a communication network in any situation that involves emergencies. Examples are search-and-rescue operations, military deployment in hostile environment, and several types of police operations.
One critical open issue is how to route messages considering the characteristics of these networks. The nodes act as routers in an environment without a fixed infrastructure, the nodes are mobile, the wireless medium has its own limitations compared to wired networks, and existing routing protocols cannot be employed at least without modifications.
Over the last few years, a number of routing protocols have been proposed and enhanced to address the issue of routing in MANETs. It is not clear how those different protocols perform under different environments. One protocol may be the best in one network configuration but the worst in another. This article provides an analysis and performance evaluation of those protocols that may be suitable for military communications. The evaluation is conducted in two phases. In the first phase, we compare the protocols based on qualitative metrics to locate those that may be fit our evaluation criteria. In the second phase, we evaluate the selected protocols from the first phase based on quantitative metrics in a mobility scenario that reflects tactical military movements. The results disclose that there is no routing protocol in the current stage without modifications that can provide efficient routing to any size of network, regardless the number of nodes and the network load and mobility.1 aBouras, Christos1 aGkamas, Apostolos1 aKioumourtzis, G  uhttp://telematics.upatras.gr/telematics/publications/performance-evaluation-ad-hoc-routing-protocols-military-communications?language=en01946nas a2200181   4500008004100000245005800041210005800099300001200157490000700169520136300176653000801539653001001547100002101557700002201578700002401600700002401624856011601648       2012                        eng d00aPerformance Evaluation of LTE for MBSFN Transmissions0 aPerformance Evaluation of LTE for MBSFN Transmissions  a227-2400 v183 a<p>Long Term Evolution (LTE) is the most promised latest step towards the 4th generation (4G) of radio technologies designed to increase the capacity and speed of mobile communications with main target the support of the so-called “Mobile Broadband”. To support Multimedia Broadcast/Multicast Services (MBMS), LTE offers the possibility to transmit Multimedia Broadcast multicast service over a Single Frequency Network (MBSFN), where a time-synchronized common waveform is transmitted from multiple cells for a given duration. In this manuscript we analytically present the MBSFN delivery method and evaluate its performance. The critical parameters of primary interest for the evaluation of the scheme are the packet delivery cost and its scalability. To this direction, a telecommunication cost analysis of the MBMS service is presented based on the transmission cost over the air interface, as well as the costs of all interfaces and nodes of the MBSFN architecture. Based on this cost analysis we determine the ideal number of cells that should participate in the MBSFN transmission in order to improve the overall MBSFN performance. Since the performance of the MBSFN scheme mainly depends on the configuration of the LTE network that is under investigation, we consider different network topologies, MBSFN deployments and user distributions.</p>
10aLTE10aMBSFN1 aBouras, Christos1 aAlexiou, Antonios1 aKokkinos, Vasileios1 aTsichritzis, George  uhttp://telematics.upatras.gr/telematics/publications/performance-evaluation-lte-mbsfn-transmissions?language=en02146nas a2200133   4500008004100000245008600041210006900127300001200196520158600208100002101794700002701815700002501842856014501867       2012                        eng d00aPerformance improvement of Distributed Virtual Environments by exploiting objects0 aPerformance improvement of Distributed Virtual Environments by e  a187-2033 aDistributed virtual environments need to address
issues related to the control of network traffic, resource
management, and scalability. Given the distributed nature
of these environments, the main problems they need to
overcome are the efficient distribution of workload among
the servers and the minimization of the communication
cost. In this direction, a lot of work has been done and
numerous relevant techniques and algorithms have been
proposed. The majority of these approaches mainly focus
on user entities and their interactions. However, most of
actual DVE systems include additional and non-dynamic
elements, denoted as objects, whose presence can affect
users? behavior. This paper introduces virtual objects?
attributes and proposes two approaches that exploit these
attributes in order to handle workload assignment and
communication cost in DVE systems. Both approaches
take into account scenario-specific aspects of DVE systems,
such as the impact that entities? attributes have on
each other and the way this impact can affect the system?s
state. These scenario-specific aspects are then combined
with quantitative factors of the system, such as workload,
communication cost, and utilization. The experiments
conducted in order to validate the behavior of the proposed
approach show that the incorporation of object?s presence
can improve the DVE system?s performance. More specifically,
objects? presence and their attributes can assist in
the significant reduction in the communication cost along
with effective workload distribution among the system?s
servers.1 aBouras, Christos1 aTsiatsos, Thrasivoulos1 aGiannaka, Eleftheria  uhttp://telematics.upatras.gr/telematics/publications/performance-improvement-distributed-virtual-environments-exploiting-objects?language=en01756nas a2200193   4500008004100000245007200041210006900113260002000182300001200202520109300214653000801307653000801315100002101323700002201344700002401366700002101390700002201411856012901433       2012                        eng d00aA Performance Study of Fractional Frequency Reuse in OFDMA Networks0 aPerformance Study of Fractional Frequency Reuse in OFDMA Network  c19-21 September  a38 - 433 a<p>Long Term Evolution (LTE) technology is considered as the most possible candidate for next generation mobile communications. LTE networks offer high capacity and are specified and designed to accommodate small, high performance, power-efficient end-user devices. One limiting factor that influences LTE performance is the interference from neighbor cells, the so called Inter-Cell Interference (ICI). Fractional Frequency Reuse (FFR) has been proposed as a technique to overcome this problem, since it can efficiently utilize the available frequency spectrum. This paper analyzes the FFR scheme and proposes a dynamic FFR mechanism that selects the optimal frequency allocation based on the cell total throughput and user satisfaction. In detail, the mechanism divides the cell into two regions (inner and outer) and selects the optimal size as well as the optimal frequency allocation between these regions with main target to maximize the overall throughput and user satisfaction. The mechanism is evaluated through several simulation scenariosthat incorporate users? mobility.</p>
10aFFR10aLTE1 aBouras, Christos1 aPapazois, Andreas1 aKokkinos, Vasileios1 aTseliou, Georgia1 aBilios, Dimitrios  uhttp://telematics.upatras.gr/telematics/publications/performance-study-fractional-frequency-reuse-ofdma-networks?language=en01908nas a2200181   4500008004100000245009200041210006900133260001500202300001000217520120500227100002101432700002401453700002101477700002401498700002701522700002701549856015001576       2012                        eng d00aPolicy recommendations for free and open source software usage by public administrators0 aPolicy recommendations for free and open source software usage b  c21-23 July  a90-973 aFree and open source software, holding a strategic position in knowledge economy, reaffirms the critical role of governments and regional authorities in establishing strategies for integrating effective and sustainable Information Technology solutions in the public sector towards economic growth and social welfare. Moreover, public services, organisations and territorial administrations collectively represent a major software user with great impact on the software market. In this sense, software selection in the public sector is not a neutral process but highly political and strategic one; various collateral implications and policy aspects should be considered in order to reach the best possible decisions. Within this context, this paper provides policy recommendations on issues and challenges pertaining to the use of free and open source software by European public administrations. The recommended policy actions are mainly based on review of the current policy framework. Main goal of this paper is to contribute in providing policy orientations and proposed actions that can help governments, public administrations and European institutions fully harvest the benefits of open source.1 aBouras, Christos1 aKokkinos, Vasileios1 aTseliou, Georgia1 aFilopoulos, Anestis1 aMichalopoulos, Sotiris1 aPapadopoulos, Dimitris  uhttp://telematics.upatras.gr/telematics/publications/policy-recommendations-free-and-open-source-software-usage-public-administrators?language=en01531nas a2200169   4500008004100000245006500041210006300106260001900169520092900188653001401117653001801131100002101149700002201170700002401192700002001216856012501236       2012                        eng d00aPower Management over Co-channel Femtocells in LTE-A Systems0 aPower Management over Cochannel Femtocells in LTEA Systems  c21-23 November3 aThe use of femtocells has been an attractive solution since it achieves better coverage and capacity and low cost for deployment and maintenance. However, their performance can be compromised by the cross-tier interference with existing macrocell infrastructure or between adjacent femtocells, especially in the case of co-channel deployment. One way to address this, is adjusting the transmit power of every femto base station with respect for overall performance. To this direction, we have implemented a framework that simulates femtocell overlays over LTE-Advanced (LTE-A) macrocellular systems. The framework allows power management over user-defined femtocell deployment, deciding their power levels according to three different power schemes. The resulting throughput is presented for every point of the macrocell in a user-friendly GUI. In this paper, we present the design of this framework and discuss the results.10aFemtocell10aPower Control1 aBouras, Christos1 aPapazois, Andreas1 aKokkinos, Vasileios1 aDiles, Georgios  uhttp://telematics.upatras.gr/telematics/publications/power-management-over-co-channel-femtocells-lte-systems?language=en01569nas a2200157   4500008004100000245006700041210006700108260001500175300001000190520099900200100002101199700002301220700002201243700001701265856012901282       2012                        eng d00aProviding Community and Collaboration Services to MMOG Players0 aProviding Community and Collaboration Services to MMOG Players  c18-20 July  a49-533 aMost of Massively Multiplayer Online Games (MMOGs) aim to support and improve the community activities among
their members. The Community Network Game (CNG) project has focused on services supporting players during their
in-game community and collaboration activities. The tools we offer use an innovative technology, namely the In-game
Graphical Insertion Technology (IGIT), which permits the addition of web-based applications without having to modify
the game code. These tools follow a design adapted to the needs of MMOG players. They are provided by the so-called
CNG Server and have been implemented based on recent advances in Web 2.0 technology. The in-game collaboration
activities provided by the underlying framework are also enhanced using Peer-to-Peer (P2P) technology for the
distribution of user-originated live video. In this paper, we concentrate our focus on the architecture of the server as well
as on the design and implementation of the community and collaboration tools.1 aBouras, Christos1 aKapoulas, Vaggelis1 aPapazois, Andreas1 aAdam, George  uhttp://telematics.upatras.gr/telematics/publications/providing-community-and-collaboration-services-mmog-players?language=en01745nas a2200169   4500008004100000245006200041210006200103260001700165300001100182520114500193100002101338700001901359700001701378700002101395700003601416856012301452       2012                        eng d00aSecurity Aspects for Large Scale Distributed Environments0 aSecurity Aspects for Large Scale Distributed Environments  c19-24 August  a7 - 133 aHeterogeneous Networks) is a tool under active development that supports a Bandwidth on Demand (BoD) service, intended to operate in a multi-domain environment using heterogeneous transmission technologies. The AutoBAHN system aims at providing a guaranteed capacity, connection-oriented service between two end points. Due to the level of access that the tool has to critical parts of the network, the importance of a trustworthy Authentication and Authorization Infrastructure (AAI) cannot be overestimated. This paper highlights the design and implementation for the Authentication and Authorization Infrastructure which is part of the AutoBAHN service and the decisions taken. The AAI is a service dedicated to enforce system security and to prevent unauthorized access and usage of resources. The BoD service modules may interact with AAI multiple times during a single request execution. After the initial authentication and authorisation check, the BoD system will apply additional, specific to BoD, rules and policies to the request. In addition, this paper presents the basic security aspects and components of the AutoBAHN system.1 aBouras, Christos1 aStamos, Kostas1 aAdam, George1 aZaoudis, Giannis1 aKalligeros, Ioannis, - Christos  uhttp://telematics.upatras.gr/telematics/publications/security-aspects-large-scale-distributed-environments?language=en01801nas a2200145   4500008004100000245009200041210006900133260001600202300001200218520120800230100002101438700002401459700002101483856015101504       2012                        eng d00aSelecting between open source and proprietary software: The public administrators' case0 aSelecting between open source and proprietary software The publi  c10-13 March  a185-1923 aThe necessity for the public sector to change over to communicating digitally is imminent. From the economic
perspective, the changeover poses great challenges, as huge investments will have to be made in Information Technology
(IT) in the public sector. It is therefore natural, in connection with these investments, for detailed assessment to be made
of what forms of technology it is anticipated to be used, and who controls the development and ownership of this
technology. This work constitutes a review of literature on pre-existing comparative studies regarding the technical,
social, economic and organizational factors on Free Open Source Software (FOSS) usage. Furthermore, this work
includes guidelines that Public Administrations (PAs) should follow for the selection between open source and
proprietary software. Main goal of this paper is to add to knowledge resources that can help public stakeholders
understand the technical / social / economic / organizational environment and reach informed decisions when selecting
the appropriate software. The paper can also be useful for FOSS developers, users and communities who are either
directly or indirectly involved in the software market.1 aBouras, Christos1 aKokkinos, Vasileios1 aTseliou, Georgia  uhttp://telematics.upatras.gr/telematics/publications/selecting-between-open-source-and-proprietary-software-public-administrators-case?language=en01675nas a2200181   4500008004100000245006900041210006600110260002000176300001200196520104600208653001401254653000801268100002101276700002201297700002401319700002901343856012101372       2012                        eng d00aA Simulation Framework for LTE-A Systems with Femtocell Overlays0 aSimulation Framework for LTEA Systems with Femtocell Overlays  c21 - 25 October  a85 - 903 aThe use of femtocells is an efficient way to improve cover- age and quality of service while on the other side the deployment cost for the service provider is kept in extremely low level. Long Term Evolution Advanced (LTE-A) systems with femtocell overlays aim to provide better indoor voice and data coverage and to increase network capacity. One of the major technical challenges that femtocell networks are facing nowadays, is the cross-tier interference, i.e., the interference between the femto base stations and the macrocell infrastructure. To this direction, we have designed and implemented a framework that simulates femtocell overlays integrated over LTE-A macrocellular systems. This framework focuses on the impact of cross-tier interference and furthermore is able to estimate the throughput at every point of integrated femtocell/macrocell LTE-A networks. In this paper, we present the design and implementation of this simulation framework and we provide significant experimental results obtained with the aid of this system.10aFemtocell10aLTE1 aBouras, Christos1 aPapazois, Andreas1 aKokkinos, Vasileios1 aKontodimas, Konstantinos  uhttp://telematics.upatras.gr/telematics/publications/simulation-framework-lte-systems-femtocell-overlays?language=en01722nas a2200133   4500008004100000245006400041210006200105300000900167520121600176100002101392700002701413700002501440856012301465       2012                        eng d00aA Simulation Modeling Tool for Dynamic Virtual Environments0 aSimulation Modeling Tool for Dynamic Virtual Environments  a1-163 a<p>Distributed Virtual Environments simulate the behaviour and activities of a great number of users 22 interacting in a virtual world over a wide area network. The size of the virtual worlds and the 23 tremendous number of users that these environments are called to support require additional 24 bandwidth and computational resources. For supporting large-scale Distributed Virtual 25 Environments, extended infrastructure is needed in terms of both hardware and software. However, 26 both researchers and application designers do not always have access to such an extended 27 infrastructure and the assessment and evaluation of developed performance improvement techniques 28 becomes extremely difficult. To address this issue, this paper presents a simulation modelling tool, 29 called STEADiVE for networked servers Distributed Virtual Environments that could be used by 30 designers for evaluating the performance of their approaches under different scenarios and system 31 settings. The validation of the simulation modelling tool has showed that it achieves high accuracy in 32 representing a real DVE system. STEADiVE comes to fill in the gap in the area of simulation tools for 33 these systems.</p>
1 aBouras, Christos1 aTsiatsos, Thrasivoulos1 aGiannaka, Eleftheria  uhttp://telematics.upatras.gr/telematics/publications/simulation-modeling-tool-dynamic-virtual-environments?language=en01581nas a2200145   4500008004100000245006300041210006200104300001400166490000700180520106300187100002101250700002201271700002001293856012201313       2012                        eng d00aTFMCC vs ASMP: Lessons learned from performance evaluation0 aTFMCC vs ASMP Lessons learned from performance evaluation  a349 - 3720 v223 a<p>In this article we present a simulation-based comparison of one of the best-known multicast congestion control schemes—TCP-friendly Multicast Congestion Control (TFMCC)—against our proposed Adaptive Smooth Multicast Protocol (ASMP). ASMP consists of a single-rate multicast congestion control mechanism which takes advantage of the RTCP Sender (SR) and Receiver Reports (RR) in order to adjust the sender?s transmission rate in respect of the network conditions. The innovation in ASMP lays in the ?smooth? transmission rate, which is TCP-friendly and prevents oscillations. We use an integrated simulation environment named Multi- Evalvid-RA for the evaluation of the two congestion control schemes. Multi-Evalvid-RA provides all the necessary tools to perform simulation studies and assess video quality by using both network-centric metrics along with video quality measurements. Performance evaluation results show that ASMP is a very efficient solution for rate-adaptive multimedia applications and a serious competitor to well-known TFMCC.</p>
1 aBouras, Christos1 aGkamas, Apostolos1 aKioumourtzis, G  uhttp://telematics.upatras.gr/telematics/publications/tfmcc-vs-asmp-lessons-learned-performance-evaluation?language=en01869nas a2200157   4500008004100000245006700041210006600108260001600174300001000190520130000200100002101500700001901521700002001540700002601560856012501586       2012                        eng d00aTRAFIL: A tool for enhancing simulation TRAce FILes processing0 aTRAFIL A tool for enhancing simulation TRAce FILes processing  c24 -27 July  a61-643 aNS-2 (Network Simulator) is one of the most popular discrete event simulators used for network simulation. Trace files produced by NS-2 provide very useful information for post simulation analysis. This paper presents the architecture and development considerations for a TRAce FILe analysis tool, which intends to simplify the management of trace files generated during network simulations. The tool is focused on NS-2 trace files, but can be extended to handle a variety of simulation trace files formats. Its purpose is to make the execution of a large number of network simulations faster, and the extraction of results from a large amount of data more flexible and productive. TRAFIL introduces a novel way of interpreting, parsing, reading and eventually utilizing NS-2 trace files by using "metafiles" and "sub-metafiles" during the trace file recognition and process procedures, making the overall operations more abstract, substantially efficient and faster than alternative approaches. Furthermore, TRAFIL facilitates the whole trace file analysis task, offering the opportunity to store each trace file as well as every measurement produced for each trace file. The tool aims to aid the analysis of simulation results offering features that other tools in this area have been missing.1 aBouras, Christos1 aStamos, Kostas1 aKioumourtzis, G1 aCharalambides, Savvas  uhttp://telematics.upatras.gr/telematics/publications/trafil-tool-enhancing-simulation-trace-files-processing?language=en01338nas a2200133   4500008004100000245004000041210003800081260002000119300001400139520090900153100002101062700002201083856009901105       2012                        eng d00aUser Personalization via W - kmeans0 aUser Personalization via W kmeans  c10-12 September  a555 - 5643 aWith the rapid explosion of online news articles, predicting userbrowsing
behavior using collaborative filtering techniques has gained much attention
in the web personalization area. However, common collaborative filtering
techniques suffer from low accuracy and performance. This research proposes
a new personalized recommendation approach that integrates user and
text clustering based on our developed algorithm, W-kmeans, with other information
retrieval techniques, like text categorization and summarization in order
to provide users with the articles that match their profiles. Our system can easily
adapt over time to divertive user preferences. Furthermore, experimental results
show that by aggregating multiple other information retrieval techniques
like categorization, summarization and clustering, our recommender generates
results that outperform the cases when clustering is not applied.1 aBouras, Christos1 aTsogkas, Vassilis  uhttp://telematics.upatras.gr/telematics/publications/user-personalization-w-kmeans?language=en01586nas a2200133   4500008004100000245010900041210006900150300001500219520099900234100002101233700002201254700002001276856015601296       2011                        eng d00aAdaptive Smooth Simulcast Protocol (ASSP) for Video Applications: Description and Performance Evaluation0 aAdaptive Smooth Simulcast Protocol ASSP for Video Applications D  a 143 - 1773 aIn this paper, we present Adaptive Smooth Simulcast Protocol (ASSP)
for simulcast transmission of multimedia data over best-effort networks. ASSP is a
new multiple-rate protocol that implements a single rate TCP-friendly protocol as
the underlying congestion control mechanism for each simulcast stream. The key
attributes of ASSP are: (a) TCP-friendly behavior, (b) adaptive per-stream trans-
mission rates, (c) adaptive scalability to large sets of receivers and (d) smooth
transmission rates that are suitable for multimedia applications. We evaluate the
performance of ASSP under an integrated simulation environment which combines
the measurements of both network and video performance metrics. We also com-
pare ASSP against other proposed solutions and the results demonstrate that the
performance of ASSP is significantly better than the tested solutions. Finally, ASSP
is a practical solution with very low implementation complexity for video trans-
mission over best-effort networks.
1 aBouras, Christos1 aGkamas, Apostolos1 aKioumourtzis, G  uhttp://telematics.upatras.gr/telematics/publications/adaptive-smooth-simulcast-protocol-assp-video-applications-description-and-performance?language=en01989nas a2200193   4500008004100000245005100041210005000092260001800142300001200160520140000172653000801572653000801580653000901588100002101597700002201618700002401640700001901664856011201683       2011                        eng d00aAL-FEC for Streaming Services over LTE Systems0 aALFEC for Streaming Services over LTE Systems  cOctober 3 - 6  a284-2883 a<p>The Third Generation Partnership Project (3GPP), recently introduced the evolution of the third generation (3G) cellular networks, the Long Term Evolution (LTE) telecommunication system. A key aspect of LTE specifications is the enhancement of Multimedia Broadcast/Multicast Services (MBMS), where the same content is transmitted to multiple users located in a specific service area. A significant point of the demanding multimedia services is the enhancement of the robustness against packet losses. To this direction, in order to support the efficient point-to-multipoint download and streaming delivery, 3GPP has included an Application Layer Forward Error Correction (AL-FEC) scheme in the MBMS standard. The standardized AL-FEC scheme is based on the systematic, fountain Raptor codes. In this paper, we investigate the application of AL-FEC over the MBMS streaming delivery method. We consider the benefits of AL-FEC for a seamless multimedia streaming transmission to multiple mobile users and we examine how the amount of FEC overhead can be adjusted under different packet loss conditions. For this purpose, we present a variety of realistic simulation scenarios for the performance evaluation of FEC considering several network and FEC encoding parameters. Furthermore, we provide suggestions in order to achieve efficient use of Raptor codes over LTE MBMS streaming services.</p>
10aFEC10aLTE10aMBMS1 aBouras, Christos1 aPapazois, Andreas1 aKokkinos, Vasileios1 aKanakis, Nikos  uhttp://telematics.upatras.gr/telematics/publications/al-fec-streaming-services-over-lte-systems?language=en00539nas a2200133   4500008004100000245007600041210006900117260001500186300001300201100002100214700002300235700001800258856012900276       2011                        eng d00aBroadband Infrastructures as a Common and the Role of Local Governments0 aBroadband Infrastructures as a Common and the Role of Local Gove  bIGI Global  a 298-3191 aBouras, Christos1 aKapoulas, Vaggelis1 aGanos, Petros  uhttp://telematics.upatras.gr/telematics/publications/broadband-infrastructures-common-and-role-local-governments?language=en01238nas a2200133   4500008004100000245004900041210004700090260002900137300001300166520077000179100002100949700002200970856011200992       2011                        eng d00aClustering user preferences using W - kmeans0 aClustering user preferences using W kmeans  cNovember 28 - December 1  a 75 - 823 aAbstract— Although commonly only document clustering is
suggested by Web mining techniques for recommendation
systems, one of the various tasks of personalized
recommendation is categorization of Web users. In this paper,
a method for clustering navigation patterns of Web users is
proposed. We adapt the WordNet-enabled W-kmeans
algorithm, an enhancement of standard k-means algorithm
which uses the external knowledge from WordNet hypernyms
and that has been previously used for document clustering, to
user profile clustering by analyzing the users? historical data.
We also investigate the effects this approach has on the
recommendation engine by evaluating the overall performance
it has in terms of precision – recall on our online
recommendation system.1 aBouras, Christos1 aTsogkas, Vassilis  uhttp://telematics.upatras.gr/telematics/publications/clustering-user-preferences-using-w-kmeans?language=en01798nas a2200193   4500008004100000245009000041210006900131300001300200520110000213653000801313653000901321653001001330100002101340700002201361700002201383700002401405700002701429856014801456       2011                        eng d00aCombining MBSFN and PTM Transmissions Schemes for Resource Efficiency in LTE Networks0 aCombining MBSFN and PTM Transmissions Schemes for Resource Effic  a 56 - 673 aLong Term Evolution (LTE) systems allow the transmission of rich
multimedia services by utilizing the Multimedia Broadcast/Multicast Service
(MBMS) over a Single Frequency Network (MBSFN). During MBSFN
transmission a time-synchronized common waveform is transmitted from
multiple cells. The 3rd Generation Partnership Project (3GPP) has specified that
Point-to-Multipoint (PTM) transmission can be used in combination with
MBSFN to provide MBMS-based services. In this paper we evaluate the
combined transmission scheme in terms of Resource Efficiency (RE). The
evaluation is performed through simulation experiments for various user
distributions and LTE network configurations. The experiments are conducted
with the aid of a proposed algorithm, which estimates the Spectral Efficiency
(SE) of each cell and the RE of the network, and is also able to formulate the
optimal network deployment that maximizes the network?s RE. For each of the
examined scenarios, we present the most efficient solution (in terms of RE)
selected by our algorithm and we compare it with other transmission schemes.10aLTE10aMBMS10aMBSFN1 aBouras, Christos1 aAlexiou, Antonios1 aPapazois, Andreas1 aKokkinos, Vasileios1 aAsimakis, Konstantinos  uhttp://telematics.upatras.gr/telematics/publications/combining-mbsfn-and-ptm-transmissions-schemes-resource-efficiency-lte-networks?language=en01737nas a2200205   4500008004100000245005900041210005900100300001400159520108900173100002101262700001301283700002201296700002401318700001301342700001601355700001601371700001301387700001101400856012001411       2011                        eng d00aCommunity Tools for Massively Multiplayer Online Games0 aCommunity Tools for Massively Multiplayer Online Games  a313 - 3233 aOne of the most attractive features of Massively
Multiplayer Online Games (MMOGs) is the possibility for users
to interact with a large number of other users in a variety
of collaborative and competitive situations. Gamers within
an MMOG typically become members of active communities
with mutual interests, shared adventures, and common objectives.
We present the EU funded Community Network Game
(CNG) project. The CNG project provides tools to enhance
collaborative activities between online gamers and offers new
tools for the generation, distribution and insertion of usergenerated
content in MMOGs. CNG allows the addition of new
engaging community services without changing the game code
and without adding new processing or network loads to the
MMOG central servers. The user-generated content considered
by the CNG project includes 3D objects and graphics, as well
as screen-captured live video of the game, which is shared using
peer-to-peer technology. We survey the state of the art in all
areas related to the project and present its concept, objectives,
and innovations.1 aBouras, Christos1 aShani, A1 aPapazois, Andreas1 aTsichritzis, George1 aAhmad, S1 aHamzaoui, R1 aPerelman, E1 aSimon, G1 aLiu, J  uhttp://telematics.upatras.gr/telematics/publications/community-tools-massively-multiplayer-online-games?language=en01739nas a2200169   4500008004100000245008700041210006900128260003400197520106500231100002101296700002301317700002201340700002001362700001701382700002201399856014801421       2011                        eng d00aCross-Layer Mechanism for Efficient Video Transmission over Mobile Ad Hoc Networks0 aCrossLayer Mechanism for Efficient Video Transmission over Mobil  cNovember 30 &#8211; December 3 aAbstract- Mobile ad hoc networks (MANETs) are becoming
more essential to wireless communications due to growing
popularity of mobile devices. However, MANETs do not seem to
effectively support multimedia applications and especially video
transmission. This paper presents a cross-layer mechanism for
efficient video transmission over this type of networks. The
proposed mechanism consists of a priority-scheduling algorithm,
at the network layer, and the use of the IEEE 802.11e standard at
the MAC layer. The priority-scheduling algorithm takes into
account the frame type of the MPEG-4 video file in order to
provide different priorities to the most important video packets.
At the MAC layer, the IEEE 802.11e protocol assigns the highest
priority to video applications to reduce delay and packets losses
due to other competing traffic. This design is easily implemented
in any ad hoc wireless network as an extension on the AODV
MANET routing protocol. Simulation results conducted with the
network simulator ns-2 show the advantages of the proposed
design.1 aBouras, Christos1 aKapoulas, Vaggelis1 aGkamas, Apostolos1 aKioumourtzis, G1 aAdam, George1 aTavoularis, Nikos  uhttp://telematics.upatras.gr/telematics/publications/cross-layer-mechanism-efficient-video-transmission-over-mobile-ad-hoc-networks?language=en01638nas a2200145   4500008004100000245004100041210003900082300001300121490000700134520117800141100002101319700002701340700002501367856010001392       2011                        eng d00aA Dynamic Management Scheme for DVEs0 aDynamic Management Scheme for DVEs  a89 - 1010 v343 a<p>Advancesincomputertechnologyandnetworkinginfrastructuresincombinationwithadvanced applicationsandservices,haveexpandedtheadoptionofdistributedvirtualenvironmentsand promotedtheiruseinawiderangeofareas,suchaslearningandtraining,collaborativework,military applicationsandmultiplayeronlinegames.ThecharacteristicsandrequirementsofsuchDVEsdiffer significantlygiventhediverseobjectives,scopeandcontextthateachvirtualworldaimsatsupporting. However,onecommoncharacteristicofDVEsistheirdynamicstatewithusersenteringandleavingthe systemrandomly,resultinginchangesoftherequirementsfortheDVEsystem.Thesechangesrequire effectiveloaddistributionandmanagementofthecommunicationcostsothatconsistencyisalways maintained.ThispaperpresentsadynamicmanagementapproachforDVEsdrivenbythediversityof differentapplications?characteristicsandrequirements.Thisapproachexploitsthedynamicnatureof these systemsforselectingandassigning,onanon-demandbasis,theresourcesnecessaryforthe efficientoperationofthesystem.Theexperimentsconductedtovalidatethebehavioroftheapproach illustratethatitcansignificantlyminimizecommunicationcostamongthesystemserverstogether with effectiveworkloaddistribution.</p>
1 aBouras, Christos1 aTsiatsos, Thrasivoulos1 aGiannaka, Eleftheria  uhttp://telematics.upatras.gr/telematics/publications/dynamic-management-scheme-dves?language=en01242nas a2200193   4500008004100000245005600041210005500097300001300152520062500165100002100790700002300811700002200834700001300856700001600869700001300885700001300898700002100911856011600932       2011                        eng d00aEvaluating P2P Live Streaming Systems: the CNG Case0 aEvaluating P2P Live Streaming Systems the CNG Case  a 126-1293 aMany peer-to-peer (P2P) systems have been proposed
for the provision of scalable live video streaming services
over the Internet. While the literature contains surveys of
the architectures of these systems, there is a lack of work
on methodologies for their evaluation. We identify the main
issues in the evaluation of P2P live streaming systems and
use the Community Network Game (CNG) project as an ex-
ample to illustrate them. The evaluation of the P2P sys-
tem consists of two phases: a laboratory one using the ns-2
network simulator and an online field test with Massively
Multiplayer Online Games (MMOG) players.1 aBouras, Christos1 aKapoulas, Vaggelis1 aPapazois, Andreas1 aAhmad, S1 aHamzaoui, R1 aSahni, A1 aSimon, G1 aBuyukkaya, Elyia  uhttp://telematics.upatras.gr/telematics/publications/evaluating-p2p-live-streaming-systems-cng-case?language=en01788nas a2200133   4500008004100000245006500041210006500106300001300171520127700184100002101461700002201482700002401504856012601528       2011                        eng d00aExploiting MIMO Technology for Optimal MBMS Power Allocation0 aExploiting MIMO Technology for Optimal MBMS Power Allocation  a 447-4643 aIn mobile networks, the provision of rich multimedia services, such as Mobile TV, is considered of key importance. To this end, Multimedia Broadcast/Multicast Service (MBMS) - that was introduced in the Release 6 of Universal Mobile Telecommunication System (UMTS) - is envisaged to play an instrumental role in the proliferation of mobile market. The reason behind the design of MBMS was the need to provide multiple users with the same data at the same time in 3GPP (3rd Generation Partnership Project) cellular networks. Still, MBMS performance is limited by the base stations? transmission power. As an aftermath, efficient power allocation techniques should be implemented so as to ensure the mass provision of multimedia applications to mobile users. This paper proposes a novel mechanism for efficient radio bearer selection during MBMS transmissions. The proposed mechanism is based on the concept of transport channels combination in any cell of the network. Furthermore, the mechanism exploits the performance enhancements emerged from Multiple Input Multiple Output (MIMO) antennas and manages to efficiently deliver multiple MBMS sessions. The proposed mechanism is thoroughly evaluated and compared with the radio bearer selection mechanisms proposed by 3GPP.1 aBouras, Christos1 aAlexiou, Antonios1 aKokkinos, Vasileios  uhttp://telematics.upatras.gr/telematics/publications/exploiting-mimo-technology-optimal-mbms-power-allocation?language=en00647nas a2200181   4500008004100000245007900041210006900120260001100189300001500200653000800215653000800223653000900231100002100240700002200261700002400283700002100307856013700328       2011                        eng d00aForward Error Correction for Reliable e-MBMS Transmissions in LTE Networks0 aForward Error Correction for Reliable eMBMS Transmissions in LTE  bInTech  a 353 - 37410aFEC10aLTE10aMBMS1 aBouras, Christos1 aPapazois, Andreas1 aKokkinos, Vasileios1 aTseliou, Georgia  uhttp://telematics.upatras.gr/telematics/publications/forward-error-correction-reliable-e-mbms-transmissions-lte-networks?language=en01480nas a2200145   4500008004100000245006800041210006600109260002300175520093400198100002101132700001901153700002101172700002001193856012101213       2011                        eng d00aImplementation of leaky bucket module for simulations in NS - 30 aImplementation of leaky bucket module for simulations in NS 3  c15 - 17 September 3 aSimulation has always been a valuable tool for experimentation and validation of models, architectures and mechanisms in the field of networking. In the case of the DiffServ framework, simulation is even more valuable, due to the fact that an analytical approach of mechanisms and services is infeasible because of the aggregation and multiplexing of flows. In this paper we present the implementation of a module for the extensible network simulator ns-3 in order to conduct experiments simulating a leaky bucket shaping mechanism for incoming flows, which is missing from ns-3. We describe the way the module has been implemented within the framework of the simulator and we discuss the merits of using a leaky bucket mechanism for shaping traffic. We also use the newly developed module in order to conduct experiments, verify its proper behavior and demonstrate its usefulness in studying the leaky bucket through simulation.1 aBouras, Christos1 aStamos, Kostas1 aZaoudis, Giannis1 aBaltzis, Petros  uhttp://telematics.upatras.gr/telematics/publications/implementation-leaky-bucket-module-simulations-ns-3?language=en01717nas a2200145   4500008004100000245008700041210006900128260001500197300001300212520113700225100002101362700001901383700002201402856014701424       2011                        eng d00aAn Improved GMPLS Survivability Mechanism Using Link Delay - Constrained Algorithm0 aImproved GMPLS Survivability Mechanism Using Link Delay Constrai  cJuly 18-21  a 45 - 503 aIt is widely accepted that GMPLS (Generalized MPLS) will be a key technology in the evolution of the next generation of reliable Internet Protocol (IP) backbone networks. Conventional GMPLS-based optical-switching network fault recovery only provides resiliency in terms of path segment selection instead of constraint-based calculation. This can create severe impact on the protocol?s transport plane when a fault occurs to a link or path with many optical connections attached to it. This paper proposes the implementation of an improved GMPLS recovery algorithm based on the metric of optical link delay which is achieved through the pre or post selection of a safer and more stable protection path with fewer connections attached to it, and therefore with a lesser link delay metric compared to other possible paths. The improved recovery algorithm is evaluated using the network simulator ns-2 and more particularly a specialized simulator add-on for GMPLS, called ASONS (ASONS - An Automatically Switched Optical Network Simulator). The results indicate improved resiliency, increased fault avoidance, and reduced packet loss.1 aBouras, Christos1 aStamos, Kostas1 aBikos, Anastasios  uhttp://telematics.upatras.gr/telematics/publications/improved-gmpls-survivability-mechanism-using-link-delay-constrained-algorithm?language=en01680nas a2200181   4500008004100000245007300041210006900114260002600183520101400209653001401223653000801237100002101245700002201266700002201288700002401310700002901334856013501363       2011                        eng d00aInterference Behavior of Integrated Femto and Macrocell Environments0 aInterference Behavior of Integrated Femto and Macrocell Environm  cOctober 10 &#8211; 123 aAbstract—Femtocells are data access points installed by the
subscribers to provide better indoor voice and data coverage and
to increase system capacity. The integrated femtocell/macrocell
networks offer an efficient way to increase access capacity by
improving coverage and quality of service while on the other
side the deployment cost for the service provider is kept in
extremely low levels. One of the major technical challenges that
femtocell networks are facing is their interference behavior when
they are placed within macrocells. The study presented in this
paper focuses on the impact of integrating femtocells in macrocell
networks in terms of adjacent cell interference that the macrocell
environment adds to users served by a femto base station and
vice versa. To this direction, we have designed and implemented
a simulation testbed that estimates the cross-tier interference and
the throughput in every point of an integrated femtocell/macrocell
Long Term Evolution-Advanced (LTE-A) network.10aFemtocell10aLTE1 aBouras, Christos1 aAlexiou, Antonios1 aPapazois, Andreas1 aKokkinos, Vasileios1 aKontodimas, Konstantinos  uhttp://telematics.upatras.gr/telematics/publications/interference-behavior-integrated-femto-and-macrocell-environments?language=en00608nas a2200133   4500008004100000245010300041210006900144260001900213300001300232100002100245700002600266700002800292856015400320       2011                        eng d00aLearning from user's behavior - A technique for personalized news search supporting result cashing0 aLearning from users behavior A technique for personalized news s  biConcept Press  a 177-1961 aBouras, Christos1 aPoulopoulos, Vassilis1 aSilintziris, Panagiotis  uhttp://telematics.upatras.gr/telematics/publications/learning-users-behavior-technique-personalized-news-search-supporting-result-cashing?language=en01753nas a2200193   4500008004100000245007700041210006900118260001600187520108700203653000801290653000901298653001001307100002101317700002201338700002201360700002401382700002101406856013201427       2011                        eng d00aOptimizing the Combination of MBSFN and PTM Transmissions in LTE Systems0 aOptimizing the Combination of MBSFN and PTM Transmissions in LTE  cApril 13-153 aThe 3rd Generation Partnership Project (3GPP) has
introduced the evolved Multimedia Broadcast/Multicast Service
(e-MBMS) feature for cellular systems as an evolution to the
existing MBMS service. To support e-MBMS in Long Term
Evolution (LTE) systems, 3GPP recommends the use of Point-to-
Multipoint (PTM) transmissions and MBMS over a Single
Frequency Network (MBSFN). MBSFN is a new feature where a
time-synchronized common waveform is transmitted from
multiple cells. In this paper we investigate the provision of
MBMS service over a combination of MBSFN and PTM
transmission methods. A cost analysis of the MBMS service is
presented based on the transmission cost over all the interfaces
and nodes of the LTE architecture. We evaluate the performance
of this transmission scheme from telecommunication cost
perspective and we compare it with other transmission schemes.
The performance evaluation has been performed with the aid of a
new simulation tool that estimates the cost for the MBMS
provision under different network topologies, MBSFN
deployments and user distributions.10aLTE10aMBMS10aMBSFN1 aBouras, Christos1 aAlexiou, Antonios1 aPapazois, Andreas1 aKokkinos, Vasileios1 aTseliou, Georgia  uhttp://telematics.upatras.gr/telematics/publications/optimizing-combination-mbsfn-and-ptm-transmissions-lte-systems?language=en01877nas a2200169   4500008004100000245010300041210006900144260002600213520119000239100002101429700002301450700002201473700002001495700001701515700002201532856015301554       2011                        eng d00aPerformance Evaluation of Routing Protocols for multimedia transmission over Mobile Ad hoc Network0 aPerformance Evaluation of Routing Protocols for multimedia trans  cOctober 26 &#8211; 283 aAbstract— Mobile ad hoc networks (MANETs) are becoming
more essential to wireless communications due to growing
popularity of mobile devices. The integration of mobile ad hoc
devices inside vehicles has led to another type of networks, called
Vehicular Ad hoc Networks (VANETs) which are also becoming
important. These networks require specialized routing protocols
due to their ad hoc nature. The performance of these protocols
has been tested for the case of general traffic but not in respect
with to multimedia traffic and especially video transmission. In
this paper we conduct a number of simulations in order to
evaluate the performance of three of the most popular routing
protocols for MANETs and VANETs, namely AODV, DSR and
OLSR, for different number of simultaneous video transmissions.
We use the packet delivery ratio, the end-to-end delay, the packet
delay variation (jitter) and the routing overhead as evaluation
metrics. The results indicate that the DSR protocol outperforms
AODV and OLSR in terms of end-to-end delay and packet delay
variation and seems to be the most efficient routing protocol
when multimedia traffic and especially video traffic is
considered.1 aBouras, Christos1 aKapoulas, Vaggelis1 aGkamas, Apostolos1 aKioumourtzis, G1 aAdam, George1 aTavoularis, Nikos  uhttp://telematics.upatras.gr/telematics/publications/performance-evaluation-routing-protocols-multimedia-transmission-over-mobile-ad-hoc?language=en01345nas a2200181   4500008004100000245007600041210006900117300001400186490000700200520068400207100002100891700002300912700002200935700001900957700002900976700002101005856013701026       2011                        eng d00aPower Management Adaptation Techniques for Video transmission over TFRC0 aPower Management Adaptation Techniques for Video transmission ov  a 414 -4310 v253 a<p>In this paper, we describe power management adaptation techniques for wireless video transmission using the TFRC protocol that take into account feedback about the received video quality and try to intelligently adapt transmitting power accordingly. The purpose of the mechanisms is to utilize TFRC feedback and thus achieve a beneficial balance between the power consumption and the received video quality. There are 2 power adaptation mechanisms proposed, each one with its own advantages. They both offer significant improvements when used in terms of both power consumption and received video quality. We use simulation in order to compare and evaluate our approach.</p>
1 aBouras, Christos1 aKapoulas, Vaggelis1 aGkamas, Apostolos1 aStamos, Kostas1 aPapapanagiotou, Vassilis1 aZaoudis, Giannis  uhttp://telematics.upatras.gr/telematics/publications/power-management-adaptation-techniques-video-transmission-over-tfrc?language=en01168nas a2200157   4500008004100000245005800041210005800099300001500157520060800172100002100780700001900801700002100820700002400841700002600865856011900891       2011                        eng d00aPower management for SVC video over wireless networks0 aPower management for SVC video over wireless networks  a 270 - 2763 aThe main idea of this paper is to study how the
emerging H.264 SVC standard can be utilized for more
efficient power management in wireless video transmissions.
Our proposal uses a cross-layer approach which adapts the
power transmission level of the sender according to the SVC
information regarding the priority of the SVC NAL frame.
Our aim is to improve transmission statistics, and therefore
user experience, without unnecessary power consumption. We
use extensive experimentation on the ns2 network simulator,
which we have specifically modified for this purpose, in order
to verify this approach.1 aBouras, Christos1 aStamos, Kostas1 aZaoudis, Giannis1 aStroumpis, Stamatis1 aCharalambides, Savvas  uhttp://telematics.upatras.gr/telematics/publications/power-management-svc-video-over-wireless-networks?language=en01742nas a2200229   4500008004100000245005600041210005500097260002100152300001500173520103400188653000801222653000801230653000901238653001001247100002101257700002201278700002201300700002401322700002701346700002101373856011801394       2011                        eng d00aReliable Multicasting over LTE: A Performance Study0 aReliable Multicasting over LTE A Performance Study  cJune 28 - July 1  a 603 - 6083 aWith the booming of multimedia services, the 3rd
Generation Partnership Project (3GPP) has introduced the
evolved Multimedia Multicast/Broadcast Service (e-MBMS)
feature for LTE systems. The main objective of MBMS is to
introduce real broadcast distribution capabilities into cellular
systems. This purposed 3GPP to introduce the MBMS over a
Single Frequency Network (MBSFN) operation. In this work
we investigate the provision of MBMS service over a
combination of MBSFN and PTM transmission schemes. We
focus on the file repair procedure, because the distribution of
binary data via MBMS must result in 100% error-free
downloaded files. In order to achieve this goal, MBMS offers a
Forward Error Correction (FEC) mechanism. Our simulation
results show that there are some file repair schemes that
achieve better performance as far as different network
configurations are concerned. Furthermore, we compare all
the file recovery methods and evaluate them against various
network parameters in a realistic simulation environment.10aFEC10aLTE10aMBMS10aMBSFN1 aBouras, Christos1 aAlexiou, Antonios1 aPapazois, Andreas1 aKokkinos, Vasileios1 aAsimakis, Konstantinos1 aTseliou, Georgia  uhttp://telematics.upatras.gr/telematics/publications/reliable-multicasting-over-lte-performance-study?language=en01988nas a2200133   4500008004100000245006000041210005800101260001500159300001300174520150800187100002101695700001901716856011901735       2011                        eng d00aSecurity issues for multi - domain resource reservation0 aSecurity issues for multi domain resource reservation  bIGI Global  a 38 - 503 a<p>In this chapter, we deal with the issue of security regarding components that are responsible for provisioning multi-domain network services, either automatically or through some form of administrator interaction. It is evident that a malicious compromise of such a component would have far-reaching implications for the stability of the network. Furthermore, trust between cooperating domains is a delicate issue and each partner in the multi-domain federation has to have some guarantees that peers in the service are not going to be security compromised. We enumerate some of the related dangers and propose ways to limit the attack surface, reduce the intrusion possibilities, and guarantee the quick resolution of any successful violations. The issue of security is studied in two main parts: Inter-domain security, for the communication between domains and the successful negotiation of resource reservations and intra-domain security, for the internal communications within a domain for the initiation of a resource reservation and its actual realization in the network devices. Resource reservation is studied both on the level of IP services based on Differentiated Services architectures, and on the level of dynamic circuit reservation based on Layer 2 technologies. The chapter is completed with a case study on the authentication and authorization framework designed in the context of a pan-european network resource reservation service, in the Geant academic and research network.</p>
1 aBouras, Christos1 aStamos, Kostas  uhttp://telematics.upatras.gr/telematics/publications/security-issues-multi-domain-resource-reservation?language=en01548nas a2200181   4500008004100000245006100041210005900102300001500161520096400176653000801140653000901148653001801157653000901175100002101184700002201205700002201227856011701249       2011                        eng d00aA study of Forward Error Correction for Mobile Multicast0 astudy of Forward Error Correction for Mobile Multicast  a 607 - 6273 a<p>3GPP has standardized the use of forward error correction for the provision of reliable data transmission in the mobile multicast framework. This error control method inevitably adds a constant overhead in the transmitted data. However, it is so simple as to meet a prime objective for mobile multicast services; that is scalability to applications with thousands of receivers. In this paper we present a study on the impact of application layer forward error correction. We examine whether it is beneficial or not, how the optimal code dimension varies based on network conditions, which parameters affect the optimal code selection, and how they achieve this. Additionally, we focus on one of the most critical aspects in mobile multicast transmission which is power control. The evaluation is performed with the aid of a novel scheme that incorporates the properties of an evolved mobile network, as they are determined by the 3GPP specifications.</p>
10aFEC10aMBMS10aPower Control10aUMTS1 aBouras, Christos1 aAlexiou, Antonios1 aPapazois, Andreas  uhttp://telematics.upatras.gr/telematics/publications/study-forward-error-correction-mobile-multicast?language=en01363nas a2200157   4500008004100000245006800041210006400109260001500173300001500188520078700203100002100990700001901011700002901030700002101059856012501080       2011                        eng d00aThe TFRC protocol and its usage for wireless video transmission0 aTFRC protocol and its usage for wireless video transmission  bIGI Global  a 300 - 3173 a<p>The subject of this chapter is to present the TFRC (TCP-Friendly Rate Control) protocol in the area of efficient wireless video transmission and its possible usage in cross-layer power management mechanisms. The basic aspects of TFRC operation are presented, along with the suitability of TFRC usage for video transmission. The chapter examines related work and presents several mechanisms for efficient wireless video transmission using TFRC that have been proposed. These mechanisms utilize cross-layer approaches for adaptation of the power transmission level of the sender and TFRC feedback information regarding the wireless connection status from the receiver for improved transmission statistics, and therefore user experience, without unnecessary power consumption.</p>
1 aBouras, Christos1 aStamos, Kostas1 aPapapanagiotou, Vassilis1 aZaoudis, Giannis  uhttp://telematics.upatras.gr/telematics/publications/tfrc-protocol-and-its-usage-wireless-video-transmission?language=en01290nas a2200145   4500008004100000245007400041210006900115300001300184520072700197100002100924700001900945700002100964700002400985856013501009       2011                        eng d00aUtilizing Video Enconding for Power Management over Wireless Networks0 aUtilizing Video Enconding for Power Management over Wireless Net  a 57 - 623 aPower management is especially important in wireless networks because of the emergence of energy
constrained mobile devices. This paper examines the ways that video encoding information can be used for
more efficient power management. In particular, we propose and evaluate cross layer mechanisms that fine-
tune transmission power depending on the video frame being encoded and we examine how this mechanism
may be combined with algorithms that adjust transmission power based on feedback reports when TFRC is
used as the transport protocol. Since typical video encoding uses frames of varying importance for the
overall quality, this approach can improve received video quality and make better usage of available power.
1 aBouras, Christos1 aStamos, Kostas1 aZaoudis, Giannis1 aStroumpis, Stamatis  uhttp://telematics.upatras.gr/telematics/publications/utilizing-video-enconding-power-management-over-wireless-networks?language=en02028nas a2200145   4500008004100000245007600041210006900117300001500186490000700201520148100208100002101689700002601710700002201736856012401758       2010                        eng d00aAdaptation of RSS feeds based on the user profile and on the end device0 aAdaptation of RSS feeds based on the user profile and on the end  a 410 - 4210 v333 a<p>In the last decade, the advances in technology along with the ease of access to information have dramatically changed the World Wide Web status during the last few years. The Internet acts as a means of finding useful information and more specifically news articles. Additionally, more and more people want to utilize their mobile devices towards the scope of reading news articles. The aforementioned situation generates a significant, yet almost untouched problem: easily locating interesting news articles on a dailybasis within the space that is available on the small screen device. In our work, we propose a framework that, by utilizing RSSfeeds, is able to personalize on the needs of the users and on the capabilities of their device, in order to present to them only a fraction of the news articles and merely the useful information that derives fromthem. Deploying a generalized,multi- functional mechanism that produces efficient results for the situation described, seems to be a panacea for most of the text-based, information retrieval needs. Within this framework we created PeRSSonal,a mechanism that is able to create personalized, pre-categorized,dynamically generated RSSfeeds focalized on the end user?s smal lscreen device. The system is based on algorithms that incorporate the user in to the categorization and summarization procedures, while the articles are presented back to him/her according to her interests and the client device capacity.</p>
1 aBouras, Christos1 aPoulopoulos, Vassilis1 aTsogkas, Vassilis  uhttp://telematics.upatras.gr/telematics/publications/adaptation-rss-feeds-based-user-profile-and-end-device?language=en01499nas a2200133   4500008004100000245005500041210005500096260002100151300001500172520101900187100002101206700002201227856011601249       2010                        eng d00aAdaptive multimedia transmission over the Internet0 aAdaptive multimedia transmission over the Internet  bWorld Scientific  a 589 - 6063 a<p>The Internet is a heterogeneous network environment and the network resources that are available to multimedia applications can be modified very quickly. Multimedia applications must have the capability to adapt their operation to network changes. In order to add adaptation characteristics to multimedia applications, we can use techniques both at the network and application layers. Adaptive multimedia transmission techniques have the capability to transmit multimedia data over heterogeneous networks and adapt media transmission to network changes. In order to provide adaptive multimedia transmission, mechanisms to monitor the network conditions and mechanisms to adapt the transmission of the data to the network changes must be implemented. This chapter concentrates on the architecture and design issues of adaptive multimedia techniques that provide the capability to transmit multimedia data over heterogeneous networks and adapt the transmission of the multimedia data to the network changes.</p>
1 aBouras, Christos1 aGkamas, Apostolos  uhttp://telematics.upatras.gr/telematics/publications/adaptive-multimedia-transmission-over-internet?language=en01833nas a2200145   4500008004100000245011800041210006900159300001500228490000700243520121900250100002101469700002201490700002001512856015501532       2010                        eng d00aAdaptive Smooth Multicast Protocol for Multimedia Transmission: Implementation Details and Performance Evaluation0 aAdaptive Smooth Multicast Protocol for Multimedia Transmission I  a 299 - 3330 v233 a<p>In this article we propose a new single-rate multicast congestion control scheme named Adaptive Smooth Multicast Protocol (ASMP), for multimedia transmission over best-effort networks. The smoothness lays in the calculation and adaptation of the transmission rate, which is based on dynamic estimations of protocols? parameters and dynamic adjustment of the “smoothness factor”, as well. ASMP key attributes are: a) TCP-friendly behavior, b) adaptive scalability to large sets of receivers, c) high bandwidth utilization, and finally d) smooth transmission rates, which are suitable for multimedia applications. We evaluate the performance of ASMP and investigate its behavior under various network conditions through extensive simulations conducted with the network simulator software (ns2). Simulation results show that ASMP can be regarded as a serious competitor of TFMCC and PGMCC. In many cases, ASMP outperforms TFMCC in terms of TCP-friendliness and smooth transmission rates, while PGMCC presents lower scalability than ASMP. We have implemented ASMP on top of RTP/RTCP protocols in ns2 by adding all the RTP/RTCP protocol?s attributes that are defined in RFC 3550 and related to QoS metrics.</p>
1 aBouras, Christos1 aGkamas, Apostolos1 aKioumourtzis, G  uhttp://telematics.upatras.gr/telematics/publications/adaptive-smooth-multicast-protocol-multimedia-transmission-implementation-details-and?language=en01192nas a2200205   4500008004100000245006100041210006100102260002000163300001500183520052800198653000800726653000800734653000900742100002100751700002200772700002200794700002400816700002400840856012200864       2010                        eng d00aAdopting FEC for Reliable Multicasting over LTE Networks0 aAdopting FEC for Reliable Multicasting over LTE Networks  cOctober 17 - 21  a 307 - 3103 aThe key feature for the provision of Multimedia
Broadcast/Multicast Services (MBMS) in Long Term Evolution
(LTE) networks is the Multimedia Broadcast over a Single
Frequency Network (MBSFN). On the other hand, the use of
Forward Error Correction (FEC) in mobile multicast transmission
has significant advantages and the 3rd Generation Partnership
Project (3GPP) has adopted the application layer FEC in the
MBMS standard. In this paper, we investigate the impact of the
application layer FEC over the MBSFN delivery method.10aFEC10aLTE10aMBMS1 aBouras, Christos1 aAlexiou, Antonios1 aPapazois, Andreas1 aKokkinos, Vasileios1 aTsichritzis, George  uhttp://telematics.upatras.gr/telematics/publications/adopting-fec-reliable-multicasting-over-lte-networks?language=en01643nas a2200193   4500008004100000245007800041210006900119260001900188300001200207520099100219653000801210653000801218653000901226653001001235100002101245700002201266700002201288856013901310       2010                        eng d00aAdopting forward error correction for multicasting over cellurar networks0 aAdopting forward error correction for multicasting over cellurar  c12 - 15 April   a307-3103 a<p>FEC is an error control method that can be used to augment or replace other methods for reliable data transmission. Such schemes inevitably add a constant overhead in the transmitted data. However, they are so simple as to meet a prime objective for UMTS multicast services, that is scalability to applications with thousands of receivers. This is the reason that 3GPP recommends the use of FEC for MBMS framework. In this paper, we use a probabilistic model for the multicast user distribution in the network and we define a scheme for multicast data delivery that combines FEC with traditional ARQ. It is important that our analysis is compliant with the 3GPP specifications and considers the latest advances in mobile networks. In this framework we investigate the impact of FEC use, we examine whether it is beneficial, how the optimal FEC code dimensioning varies based on the network conditions, which parameters affect the optimal FEC code selection, and how they do it.</p>
10aFEC10aLTE10aMBMS10aMBSFN1 aBouras, Christos1 aAlexiou, Antonios1 aPapazois, Andreas  uhttp://telematics.upatras.gr/telematics/publications/adopting-forward-error-correction-multicasting-over-cellurar-networks?language=en01219nas a2200133   4500008004100000245003500041210003500076260001500111300000800126520081100134100002100945700002200966856009700988       2010                        eng d00aAssigning Web News to Clusters0 aAssigning Web News to Clusters  cMay 9 - 15  a1-53 aThe Web is overcrowded with news articles, an
overwhelming information source both with its amount and
diversity. Assigning news articles to similar groups, on the 
other hand, provides a very powerful data mining and
manipulation technique for topic discovery from text
documents. In this paper, we are investigating the application 
of a great spectrum of clustering algorithms, as well as 
similarity measures, to news articles that originate from the 
Web and compare their efficiency for use in an online Web
news service application. We also examine the effect of
preprocessing on clustering. Our experimentation showed that
k-means, despite its simplicity, accompanied with preliminary
steps for data cleaning and normalizing, gives better aggregate
results when it comes to efficiency.1 aBouras, Christos1 aTsogkas, Vassilis  uhttp://telematics.upatras.gr/telematics/publications/assigning-web-news-clusters?language=en01551nas a2200145   4500008004100000245009300041210006900134260001500203300001500218520095300233100002101186700002201207700002701229856014901256       2010                        eng d00aBest Practices and Strategies for Broadband Deployment: Lessons learned around the world0 aBest Practices and Strategies for Broadband Deployment Lessons l  bIGI Global  a 128 - 1423 a<p>Broadband deployment is a necessity nowadays. It could help each country, municipality and region to grow and offer better quality of life to the citizens. Today, the emphasis on the development of broadband networks is on fixed Fibre To The Home solutions The lessons learned from countries that are leaders in broadband penetration and Fibre To The Home deployment could be proven very useful for under-served communities, regions and countries where the broadband penetration is low. Therefore, this chapter summarises the lessons learned from implementing (a) country-wide strategies formulated at the national level, and (b) local strategies formulated by the municipalities. Concerning the role of national and local governments, it should be noted that nowadays it is very urgent the involvement of government in the development of broadband infrastructure. Proposed noteworthy remarkable cases are Japan, South Korea and Singapore.</p>
1 aBouras, Christos1 aGkamas, Apostolos1 aTsiatsos, Thrasivoulos  uhttp://telematics.upatras.gr/telematics/publications/best-practices-and-strategies-broadband-deployment-lessons-learned-around-world?language=en01700nas a2200193   4500008004100000245004800041210004800089260002200137300001500159520109800174653001801272653000801290653001001298100002101308700002201329700002401351700002401375856010701399       2010                        eng d00aCommunication Cost Analysis of MBSFN in LTE0 aCommunication Cost Analysis of MBSFN in LTE  cSeptember 26 - 30  a 1366-13713 aLong Term Evolution (LTE) is the latest step towards
the 4th generation (4G) of radio technologies designed to increase
the capacity and speed of mobile communications. To support
Multimedia Broadcast/Multicast Services (MBMS), LTE offers
the possibility to transmit Multimedia Broadcast multicast
service over a Single Frequency Network (MBSFN), where a
time-synchronized common waveform is transmitted from
multiple cells for a given duration. In this paper we analytically
present the MBSFN delivery method and evaluate its
performance. The critical parameters of primary interest for the
evaluation of the scheme are the packet delivery cost and its
scalability. To this direction, a telecommunication cost analysis of
the MBMS service is presented based on the transmission cost
over the air interface, as well as the costs of all interfaces and
nodes of the MBSFN architecture. Since the performance of the
MBSFN scheme mainly depends on the configuration of the LTE
network that is under investigation, we consider different
network topologies, MBSFN deployments and user distributions.10aCost analysis10aLTE10aMBSFN1 aBouras, Christos1 aAlexiou, Antonios1 aKokkinos, Vasileios1 aTsichritzis, George  uhttp://telematics.upatras.gr/telematics/publications/communication-cost-analysis-mbsfn-lte?language=en01341nas a2200181   4500008004100000245009100041210006900132260002000201520067600221100002100897700002200918700001300940700001600953700001600969700001300985700001300998856014801011       2010                        eng d00aThe Community Network Game Project: Enhancing Collaborative Activities in Online Games0 aCommunity Network Game Project Enhancing Collaborative Activitie  c14 - 15 October3 aThe EU-funded Community Network Game (CNG)
project aims at enhancing collaborative activities between
Massively Multiplayer Online Games (MMOG) players. This
will be achieved by developing new tools for the generation,
distribution and insertion of user-generated content (UGC) into
existing MMOGs without changing the game code and without
adding new processing or network loads to the MMOG central
servers. This UGC may include items (e.g., textures, 3D objects)
to be added to the game and live video captured from the game
screen and streamed to other players. We present the objectives
of the project, focusing on its main scientific and technological
contributions.1 aBouras, Christos1 aPapazois, Andreas1 aAhmad, S1 aHamzaoui, R1 aPerelman, E1 aSahni, A1 aSimon, G  uhttp://telematics.upatras.gr/telematics/publications/community-network-game-project-enhancing-collaborative-activities-online-games?language=en01745nas a2200193   4500008004100000245010300041210006900144260002100213520102900234100002101263700002201284700002401306700001301330700001601343700001601359700001301375700001301388856015001401       2010                        eng d00aThe Community Network Game Project: Enriching Online Gamers Experience with User Generated Content0 aCommunity Network Game Project Enriching Online Gamers Experienc  cNovember 21 - 263 a<p>One of the most attractive features of Massively Multiplayer Online Games (MMOGs) is the possibility for users to interact with a large number of other users in a variety of collaborative and competitive situations. Gamers within an MMOG typically become members of active communities with mutual interests, shared adventures, and common objectives. We present the EU funded Community Network Game (CNG) project. The CNG project will provide tools to enhance col- laborative activities between online gamers and will develop new tools for the generation, distribution and insertion of user generated content (UGC) into existing MMOGs. CNG will allow the addition of new engaging community services without changing the game code and without adding new processing or network loads to the MMOG central servers. The UGC considered by the CNG project includes 3D objects and graphics as well as video to be shared using peer-to-peer (P2P) technology. We describe the concept, innovations, and objectives of the project.</p>
1 aBouras, Christos1 aPapazois, Andreas1 aTsichritzis, George1 aAhmad, S1 aHamzaoui, R1 aPerelman, E1 aSahni, A1 aSimon, G  uhttp://telematics.upatras.gr/telematics/publications/community-network-game-project-enriching-online-gamers-experience-user-generated?language=en01354nas a2200145   4500008004100000245007400041210006900115260003400184300001300218520077900231100002101010700002201031700002001053856013501073       2010                        eng d00aCross Layer Design for Multimedia Transmission over Wireless Networks0 aCross Layer Design for Multimedia Transmission over Wireless Net  bInformation Science Reference  a 35 - 423 a<p>Over the last years a number of new protocols have been developed for multimedia applications in the whole OSI layer?s scale. In addition wireless communications and networking fast occupy centre stage in research and development activity in the area of communication networks. In order to support better wireless user the cross layer design paradigm has been proposed. This chapter presents the challenges in design and implementation of cross layer adaptation schemes for multimedia transmission over wireless networks. In addition this chapter presents the most important parameters and constrains that should be taken into consideration when attempting cross layer adaptation in wireless networks that involves different protocols in the overall protocol stack.</p>
1 aBouras, Christos1 aGkamas, Apostolos1 aKioumourtzis, G  uhttp://telematics.upatras.gr/telematics/publications/cross-layer-design-multimedia-transmission-over-wireless-networks?language=en01534nas a2200133   4500008004100000245006300041210006100104260001700165300001500182520103300197100002101230700002601251856012301277       2010                        eng d00aDynamic User Context Web Personalization in Meta - Portals0 aDynamic User Context Web Personalization in Meta Portals  cJune 22 - 25  a 925 - 9303 a<p>We present the dynamic web personalization and document grouping infrastructure for meta-portals and the evaluation of the mechanism on peRSSonal, a system that collects articles from news portals and blogs worldwide. A meta-portal is an informational node where articles from different sources are collected and presented in a categorized and personalized manner. The web personalization mechanism is based on dynamic creation and update of user profile according to the user's preferences when browsing and on user grouping details. Assuming that required information, such as article tagging, keywords to categories matching and articles to categories relation is already part of the meta-portal we present a novel mechanism that can build and maintain a user profile which is formed without disturbing the user. Furthermore, we describe the real-time user centered document grouping mechanism that is implemented to support the web personalization system and present the experimental evaluation of the whole system.</p>
1 aBouras, Christos1 aPoulopoulos, Vassilis  uhttp://telematics.upatras.gr/telematics/publications/dynamic-user-context-web-personalization-meta-portals?language=en01613nas a2200145   4500008004100000245006400041210006400105260001800169300000800187520108500195100002101280700002601301700001701327856012301344       2010                        eng d00aEfficient extraction of news articles based on RSS crawling0 aEfficient extraction of news articles based on RSS crawling  c3 - 5 October  a1-73 a<p>The expansion of the World Wide Web has led to a state where a vast amount of Internet users face and have to overcome the major problem of discovering desired information. It is inevitable that hundreds of web pages and weblogs are generated daily or changing on a daily basis. The main problem that arises from the continuous generation and alteration of web pages is the discovery of useful information, a task that becomes difficult even for the experienced internet users. Many mechanisms have been constructed and presented in order to overcome the puzzle of information discovery on the Internet and they are mostly based on crawlers which are browsing the WWW, downloading pages and collect the information that might be of user interest. In this manuscript we describe a mechanism that fetches web pages that include news articles from major news portals and blogs. This mechanism is constructed in order to support tools that are used to acquire news articles from all over the world, process them and present them back to the end users in a personalized manner</p>
1 aBouras, Christos1 aPoulopoulos, Vassilis1 aAdam, George  uhttp://telematics.upatras.gr/telematics/publications/efficient-extraction-news-articles-based-rss-crawling?language=en01707nas a2200205   4500008004100000245007000041210006900111260002000180520102200200653000801222653000901230653001001239653000801249100002101257700002201278700002201300700002401322700002401346856013101370       2010                        eng d00aEfficient MCS Selection for MBSFN Transmissions over LTE Networks0 aEfficient MCS Selection for MBSFN Transmissions over LTE Network  cOctober 20 - 223 aLong Term Evolution (LTE), the next-generation
network beyond 3G, is designed to support the explosion in
demand for bandwidth-hungry multimedia services that are
already experienced in wired networks. To support Multimedia
Broadcast/Multicast Services (MBMS), LTE offers functionality
to transmit MBMS over a Single Frequency Network (MBSFN),
where a time-synchronized common waveform is transmitted
from multiple cells for a given duration. This significantly
improves the Spectral Efficiency (SE) compared to conventional
MBMS operation. The achieved SE is mainly determined by the
Modulation and Coding Scheme (MCS) utilized by the LTE
physical layer. In this paper we propose and evaluate four
approaches for the selection of the MCS that will be utilized for
the transmission of the MBSFN data. The evaluation of the
approaches is performed for different users? distribution and
from SE perspective. Based on the SE measurement, we
determine the most suitable approach for the corresponding
users? distribution.10aLTE10aMBMS10aMBSFN10aMCS1 aBouras, Christos1 aAlexiou, Antonios1 aPapazois, Andreas1 aKokkinos, Vasileios1 aTsichritzis, George  uhttp://telematics.upatras.gr/telematics/publications/efficient-mcs-selection-mbsfn-transmissions-over-lte-networks?language=en01462nas a2200157   4500008004100000245008000041210006900121260002100190300001500211520085700226100002101083700002601104700001701130700002701147856013001174       2010                        eng d00aAn Efficient Mechanism for Stemming and Tagging: the Case of Greek Language0 aEfficient Mechanism for Stemming and Tagging the Case of Greek L  c8 - 10 September  a 389 - 3973 aIn an era that, searching the WWW for information becomes a tedious task, it is obvious that mainly search engines and other data mining mechanisms need to be enhanced with characteristics such as NLP in order to better analyze and recognize user queries and fetch data. We present an efficient mechanism for stemming and tagging for the Greek language. Our system is constructed in such a way that can be easily adapted to any existing system and support it with recognition and analysis of Greek words. We examine the accuracy of the system and its ability to support peRSSonal a medium constructed for offering meta-portal news services to internet users. We present experimental evaluation of the system compared to already existing stemmers and taggers of the Greek language and we prove the higher efficiency and quality of results of our system.1 aBouras, Christos1 aPoulopoulos, Vassilis1 aAdam, George1 aAsimakis, Konstantinos  uhttp://telematics.upatras.gr/telematics/publications/efficient-mechanism-stemming-and-tagging-case-greek-language?language=en01577nas a2200169   4500008004100000245005400041210005100095300001400146490000700160520104500167653000901212653000901221100002101230700002201251700002201273856011201295       2010                        eng d00aAn Efficient Mechanism for UMTS Multicast Routing0 aEfficient Mechanism for UMTS Multicast Routing  a802 - 8150 v153 a<p>In this paper, we present a novel scheme for the multicast transmission of data over Universal Mobile Telecommunications System (UMTS) networks. Apart from the normal multicast transmission over UMTS, we consider the handling of exceptional cases caused by user mobility scenarios. The proposed scheme is in accordance with the current specifications of the Multimedia Multicast/ Broadcast Service (MBMS) defined by the 3rd Generation Partnership Project (3GPP) and introduces minor modifications in the UMTS architecture and the mobility management mechanisms. The proposed scheme is implemented as an ns-2 network simulator module. The performance of the proposed scheme is validated and analyzed through ns-2 simulation experiments. This new module can be employed to investigate various aspects of UMTS multicast. Furthermore, in order to further highlight the contribution of our mechanism, we have implemented two multicast congestion control mechanisms for UMTS and we have measured their performance for MBMS transmissions.</p>
10aMBMS10aUMTS1 aBouras, Christos1 aAlexiou, Antonios1 aPapazois, Andreas  uhttp://telematics.upatras.gr/telematics/publications/efficient-mechanism-umts-multicast-routing?language=en01654nas a2200181   4500008004100000245006100041210006000102260001500162300001500177520105500192653000801247653000901255653001801264100002101282700002201303700002401325856012301349       2010                        eng d00aEfficient Power Allocation in E-MBMS Enabled 4G Networks0 aEfficient Power Allocation in EMBMS Enabled 4G Networks  bIGI Global  a 458 - 4883 a<p>The plethora of mobile multimedia services that are expected to face high penetration, poses the need for the deployment of a resource economic scheme in Long Term Evolution (LTE) networks. To this direction, the Evolved - Multimedia Broadcast / Multicast Service (E- MBMS) is envisaged to play an instrumental role for LTE proliferation and set the basis for a successful 4th Generation (4G) standardization process. One of the most critical aspects of E- MBMS performance is the selection of the most efficient radio bearer, in terms of power consumption. This chapter presents the prevailing radio bearer selection mechanisms and examines their performance in terms of power consumption. Furthermore, it discusses problems regarding the high power requirements for the realization of E-MBMS and evaluates the proposed techniques/solutions. Finally, this chapter presents a novel mechanism for efficient power control during E-MBMS transmissions that conforms to LTE requirements for simultaneous provision of multiple multimedia sessions.</p>
10aLTE10aMBMS10aPower Control1 aBouras, Christos1 aAlexiou, Antonios1 aKokkinos, Vasileios  uhttp://telematics.upatras.gr/telematics/publications/efficient-power-allocation-e-mbms-enabled-4g-networks?language=en01072nas a2200157   4500008004100000245007500041210006900116260001500185300001200200520047600212100002100688700001900709700002900728700002100757856013600778       2010                        eng d00aEfficient Power Management Adaptation for Video Transmission over TFRC0 aEfficient Power Management Adaptation for Video Transmission ove  cMay 9 - 15  a509-5143 aIn this paper, we describe a power management
mechanism for wireless video transmission using the TFRC
protocol that takes into account feedback about the received
video quality and tries to intelligently adapt transmitting
power accordingly. The purpose of the mechanism is to utilize
TFRC feedback and thus achieve a beneficial balance between
the power consumption and the received video quality. We use
simulation in order to compare and evaluate our approach.1 aBouras, Christos1 aStamos, Kostas1 aPapapanagiotou, Vassilis1 aZaoudis, Giannis  uhttp://telematics.upatras.gr/telematics/publications/efficient-power-management-adaptation-video-transmission-over-tfrc?language=en01674nas a2200205   4500008004100000245005500041210005500096260002000151520103500171653000801206653000801214653000901222653001001231100002101241700002201262700002201284700002401306700002101330856011701351       2010                        eng d00aEnhancing FEC Application in LTE Cellular Networks0 aEnhancing FEC Application in LTE Cellular Networks  cOctober 20 - 223 a3rd Generation Partnership Project?s (3GPP) Long
Term Evolution (LTE) is focused on enhancing the Universal
Terrestrial Radio Access (UTRA). Evolved-Multimedia
Broadcast and Multicast Service (e-MBMS) uses Multimedia
Broadcast over a Single Frequency Network (MBSFN) operation
in order to improve its performance. In MBSFN operation, data
are transmitted simultaneously over the air from multiple tightly
time-synchronized cells. Raptor codes have been standardized as
the main application layer Forward Error Correction (FEC)
method for e-MBMS due to the advanced error protection they
offer and their overall performance. In this study, we investigate
the application of FEC in MBSFN-enabled LTE cellular
networks and we propose a new scheme that takes into account
the properties of MBSFN in order to provide a more efficient
operation of FEC during e-MBMS transmissions. The proposed
scheme is compared with other file recovery methods and is
evaluated against various network parameters in a realistic
simulation environment.10aFEC10aLTE10aMBMS10aMBSFN1 aBouras, Christos1 aAlexiou, Antonios1 aPapazois, Andreas1 aKokkinos, Vasileios1 aTseliou, Georgia  uhttp://telematics.upatras.gr/telematics/publications/enhancing-fec-application-lte-cellular-networks?language=en01710nas a2200145   4500008004100000245011200041210006900153260001500222300001300237520108900250100002101339700002701360700002501387856015201412       2010                        eng d00aExploiting Virtual Environments and Web2.0 Immersive Worlds to Support Collaborative e-Learning Communities0 aExploiting Virtual Environments and Web20 Immersive Worlds to Su  bIGI Global  a 20 - 453 a<p>The main goal of this chapter is to facilitate educational designers and developers by providing a point of reference for making decisions on how to incorporate 3D environments into the applications they develop as well as for extending their capabilities by integrating more functionality. Therefore, this chapter presents the design principles for virtual spaces, which aim at supporting multi-user communication in web-based learning communities. In addition the implementation of these principles is presented using as point of reference EVE Training Area. This environment constitutes a three-dimensional space where participants, represented by 3D humanoid avatars, have the ability to use a variety of 3D e-collaboration tools for learning together. Furthermore, this chapter presents how these principles could be used as criteria for validating and extending ready Web2.0 Immersive worlds for supporting collaborative e-learning. Finally, collaborative e-learning usage scenarios that could be realized by exploiting collaborative virtual environments are described.</p>
1 aBouras, Christos1 aTsiatsos, Thrasivoulos1 aGiannaka, Eleftheria  uhttp://telematics.upatras.gr/telematics/publications/exploiting-virtual-environments-and-web20-immersive-worlds-support-collaborative-e?language=en01309nas a2200157   4500008004100000245005700041210005400098260001600152300001600168520075700184100002100941700002700962700002600989700002401015856011201039       2010                        eng d00aHANIME: An H - Anim Compliant Avatar Editor for NVEs0 aHANIME An H Anim Compliant Avatar Editor for NVEs  cMay 17 - 21  a  347 - 3523 aThis paper addresses the problem of a visual H-Anim avatar editor. Although H-Anim is a very promising
standard for interchangeable avatars and avatar?s animation, the lack of an effective yet simple to use visual
avatar editor could repel users from H-Anim compliant Networked Virtual Environments. Therefore this
paper presents an H-Anim compliant editor, called HanimE, for creating avatars for Networked Virtual
Environments. This editor is entirely based on a graphical user interface and allows users to customize H-
Anim avatars, in a simple yet effective manner. The avatars created by HanimE can be integrated in various
H-Anim compliant Networked Virtual Environments regardless of the technology they are built on, since
they are X3D files.
1 aBouras, Christos1 aTsiatsos, Thrasivoulos1 aTriglianos, Vasileios1 aKartsakalis, Kostas  uhttp://telematics.upatras.gr/telematics/publications/hanime-h-anim-compliant-avatar-editor-nves?language=en01551nas a2200145   4500008004100000245004600041210004600087260001900133300001500152520106800167100002101235700002601256700001701282856010601299       2010                        eng d00aImage extraction from online text streams0 aImage extraction from online text streams  c20 - 23 April   a 609 - 6143 aIn this paper we present an efficient system that
processes HTML pages in order to extract the useful images from them. The proposed mechanism is template independent and is focalized on HTML pages that include news articles from major portals and blogs. As useful images we define the pictures that
are relevant to the news report. In order to extract the image objects of the article we deconstruct the HTML page to its DOM model and we apply a set of algorithms in order to clean and correct the HTML code, locate and characterize each node of the
DOM model and finally keep the nodes that are characterized as useful nodes. The proposed mechanism is applied as a subsystem of peRSSonal, a web tool that is used to obtain news articles from
all over the world, process them and present them back to the end users in a personalized manner. The role of the mechanism is to feed peRSSonal?s database with digital images for browsing and searching purposes. We present the basic algorithms and experimental results on the efficiency of the proposed implementation.1 aBouras, Christos1 aPoulopoulos, Vassilis1 aAdam, George  uhttp://telematics.upatras.gr/telematics/publications/image-extraction-online-text-streams?language=en01213nas a2200193   4500008004100000245005600041210005200097260001500149300000800164520062800172653000800800653000800808653000900816653001800825100002100843700002200864700002200886856011100908       2010                        eng d00aThe Impact of FEC on Mobile Multicast Power Control0 aImpact of FEC on Mobile Multicast Power Control  cMay 9 - 15  a1-63 a3GPP has standardized the use of forward error
correction for the provision of reliable data transmission in the
mobile multicast framework. In this paper we present a study
of the impact of application layer forward error correction on
power control during mobile multicast transmission. The
evaluation is performed with the aid of a novel scheme that
allows the simulation of FEC impact on both streaming
delivery and download delivery over a multicast session. It is
important that the proposed scheme incorporates the
properties of an evolved mobile network, as they are
determined by the 3GPP specifications.10aFEC10aLTE10aMBMS10aPower Control1 aBouras, Christos1 aAlexiou, Antonios1 aPapazois, Andreas  uhttp://telematics.upatras.gr/telematics/publications/impact-fec-mobile-multicast-power-control?language=en01740nas a2200181   4500008004100000245007400041210006900115300001500184490000700199520111600206653000801322653000901330653001801339100002101357700002201378700002201400856013601422       2010                        eng d00aAn Improved MBMS Power Counting Mechanism towards Long Term Evolution0 aImproved MBMS Power Counting Mechanism towards Long Term Evoluti  a 109 - 1190 v433 a<p>One of the key objectives of beyond 3rd generation mobile networks is the realization of enhanced end-user experience through the provision of rich multimedia services. Multimedia Broadcast/Multicast Services (MBMS) framework epitomizes the increasing popularity of such applications and is envisaged to play an instrumental role for the Long Term Evolution (LTE) proliferation in mobile market. For exploiting resource efficiency, MBMS specifications consider the Counting Mechanism which decides whether it is more efficient to deliver MBMS multicast traffic over Point-to-Point (PTP) or Point-to-Multipoint (PTM) bearers. However, the necessity to further improve MBMS resource efficiency and integrate new technologies in the frame of LTE stresses the need for an advanced Counting Mechanism. In this work we propose a novel Power Counting Mechanism for efficient selection of MBMS bearers. The proposed mechanism optimally utilizes power resources and exploits broadband characteristics and performance enhancements emerged from Multiple Input Multiple Output (MIMO) antennas used in LTE networks.</p>
10aLTE10aMBMS10aPower Control1 aBouras, Christos1 aAlexiou, Antonios1 aRekkas, Evangelos  uhttp://telematics.upatras.gr/telematics/publications/improved-mbms-power-counting-mechanism-towards-long-term-evolution?language=en01973nas a2200193   4500008004100000245008900041210006900130300001500199490000700214520128900221653000901510653001801519653000901537100002101546700002201567700002401589700002201613856014401635       2010                        eng d00aAn Improved Mechanism for Multiple MBMS Sessions Assignment in B3G Cellurar Networks0 aImproved Mechanism for Multiple MBMS Sessions Assignment in B3G   a 671 - 6860 v163 a<p>In Universal Mobile Telecommunication System (UMTS), the downlink capacity is limited by the base station transmission power. Therefore, power control plays an important role to minimize the transmitted power shared among unicast and multicast users within a cell. In Multimedia Broadcast/Multicast Service (MBMS), power control targets to the efficient utilization of radio and network resources. However, the expected high demand for such services stresses the need for an efficient scheme, capable of dynamically allocating radio resources to parallel MBMS sessions. This paper proposes a power control mechanism for efficient MBMS session assignment in next generation UMTS networks. The mechanism shares efficiently the available power resources of UMTS base stations to MBMS sessions running in the network. Furthermore, the mechanism is evaluated through several realistic scenarios and the results indicate the ability of the mechanism to utilize efficiently the radio resources and to ensure the service continuity when parallel MBMS services run in the network. Our approach is compared with current 3rd Generation Partnership Project (3GPP) approaches, such as these presented in TS 25.346 and in TR 25.922, in order to highlight the enhancements that it provides.</p>
10aMBMS10aPower Control10aUMTS1 aBouras, Christos1 aAlexiou, Antonios1 aKokkinos, Vasileios1 aRekkas, Evangelos  uhttp://telematics.upatras.gr/telematics/publications/improved-mechanism-multiple-mbms-sessions-assignment-b3g-cellurar-networks?language=en00571nas a2200169   4500008004100000245004400041210004400085260001100129300001500140100002100155700002300176700001900199700002200218700002600240700002900266856010600295       2010                        eng d00aLayer 2 Quality of Service Architecture0 aLayer 2 Quality of Service Architecture  bInTech  a 399 - 4121 aBouras, Christos1 aKapoulas, Vaggelis1 aStamos, Kostas1 aPrimpas, Dimitris1 aPoulopoulos, Leonidas1 aPapapanagiotou, Vassilis  uhttp://telematics.upatras.gr/telematics/publications/layer-2-quality-service-architecture?language=en01706nas a2200181   4500008004100000245009700041210006900138260002100207300001300228520102600241653000901267653000901276100002101285700002201306700002401328700002201352856015001374       2010                        eng d00aThe Multimedia Broadcast/Multicast Service of the Universal Mobile Telecommunications System0 aMultimedia BroadcastMulticast Service of the Universal Mobile Te  bWorld Scientific  a 43 - 783 a<p>The Universal Mobile Telecommunications System (UMTS) constitutes the premier third generation (3G) wireless technology that is dominating the global market. Multicasting is an efficient method of supporting group communication as it allows the transmission of packets to multiple destinations, using fewer network resources. The need for broadcasting and multicasting in UMTS led to the definition of the Multimedia Broadcast/Multicast Service (MBMS) framework, which targets the efficient utilization of radio and network resources of the UMTS network. This chapter introduces the key concepts of UMTS and in particular the MBMS framework of UMTS. Moreover, it investigates the power profiles of several transport channels (common and dedicated) which could be employed for the transmission of MBMS services to mobile users. Problems regarding the high power requirements for the realization of MBMS are also presented. The reader will become familiar with these problems and the proposed techniques/solutions.</p>
10aMBMS10aUMTS1 aBouras, Christos1 aAlexiou, Antonios1 aKokkinos, Vasileios1 aRekkas, Evangelos  uhttp://telematics.upatras.gr/telematics/publications/multimedia-broadcastmulticast-service-universal-mobile-telecommunications-system?language=en01618nas a2200133   4500008004100000245011300041210006900154300001500223490000700238520104000245100002101285700002201306856015601328       2010                        eng d00aNoun Retrieval Effect on Text Summarization and Delivery of Personalized News Articles to the User's Desktop0 aNoun Retrieval Effect on Text Summarization and Delivery of Pers  a 664 - 6770 v693 a<p>Text summarization and categorization, as well as personalization of the results, have always been some of the most demanding information retrieval tasks. Deploying a generalized, multi-functional mechanism that produces good results for the aforementioned tasks seems to be a panacea for most of the text-based, information retrieval needs. In this article, we present the keyword extraction techniques, exploring the effects that part of speech tagging has on the summarization procedure of an existing system. Moreover, we describe the profiling features that are used as an extension to an already constructed news indexing system, PeRSSonal. We are thus enhancing the personalization algorithm that the system utilizes with various features derived from the user?s profile, such as the list of viewed articles and the time spent on them. In addition, we analyze the system?s interconnection channels that are used with the client-side desktop application that was developed and we evaluate the approaches that we propose.</p>
1 aBouras, Christos1 aTsogkas, Vassilis  uhttp://telematics.upatras.gr/telematics/publications/noun-retrieval-effect-text-summarization-and-delivery-personalized-news-articles-users?language=en01481nas a2200145   4500008004100000245010700041210006900148260001700217300001500234520087000249100002101119700002201140700002001162856015301182       2010                        eng d00aPerformance Evaluation of MPEG-4 Video Transmission with the Adaptive Smooth Multicast Protocol (ASMP)0 aPerformance Evaluation of MPEG4 Video Transmission with the Adap  cJune 22 - 25  a 540 - 5453 aWe present in this work the performance
evaluation of MPEG-4 video transmission with our proposed  
single rate multicast protocol named Adaptive Smooth
Multicast Protocol (ASMP). ASMP key attributes are: a)
adaptive scalability to large sets of receivers, b) TCP-
friendly behavior, c) high bandwidth utilization, and finally
d) smooth transmission rates which are suitable for  
multimedia applications. We evaluate the performance of 
ASMP under an integrated simulation environment which
extends ns-2 and Evalvid-RA to the multicast domain with
the use of the RTP/RTCP protocols. Simulations conducted
under this environment combine the measurements of
network-centric along with video quality metrics. This
“joint” evaluation process provides a better understanding
of the benefits and limitations of any proposed protocol for
multimedia data transmission.1 aBouras, Christos1 aGkamas, Apostolos1 aKioumourtzis, G  uhttp://telematics.upatras.gr/telematics/publications/performance-evaluation-mpeg-4-video-transmission-adaptive-smooth-multicast-protocol?language=en01138nas a2200145   4500008004100000245008700041210006900128260001600197300001200213520056400225100002100789700001900810700002100829856014200850       2010                        eng d00aPower management of video transmission on wireless networks for multiple receivers0 aPower management of video transmission on wireless networks for   cSept. 23-25  a300-3043 aThe main idea of this paper is an efficient power
management mechanism in order to transmit to multiple
receivers. The proposed mechanism consists of a module for
efficiently managing the power when transmitting video over
wireless networks by using the TFRC protocol reports and then
adjusts transmission power using a binary-like approach. In
order to extend to multiple receivers, several methods are
proposed for calculating an appropriate power transmission
level based on all TFRC reports and adjust the server?s
transmission power accordingly.1 aBouras, Christos1 aStamos, Kostas1 aZaoudis, Giannis  uhttp://telematics.upatras.gr/telematics/publications/power-management-video-transmission-wireless-networks-multiple-receivers?language=en01814nas a2200133   4500008004100000245007300041210006900114260002800183300001500211520128200226100002101508700001901529856013201548       2010                        eng d00aProviding quality end-to-end videoconference services in IP networks0 aProviding quality endtoend videoconference services in IP networ  bNova Science Publishers  a 111 - 1223 a<p>The development of quality and user satisfying videoconference applications at a low cost has been hindered in the past by, among other reasons, low quality connections and a difficulty for the average user to establish end-to-end connections without hassle. In this chapter, we describe some of the latest methods and developments that overcome these problems. In particular, we discuss ways to make establishment of universal videoconference connections easier by overcoming the problem of participants that reside behind NAT routers, by deploying new protocols at the application or even the network layer. An example of the former case is the development of establishment protocols specifically designed for this purpose, while an example for the latter case is the deployment of IPv6, which aims to make NAT deployments obsolete. Furthermore, we discuss efforts to provide targeted support for quality of experience in networks that support some kind of traffic classification through the usage of dynamic mechanisms and dynamic network re-configurations. Apart from describing the state of the art in the aforementioned areas, we provide detailed insight in specific research efforts that have taken place and assess their results in the overall user experience.</p>
1 aBouras, Christos1 aStamos, Kostas  uhttp://telematics.upatras.gr/telematics/publications/providing-quality-end-end-videoconference-services-ip-networks?language=en01552nas a2200145   4500008004100000245010900041210006900150260001500219300001500234520093800249100002101187700002201208700001901230856015701249       2010                        eng d00aProviding Quality of Service across multiple providers: The case of European research and academic space0 aProviding Quality of Service across multiple providers The case   bIGI Global  a 280 - 2963 a<p>In this chapter, the authors present some of the latest developments related to the provisioning of Quality of Service (QoS) in today?s networks and the associated network management structures that are or will be deployed to support them. They first give a brief overview of the most important Quality of Service proposals in the areas of Layer 2 (L2) and Layer 3 (L3) QoS provisioning in backbone networks, and they discuss the network management structures and brokers that have been proposed in order to implement these services. As a case study, they describe the pan-european research and academic network, which is supported centrally by GEANT and which encompasses multiple independent NRENs (National Research and Education Networks). In the last few years, GEANT has developed and deployed a number of production and pilot services meant for the delivery of quality network services to the end users across Europe.</p>
1 aBouras, Christos1 aGkamas, Apostolos1 aStamos, Kostas  uhttp://telematics.upatras.gr/telematics/publications/providing-quality-service-across-multiple-providers-case-european-research-and-academic?language=en01839nas a2200181   4500008004100000245006700041210006600108260006300174300001500237520117500252653000801427653000901435653001801444100002101462700002201483700002401505856012801529       2010                        eng d00aRadio Resource Management for E-MBMS Transmissions towards LTE0 aRadio Resource Management for EMBMS Transmissions towards LTE  bAuerbach Publications, CRC Press, Taylor and Francis Group  a 331 - 3603 a<p>Long Term Evolution (LTE) constitutes a key standard that paves the way for the future mobile broadband landscape envisioned by 4th Generation (4G) wireless networks. Actu- ally, LTE addresses the emerging trend for the mass provision of rich multimedia services, such as Mobile TV, in a more power and spectral e±cient way than its predecessors. To this direction, the Evolved - Multimedia Broadcast/Multicast Service (E-MBMS) frame- work is envisaged to play an instrumental role for the LTE proliferation in mobile. E-MBMS constitutes the evolutionary successor of MBMS, which was introduced in the Release 6 of Universal Mobile Telecommunication System (UMTS). MBMS is designed in order to deliver multimedia data from a single source entity to multiple destinations. However, downlink ca- pacity in such networks is limited by base station transmission power. As an aftermath, in MBMS e±cient power allocation techniques should be implemented so as to ensure the mass provision of multimedia applications to mobile users. This chapter presents several techniques and mechanisms used today for MBMS power optimization in next generation cellular networks.</p>
10aLTE10aMBMS10aPower Control1 aBouras, Christos1 aAlexiou, Antonios1 aKokkinos, Vasileios  uhttp://telematics.upatras.gr/telematics/publications/radio-resource-management-e-mbms-transmissions-towards-lte?language=en01676nas a2200217   4500008004100000245006600041210006500107260002000172300001500192520097500207653000801182653000901190653001001199653000801209100002101217700002201238700002201260700002401282700002401306856012801330       2010                        eng d00aSpectral Efficiency Performance of MBSFN-enabled LTE Networks0 aSpectral Efficiency Performance of MBSFNenabled LTE Networks  cOctober 11 - 13  a 361 - 3673 aLong Term Evolution (LTE) constitutes the latest step
before the 4th generation (4G) of radio technologies designed to
increase the capacity and speed of mobile communications. To
support Multimedia Broadcast/Multicast Services (MBMS), LTE
offers the possibility to transmit Multimedia Broadcast multicast
service over a Single Frequency Network (MBSFN), where a
time-synchronized common waveform is transmitted from
multiple cells for a given duration. This enables over-the-air
combining, thus improving the Signal to Interference plus Noise
Ratio (SINR) and spectral efficiency (SE) significantly compared
to conventional MBMS operation. In this paper, we analytically
calculate the SE performance achieved in a MBSFN area for a
dynamically changing user topology and different modulation
and coding schemes (MCS). Finally, based on the SE
measurement, we determine the MCS scheme that either
maximizes or achieves a target SE for the corresponding user
distribution.10aLTE10aMBMS10aMBSFN10aMCS1 aBouras, Christos1 aAlexiou, Antonios1 aPapazois, Andreas1 aKokkinos, Vasileios1 aTsichritzis, George  uhttp://telematics.upatras.gr/telematics/publications/spectral-efficiency-performance-mbsfn-enabled-lte-networks?language=en01599nas a2200145   4500008004100000245006900041210006800110260001500178300001400193520104400207100002101251700002601272700002201298856013301320       2010                        eng d00aSqueak Etoys: Interactive and Collaborative Learning Environment0 aSqueak Etoys Interactive and Collaborative Learning Environment  bIGI Global  a417 - 4273 a<p>Squeak Etoys is a free software program and media-rich authoring system with a user-friendly visual interface. The software is designed to help six to twelve year-old children learn through interaction and collaboration; it comes preinstalled on XO laptop computers distributed by the One Laptop Per Child Foundation. The goal of the One Laptop Per Child initiative is to create novel educational opportunities for the world?s children by providing each child with a book-size, light and portable computer for personal use at school and at home. This chapter elaborates on the educational dimensions of the XO laptop and the Etoys environment developed to empower teachers and students with the capacity for creative learning, exploration, interaction, and collaboration. The authors focus on how the hardware and software capabilities of XO laptops can be utilized to allow children to interact, work together on projects, and engage in computer simulations and games while learning mathematics, physics, chemistry, and geometry.</p>
1 aBouras, Christos1 aPoulopoulos, Vassilis1 aTsogkas, Vassilis  uhttp://telematics.upatras.gr/telematics/publications/squeak-etoys-interactive-and-collaborative-learning-environment?language=en00405nam a2200085   4500008004100000245006800041210006500109100002100174856012400195       2010                        eng d00aTrends in Telecommunications Technologies (Edited by C. Bouras)0 aTrends in Telecommunications Technologies Edited by C Bouras1 aBouras, Christos  uhttp://telematics.upatras.gr/telematics/publications/trends-telecommunications-technologies-edited-c-bouras?language=en01278nas a2200133   4500008004100000245005500041210005200096260002100148300001500169520080000184100002100984700002201005856011701027       2010                        eng d00aW - kmeans: Clustering News Articles using WordNet0 aW kmeans Clustering News Articles using WordNet  cSeptember 8 - 10  a 379 - 3883 aDocument clustering is a powerful technique that has been widely
used for organizing data into smaller and manageable information kernels.
Several approaches have been proposed suffering however from problems like
synonymy, ambiguity and lack of a descriptive content marking of the
generated clusters. We are proposing the enhancement of standard kmeans
algorithm using the external knowledge from WordNet hypernyms in a twofold
manner: enriching the “bag of words” used prior to the clustering process and
assisting the label generation procedure following it. Our experimentation
revealed a significant improvement over standard kmeans for a corpus of news
articles derived from major news portals. Moreover, the cluster labeling process
generates useful and of high quality cluster tags.1 aBouras, Christos1 aTsogkas, Vassilis  uhttp://telematics.upatras.gr/telematics/publications/w-kmeans-clustering-news-articles-using-wordnet?language=en01347nas a2200145   4500008004100000245006700041210006700108260001500175300001500190520080500205100002101010700002201031700002001053856012801073       2009                        eng d00aAdaptive Smooth Simulcast Protocol for Multimedia Transmission0 aAdaptive Smooth Simulcast Protocol for Multimedia Transmission  cJuly 5 - 8  a 437 - 4423 a<p>We introduce Adaptive Smooth Simulcast Protocol (ASSP) for simulcast transmission over best-effort networks. ASSP is a new multiple-rate protocol that implements a single rate TCP-friendly protocol as the underlying congestion control mechanism for each simulcast stream. ASSP is build on top of the RTP/RTCP protocol and exploits the RTCP sender and receiver reports for the dissemination of feedback information. The key attributes of ASSP are: a) TCPfriendly behavior, b) adaptive per-stream transmission rates, c) adaptive scalability to large sets of receivers and finally d) smooth transmission rates that are suitable for multimedia applications. We evaluate the performance of ASSP and investigate its behavior through simulations conducted with the network simulator software (ns2).</p>
1 aBouras, Christos1 aGkamas, Apostolos1 aKioumourtzis, G  uhttp://telematics.upatras.gr/telematics/publications/adaptive-smooth-simulcast-protocol-multimedia-transmission?language=en01406nas a2200133   4500008004100000245006600041210006600107300001500173490000700188520090600195100002101101700002201122856012801144       2009                        eng d00aArchitectures and Performance Evaluation of Bandwidth Brokers0 aArchitectures and Performance Evaluation of Bandwidth Brokers  a 110 - 1170 v193 a<p>DiffServ is the basis of contemporary QoS-enabled networks. Setting up DiffServ QoS requires extensive engineering effort in dimensioning and provisioning, especially for adjacent networks under different administrations linked in a “federated” hierarchy. The bandwidth broker is an entity that is responsible for the management of the resources and the QoS service operation in an automated way. In this paper, we present, test and compare 2 different architectures of bandwidth brokers, a centralized one and a distributed one. We also deal with the inter-domain operation of the bandwidth broker in order to perform end to end provisioning. The paper presents the relevant aspects for inter-domain operation of a bandwidth broker and focuses on pathfinding issues. We discuss two models for inter domain routing through bandwidth brokers, analyzing their advantages and comparing them.</p>
1 aBouras, Christos1 aPrimpas, Dimitris  uhttp://telematics.upatras.gr/telematics/publications/architectures-and-performance-evaluation-bandwidth-brokers?language=en01578nas a2200157   4500008004100000245007800041210006900119300001500188520095900203100002101162700002201183700002701205700002401232700002701256856013701283       2009                        eng d00aBroadband Municipal Optical Networks in Greece: A Suitable Business Model0 aBroadband Municipal Optical Networks in Greece A Suitable Busine  a 391 - 4093 aThis paper proposes a business model for the optimal exploitation of the currently developing
broadband metropolitan area networks in Greece. Having recorded and examined
relevant international practices, we describe in detail the way that these networks should
be managed, operated, maintained and expanded. Taking into consideration that these
infrastructures will widely alter the broadband map of Greece, that Greece has currently
one of the lowest broadband penetration percentages in Europe and that the proper exploitation
strategy of the networks to be deployed could boost the demand for broadband connections
and applications, the application of the optimal business model appears to be of
vital importance. We describe the proposed business model in detail, including ways for
expanding the broadband infrastructures, as well as tackling of viability issues regarding
the authority responsible for managing the broadband metropolitan networks.1 aBouras, Christos1 aGkamas, Apostolos1 aTsiatsos, Thrasivoulos1 aPapagiannopoulos, J1 aTheofilopoulos, George  uhttp://telematics.upatras.gr/telematics/publications/broadband-municipal-optical-networks-greece-suitable-business-model?language=en00984nas a2200145   4500008004100000245004800041210004700089260002100136300001300157520049600170100002100666700002200687700002400709856010500733       2009                        eng d00aCaching News Channels on the User's Desktop0 aCaching News Channels on the Users Desktop  cNovember 19 - 21  a 35 - 423 aThe exponential growth of the Web probes for new, better filtering systems and latency diminishing applications. We are presenting the caching features that are deployed in the client-side application that is developed within the scope of PeRSSonal, the generalized, multi-functional mechanism that delivers personalized, summarized and categorized news articles. We also evaluate the caching algorithm depicting the overall improvement that it offers to the client side desktop application.1 aBouras, Christos1 aTsogkas, Vassilis1 aTsichritzis, George  uhttp://telematics.upatras.gr/telematics/publications/caching-news-channels-users-desktop?language=en01869nas a2200169   4500008004100000245006000041210006000101260005000161300001500211520125500226653002301481653000901504100002101513700002201534700002201556856012101578       2009                        eng d00aCongestion Control for Multicast Transmission over UMTS0 aCongestion Control for Multicast Transmission over UMTS  bAuerbach Publications, Taylor & Francis Group  a 291 - 3123 a<p>In this chapter, we present a novel mechanism for the multicast congestion control over Universal Mobile Telecommunications System (UMTS) networks. The proposed mechanism is based on the well known TCP-Friendly Multicast Congestion Control (TFMCC) scheme. TFMCC is an equation-based multicast congestion control mechanism intended to scale to groups of several thousand receivers. It is based on the concept of Current Limiting Receiver (CLR). The CLR is the receiver that the sender believes currently has the lowest expected throughput of the multicast group. The key challenge in the design of the new scheme lies in extending TFMCC in order to support the UMTS Terrestrial Radio-Access Network (UTRAN). Our major contribution is that the TFMCC mechanism was improved in order to cope with the packet losses caused by either the temporary or the permanent degradation of the wireless channel. One of the major advantages of the proposed scheme is that it introduces minor modifications in the UMTS nodes with respect to the computing power of the mobile terminals. Finally, we implement our approach in the ns-2 network simulator and we evaluate it under various conditions. The simulation results are presented along with their analysis.</p>
10aCongestion Control10aUMTS1 aBouras, Christos1 aAlexiou, Antonios1 aPapazois, Andreas  uhttp://telematics.upatras.gr/telematics/publications/congestion-control-multicast-transmission-over-umts?language=en01774nas a2200193   4500008004100000245008200041210006900123300001700192520108500209653001801294653000901312653001801321653000901339100002101348700002201369700002401391700002201415856014301437       2009                        eng d00aCost Analysis and Efficient Radio Bearer Selection for Multicasting over UMTS0 aCost Analysis and Efficient Radio Bearer Selection for Multicast  a 1159 - 11723 aAlong with the widespread deployment of the Third Generation (3G) cellular networks, the fast-improving
capabilities of the mobile devices, content, and service providers are increasingly interested in supporting
multicast communications over wireless networks and in particular over Universal Mobile Telecommunications
System (UMTS). To this direction, the Third Generation Partnership Project (3GPP) is currently standardizing the
Multimedia Broadcast/Multicast Service (MBMS) framework of UMTS. In this paper, we present an overview of
the MBMS multicast mode of UMTS. We analytically present the multicast mode of the MBMS and analyze its
performance in terms of packet delivery cost under various network topologies, cell types, and multicast users?
distributions. Furthermore, for the evaluation of the scheme, we consider different transport channels for the
transmission of the multicast data over the UMTS Terrestrial Radio-Access Network (UTRAN) interfaces. Finally,
we propose a scheme for the efficient radio bearer selection that minimizes total packet delivery cost.10aCost analysis10aMBMS10aPower Control10aUMTS1 aBouras, Christos1 aAlexiou, Antonios1 aKokkinos, Vasileios1 aRekkas, Evangelos  uhttp://telematics.upatras.gr/telematics/publications/cost-analysis-and-efficient-radio-bearer-selection-multicasting-over-umts?language=en01542nas a2200145   4500008004100000245005700041210005600098260001600154300001500170520102900185100002101214700002601235700001701261856011801278       2009                        eng d00aCUTER: An Efficient Useful Text Extraction Mechanism0 aCUTER An Efficient Useful Text Extraction Mechanism  c26 - 29 May  a 703 - 7083 aIn this paper we present CUTER, a system that processes HTML pages in order to extract the useful text from them. The mechanism is focalized on HTML pages that include news articles from major portals and blogs. As useful text we define the body of the article that contains the news report. In order to extract the body of the article we deconstruct the HTML page to its DOM model and we apply a set of algorithms in order to clean and correct the HTML code, locate and characterize each node of the DOM model and finally store the text from the nodes that are characterized as useful text nodes. CUTER is a subsystem of peRSSonal, a web tool that is used to obtain news articles from all over the world, process them and present them back to the end users in a personalized manner. The role of CUTER is to feed peRSSonal with the body of the articles that are collected from major news portals and blogs. In this paper we present the basic algorithms and experimental results on the efficiency of the CUTER text extractor.1 aBouras, Christos1 aPoulopoulos, Vassilis1 aAdam, George  uhttp://telematics.upatras.gr/telematics/publications/cuter-efficient-useful-text-extraction-mechanism?language=en01788nas a2200145   4500008004100000245004300041210004100084260001700125300001000142520130900152100002101461700002601482700002801508856010601536       2009                        eng d00aDate - based dynamic caching mechanism0 aDate based dynamic caching mechanism  cJune 18 - 20  a67-743 aNews portals based on the RSS protocol are becoming nowadays one of the dominant ways that Internet users follow in order to locate the information they are looking for. Search engines, which operate at the back-end of a big portion of these web sites, receive millions of queries per day on any and every walk of web life. While these queries are submitted by thousands of unrelated users, studies have shown that small sets of popular queries account for a significant fraction of the query stream. A second truth has to do with the high frequency that a particular user tends to submit the same or highly relative search requests to the engine. By combining these facts, in this paper, we design and analyze the caching algorithm deployed in our personalized RSS portal, a web-based mechanism for the retrieval, processing and presentation in a personalized view of articles and RSS feeds collected from major Internet news portals. By using moderate amounts of memory and little computational overhead, we achieve to cache query results in the server, both for personalized and non-personalized user searches. Our caching algorithm operates not in a stand-alone manner but it co-operates and binds with the rest of the modules of our Portal in order to accomplish maximum integration with the system.1 aBouras, Christos1 aPoulopoulos, Vassilis1 aSilintziris, Panagiotis  uhttp://telematics.upatras.gr/telematics/publications/date-based-dynamic-caching-mechanism?language=en01566nas a2200169   4500008004100000245006400041210006300105260002100168300001500189520098200204653000801186653000901194100002101203700002201224700002401246856012601270       2009                        eng d00aEfficient Assignment of Multiple E-MBMS Sessions toward LTE0 aEfficient Assignment of Multiple EMBMS Sessions toward LTE  c9 - 11 September  a 240 - 2503 aOne of the major prerequisites for Long Term Evolution (LTE) networks
is the mass provision of multimedia services to mobile users. To this end,
Evolved - Multimedia Broadcast/Multicast Service (E-MBMS) is envisaged to
play an instrumental role during LTE standardization process and ensure LTE?s
proliferation in mobile market. E-MBMS targets at the economic delivery, in
terms of power and spectral efficiency, of multimedia data from a single source
entity to multiple destinations. This paper proposes a novel mechanism for efficient
radio bearer selection during E-MBMS transmissions in LTE networks.
The proposed mechanism is based on the concept of transport channels combination
in any cell of the network. Most significantly, the mechanism manages to
efficiently deliver multiple E-MBMS sessions. The performance of the proposed
mechanism is evaluated and compared with several radio bearer selection
mechanisms in order to highlight the enhancements that it provides.10aLTE10aMBMS1 aBouras, Christos1 aAlexiou, Antonios1 aKokkinos, Vasileios  uhttp://telematics.upatras.gr/telematics/publications/efficient-assignment-multiple-e-mbms-sessions-toward-lte?language=en01496nas a2200181   4500008004100000245008000041210006900121260001600190300001800206520085200224653000901076653001801085653000901103100002101112700002201133700002401155856013501179       2009                        eng d00aAn Efficient Mechanism for Power Control Optimization in MBMS Enabled UTRAN0 aEfficient Mechanism for Power Control Optimization in MBMS Enabl  c5 - 8 April  a 1292 - 1297 3 aThis paper proposes a power control mechanism for
the efficient radio bearer selection in the Multimedia
Broadcast/Multicast Service (MBMS) framework of Universal
Mobile Telecommunications System (UMTS). The selection of the
most efficient transport channel in terms of power consumption
is a key point for MBMS enabled UMTS networks, since a wrong
transport channel selection for the transmission of the MBMS
data could result to a significant decrease in the total capacity of
the network. Different UMTS transport channels and power
saving techniques are examined and an algorithm that selects the
most efficient combination of the above parameters is proposed.
The proposed MBMS power control mechanism selects the
transport channel that minimizes the base station?s transmission
power in every cell of the network that serves multicast users.10aMBMS10aPower Control10aUMTS1 aBouras, Christos1 aAlexiou, Antonios1 aKokkinos, Vasileios  uhttp://telematics.upatras.gr/telematics/publications/efficient-mechanism-power-control-optimization-mbms-enabled-utran?language=en01675nas a2200169   4500008004100000245007300041210006900114260001800183520106700201653000801268653000901276653001801285100002101303700002201324700002401346856013501370       2009                        eng d00aAn Enhanced MBMS Power Control Mechanism towards Long Term Evolution0 aEnhanced MBMS Power Control Mechanism towards Long Term Evolutio  c22 - 24 April3 aLong Term Evolution (LTE) promises the delivery
of rich multimedia services in a more power and spectral
efficient way than its predecessor Universal Mobile
Telecommunication System (UMTS). To this direction, the newly
introduced Enhanced - Multimedia Broadcast/Multicast Service
(E-MBMS) framework is envisaged to play a fundamental role
during the LTE standardization. E-MBMS constitutes the
successor of MBMS which was introduced in the Release 6 of
UMTS in order to deliver multimedia data from a single source
entity to multiple destinations. This paper proposes a novel
mechanism for efficient radio bearer selection during E-MBMS
transmissions in LTE networks. The proposed mechanism is
based on the concept of transport channels combination (pointto-
point and/or point-to-multipoint radio bearers) in any
cell/sector of the network in which multicast users are residing.
The mechanism is evaluated through several realistic scenarios
and is compared with several radio bearer selection mechanisms
in order to highlight the enhancements that it provides.10aLTE10aMBMS10aPower Control1 aBouras, Christos1 aAlexiou, Antonios1 aKokkinos, Vasileios  uhttp://telematics.upatras.gr/telematics/publications/enhanced-mbms-power-control-mechanism-towards-long-term-evolution?language=en01931nas a2200193   4500008004100000245008400041210006900125260002000194300001500214520125800229653000801487653000901495653001801504653000901522100002101531700002201552700002401574856013901598       2009                        eng d00aAn Enhanced Mechanism for Efficient Assignment of Multiple sessions towards LTE0 aEnhanced Mechanism for Efficient Assignment of Multiple sessions  c26 - 30 October  a 384 - 3913 aThe provision of rich multimedia services, such as Mobile TV, is considered of key importance for the Long Term Evolution (LTE) proliferation in mobile market. To this direction, Evolved - Multimedia Broadcast/Multicast Service (E-MBMS) that targets at the efficient delivery of multimedia data from a single source entity to multiple destinations, is envisaged to play an instrumental role during LTE standardization process. However, both LTE and E-MBMS performance are limited by the base station?s transmission power. As an aftermath, efficient power allocation techniques should be implemented so as to ensure the mass provision of multimedia applications to mobile users. This paper proposes a novel mechanism for efficient radio bearer selection during E-MBMS transmissions in LTE networks. The proposed mechanism is based on the concept of transport channels combination in any cell of the network. Most significantly, the mechanism exploits the performance enhancements emerged from Multiple Input Multiple Output (MIMO) antennas used in LTE networks and manages to efficiently deliver multiple E-MBMS sessions. The proposed mechanism is thoroughly evaluated and compared with several radio bearer selection mechanisms existing in bibliography.10aLTE10aMBMS10aPower Control10aUMTS1 aBouras, Christos1 aAlexiou, Antonios1 aKokkinos, Vasileios  uhttp://telematics.upatras.gr/telematics/publications/enhanced-mechanism-efficient-assignment-multiple-sessions-towards-lte?language=en01699nas a2200157   4500008004100000245007000041210006900111520113100180653000801311653000901319653001801328100002101346700002201367700002401389856012801413       2009                        eng d00aEvaluation of Different Power Saving Techniques for MBMS Services0 aEvaluation of Different Power Saving Techniques for MBMS Service3 aOver the last years we have witnessed an explosive growth of multimedia computing, wireless communication and applications.
Following the rapid increase in penetration rate of broadband services, the Third Generation Partnership Project (3GPP) is
currently standardizing the Evolved-Multimedia Broadcast/Multicast Service (E-MBMS) framework of Long Term Evolution
(LTE), the successor ofUniversalMobile Telecommunications System (UMTS).MBMS constitutes a point-to-multipoint downlink
bearer service that was designed to significantly decrease the required radio and wired link resources. However, several obstacles
regarding the high-power requirements should be overcome for the realization of MBMS. Techniques, such as Macrodiversity
Combining and Rate Splitting, could be utilized to reduce the power requirement of delivering multicast traffic toMBMS users. In
this paper, we analytically present several power saving techniques and analyze their performance in terms of power consumption.
We provide simulation results that reveal the amount of power that is saved and reinforce the need for the usage of such techniques.10aLTE10aMBMS10aPower Control1 aBouras, Christos1 aAlexiou, Antonios1 aKokkinos, Vasileios  uhttp://telematics.upatras.gr/telematics/publications/evaluation-different-power-saving-techniques-mbms-services?language=en01581nas a2200133   4500008004100000245009700041210006900138260001500207520100700222100002101229700002201250700002001272856015501292       2009                        eng d00aEvaluation of Single Rate Multicast Congestion Control Schemes for MPEG-4 Video Transmission0 aEvaluation of Single Rate Multicast Congestion Control Schemes f  cJuly 1 - 33 aWe present in this paper a simulation-based
comparison of one of the best known multicast congestion
control schemes - TFMCC - against our proposed Adaptive
Smooth Multicast Protocol (ASMP). ASMP consists of a singlerate
multicast congestion control, which takes advantage of the
RTCP Sender (SR) and Receiver Reports (RR) in order to
adjust the sender?s transmission rate in respect of the network
conditions. The innovation in ASMP lays in the “smooth”
transmission rate, which is TCP-friendly and prevent
oscillations. We use an integrated simulation environment
named Multi-Evalvid-RA for the evaluation of the two
congestion control schemes. Multi-Evalvid-RA provides all the
necessary tools to perform simulation studies and assess the
video quality by using both network related metrics along with
video quality measurements. The performance evaluation
results show that ASMP is a very efficient solution for rate
adaptive multimedia applications and a serious competitor to
well know TFMCC.1 aBouras, Christos1 aGkamas, Apostolos1 aKioumourtzis, G  uhttp://telematics.upatras.gr/telematics/publications/evaluation-single-rate-multicast-congestion-control-schemes-mpeg-4-video-transmission?language=en01288nas a2200157   4500008004100000245004300041210004000084260001900124300001500143520077900158100002100937700002700958700002600985700002001011856009901031       2009                        eng d00aA Framework for H-Anim Support in NVEs0 aFramework for HAnim Support in NVEs  c5 - 9 February  a 286 - 2913 aMany applications of Networked Virtual Environment presuppose the users? representation by humanoid avatars
that are able to perform animations such as gestures and mimics. Example applications are computer supported
collaborative work or e-learning applications. Furthermore, there is a need for a flexible and easy way to
integrate humanoid standardized avatars in many different NVE platforms. Thus, the main aim of this paper is to
introduce a procedure of adding animations to an avatar that is complying with H-Anim standard and to present
a standardized way to integrate avatars among various NVEs. More specifically this paper presents a framework
for adding/loading custom avatars to an NVE and applying to them a set of predefined animations, using HAnim
standard.1 aBouras, Christos1 aTsiatsos, Thrasivoulos1 aTriglianos, Vasileios1 aChatziprimou, K  uhttp://telematics.upatras.gr/telematics/publications/framework-h-anim-support-nves?language=en01504nas a2200133   4500008004100000245004400041210004200085260001600127520105100143100002101194700002701215700002501242856010301267       2009                        eng d00aA Framework Model for DVEs using SIMUL80 aFramework Model for DVEs using SIMUL8  c3 - 6 March3 aDistributed Virtual Environment systems simulate the behaviour
and activities of a great number of users interacting in a virtual
world over a wide area network. The sizes of the virtual worlds
and the tremendous number of users that DVEs are called to
support require additional bandwidth and computational
resources. For handling these growing requirements a lot of work
has been done both to the direction of alternative architectural
solutions as well as to techniques and algorithms for handling the
limitations of these environments. For supporting large-scale
DVEs, extended infrastructure is needed in terms of both
hardware and software. However, both researchers and
application designers do not always have access to such extended
infrastructure and the assessment and evaluation of developed
techniques becomes extremely difficult. To this direction, this
paper presents a simulation modelling tool for networked servers
DVEs that could be used by designers for simulating the
performance of their approaches under different scenarios1 aBouras, Christos1 aTsiatsos, Thrasivoulos1 aGiannaka, Eleftheria  uhttp://telematics.upatras.gr/telematics/publications/framework-model-dves-using-simul8?language=en01428nas a2200133   4500008004100000245008900041210006900130300001500199520085800214100002101072700002701093700002501120856014901145       2009                        eng d00aIdentifying Best Practices for Supporting Broadbnad Growth: Methodology and Analysis0 aIdentifying Best Practices for Supporting Broadbnad Growth Metho  a 795 - 8073 aThis paperpresentsamethodologyforidentifyingbestpracticesfollowedbyvariouscountries
worldwide forsupportingbroadbandgrowth.Italsoinvestigatesandanalyzesthesepracticesusing
data concerningbroadbandpenetration,accesstechnologies,market,pricesandservicesforOECD
countriesduringtheperiod2004–2006.Themethodologyusedtolocatethebestpracticesisbasedon
three mainsteps:(a)thepresentationofthemainfactorsthathaveamajorimpactonbroadband
growth;(b)thedefinitionofwhatisa??bestpractice??basedonquantitativecriteriaand(c)the
calculationofabestpracticeindexandagoodpracticeindex,whichindicatesthatacountryfollowed
these bestorgoodpracticestosupportitsbroadbandgrowth,respectively.Thismethodologyindicated
that Denmark,UnitedStates,Japan,CanadaandRepublicofKoreafollowedbestpracticesfortheir
broadband growth,whileUnitedKingdomandtheNetherlandsfollowedgoodpractices.1 aBouras, Christos1 aTsiatsos, Thrasivoulos1 aGiannaka, Eleftheria  uhttp://telematics.upatras.gr/telematics/publications/identifying-best-practices-supporting-broadbnad-growth-methodology-and-analysis?language=en01573nas a2200169   4500008004100000245003300041210003300074260001700107300001500124520108100139100002101220700002501241700001301266700001501279700001401294856009501308       2009                        eng d00aManaging Objects in P2P DVEs0 aManaging Objects in P2P DVEs  cJuly 13 - 16  a 783 - 7893 aPeer to Peer Distributed Virtual Environment
systems have become a scalable solution for supporting a large
number of users. One of the main challenges for these systems is
to solve the awareness problem, since it is necessary for providing
a consistent view of the environment to each participant of the
simulation. Although different strategies have been proposed,
they exclusively focus on users. Nevertheless, most of current
DVE systems include additional non-autonomous elements,
denoted as objects, whose state should also be known to system
clients. This paper studies the different attributes and
characteristics that objects can have and can affect to their
management. Based on this study, this paper presents an
extension of a previously proposed avatar awareness method
(COVER), re-designed and modified for providing object
awareness in a distributed way. The performance evaluation
results show that the resulting awareness technique allows system
users to efficiently manage objects in a distributed way without
affecting the overall performance of the system.1 aBouras, Christos1 aGiannaka, Eleftheria1 aRueda, S1 aMorillo, P1 aOrduna, J  uhttp://telematics.upatras.gr/telematics/publications/managing-objects-p2p-dves?language=en01671nas a2200145   4500008004100000245002500041210002500066260002000091300001200111520124800123100002101371700002601392700001701418856009001435       2009                        eng d00aMonitoring RSS feeds0 aMonitoring RSS feeds  c2 - 4 September  a189-1983 aThe expansion of the World Wide Web has led to a chaotic state where the users of
the internet have to face and overcome the major problem of discovering information. For the
solution of this problem, many mechanisms were created based on crawlers who are browsing
the www and downloading pages. In this paper we describe “advaRSS” crawling mechanism
which intends to be the base utility for systems offering collections of news in real time to
internet user. In contrast to the common crawling mechanisms our system is focused on
fetching the latest news from the major and minor portals worldwide by utilizing their RSS
feeds. The news is produced in a random order any time of the day and thus the freshness of the
offline collection can be measured even in minutes. This means that the system has to be
updated with news every single time they occur. In order to achieve this we utilize the
communication channels that exist on the modern architecture of the WWW and more
specifically in the architecture of Web 2.0. As the RSS feeds are used by every major and
minor portal it is possible to keep our crawler up to date and retain a high freshness of the
“offline content” that is maintained in our system?s database.1 aBouras, Christos1 aPoulopoulos, Vassilis1 aAdam, George  uhttp://telematics.upatras.gr/telematics/publications/monitoring-rss-feeds?language=en01447nas a2200145   4500008004100000245007400041210006900115300001500184490000600199520090100205100002101106700002601127700002201153856012601175       2009                        eng d00aNetworking and Security Issues for Remote Gaming: The Approach of G@L0 aNetworking and Security Issues for Remote Gaming The Approach of  a 171 - 1810 v23 a<p>As the evolution of computer technology introduces new advances in networks among others, online gaming becomes a new trend. Following the trends of our era, The Games At Large IST Project introduces an innovative platform for running interactive, rich content multimedia applications over a Wireless Local Area Network. The Games at Large project's vision is to provide a new system architecture for Interactive Multimedia that will enhance existing CE devices such as, Set Top Boxes (STB), Small Screen and other devices, which are lacking both the CPU power and the graphical performance to provide a rich user experience. In this study we present the controllers' sub-system of the innovative mechanism that is implemented within the context of the Games at Large project. We furthermore provide information on the encryption and security of the aforementioned communication channel.</p>
1 aBouras, Christos1 aPoulopoulos, Vassilis1 aTsogkas, Vassilis  uhttp://telematics.upatras.gr/telematics/publications/networking-and-security-issues-remote-gaming-approach-gl?language=en01438nas a2200133   4500008004100000245005400041210005400095260001500149520096300164100002101127700002601148700002201174856010801196       2009                        eng d00aNetworking Aspects for the Security of Game Input0 aNetworking Aspects for the Security of Game Input  c13 January3 aFollowing the trends of our era, Games At Large IST Project introduces an innovative platform for running interactive, rich content multimedia applications over a Wireless Local Area Network. Games@Large project?s vision is to provide a new system architecture for Interactive Multimedia which will enhance existing CE devices such as, Set Top Boxes (STB), Small Screen and other devices, which are lacking both the CPU power and the graphical performance to provide a rich user experience. This paper presents the input command transferring module that provides encryption capabilities for ensuring the security of the transmitted sensitive user data. In a nutshell, the client software when capturing input from a keyboard device encrypts the commands that are transmitted over a Wireless Local Area Network, using a public key encryption scheme and the server is responsible for decrypting and executing the commands to the corresponding game application.1 aBouras, Christos1 aPoulopoulos, Vassilis1 aTsogkas, Vassilis  uhttp://telematics.upatras.gr/telematics/publications/networking-aspects-security-game-input?language=en01860nas a2200181   4500008004100000245006600041210006600107260001800173520123500191653000801426653000901434653001801443100002101461700002201482700002401504700002201528856012801550       2009                        eng d00aOptimal MBMS Power Allocation Exploiting MIMO in LTE Networks0 aOptimal MBMS Power Allocation Exploiting MIMO in LTE Networks  c26 - 29 April3 aIn the frame of the Long Term Evolution (LTE) of mobile networks, the provision of rich multimedia services, such as Mobile TV, is considered of key importance for the LTE proliferation in mobile market. To this end, Multimedia Broadcast/Multicast Service (MBMS) is envisaged to play an instrumental role during LTE standardization process. MBMS was introduced in the Release 6 of Universal Mobile Telecommunication System (UMTS) in order to deliver multimedia data from a single source entity to multiple destinations. However, downlink capacity in such networks is limited by base station transmission power. As an aftermath, in MBMS efficient power allocation techniques should be implemented so as to ensure the mass provision of multimedia applications to mobile users. In this paper we propose a power control scheme for efficient selection of MBMS bearers. The proposed mechanism on the one hand manages to economically utilize power resources during MBMS transmissions, while on the other hand exploits the performance enhancements emerged from Multiple Input Multiple Output (MIMO) antennas used in LTE networks. Simulation results indicate that the proposed scheme results to significant power and capacity improvements.10aLTE10aMBMS10aPower Control1 aBouras, Christos1 aAlexiou, Antonios1 aKokkinos, Vasileios1 aRekkas, Evangelos  uhttp://telematics.upatras.gr/telematics/publications/optimal-mbms-power-allocation-exploiting-mimo-lte-networks?language=en01682nas a2200181   4500008004100000245006500041210006500106260001600171300001500187520106700202653000901269653001801278653000901296100002101305700002201326700002201348856013001370       2009                        eng d00aOptimizing MBMS Power Allocation Through HSDPA Transmissions0 aOptimizing MBMS Power Allocation Through HSDPA Transmissions  c24 - 28 May  a 327 - 3323 aLong Term Evolution (LTE) promises the delivery of rich multimedia services in a more power and spectral efficient way than its predecessor Universal Mobile Telecommunication System (UMTS). To this direction, the newly introduced Enhanced - Multimedia Broadcast/Multicast Service (E-MBMS) framework is envisaged to play a fundamental role
during the LTE standardization. E-MBMS constitutes the successor of MBMS which was introduced in the Release 6 of UMTS in order to deliver multimedia data from a single source entity to multiple destinations. This paper proposes a novel
mechanism for efficient radio bearer selection during E-MBMS transmissions in LTE networks. The proposed mechanism is based on the concept of transport channels combination (point to-point and/or point-to-multipoint radio bearers) in any cell/sector of the network in which multicast users are residing.
The mechanism is evaluated through several realistic scenarios and is compared with several radio bearer selection mechanisms in order to highlight the enhancements that it provides.10aMBMS10aPower Control10aUMTS1 aBouras, Christos1 aAlexiou, Antonios1 aRekkas, Evangelos  uhttp://telematics.upatras.gr/telematics/publications/optimizing-mbms-power-allocation-through-hsdpa-transmissions?language=en01423nas a2200133   4500008004100000245008800041210006900129300001500198490000700213520087800220100002101098700002201119856014801141       2009                        eng d00aPerformance analysis of Relative service using TCP - aware marking and dynamic WRED0 aPerformance analysis of Relative service using TCP aware marking  a 277 - 3050 v223 a<p>The implementation of successful Assured Forwarding (AF) services according to the DiffServ framework remains a challenging problem today, despite the numerous proposals for AF PHB mechanisms and AF-based service implementations. The interaction of TCP and UDP traffic under an AF-based service and a number of relative issues such as fairness among flows, achievable bandwidth guarantees and qualitative performance have been taken into consideration in this work in order to address the existing limitations. We propose two modules, the TCP-Window Aware Marker (TWAM) and the Dynamic WRED (WRED) mechanism for implementing the DiffServ AF PHB. We provide analytical models and an experimental evaluation in order to demonstrate how they succeed in enhancing the quality, improving the performance and easing the deployment of a production level AF-based service.</p>
1 aBouras, Christos1 aSevasti, Afroditi  uhttp://telematics.upatras.gr/telematics/publications/performance-analysis-relative-service-using-tcp-aware-marking-and-dynamic-wred?language=en01963nas a2200133   4500008004100000245010400041210006900145260001800214520137700232100002101609700002701630700002501657856014701682       2009                        eng d00aPerformance Evaluation of a Dynamic Approach for Networked Servers Distributed Virtual Environments0 aPerformance Evaluation of a Dynamic Approach for Networked Serve  c22 - 27 March3 aDistributed Virtual Environment systems simulate the
behaviour and activities of a great number of concurrent
users interacting in a virtual world over a wide area
network. The advances both in computer technology and
networking infrastructures in combination to the advanced
applications and services developed, expanded the
popularity of DVEs and promoted their use in a wide range
of areas, such as learning and training, collaborative work,
military applications and multiplayer online games. The
sizes of the virtual worlds simulated and the tremendous
number of users that DVEs are called to support require
additional bandwidth and computational resources. For
handling these growing requirements a lot of work has been
done both to the direction of alternative architectural
solutions as well as to techniques and algorithms for
handling and overcoming the limitations of these
environments. However, recent research has shown that one
of the major limitations of networked servers DVE systems
is scalability. To this direction this paper presents on the one
hand a dynamic approach for DVEs, which exploits the
nature of these systems for the optimal resource
management and extended scalability support and on the
other hand, evaluates its performance through a series of
experiments and under various settings of the virtual world,
using Simul8 simulation tool.1 aBouras, Christos1 aTsiatsos, Thrasivoulos1 aGiannaka, Eleftheria  uhttp://telematics.upatras.gr/telematics/publications/performance-evaluation-dynamic-approach-networked-servers-distributed-virtual?language=en01913nas a2200145   4500008004100000245009100041210006900132260001800201300001200219520132100231100002101552700002201573700002001595856015201615       2009                        eng d00aPerformance Evaluation of Simulcast vs. Layered Multicasting over Best-effort Networks0 aPerformance Evaluation of Simulcast vs Layered Multicasting over  cSept. 24 - 26  a338-3483 aMulti-rate multicast schemes can be broadly classified
into two categories. In layered multicast, a video file is
transmitted by a base layer, which contains the most important
features of the video. Additional layers, called enhancement
layers, contain data that refine the quality of the base layer. In
simulcast, the video file is transmitted by replicated layers that
contain the same content at different quality. The benefits of
layered multicast versus simulcast are still under question, as
layered multicast presents higher complexity and more
challenging deployment than simulcast. In this paper, two multirate
multicast control schemes are compared. The layered
multicast SMCC congestion control against our proposed
solution for simulcast transmission, named ASSP. We compare
the two schemes under a controlled simulation environment
with the network simulator software (ns-2) by taking into
account the evaluation criteria in RFC 5166. The results
demonstrate that both SMCC and ASSP are TCP-friendly while
SMCC seems to suffers from small oscillations of the
transmission rate. In network topologies with low complexity
ASSP consumes no more bandwidth than SMCC for the
transmission of the different simulcast streams, while being a
simpler solution than the more complicated SMCC.1 aBouras, Christos1 aGkamas, Apostolos1 aKioumourtzis, G  uhttp://telematics.upatras.gr/telematics/publications/performance-evaluation-simulcast-vs-layered-multicasting-over-best-effort-networks?language=en01002nas a2200133   4500008004100000245008200041210006900123260001600192300001500208520046800223100002100691700002200712856013400734       2009                        eng d00aPersonalization  Mechanism for Delivering News Articles on the User's Desktop0 aPersonalization Mechanism for Delivering News Articles on the Us  c24 - 28 May  a 157 - 1623 aDeploying a generalized, multi-functional
mechanism that produces good results for personalizing
summarized and categorized news articles, seems to be a
panacea for most of the text-based, information retrieval
needs. In this paper, we present the personalization
algorithm, as well as a client side application that are
used as an extension to an already constructed system,
PeRSSonal, in order to deliver summarized and precategorized
news articles to the user.1 aBouras, Christos1 aTsogkas, Vassilis  uhttp://telematics.upatras.gr/telematics/publications/personalization-mechanism-delivering-news-articles-users-desktop?language=en01817nas a2200145   4500008004100000245006500041210006300106260001600169300001500185520127400200100002101474700002601495700002801521856012201549       2009                        eng d00aPersonalized News Search in WWW: Adapting on user's behavior0 aPersonalized News Search in WWW Adapting on users behavior  c24 - 28 May  a 125 - 1303 aPersonalized Web Search becomes nowadays a
promising option in the field of Information Retrieval and
search engines design by improving both output quality and
user experience. In this paper, we present and evaluate the
subsystem, which conducts the Advanced and Personalized
search of PeRSSonal, a web-based mechanism for the retrieval,
processing and presentation of articles and RSS feeds collected
from major news portals of the Internet. The proposed
technique uses information explicitly provided by the user in
his profile as well as information that the mechanism can learn
from the user?s behavior during his search and browsing
sessions in the system. As this behavior dynamically evolves,
the same happens to the user?s interests under the prism of the
search engine. By adopting this user-centric approach, we
manage to present the user with better-refined and more
focused results, incorporating his personal preferences to the
output. The algorithm operates not in a stand-alone manner
but it co-operates and binds with the rest of modules of
PeRSSonal in order to accomplish maximum integration with
the system. Furthermore, we introduce an enhancement in the
search function, based on cached results from past search
sessions of each user individually.1 aBouras, Christos1 aPoulopoulos, Vassilis1 aSilintziris, Panagiotis  uhttp://telematics.upatras.gr/telematics/publications/personalized-news-search-www-adapting-users-behavior?language=en01661nas a2200229   4500008004100000245003900041210003900080520097300119100002101092700002601113700002501139700001701164700001401181700001601195700001801211700003201229700002401261700001801285700001401303700001401317856010001331       2009                        eng d00aPlatform for Distributed 3D Gaming0 aPlatform for Distributed 3D Gaming3 aVideo games are typically executed on Windows platforms with DirectX API and require high performance CPUs and graphics
hardware. For pervasive gaming in various environments like at home, hotels, or internet cafes, it is beneficial to run games also
on mobile devices and modest performance CE devices avoiding the necessity of placing a noisy workstation in the living room or
costly computers/consoles in each room of a hotel. This paper presents a new cross-platform approach for distributed 3D gaming
in wired/wireless local networks.We introduce the novel system architecture and protocols used to transfer the game graphics data
across the network to end devices. Simultaneous execution of video games on a central server and a novel streaming approach of
the 3D graphics output to multiple end devices enable the access of games on low cost set top boxes and handheld devices that
natively lack the power of executing a game with high-quality graphical output.1 aBouras, Christos1 aPoulopoulos, Vassilis1 aJurgelionis, Audrius1 aFechteler, P1 aEisert, P1 aBellotti, F1 aDavid, Haggai1 aLaulajainen, Jukka, - Pekka1 aCarmichael, Richard1 aLaikari, Arto1 aPerala, P1 aGloria, A  uhttp://telematics.upatras.gr/telematics/publications/platform-distributed-3d-gaming?language=en01893nas a2200169   4500008004100000245004400041210004400085300001500129490000700144520137100151100002101522700002201543700001901565700001601584700001701600856010601617       2009                        eng d00aQoS experiences in native IPv6 networks0 aQoS experiences in native IPv6 networks  a 119 - 1370 v193 a<p>Deployment of IPv6 technology in research and commercial networks has been accelerated in the last few years. Inevitably, as more advanced services take advantage of the new technology, IPv6 traffic gradually increases. Today, there is limited experience in the deployment of Quality of Service (QoS) for IPv6 traffic in backbone networks that support the Differentiated Services framework. As available software and hardware is designed to handle IPv4 packets, there is a need to accurately measure and validate performance of QoS mechanisms in an IPv6 environment. This paper discusses tests and technical challenges in the deployment of IPv6 QoS in core networks, namely the production dual stack gigabit-speed Greek Research &amp; Education Network - GRNET and the IPv6-only 6NET European test network, using both hardware and software platforms. In either case, we succeeded in delivering advanced transport services to IPv6 traffic and provided different performance guarantees to portions of traffic. The deployed QoS schema was common for IPv6 and IPv4; in most cases both v4 and v6 traffic exhibited comparable performance per class while imposing no significantly different overhead on network elements. A major conclusion of our tests is that the IPv6 QoS mechanisms are efficiently supported with state-of-the-art router cards at gigabit speeds.</p>
1 aBouras, Christos1 aPrimpas, Dimitris1 aLiakopoulos, A1 aMaglaris, B1 aKalogeras, D  uhttp://telematics.upatras.gr/telematics/publications/qos-experiences-native-ipv6-networks?language=en01670nas a2200133   4500008004100000245006300041210006300104300001300167520116600180100002101346700002601367700002401393856011901417       2009                        eng d00aScalable Text Classification as a tool for Personalization0 aScalable Text Classification as a tool for Personalization  a 51 - 603 aWe consider scalability issues of the text classification problem where by
using (multi)-labeled training documents, we try to build classifiers that assign
documents into classes permitting classification in multiple classes. A new class of
classification problems; called ?scalable?, is introduced, with applications on web
mining. Scalable classification utilizes newly classified instances in order to improve the
accuracy of future classifications and capture changes in semantic representation of
different topics. In addition, definition of different similarity classes is allowed,
resulting in a ?per-user? classification procedure. Such an approach provides a new
methodology for building personalized applications. This is due to the fact that the user
becomes a part of the classification procedure. We explore solutions for the scalable text
classification problem and introduce an algorithm that exploits a new text analysis
technique that decomposes documents into the vector representation of their sentences
according to the user expertise. Finally, a web-based personalized news categorization
system that bases upon this approach is presented.1 aBouras, Christos1 aPoulopoulos, Vassilis1 aAntonellis, Ioannis  uhttp://telematics.upatras.gr/telematics/publications/scalable-text-classification-tool-personalization?language=en01667nas a2200145   4500008004100000245011600041210006900157260001700226300001200243520104700255100002101302700002201323700002001345856015601365       2009                        eng d00aSimulcast Transmission for Video Applications: Performance Evaluation with an Integrated Simulation Environment0 aSimulcast Transmission for Video Applications Performance Evalua  cJuly 13 - 16  a339-3463 aThis paper presents the performance evaluation of a
multi-rate multicast protocol named Adaptive Smooth Simulcast
Protocol (ASSP) for simulcast video transmission. ASSP
implements a single rate TCP-friendly protocol as the underlying
congestion control mechanism for each simulcast stream. ASSP is
built on top of the RTP/RTCP protocol and exploits the RTCP
sender and receiver reports for the dissemination of feedback
information. The key attributes of ASSP are: a) TCP-friendly
behavior, b) adaptive per-stream transmission rates, c) adaptive
scalability to large sets of receivers and finally d) smooth
transmission rates that are suitable for multimedia applications.
We evaluate the performance of ASSP under an integrated
simulation environment, which extends ns-2 and Evalvid-RA into
the multicast domain with the use of RTP/RTCP protocols.
Simulations conducted under this environment combine the
measurements of network metrics along with objective evaluation
criteria on the perceived video quality by the end user.1 aBouras, Christos1 aGkamas, Apostolos1 aKioumourtzis, G  uhttp://telematics.upatras.gr/telematics/publications/simulcast-transmission-video-applications-performance-evaluation-integrated-simulation?language=en01464nas a2200169   4500008004100000245005300041210005100094300001500145520091900160653002301079653000901102653000901111100002101120700002201141700002201163856010901185       2009                        eng d00aA Study of Multicast Congestion Control for UMTS0 aStudy of Multicast Congestion Control for UMTS  a 739 - 7543 aIn this paper, we study the applicability of multicast congestion control over universal mobile telecommunications
system (UMTS) networks. We analyze two well-known multicast congestion control schemes
for fixed networks, namely TCP-friendly multicast congestion control and pragmatic general multicast
congestion control. We investigate their behavior when they are employed in UMTS networks and we
analyze the problems arose when these mechanisms are applied over the wireless links of the UMTS
terrestrial radio-access network. Additionally, we propose necessary improvements to these legacy schemes
and explain the necessity of these modifications. The proposed schemes are implemented in the ns-2
network simulator and are evaluated under various network conditions and topologies. Finally, we measure
the performance of the proposed modified schemes and compare them with the corresponding legacy
mechanisms.10aCongestion Control10aMBMS10aUMTS1 aBouras, Christos1 aAlexiou, Antonios1 aPapazois, Andreas  uhttp://telematics.upatras.gr/telematics/publications/study-multicast-congestion-control-umts?language=en01560nas a2200145   4500008004100000245006000041210006000101260002100161300001100182520102500193100002101218700002601239700002401265856012501289       2009                        eng d00aTrash Article Detection using Categorization Techniques0 aTrash Article Detection using Categorization Techniques  cNovember 19 - 21  a 51-583 aWe explore techniques for detecting news articles containing invalid information, using the help of text categorization technology. The information that exists on the World Wide Web is huge enough in order to distract the users when trying to find useful information. In order to overcome the large amounts of data many methodologies of text categorization have been presented. One major problem we have to deal with is that many articles fetched by a crawler, then stored in a back-end database, and finally given as an input to a categorization subsystem, may not contain valid information for the user (trashy articles). This may lead to the user losing his trust towards the system. In this paper, we analyze the special properties of trashy news articles? categorization that allows us to detect them and we propose a specific methodology for trash detection. Finally, we evaluate the proposed algorithm on a news categorization system and we depict the overall benefit of a trash detection mechanism on the system.1 aBouras, Christos1 aPoulopoulos, Vassilis1 aTsichritzis, George  uhttp://telematics.upatras.gr/telematics/publications/trash-article-detection-using-categorization-techniques?language=en01563nas a2200145   4500008004100000245004500041210004500086260001600131300001500147520108900162100002101251700002601272700001701298856010201315       2009                        eng d00aUtilizing RSS feeds for crawling the Web0 aUtilizing RSS feeds for crawling the Web  c24 - 28 May  a 211 - 2163 aWe present “advaRSS” crawling mechanism which
is created in order to support peRSSonal, a mechanism used to
create personalized RSS feeds. In contrast to the common
crawling mechanisms our system is focalized on fetching the
latest news from the major and minor portals worldwide by
utilizing their communication channels. The challenge between
“advaRSS” and a usual crawler is the fact that the news is
produced in a random order any time of the day and thus the
freshness of the offline collection can be measured even in
minutes. This means that the system has to be updated with
news every single time they occur. In order to achieve this we
utilize the communication channels that exist on the modern
architecture of the WWW and more specifically in almost
every modern news portal. As the RSS feeds are used by every
major and minor portal it is possible to keep our crawler up to
date and retain a high freshness of the “offline content” that is
maintained in our system?s database by applying algorithms in
order to observe the temporal behaviour of each RSS feed.1 aBouras, Christos1 aPoulopoulos, Vassilis1 aAdam, George  uhttp://telematics.upatras.gr/telematics/publications/utilizing-rss-feeds-crawling-web?language=en01321nas a2200181   4500008004100000245006800041210006700109260002000176300001200196520066300208100002100871700002300892700002200915700001900937700002900956700002100985856013301006       2009                        eng d00aVideo Transmission over TFRC using cross-layer power management0 aVideo Transmission over TFRC using crosslayer power management  cSeptember 24-26  a333-3373 a<p>This paper presents the issues related to efficient transmission of encoded video (such as H.264) over wireless links using the TFRC protocol. It proposes a novel mechanism that utilizes cross-layer approaches for adaptation of the power transmission level of the sender and feedback information regarding the wireless connection status from the receiver for improved transmission statistics and therefore user experience without unnecessary power consumption. The mechanism is tested through simulations using ns2. Compared to the operation of the video transmission without the mechanism, we observe that it has benefits in terms of video quality.</p>
1 aBouras, Christos1 aKapoulas, Vaggelis1 aGkamas, Apostolos1 aStamos, Kostas1 aPapapanagiotou, Vassilis1 aZaoudis, Giannis  uhttp://telematics.upatras.gr/telematics/publications/video-transmission-over-tfrc-using-cross-layer-power-management?language=en01300nas a2200145   4500008004100000245008600041210006900127260001700196300001500213520071600228100002100944700002200965700002000987856014701007       2008                        eng d00aAdaptive Smooth Multicast Congestion Control for Adaptive Multimedia Transmission0 aAdaptive Smooth Multicast Congestion Control for Adaptive Multim  c16 - 18 June  a 269 - 2763 aWe introduce Adaptive Smooth Multicast Protocol
(ASMP), for multimedia transmission over best-effort networks.
The smoothness lays in the calculation and adaptation of the
transmission rate, which is based on dynamic estimation of
protocol parameters and dynamic adjustment of the “smoothness
factor”. ASMP key attributes are: a) adaptive scalability to large
sets of receivers, b) TCP-friendly behavior, c) high bandwidth
utilization, and finally d) smooth transmission rates, which are
suitable for multimedia applications. We evaluate the
performance of ASMP and investigate its behavior under various
network conditions through extensive simulations, conducted
with the network simulator software (ns2).1 aBouras, Christos1 aGkamas, Apostolos1 aKioumourtzis, G  uhttp://telematics.upatras.gr/telematics/publications/adaptive-smooth-multicast-congestion-control-adaptive-multimedia-transmission?language=en00519nas a2200133   4500008004100000245006300041210006300104300001300167100002100180700002200201700001900223700002200242856012100264       2008                        eng d00aAdaptive transmission of multimedia data over the Internet0 aAdaptive transmission of multimedia data over the Internet  a 16 - 221 aBouras, Christos1 aGkamas, Apostolos1 aStamos, Kostas1 aPrimpas, Dimitris  uhttp://telematics.upatras.gr/telematics/publications/adaptive-transmission-multimedia-data-over-internet?language=en01543nas a2200181   4500008004100000245009000041210006900131260001800200300001500218520087300233653000901106653001801115653000901133100002101142700002201163700002401185856015201209       2008                        eng d00aBalancing between Power Optimization and Iub Efficiency in MBMS enabled UMTS Networks0 aBalancing between Power Optimization and Iub Efficiency in MBMS   c1 - 3 October  a 355 - 3683 aMulticast transmission is one of the major goals for Universal Mobile
Telecommunication System (UMTS) that motivated the 3rd Generation Partnership
Project (3GPP) to launch the Multimedia Broadcast/Multicast Service (MBMS)
framework. MBMS constitutes a significant step towards the so-called Mobile
Broadband, since it allows the efficient utilization of network and radio resources.
One of most important problems that MBMS is currently facing is the assignment
of the appropriate transport channel for the transmission of MBMS data. This
paper proposes an alternative solution to this problem, by introducing a cost-based
scheme for the efficient radio bearer selection that minimizes the overall delivery
cost. Our approach, calculates the telecommunication cost over the most crucial
interfaces of UMTS; and based on this cost selects the appropriate radio bearer.10aMBMS10aPower Control10aUMTS1 aBouras, Christos1 aAlexiou, Antonios1 aKokkinos, Vasileios  uhttp://telematics.upatras.gr/telematics/publications/balancing-between-power-optimization-and-iub-efficiency-mbms-enabled-umts-networks?language=en01422nas a2200157   4500008004100000245005000041210004800091260001600139520091600155653000901071653000901080100002101089700002201110700002201132856011001154       2008                        eng d00aBridging UMTS and Multicast Routing in ns - 20 aBridging UMTS and Multicast Routing in ns 2  c3 - 7 March3 aIn this paper, we present the design and the implementation of a novel scheme for the multicast transmission of data over Universal Mobile Telecommunications System (UMTS) networks. The proposed scheme is implemented as an ns-2 network simulator module which can be employed to investigate various aspects of UMTS multicast. Apart from the normal multicast transmission over UMTS, we consider the handling of exceptional cases induced by user mobility scenarios. The proposed scheme is in accordance with the current specifications of the Multimedia Multicast/Broadcast Service (MBMS) defined by the 3rd Generation Partnership Project (3GPP) and introduces minor modifications in the UMTS architecture and the mobility management mechanisms. The performance of the proposed scheme is validated and analyzed through simulation experiments. Finally, the simulation results are presented along with their analysis.10aMBMS10aUMTS1 aBouras, Christos1 aAlexiou, Antonios1 aPapazois, Andreas  uhttp://telematics.upatras.gr/telematics/publications/bridging-umts-and-multicast-routing-ns-2?language=en00507nas a2200133   4500008004100000245005300041210005300094300001500147100002100162700002200183700002700205700002700232856011400259       2008                        eng d00aBusiness Models For Municipal Broadband Networks0 aBusiness Models For Municipal Broadband Networks  a 457 - 4651 aBouras, Christos1 aGkamas, Apostolos1 aTsiatsos, Thrasivoulos1 aTheofilopoulos, George  uhttp://telematics.upatras.gr/telematics/publications/business-models-municipal-broadband-networks?language=en01406nas a2200121   4500008004100000245008800041210006900129260002000198520087700218100002101095700002201116856014601138       2008                        eng d00aChallenges in Cross Layer Design for Multimedia Transmission over Wireless Networks0 aChallenges in Cross Layer Design for Multimedia Transmission ove  c13 - 15 October3 aThis paper examines the challenges of cross layer design for multimedia transmission over wireless networks. In wireless networks multimedia data transmission inherits also all the characteristics and constrains related to the propagation to the free space. One first striking difference between wired and wireless networks is the cause of packet losses. Packet losses in wired networks occur mainly due to congestion in the path between the sender and the receiver, while in wireless networks packet losses occur mainly due to corrupted packets as a result of the low Signal to Noise Ratio (SNR), the multi-path signal fading and the interference from neighbouring transmissions. A second difference between wired and wireless networks is the “mobility factor”. Mobility in wireless networks introduces a number of additional barriers in multimedia data transmission.1 aBouras, Christos1 aGkamas, Apostolos  uhttp://telematics.upatras.gr/telematics/publications/challenges-cross-layer-design-multimedia-transmission-over-wireless-networks?language=en01504nas a2200145   4500008004100000245007800041210006900119260002100188300001200209520093600221100002101157700002201178700002001200856013801220       2008                        eng d00aComparison of Single - Rate multicast Congestion Control protocol vs ASMP0 aComparison of Single Rate multicast Congestion Control protocol   c8 - 10 September  a309-3163 a<p>We present in this paper a simulation-based comparison of two single-rate multicast congestion control schemes (TFMCC and PGMCC) against our proposed Adaptive Smooth Multicast Protocol (ASMP). ASMP consists of a single-rate multicast congestion control, which takes advantage of RTCP Sender (SR) and Receiver Reports (RR). The innovation in ASMP lays in the “smooth” transmission rate, which is TCP-friendly and prevent oscillations. The smooth behavior is naturally well suited to multimedia applications as high oscillations of the sending rate may create distortions of Audio-Video (AV) encoders and decoders. Simulation results, which are conducted with the network simulator ns2 software, showed that ASMP can be regarded as a serious competitor of TFMCC and PGMCC. In many cases, ASMP outperforms TFMCC in terms of TCP-friendliness and smooth transmission rates, while PGMCC presents lower scalability than ASMP.</p>
1 aBouras, Christos1 aGkamas, Apostolos1 aKioumourtzis, G  uhttp://telematics.upatras.gr/telematics/publications/comparison-single-rate-multicast-congestion-control-protocol-vs-asmp?language=en01572nas a2200145   4500008004100000245004800041210004800089260001700137300001200154520107800166100002101244700002601265700002201291856011301313       2008                        eng d00aCreating dynamic personalized RSS summaries0 aCreating dynamic personalized RSS summaries  c16 - 18 July  a 1 - 153 aAutomatically generated, human-quality text summarization systems are difficult both to develop and to evaluate, partly because articles differ along several dimensions: length, writing style and lexical usage. In this paper we propose a framework that, by utilizing RSS feeds, is able to personalize on the needs of the users and on the needs of their device, in order to present to the end-user only a fraction of the news articles covering just the useful information that derives from them. The created summaries utilize a weighted combination of statistical and linguistic features which leads to sentence scoring and selection. The procedure is assisted by categorization results as well as personalization algorithms that enhance the summarization module. The mechanism is evaluated using classic precision-recall metrics together with statistical results from real users. Within this framework we have created the PeRSSonal system that is able to create personalized, pre-categorized, dynamically generated RSS feeds focalized on the end user?s small screen device.1 aBouras, Christos1 aPoulopoulos, Vassilis1 aTsogkas, Vassilis  uhttp://telematics.upatras.gr/telematics/publications/creating-dynamic-personalized-rss-summaries?language=en00555nam a2200121   4500008004100000245009200041210006900133100002100202700002300223700001900246700002400265856014400289       2008                        eng d00aDiscrete Mathematics: A) The Mathematics of Computer Science, B) Problems and Solutions0 aDiscrete Mathematics A The Mathematics of Computer Science B Pro1 aBouras, Christos1 aKirousis, Lefteris1 aSpirakis, Paul1 aVoutsadakis, George  uhttp://telematics.upatras.gr/telematics/publications/discrete-mathematics-mathematics-computer-science-b-problems-and-solutions?language=en00478nas a2200121   4500008004100000245005500041210005300096300001500149100002100164700002700185700002500212856011900237       2008                        eng d00ae-Collaboration Concepts, Systems and Applications0 aeCollaboration Concepts Systems and Applications  a 165 - 1711 aBouras, Christos1 aTsiatsos, Thrasivoulos1 aGiannaka, Eleftheria  uhttp://telematics.upatras.gr/telematics/publications/e-collaboration-concepts-systems-and-applications?language=en01536nas a2200121   4500008004100000245007300041210006900114300001300183520105000196100002101246700001901267856012801286       2008                        eng d00aAn Efficient Architecture for Bandwidth Brokers in DiffServ Networks0 aEfficient Architecture for Bandwidth Brokers in DiffServ Network  a 27 - 463 aIn this article we examine the architecture of an entity used for automatic management and provisioning of resources for DiffServ networks. We examine the existing literature and implementations in this area, focusing on the design choices made, and we propose an architecture for the design of Bandwidth Brokers that combines an adaptive admission control algorithm for increased utilization of network resources and a mechanism for reducing the complexity overhead that intends to be both simple and effective. Specifically, we present a novel architecture for the admission control module that aims at achieving a satisfactory balance between maximizing the resource utilization for the network provider and minimizing the overhead of the module. We complement our theoretical discussion with extensive experimental simulations for the proposed Bandwidth Broker components and analysis of the results. The simulations study the possible configurations of the proposed algorithm and also compare it with alternative admission control policies.1 aBouras, Christos1 aStamos, Kostas  uhttp://telematics.upatras.gr/telematics/publications/efficient-architecture-bandwidth-brokers-diffserv-networks?language=en01732nas a2200193   4500008004100000245006700041210006700108260002100175300001100196520108000207653000901287653001801296653000901314100002101323700002201344700002401366700002201390856012601412       2008                        eng d00aEfficient Assignment of Multiple MBMS Sessions in B3G Networks0 aEfficient Assignment of Multiple MBMS Sessions in B3G Networks  c22 - 25 Septemer  a 1 - 53 aIn Universal Mobile Telecommunication System
(UMTS), the downlink capacity is limited by the base station
transmission power. Therefore, power control plays an important
role to minimize the transmitted power shared among unicast and
multicast users within a cell. In Multimedia Broadcast/Multicast
Service (MBMS), power control targets to the efficient utilization
of radio and network resources. However, the expected high
demand for such services stresses the need for an efficient
scheme, capable of dynamically allocating radio resources to
parallel MBMS sessions. This paper proposes a power control
mechanism for efficient MBMS session assignment in next
generation UMTS networks. The mechanism shares efficiently the
available power resources of UMTS base stations to MBMS
sessions running in the network. Furthermore, the mechanism is
evaluated through several realistic scenarios and the results
indicate the ability of the mechanism to utilize efficiently the
radio resources and to ensure the service continuity when parallel
MBMS services running in the network.10aMBMS10aPower Control10aUMTS1 aBouras, Christos1 aAlexiou, Antonios1 aKokkinos, Vasileios1 aRekkas, Evangelos  uhttp://telematics.upatras.gr/telematics/publications/efficient-assignment-multiple-mbms-sessions-b3g-networks?language=en01529nas a2200169   4500008004100000245006000041210006000101260001100161300001300172520096900185653000901154653000901163100002101172700002201193700002201215856012201237       2008                        eng d00aEfficient Delivery of MBMS Multicast Traffic over HSDPA0 aEfficient Delivery of MBMS Multicast Traffic over HSDPA  c6 July  a 50 - 553 aMultimedia Broadcast/Multicast Service (MBMS) and High-Speed Downlink Packet Access (HSDPA) are two key technologies that constitute a significant step towards the Mobile Broadband. MBMS was introduced by the third Generation Partnership Project (3GPP) in order to support broadcast and multicast communication over wireless networks and in particular over Universal Mobile Telecommunications System (UMTS). Concurrently, HSDPA aims to ensure the transmission of high peak data rates and increase system capacity. In this paper we evaluate the performance of MBMS multicast transmission over the premier transport channel used in HSDPA, named High Speed-Downlink Shared Channel (HS-DSCH). Due to the fact that downlink transmission power is the scarcest resource in UMTS networks, the evaluation is performed through an analytical dimensioning of the MBMS downlink transmission power. Furthermore, the impacts of power allocation on MBMS capacity are investigated.10aMBMS10aUMTS1 aBouras, Christos1 aAlexiou, Antonios1 aRekkas, Evangelos  uhttp://telematics.upatras.gr/telematics/publications/efficient-delivery-mbms-multicast-traffic-over-hsdpa?language=en01424nas a2200157   4500008004100000245006700041210006400108300001500172520087000187653000901057653000901066100002101075700002201096700002601118856012201144       2008                        eng d00aAn Efficient Mechanism for Multicast Data Transmission in UMTS0 aEfficient Mechanism for Multicast Data Transmission in UMTS  a 455 - 4713 aIn this paper, we present an efficient scheme for the multicast transmission of the data in the Universal Mobile Telecommunications System (UMTS). We take advantage of the tree topology of the examined network and we introduce the use of Routing Lists (RLs) in the nodes of the UMTS. The adoption of these lists leads to the decrement of the transmitted packets and to the efficient use of network resources in the multicast transmission of the data. We describe in detail the appropriate steps for the successful multicast transfer of data. Furthermore, we analyze the handling of special cases such as user mobility scenarios. Especially, the various handover types are examined along with the Serving Radio Network Subsystem relocation procedure. Finally, we implement our approach in the NS-2 simulator and we present the performance of the multicast mechanism.10aMBMS10aUMTS1 aBouras, Christos1 aAlexiou, Antonios1 aAntonellis, Dimitrios  uhttp://telematics.upatras.gr/telematics/publications/efficient-mechanism-multicast-data-transmission-umts?language=en01344nas a2200133   4500008004100000245008300041210006900124260002000193520078700213100002101000700002601021700002201047856014101069       2008                        eng d00aEvaluating PeRSSonal: A Medium for Personalized Dynamically Created News Feeds0 aEvaluating PeRSSonal A Medium for Personalized Dynamically Creat  c13 - 15 October3 aIn this paper we present the evaluation of PeRSSonal, a system which generates personalized, dynamically created RSS feeds and is focalized on small screen devices. PeRSSonal is a complete system able to consolidate news from major news portals, categorize and summarize them, and finally syndicate them personalized to the end users. In an era where news feeds, become a part of the daily Internet life and small screen devices gain more and more attention by the end users, PeRSSonal seems the panacea that could provide fast and easy access to everyday news. The system is based on algorithms that incorporate the user into the categorization and summarization procedure of news articles, while the results are presented to the user according to his/her interests and end device.1 aBouras, Christos1 aPoulopoulos, Vassilis1 aTsogkas, Vassilis  uhttp://telematics.upatras.gr/telematics/publications/evaluating-perssonal-medium-personalized-dynamically-created-news-feeds?language=en01790nas a2200181   4500008004100000245008700041210006900128260002100197520112300218653000901341653001801350653000901368100002101377700002201398700002401420700002201444856014201466       2008                        eng d00aEvaluation of Different Radio Bearer Selection Approaches for MBMS in B3G Networks0 aEvaluation of Different Radio Bearer Selection Approaches for MB  c24 - 27 November3 aThe spread of multimedia data has drastically differentiated the current landscape of Universal Mobile Telecommunication System (UMTS) networks, posing the need for further enhancements in its Radio Resource Management (RRM) strategies. Introduced in 3rd Generation Partnership Project (3GPP) Release 6, the Multimedia Broadcast/Multicast Services (MBMS) framework aims at the efficient usage of network and radio resources for the transmission of multimedia services. The main requirement during the provision of MBMS multicast services is to minimize the transmission power of UMTS base stations. To this direction, several mechanisms have been proposed that either allow a simultaneous deployment of Point-to-Point (PTP) and Point-to-Multipoint (PTM) transmissions, or a single transport channel deployment (PTP or PTM) in a cell at any given time. Main objective of this paper is to study these mechanisms, compare them in terms of power consumption, underline the advantages that they may offer; and finally to propose enhancements that will ensure the lowest possible power consumption during MBMS transmissions.10aMBMS10aPower Control10aUMTS1 aBouras, Christos1 aAlexiou, Antonios1 aKokkinos, Vasileios1 aRekkas, Evangelos  uhttp://telematics.upatras.gr/telematics/publications/evaluation-different-radio-bearer-selection-approaches-mbms-b3g-networks?language=en01463nas a2200133   4500008004100000245008400041210006900125300001200194520090400206100002101110700002701131700002501158856014601183       2008                        eng d00aExploiting Virtual Environments to Support Collaborative e-Learning Communities0 aExploiting Virtual Environments to Support Collaborative eLearni  a 1 - 223 aThe main goal of this paper is to facilitate educational designers and developers by providing a point of reference for making decisions on how to incorporate 3D environments into the applications they develop as well as for extending their capabilities by integrating more functionality. Therefore, this paper presents the design principles for virtual spaces, which aim at supporting multi-user communication in web-based learning communities. In addition the implementation of these principles is presented using as point of reference EVE Training Area. This environment constitutes a three-dimensional space where participants, represented by 3D humanoid avatars, have the ability to use a variety of 3D e-collaboration tools for learning together. Furthermore, this paper presents collaborative e-learning usage scenarios that could be realized by exploiting collaborative virtual environments.1 aBouras, Christos1 aTsiatsos, Thrasivoulos1 aGiannaka, Eleftheria  uhttp://telematics.upatras.gr/telematics/publications/exploiting-virtual-environments-support-collaborative-e-learning-communities?language=en01157nas a2200169   4500008004100000245005000041210005000091260001700141520058200158100002100740700002300761700001900784700002200803700002600825700002900851856010700880       2008                        eng d00aExtending QoS support from Layer 3 to Layer 20 aExtending QoS support from Layer 3 to Layer 2  c16 - 19 June3 aThis paper presents some of the results
obtained by the application of Ethernet Layer 2 Quality
of Service in IP networks. IP networks traditionally
provide Quality of Service in Layer 3. However, since
there is an enormous existing Layer 2 infrastructure,
today?s networks could benefit from the deployment of
Layer 2 Quality of Service and the cooperation between
Layer 2 Quality of Service and Layer 3 Quality of
Service. In this paper, experiments are suggested and
conducted and a scheme is suggested for efficient
cooperation between Layer 2 and Layer 3 QoS
provisioning.1 aBouras, Christos1 aKapoulas, Vaggelis1 aStamos, Kostas1 aPrimpas, Dimitris1 aPoulopoulos, Leonidas1 aPapapanagiotou, Vassilis  uhttp://telematics.upatras.gr/telematics/publications/extending-qos-support-layer-3-layer-2?language=en01281nas a2200133   4500008004100000245009100041210006900132260001600201520071800217100002100935700002200956700002000978856014900998       2008                        eng d00aExtending the Functionality of RTP/RTCP Implementation in Network Simulator (ns – 2)0 aExtending the Functionality of RTPRTCP Implementation in Network  c3 - 7 March3 aIn this paper, we present a modification of the ns2 code for the RTP/RTCP protocols. The legacy RTP/RTCP code in ns2 has not yet been validated but it provides a framework of the protocol?s specification for experimental use. We have modified the code by adding all the RTP/RTCP protocol?s attributes that are defined in RFC 3550 and related to QoS metrics. We have also implemented additional algorithms and functions in order to enhance our modified code with TCP friendly bandwidth share behavior. Our protocol, named RTPUP (“UP” stands for the University of Patras), is offered as a package and is fully documented so that it can be used for simulations and research within the ns2 simulation environment.1 aBouras, Christos1 aGkamas, Apostolos1 aKioumourtzis, G  uhttp://telematics.upatras.gr/telematics/publications/extending-functionality-rtprtcp-implementation-network-simulator-ns-%E2%80%93-2?language=en01262nas a2200157   4500008004100000245004400041210004400085260001900129300001200148520075000160100002100910700002300931700002200954700002600976856010201002       2008                        eng d00aExtending the QoS provisioning in GRNET0 aExtending the QoS provisioning in GRNET  cSept. 25 - 27   a152-1563 aThis work presents the extension of QoS provisioning in GRNET, so as to include a “second chance” mechanism for rejected premium-traffic requests. Regularly, accepted requests can be satisfied even if there is a single failure in the network and no specific path is allocated within the network core. The extended mechanism allows for rejected requests to be reconsidered for acceptance over a specific path, under the condition that if a failure occurs in this path, then the corresponding traffic will lose the premium handling and will be then considered as best effort. The extended scheme allows for more flexibility and gives a balanced alternative to the “either full guarantees or no QoS at all” situation of the existing scheme.1 aBouras, Christos1 aKapoulas, Vaggelis1 aPrimpas, Dimitris1 aPoulopoulos, Leonidas  uhttp://telematics.upatras.gr/telematics/publications/extending-qos-provisioning-grnet?language=en00990nas a2200133   4500008004100000245006500041210006500106260002000171300001500191520047700206100002100683700002200704856013000726       2008                        eng d00aImproving text summarization using noun retrieval techniques0 aImproving text summarization using noun retrieval techniques  c3 - 5 September  a 593 - 6003 aText Summarization and categorization have always been two of the
most demanding information retrieval tasks. Deploying a generalized, multifunctional
mechanism that produces good results for both of the aforementioned
tasks seems to be a panacea for most of the text-based, information retrieval
needs. In this paper, we present the keyword extraction techniques, exploring
the effects that part of speech tagging has on the summarization procedure of an
existing system.1 aBouras, Christos1 aTsogkas, Vassilis  uhttp://telematics.upatras.gr/telematics/publications/improving-text-summarization-using-noun-retrieval-techniques?language=en01502nas a2200145   4500008004100000245006600041210006300107260002600170300001500196520094800211100002101159700002701180700002501207856012401232       2008                        eng d00aAn Integrated Architecture for Supporting Vocational Training0 aIntegrated Architecture for Supporting Vocational Training  bIDEA Group Publishing  a 197 - 2183 a<p>E-learning and Web-based training have evolved over time from a newborn trend for complementing the learning process to a major form of education and training for supporting mainly geographically scattered users. The basic aim of this chapter is the description of a platform for open and distance training, which is mainly focused at supporting the needs of Vocational Training Centers as well as of institutions providing life-long adult training and learning. In particular, the issues that this chapter focuses on are vocational education and training characteristics and requirements, the current situation and technological trends in ICT-supported VET, the development framework and processes while it also proposes basic vocational training services and the system architecture of the integrated platform. The presented platform aims to provide services of both synchronous and asynchronous and collaborative distance learning.</p>
1 aBouras, Christos1 aTsiatsos, Thrasivoulos1 aGiannaka, Eleftheria  uhttp://telematics.upatras.gr/telematics/publications/integrated-architecture-supporting-vocational-training?language=en00397nas a2200133   4500008004100000245002200041210001800063300001500081100002100096700002200117700001900139700002200158856008300180       2008                        eng d00aThe IPv6 protocol0 aIPv6 protocol  a 257 - 2621 aBouras, Christos1 aGkamas, Apostolos1 aStamos, Kostas1 aPrimpas, Dimitris  uhttp://telematics.upatras.gr/telematics/publications/ipv6-protocol?language=en01930nas a2200169   4500008004100000245009100041210006900132260002600201300001500227490000600242520126800248100002101516700002201537700002201559700002401581856015501605       2008                        eng d00aMetropolitan Broadband Networks: Design and implementation aspects and business models0 aMetropolitan Broadband Networks Design and implementation aspect  bIDEA Group Publishing  a 196 - 2100 v13 a<p>This chapter presents the design principles that cover the implementation of broadband infrastructure in the region of Western Greece, by examining all the necessary parameters that arise while implementing such a critical developmental project. The broadband infrastructure that is deployed is either based on optical fiber (on big municipalities) or on wireless systems (OFDM based and WiFi cells). Furthermore, we present as two case studies, all issues of the designing of the Metropolitan Area Network of Patras, the third biggest city of Greece and the Wireless Access Network of Messatida. The major target of the broadband networks is to interconnect the buildings of the public sector in the city and also deploy infrastructure (fibers or wireless systems) that will create conditions of competition in providing both access and content services in advantage of the end consumer. The usage of the broadband infrastructure by service providers will be based on the open availability of the infrastructure in a cost effective way. Finally, we present the main characteristics of a proposed business plan that ensures financial viability of the broadband infrastructure and guarantees the administration, growth, and exploitation of infrastructure.</p>
1 aBouras, Christos1 aPrimpas, Dimitris1 aAlexiou, Antonios1 aPapagiannopoulos, J  uhttp://telematics.upatras.gr/telematics/publications/metropolitan-broadband-networks-design-and-implementation-aspects-and-business-models?language=en01291nas a2200145   4500008004100000245008400041210006900125260001600194300001200210520071800222100002100940700002200961700001900983856014301002       2008                        eng d00aMonitoring End to End Bandwidth on Demand Circuits over Ethernet Infrastructure0 aMonitoring End to End Bandwidth on Demand Circuits over Ethernet  c8 - 10 July  a 3 - 133 aAutoBAHN (Automated Bandwidth Allocation across Heterogeneous Networks) has specified and is now prototyping a Bandwidth on Demand (BoD) service intended to operate in a multi-domain environment using heterogeneous transmission technologies. The AutoBAHN system aims at providing a guaranteed capacity, connection-oriented service between two end points. This paper highlights the architecture of the monitoring system for the AutoBAHN service, the implementations challenges and the decisions taken, focusing on monitoring end to end BoD reservations over ethernet infrastructure. In addition this paper presents the architecture and the components of the AutoBAHN monitoring system for ethernet infrastructures.1 aBouras, Christos1 aGkamas, Apostolos1 aStamos, Kostas  uhttp://telematics.upatras.gr/telematics/publications/monitoring-end-end-bandwidth-demand-circuits-over-ethernet-infrastructure?language=en01480nas a2200145   4500008004100000245005400041210005300095300001400148520099600162653000901158653000901167100002101176700002201197856011501219       2008                        eng d00aMulticast in UMTS: Evaluation and Recommendations0 aMulticast in UMTS Evaluation and Recommendations  a463 - 4813 aIt is known that multicasting is an efficient method of supporting group communication as it allows the transmission of packets to multiple destinations using fewer network resources. Along with the widespread deployment of the third generation cellular networks, the fast-improving capabilities of the mobile devices, content and service providers are increasingly interested in supporting multicast communications over wireless networks and in particular over Universal Mobile Telecommunications System (UMTS). Multicasting is a more efficient method of supporting group communication than unicasting or broadcasting, as it allows transmission and routing of packets to multiple destinations using fewer network resources. In this paper the three above mentioned methods of supporting group communication are analyzed in terms of their performance. The critical parameters of primary interest for the evaluation of any method are the packet delivery cost and the scalability of the method.10aMBMS10aUMTS1 aBouras, Christos1 aAlexiou, Antonios  uhttp://telematics.upatras.gr/telematics/publications/multicast-umts-evaluation-and-recommendations?language=en00435nas a2200133   4500008004100000245003300041210003300074300001500107100002100122700002200143700001900165700002200184856009500206       2008                        eng d00aMulticast of Multimedia Data0 aMulticast of Multimedia Data  a 316 - 3221 aBouras, Christos1 aGkamas, Apostolos1 aStamos, Kostas1 aPrimpas, Dimitris  uhttp://telematics.upatras.gr/telematics/publications/multicast-multimedia-data?language=en00425nas a2200121   4500008004100000245003500041210003500076300001700111100002100128700002700149700002500176856010200201       2008                        eng d00aNetworked Virtual Environments0 aNetworked Virtual Environments  a 2789 - 27931 aBouras, Christos1 aTsiatsos, Thrasivoulos1 aGiannaka, Eleftheria  uhttp://telematics.upatras.gr/telematics/publications/networked-virtual-environments-0?language=en01751nas a2200157   4500008004100000245004200041210004200083260001600125300001500141520124200156100002101398700002601419700002201445700002301467856010301490       2008                        eng d00aNetworking Aspects for Gaming Systems0 aNetworking Aspects for Gaming Systems  c8 - 13 June  a 650 - 6553 a<p>As the evolution of computer technology introduces new advances in networks among others, online gaming becomes a new trend. Following the trends of our era, Games At Large IST Project introduces an innovative platform for running interactive, rich content multimedia applications over a Wireless Local Area Network. Games at Large project?s vision is to provide a new system architecture for Interactive Multimedia which will enhance existing CE devices such as, Set Top Boxes (STB), Small Screen and other devices, which are lacking both the CPU power and the graphical performance to provide a rich user experience. This paper presents the controllers? subsystem of the innovative mechanism that will be implemented in the context of Games at Large project. More specifically, it presents the general architecture of the complete system and focuses on the “capturing” and “execution of commands” modules at the different clients and the remote execution of the commands on server side. The client software captures the input from the different input devices, sends the commands over a Wireless Local Area Network and the server is responsible for receiving and executing the commands to the corresponding application.</p>
1 aBouras, Christos1 aPoulopoulos, Vassilis1 aTsogkas, Vassilis1 aSengounis, Ioannis  uhttp://telematics.upatras.gr/telematics/publications/networking-aspects-gaming-systems?language=en01920nas a2200193   4500008004100000245009500041210006900136260002000205300001500225520121000240653000901450653001801459653000901477100002101486700002201507700002401529700002201553856015101575       2008                        eng d00aA Novel Mechanism for Radio Capacity Maximization during MBMS transmission in B3G Networks0 aNovel Mechanism for Radio Capacity Maximization during MBMS tran  c27 - 31 October  a 185 - 1923 aThis paper proposes a novel mechanism for efficient power
control during multicast transmissions in Beyond 3rd Generation
(B3G) mobile networks. The mechanism utilizes optimally the
available power resources of Universal Mobile
Telecommunication System (UMTS) base stations, resulting to
network capacity maximization. The proposed mechanism is
based on the concept of transport channels combination (point-topoint
and/or point-to-multipoint radio bearers) in any cell/sector
of the network in which Multimedia Broadcast/Multicast Service
(MBMS) users are residing. In particular, the transport channel
combination that minimizes the transmission power of the base
station is selected for the transmission of the MBMS traffic to the
corresponding cell. The mechanism is evaluated through several
realistic scenarios and the results indicate the ability of the
mechanism to utilize optimally the radio resources of the network.
Furthermore, our approach is compared with several power
control mechanisms existing in the bibliography, including the 3rd
Generation Partnership Project (3GPP) approaches (presented in
3GPP TS 25.346 and 3GPP TR 25.922), in order to highlight the
enhancements that it provides10aMBMS10aPower Control10aUMTS1 aBouras, Christos1 aAlexiou, Antonios1 aKokkinos, Vasileios1 aRekkas, Evangelos  uhttp://telematics.upatras.gr/telematics/publications/novel-mechanism-radio-capacity-maximization-during-mbms-transmission-b3g-networks?language=en01802nas a2200181   4500008004100000245008400041210006900125260002900194300001300223520114300236653000901379653001801388653000901406100002101415700002201436700002201458856014001480       2008                        eng d00aA Novel Power Counting Mechanism for Enhanced MBMS Performance in UMTS Networks0 aNovel Power Counting Mechanism for Enhanced MBMS Performance in   c30 September - 2 October  a 57 - 683 aOne of the key objectives of Universal Mobile Telecommunications System (UMTS) is the realization of enhanced end-user experience through the provision of rich multimedia services, ensuring in parallel an economical delivery cost for service providers. Multimedia Broadcast/Multicast Services (MBMS) framework of UMTS epitomizes the increasing popularity of such applications by efficiently delivering multimedia traffic to a large number of users and optimizing the radio interface of UMTS networks. For exploiting resource efficiency, MBMS specifications consider the Counting Mechanism which decides whether it is more economic to deliver MBMS multicast traffic over point-to-point (PTP) or point-to-multipoint (PTM) bearers. However, the necessity to further improve MBMS resource efficiency and integrate new technologies such as High Speed Downlink Packet Access (HSDPA) stresses the need for an advanced Counting Mechanism. To this direction, in this paper we propose a novel Power Counting Mechanism which performs optimal power resource utilization and incorporates the HSDPA broadband extension of UMTS for enhanced performance.10aMBMS10aPower Control10aUMTS1 aBouras, Christos1 aAlexiou, Antonios1 aRekkas, Evangelos  uhttp://telematics.upatras.gr/telematics/publications/novel-power-counting-mechanism-enhanced-mbms-performance-umts-networks?language=en01405nas a2200133   4500008004100000245010300041210006900144260002900213520080900242100002101051700002201072700002001094856015701114       2008                        eng d00aPerformance Evaluation of Cross Layer Adaptive Multimedia Transmission: The case of Wired Networks0 aPerformance Evaluation of Cross Layer Adaptive Multimedia Transm  c28 September - 2 October3 aThis paper presents the performance evaluation of the wired part of a proposed framework with cross layer adaptation mechanisms, for multimedia transmission over wired and wireless networks. The performance evaluation of the proposed framework is contacted through a number of simulations with the network simulator software (ns2), which has been enhanced in order to support the functionality of the proposed framework. The performance evaluation includes various simulation scenarios in order to investigate the behavior of the proposed framework under different conditions. The proposed framework can support both wired and wireless receivers in one platform in which, cross layer information are used to support the wireless users whereas TCP friendly estimations are used to support the wired users.1 aBouras, Christos1 aGkamas, Apostolos1 aKioumourtzis, G  uhttp://telematics.upatras.gr/telematics/publications/performance-evaluation-cross-layer-adaptive-multimedia-transmission-case-wired-networks?language=en01096nas a2200145   4500008004100000245006900041210006900110260001700179300001500196520054800211100002100759700001900780700002400799856012700823       2008                        eng d00aPerformance Study of the Mobile IPv6 Protocol and its Variations0 aPerformance Study of the Mobile IPv6 Protocol and its Variations  c23 - 25 July  a 438 - 4423 aIn this paper, we use the OMNET++ simulator in 
order to evaluate the performance of the basic Mobile IPv6 
protocol  and  some  of  its  proposed  variations.  The  most 
important  metric  we  are  interested  in  is  the  handover 
latency, which is measured for various combinations of the 
proposed Mobile  IPv6  variations  and  then  this  metric  is 
used, combined with  factors  such as  the complexity of  the 
implementation,  in order  to evaluate and  identify  the best 
possible configuration for the operation of the protocol.1 aBouras, Christos1 aStamos, Kostas1 aAristomenopoulos, G  uhttp://telematics.upatras.gr/telematics/publications/performance-study-mobile-ipv6-protocol-and-its-variations?language=en01637nas a2200133   4500008004100000245010200041210006900143300001500212520105200227100002101279700002601300700002201326856015501348       2008                        eng d00aPeRSSonal's core functionality evaluation: Enhancing text labeling through personalized summaries0 aPeRSSonals core functionality evaluation Enhancing text labeling  a 330 - 3453 aIn this manuscript we present the summarization and categorization subsystems of a complete mechanism
that begins with web-page fetching and concludes with representation of the collected data to the
end users through a personalized portal. The system intends to collect articles from major news portals
and, following an algorithmic procedure, to create a more user friendly and personalized “view”
of the articles. Before presenting the information back to the end user, the core of our mechanism automatically
categorizes data and then extracts personalized summaries. We focalize to the core of the
mechanism and more specifically, we present the algorithms used for the summarization and the categorization
of texts. The algorithms are not utilized only for producing isolated data, targeted to a specific
subsystem, but a combination of the algorithms, which achieves co-operation of the categorization and
summarization mechanisms, is introduced in order to enhance text labeling through the personalized
summaries that are constructed.1 aBouras, Christos1 aPoulopoulos, Vassilis1 aTsogkas, Vassilis  uhttp://telematics.upatras.gr/telematics/publications/perssonals-core-functionality-evaluation-enhancing-text-labeling-through-personalized?language=en01822nas a2200181   4500008004100000245005700041210005700098260001500155300001500170520123700185653000901422653001801431653000901449100002101458700002201479700002401501856011501525       2008                        eng d00aPower Saving Methods for MBMS Transmissions in UTRAN0 aPower Saving Methods for MBMS Transmissions in UTRAN  c6 - 9 July  a 374 - 3793 aThe demand for wireless multimedia communications thrives in today?s consumer and corporate market. The need to evolve multimedia applications and services is at a critical point given the proliferation and integration of wireless systems. Multimedia Broadcast Multicast Services (MBMS) was introduced in Third Generation Partnership Project (3GPP) Release 6 in order to more efficiently use network and radio resources for the transmission of multimedia data, both in the core network and most importantly in the air interface of UTRAN (UMTS Terrestrial Radio Access Network). However, several obstacles, regarding the high power requirements, should be overcome for the realization of MBMS. The fact that Node B?s transmission power is a limited resource and must be shared among all MBMS users in a cell indicates the need for power control during MBMS transmissions. Several techniques, such as Dynamic Power Setting and Macro Diversity Combining, have been proposed in order to reduce the power requirements of delivering multicast traffic to MBMS users. This paper examines the efficiency of the utilization of these power saving techniques, by presenting simulation results that will reveal the amount of power that is saved.10aMBMS10aPower Control10aUMTS1 aBouras, Christos1 aAlexiou, Antonios1 aKokkinos, Vasileios  uhttp://telematics.upatras.gr/telematics/publications/power-saving-methods-mbms-transmissions-utran?language=en00492nas a2200133   4500008004100000245005200041210005200093300001500145100002100160700002200181700002200203700001900225856011400244       2008                        eng d00aQuality of Service and Service Level Agreements0 aQuality of Service and Service Level Agreements  a 418 - 4241 aBouras, Christos1 aGkamas, Apostolos1 aPrimpas, Dimitris1 aStamos, Kostas  uhttp://telematics.upatras.gr/telematics/publications/quality-service-and-service-level-agreements?language=en00447nas a2200133   4500008004100000245003700041210003700078300001500115100002100130700002200151700001900173700002200192856009900214       2008                        eng d00aQuality of Service architectures0 aQuality of Service architectures  a 425 - 4311 aBouras, Christos1 aGkamas, Apostolos1 aStamos, Kostas1 aPrimpas, Dimitris  uhttp://telematics.upatras.gr/telematics/publications/quality-service-architectures?language=en00437nas a2200133   4500008004100000245003500041210003100076300001500107100002100122700002200143700001900165700002200184856009700206       2008                        eng d00aReal-time protocols - RTP/RTCP0 aRealtime protocols RTPRTCP  a 463 - 4681 aBouras, Christos1 aGkamas, Apostolos1 aStamos, Kostas1 aPrimpas, Dimitris  uhttp://telematics.upatras.gr/telematics/publications/real-time-protocols-rtprtcp?language=en01627nas a2200145   4500008004100000245005200041210005000093260002000143300001500163520112200178100002101300700002701321700002601348856010701374       2008                        eng d00aA SIP spatial audio server for the EVE platform0 aSIP spatial audio server for the EVE platform  c22 - 25 January  a 395 - 4023 aWhen it comes to 3D Virtual Environments it is well known that 3D sound is of great importance to the whole interactive experience. The percept of sound is a major counterpart for the eyesight, since it describes the location, the momentum and the attitude towards the listener, of each surrounding entity. The sound can offer precision of spatial perception that cannot be achieved by the eye itself. Thus the support of 3D surround sound of high fidelity is mandatory for a 3D Virtual platform. The evolution of Internet telephony led to the introduction of new session establishment and management protocols. The most important of them, the Session Initiation Protocol (SIP), is a robust, lightweight reliable and fast application-layer control (signaling) protocol that is highly adopted for creating, modifying and terminating sessions. This protocol can be of extreme importance in establishing audio sessions for multi-user platforms. This paper presents the work done for developing a SIP 3D spatial audio server for a multi-user virtual environments platform, called EVE, in order to support 3D spatial audio1 aBouras, Christos1 aTsiatsos, Thrasivoulos1 aTriglianos, Vasileios  uhttp://telematics.upatras.gr/telematics/publications/sip-spatial-audio-server-eve-platform?language=en01502nas a2200145   4500008004100000245007600041210006900117260001800186300001200204520094000216100002101156700002201177700002001199856013701219       2008                        eng d00aSmooth Multicast Congstion Control for Adaptive Multimedia Transmission0 aSmooth Multicast Congstion Control for Adaptive Multimedia Trans  c28 - 30 April  a146-1523 aIn this paper we introduce an equation-based
smooth multicast congestion control for adaptive multimedia
transmission over best-effort wired networks. Target of the
proposed schema is (a) smooth transmission rate, in order to
minimize the Audio-Video (AV) encoding and decoding
distortion and (b) TCP friendly transmission. The “smoothness”
lays in the way the TCP-Friendly transmission rate is filtered.
We integrate the congestion control functions in the RTP
protocol and use the RTCP sender and receiver reports to
provide the necessary feedback information for the sender?s
adaptive transmission rate. The performance evaluation of the
smooth adaptation and TCP-friendliness is conducted through a
number of simulations with the network simulator software
(ns2). Our intention is to use this congestion control in the context
of a proposed framework for multimedia transmission over wired
and wireless networks.1 aBouras, Christos1 aGkamas, Apostolos1 aKioumourtzis, G  uhttp://telematics.upatras.gr/telematics/publications/smooth-multicast-congstion-control-adaptive-multimedia-transmission?language=en01465nas a2200145   4500008004100000245013300041210006900174300001500243520082600258100002101084700002401105700001601129700001701145856015701162       2008                        eng d00aThe status of broadband in western Greece: a study on the supply and the demand of Broadband Services for e-Government promotion0 astatus of broadband in western Greece a study on the supply and   a 326 - 3443 aFast and reliable access technology is necessary for developing efficient and effective e-Government services. The existence of a direct relationship between the presence of a broadband network and the availability of e-Government services has frequently been debated in the literature. This paper presents the results of a study conducted by the RACTI (Research Academic Computer Technology Institute), which investigates the current status of broadband with regards to the demand for and the supply of broadband services and infrastructures that will support these services, in the Western Greece Region. Broadband promotes open effective governance and improved services to citizens while creating a new economy based on knowledge. Broadband development has a significant impact on e-Government support and diffusion. 1 aBouras, Christos1 aPapagiannopoulos, J1 aKatsikas, S1 aGritzalis, S  uhttp://telematics.upatras.gr/telematics/publications/status-broadband-western-greece-study-supply-and-demand-broadband-services-e-government?language=en01201nas a2200157   4500008004100000245009600041210006900137260001600206300001500222520056400237100002100801700002200822700002700844700002500871856014700896       2008                        eng d00aSupporting Broadband Growth in an Interregional Level: The Case of Greece-Italy Partnership0 aSupporting Broadband Growth in an Interregional Level The Case o  c15 - 16 May  a 151 - 1613 aBroadband is a key element of the developments that are taking place in the electronic communications markets and the European Commission has been particularly active in promoting broadband developments. This paper presents the objectives and the methodology of a project for supporting the broadband growth in an Interregional Level between regions of Italy and Greece. Main target of the project is the technology and knowhow transfer (relative to broadband) to SMEs (Small and Medium Enterprises) and the demonstration of broadband advantages and benefits.1 aBouras, Christos1 aGkamas, Apostolos1 aTsiatsos, Thrasivoulos1 aGiannaka, Eleftheria  uhttp://telematics.upatras.gr/telematics/publications/supporting-broadband-growth-interregional-level-case-greece-italy-partnership?language=en01378nas a2200169   4500008004100000245010600041210006900147300001400216520069600230100002100926700002700947700002500974700002600999700001601025700001501041856015201056       2008                        eng d00aA Unified Framework for Political Parties to Support e-Democracy Practices: the case of a Greek Party0 aUnified Framework for Political Parties to Support eDemocracy Pr  a 98 - 1173 aE-government and e-democracy constitute a central theme
in information society policy at all levels: local, regional, national, European
and even globally. To this direction, a variety of efforts have been made, and
many systems have been developed. This paper proposes a methodology for
designing and implementing web-based services that can support e-democracy
practices. Furthermore, the paper presents and describes the effort made by
a Greek political party to this direction, for the design and development of
a unified framework for providing, supporting and managing e-democracy
services. The paper describes the actions taken and the work done according to
the proposed methodology.1 aBouras, Christos1 aTsiatsos, Thrasivoulos1 aGiannaka, Eleftheria1 aPoulopoulos, Vassilis1 aKarounos, T1 aPriftis, A  uhttp://telematics.upatras.gr/telematics/publications/unified-framework-political-parties-support-e-democracy-practices-case-greek-party?language=en00374nas a2200121   4500008004100000245002100041210002000062300001500082100002100097700002200118700002600140856008600166       2008                        eng d00aWi-Fi Technology0 aWiFi Technology  a 711 - 7161 aBouras, Christos1 aAlexiou, Antonios1 aAntonellis, Dimitrios  uhttp://telematics.upatras.gr/telematics/publications/wi-fi-technology?language=en01475nas a2200157   4500008004100000245008000041210006900121300001300190520087200203653002301075653000901098100002101107700002201128700002601150856014101176       2007                        eng d00aAdaptive and Reliable Video Transmission over UMTS for Enhanced Performance0 aAdaptive and Reliable Video Transmission over UMTS for Enhanced   a 65 - 813 aThis paper proposes a mechanism for the congestion control for video transmission over universal mobile telecommunications system (UMTS). Our scheme is applied when the mobile user experiences real-time multimedia content and adopts the theory of a widely accepted rate control method in wired networks, namely equation-based rate control. In this approach, the transmission rate of the multimedia data is determined as a function of the packet loss rate, the round trip time and the packet size and the server explicitly adjusts its sending rate as a function of these parameters. Furthermore, we examine the performance of the UMTS for real-time video transmission using real-time protocols. Through a number of experiments, we measure performance parameters such as end-to-end delay, delay in radio access network, delay jitter and throughput in the wireless link.10aCongestion Control10aUMTS1 aBouras, Christos1 aAlexiou, Antonios1 aAntonellis, Dimitrios  uhttp://telematics.upatras.gr/telematics/publications/adaptive-and-reliable-video-transmission-over-umts-enhanced-performance?language=en00493nas a2200133   4500008004100000245005500041210005500096300001300151653000900164100002100173700002200194700002600216856011700242       2007                        eng d00aAdaptive Transmission of Multimedia Data over UMTS0 aAdaptive Transmission of Multimedia Data over UMTS  a 20 - 2410aUMTS1 aBouras, Christos1 aAlexiou, Antonios1 aAntonellis, Dimitrios  uhttp://telematics.upatras.gr/telematics/publications/adaptive-transmission-multimedia-data-over-umts?language=en00606nas a2200145   4500008004100000245009300041210006900134260001600203100002100219700001900240700002200259700002000281700001800301856014100319       2007                        eng d00aAMPS - ANStool: Interoperability of automated tools for the provisioning of QoS services0 aAMPS ANStool Interoperability of automated tools for the provisi  c21 - 24 May1 aBouras, Christos1 aStamos, Kostas1 aPrimpas, Dimitris1 aVarvitsiotis, A1 aHaniotakis, V  uhttp://telematics.upatras.gr/telematics/publications/amps-anstool-interoperability-automated-tools-provisioning-qos-services?language=en01576nas a2200121   4500008004100000245006900041210006400110300001700174520109500191100002101286700002201307856012501329       2007                        eng d00aAn analytical QoS service model for delay - based differentation0 aanalytical QoS service model for delay based differentation  a 3549 - 35633 aThe increased need for Quality of Service (QoS) in today?s IP networks has concentrated a lot of research and implementation efforts. Carefully designed and managed priority services are essential for quality-demanding traffic, especially in large-scale IP-based environments where aggregation of flows is extensive and a variety of traffic types co-exist. Although individual mechanisms have been widely investigated, not much related work exists on integrated approaches to QoS provisioning that are also feasible to implement. This work presents a thorough approach to the design, dimensioning and provisioning of a high priority service for high-quality demanding traffic over an IP network. Our approach employs efficient scheduling and a dynamic admission control scheme while demonstrating an outstanding performance in terms of the quality offered to QoS-demanding traffic. A novel feature is also introduced: while other existing schemes only focus on provisioning of service rate guarantees, ours achieves in addition differentiation of the end-to-end delay perceived by IP flows.1 aBouras, Christos1 aSevasti, Afroditi  uhttp://telematics.upatras.gr/telematics/publications/analytical-qos-service-model-delay-based-differentation?language=en01355nas a2200169   4500008004100000245005200041210004500093260001900138300001300157520081400170653002300984653000901007100002101016700002201037700002201059856010401081       2007                        eng d00aOn the Applicability of pgmcc to UMTS Multicast0 aApplicability of pgmcc to UMTS Multicast  c5 - 7 December  a 67 - 723 aIn this paper, we investigate the applicability of the Pragmatic General Multicast Congestion Control (pgmcc) scheme to the multicast data delivery over Universal Mobile Telecommunications System (UMTS) networks. We show that the pgmcc scheme cannot support the degradation of the radio channels in the UMTS Terrestrial Radio-Access Network (UTRAN). Our major contribution is that the legacy scheme is modified in order to cope with the packet losses caused by either the temporary or the permanent degradation of the radio channel. The proposed scheme introduces minor modifications in the UMTS nodes and respects the limited computing power of the mobile equipment. Finally, we simulate our approach and we evaluate it under various conditions. The simulation results are presented along with their analysis10aCongestion Control10aUMTS1 aBouras, Christos1 aAlexiou, Antonios1 aPapazois, Andreas  uhttp://telematics.upatras.gr/telematics/publications/applicability-pgmcc-umts-multicast?language=en01668nas a2200169   4500008004100000245009800041210006900139260001500208300001500223520099100238100002101229700002201250700002701272700002401299700002701323856014801350       2007                        eng d00aBusiness Models for Broadband Municipal Optical Networks: A proposed model for the Greek case0 aBusiness Models for Broadband Municipal Optical Networks A propo  c1 - 4 July  a 727 - 7323 aThis paper proposes an optimal business model for the successful operation of the currently developing broadband metropolitan area networks in Greece. Having recorded and examined relevant international practices, we describe in detail the way that these networks should be managed, operated, maintained and expanded. Taking into consideration that these infrastructures will alter the broadband map of Greece widely, that Greece currently has one of the lowest broadband penetration percentages in Europe and that the proper exploitation of the networks to be deployed could boost the demand for broadband connections and applications, the proposition of the optimal business model appears to be of vital importance. We present the proposed optimal business model in detail including information regarding network management and network expansion of the broadband metropolitan networks and viability issues regarding the authority which will manage the broadband metropolitan networks.1 aBouras, Christos1 aGkamas, Apostolos1 aTsiatsos, Thrasivoulos1 aPapagiannopoulos, J1 aTheofilopoulos, George  uhttp://telematics.upatras.gr/telematics/publications/business-models-broadband-municipal-optical-networks-proposed-model-greek-case?language=en01320nas a2200145   4500008004100000245006900041210006900110260001500179300001500194520077500209100002100984700002201005700002001027856012701047       2007                        eng d00aChallenges in cross layer adaptation for multimedia transmission0 aChallenges in cross layer adaptation for multimedia transmission  c3 - 8 July  a 129 - 1333 aOver the last years a number of new protocols have been developed for multimedia applications in the whole OSI layer?s scale. In order to support better wireless user the cross layer design paradigm has been proposed. This paper presents the challenges in designing and implementation of cross layer adaptation schemes for multimedia transmission over wired and wireless networks. In addition, the paper proposes the basic aspects of a cross-layer adaptation framework for multimedia transmission over wired and wireless networks. The main concept is based on a “holistic approach” in which all layers participate to the adaptation process and make its own contributions. Finally, the proposed framework can support both wired and wireless receivers in one platform.1 aBouras, Christos1 aGkamas, Apostolos1 aKioumourtzis, G  uhttp://telematics.upatras.gr/telematics/publications/challenges-cross-layer-adaptation-multimedia-transmission?language=en00428nas a2200121   4500008004100000245003800041210003800079300001500117100002100132700002600153700002400179856010300203       2007                        eng d00aContent Transformation Techniques0 aContent Transformation Techniques  a 119 - 1231 aBouras, Christos1 aPoulopoulos, Vassilis1 aAntonellis, Ioannis  uhttp://telematics.upatras.gr/telematics/publications/content-transformation-techniques?language=en01483nas a2200181   4500008004100000245005300041210005300094260001500147300001500162520091500177653001801092653000901110653000901119100002101128700002201149700002201171856010801193       2007                        eng d00aCost Analysis of the MBMS Multicast Mode of UMTS0 aCost Analysis of the MBMS Multicast Mode of UMTS  c1 - 4 July  a 797 - 8023 aAlong with the widespread deployment of the third generation cellular networks, the fast-improving capabilities of the mobile devices, content and service providers are increasingly interested in supporting multicast communications over wireless networks and in particular over Universal Mobile Telecommunications System (UMTS). To this direction, the third Generation Partnership Project (3GPP) is currently standardizing the Multimedia Broadcast/Multicast Service (MBMS) framework of UMTS. In this paper, we present an overview of the MBMS multicast mode of UMTS. We analytically present the multicast mode of the MBMS and analyze its performance in terms of packet delivery cost under various network topologies, cell types and multicast users? distributions. Furthermore, for the evaluation of the scheme, we consider different transport channels for the transmission of the data over the UTRAN interfaces.10aCost analysis10aMBMS10aUMTS1 aBouras, Christos1 aAlexiou, Antonios1 aRekkas, Evangelos  uhttp://telematics.upatras.gr/telematics/publications/cost-analysis-mbms-multicast-mode-umts?language=en01597nas a2200133   4500008004100000245008600041210006900127260002200196520103100218100002101249700002701270700002501297856014101322       2007                        eng d00aDesign and architecture of an online system for Vocational Education and Training0 aDesign and architecture of an online system for Vocational Educa  c26 - 28 September3 aE-learning and tele-training have been evolved over time from a newborn trend for complementing the learning process to a major form of education and training for supporting mainly geographically scattered users. Learning and training, can be applied to a wide variety of fields and areas, each of which is accompanied by some special characteristics related to the field of learning/training, to the tools needed for the realization of the training process as well as to the familiarization of the target audience to the selected technologies. Basic aim of this paper is the description of a platform for open and distance training, which is mainly focused at supporting the needs of Vocational Training Centres as well as of institutions providing life-long adult training and learning. In particular, the issues that this paper focuses on are vocational education and training characteristics and requirements while it also proposes basic vocational training services and the system architecture of the integrated platform.1 aBouras, Christos1 aTsiatsos, Thrasivoulos1 aGiannaka, Eleftheria  uhttp://telematics.upatras.gr/telematics/publications/design-and-architecture-online-system-vocational-education-and-training?language=en01567nas a2200157   4500008004100000245007900041210006900120260001500189300001300204520097900217653000901196100002101205700002201226700002701248856013401275       2007                        eng d00aAn efficient mechanism for adaptive multimedia transmission in 3G networks0 aefficient mechanism for adaptive multimedia transmission in 3G n  c3 - 8 July  a 11 - 183 aThis paper proposes a mechanism for the congestion control for video transmission over Universal Mobile Telecommu-nications System (UMTS). Our scheme is applied when the mobile user experiences real time multimedia content and adopts the theory of a widely accepted rate control method in wired networks, namely equation based rate control. In this approach, the transmission rate of the multimedia data is determined as a function of the packet loss rate, the round trip time and the packet size and the server explicitly adjusts its sending rate as a function of these parameters. Through a number of simulations and experiments we validate the correctness and measure the performance and efficiency of the mechanism. The mechanism at first level is evaluated through simulations that carried out in the ns-2 simulator. At sec-ond level, in order to validate the proposed mechanism in real world traffic scenar-ios we perform some experiments in a commercial UMTS network.10aUMTS1 aBouras, Christos1 aAlexiou, Antonios1 aBarounis, Konstantinos  uhttp://telematics.upatras.gr/telematics/publications/efficient-mechanism-adaptive-multimedia-transmission-3g-networks?language=en01758nas a2200133   4500008004100000245005800041210005800099260001700157520126100174100002101435700002601456700002201482856012001504       2007                        eng d00aEfficient Summarization Based On Categorized Keywords0 aEfficient Summarization Based On Categorized Keywords  c25 - 28 June3 aThe information that exists on the World Wide Web is enormous enough in order to distract the users when trying to find useful information. In order to overcome the large amounts of data many personalization and summarization mechanisms have been presented. In this paper we propose a mechanism that applies summarization techniques on articles extracted from the web, based on the categorization procedure (also applied on the same articles). Through extensive experiments we proved that the summarization procedure can affect the categorization mechanism and vice versa. This means that when the results of the summarization mechanism seem to be weak, then the categorization can be used in order to provide a more efficient summary and on the other hand when the categorization procedure becomes too overloaded, the summarized articles can be used in order to categorize the article more efficiently. Moreover this paper introduces that the combination of summarization and categorization can lead to more efficient results not only for both mechanisms but for a personalized portal also. Finally, we propose a complete mechanism that can be used in order to provide the users with helpful tools in order to locate more easily the information they need.1 aBouras, Christos1 aPoulopoulos, Vassilis1 aTsogkas, Vassilis  uhttp://telematics.upatras.gr/telematics/publications/efficient-summarization-based-categorized-keywords?language=en01319nas a2200145   4500008004100000245004600041210004500087260001800132300001500150520084000165100002101005700001901026700002201045856010601067       2007                        eng d00aEnhancing ns-2 with DiffServ QoS features0 aEnhancing ns2 with DiffServ QoS features  c25 - 29 March  a 117 - 1243 aIn this paper, we present work that we have carried out in extending the ns-2 simulator in order to study and validate Quality of Service issues and related architectures. In the case of the DiffServ framework, simulation is valuable since an analytical approach of mechanisms and services is infeasible due to the aggregation and multiplexing of flows. This paper covers work in extending ns-2 functionality towards the direction of realistic traffic generation and a series of mechanisms defined by the DiffServ architecture. We have also extended ns-2 with the functionality of Bandwidth Brokers, which are entities for managing the resources and negotiating end to end resource reservations between domains. The Bandwidth Broker ns-2 implementation is useful for studying the related architectures and admission control procedures.1 aBouras, Christos1 aStamos, Kostas1 aPrimpas, Dimitris  uhttp://telematics.upatras.gr/telematics/publications/enhancing-ns-2-diffserv-qos-features?language=en01623nas a2200169   4500008004100000245004500041210004500086260002000131520109500151653000901246653000901255100002101264700002201285700002401307700002201331856010001353       2007                        eng d00aEvaluation of the multicast mode of MBMS0 aEvaluation of the multicast mode of MBMS  c3 - 6 September3 aMulticasting is an efficient way for delivering rich
multimedia applications to large user groups as it allows the
transmission of packets to multiple destinations using fewer
network resources. Content and service providers are
increasingly interested in supporting multicast
communications over wireless networks and in particular over
Universal Mobile Telecommunications System (UMTS). To
this direction, the third Generation Partnership Project (3GPP)
is currently standardizing the Multimedia Broadcast/Multicast
Service (MBMS) framework of UMTS. In this paper, we
present an overview of the MBMS multicast mode of UMTS.
We analytically present the multicast mode of the MBMS and
analyze its performance in terms of packet delivery cost under
various network topologies, cell environments and multicast
users? distributions. Furthermore, for the evaluation of the
scheme, we consider different transport channels for the
transmission of the data over the UTRAN interfaces and
propose a cost based scheme for the efficient radio bearer
selection that minimizes the packet delivery cost.10aMBMS10aUMTS1 aBouras, Christos1 aAlexiou, Antonios1 aKokkinos, Vasileios1 aRekkas, Evangelos  uhttp://telematics.upatras.gr/telematics/publications/evaluation-multicast-mode-mbms?language=en01887nas a2200145   4500008004100000245008400041210006900125260002100194300001500215520129200230100002101522700002701543700002501570856014601595       2007                        eng d00aExploiting Virtual Objects Attributes and Avatars Behavior in DVEs Partitioning0 aExploiting Virtual Objects Attributes and Avatars Behavior in DV  c28 - 30 November  a 157 - 1633 aPartitioning constitutes one of the most critical challenges a distributed virtual environment needs to handle and is related to the efficient assignment of the existing entities of the virtual world to the available resources of the system. The efficient partitioning arises from the need of high consistency maintenance among participating users? view, as virtual reality applications are characterized by the high degree of realism they aim to achieve. To the direction of partitioning algorithms, a lot of work has been done, which has been more intense due to the evolution of network technologies and the familiarization of users with virtual reality systems. This paper presents a partitioning approach, which is based on the degree of interaction of each virtual object and the behavior of the participating users, in terms of moving trends, which is usually directed by the actions they can perform on the surrounding objects. In particular, the partitioning takes place when the virtual world contains only objects, in the sense that no avatars are yet connected and objects? attributes are handled as indicators for avatars? future behavior in the system. This prediction of avatars? behavior based on objects? attributes defines the initial partitioning of the virtual space.1 aBouras, Christos1 aTsiatsos, Thrasivoulos1 aGiannaka, Eleftheria  uhttp://telematics.upatras.gr/telematics/publications/exploiting-virtual-objects-attributes-and-avatars-behavior-dves-partitioning?language=en01340nas a2200145   4500008004100000245010400041210006900145260001700214300001500231520073500246100002100981700002201002700002001024856015001044       2007                        eng d00aA Framework for Cross Layer Adaptation for Multimedia Transmission over Wired and Wireless Networks0 aFramework for Cross Layer Adaptation for Multimedia Transmission  c25 - 28 June  a 153 - 1593 aThis paper proposes a framework for cross-layer adaptation for multimedia transmission over wired and wireless networks. The proposed framework consists of four entities: The sender, the proxy, which is located at the edge of the wired network, the access point, which co-located with the proxy and finally the wired and wireless receivers. The main concept is based on a “holistic approach” in which all layers participate to the adaptation process and make its own contributions. In addition, the proposed framework can support both wired and wireless receivers in one platform and cross layer information are used in order to support wireless users whereas TCP friendly estimations are used in order to support wired users.1 aBouras, Christos1 aGkamas, Apostolos1 aKioumourtzis, G  uhttp://telematics.upatras.gr/telematics/publications/framework-cross-layer-adaptation-multimedia-transmission-over-wired-and-wireless?language=en01504nas a2200145   4500008004100000245007100041210006900112260001700181300001500198520095400213100002101167700002201188700002201210856012601232       2007                        eng d00aFramework for Dynamic and On-Demand QoS to Videoconference Session0 aFramework for Dynamic and OnDemand QoS to Videoconference Sessio  c25 - 28 June  a 110 - 1163 aThis paper deals with the design and investigation of an approach for dynamic and on demand QoS on videoconference sessions for GRNET?s (Greek NREN) network. After the activation of QoS service in GRNET, a new need for automation of mechanisms for QoS in Videoconferencing session arises. The traditional QoS workflow inserts important administrative cost when a connected institute wants to have a videoconference service with specific QoS guaranties. In such case, the network administrator must manual configure the network?s edge routers. In order to overcome the above limitation, an “automatic” procedure for providing QoS guaranties to videoconference session was investigated. The result was an automatic solution that provides QoS using the QoS Policy Propagation via BGP mechanism for signaling. This automatic QoS deployment solution was tested successfully on the network and some performance measurement are presented in this paper.1 aBouras, Christos1 aGkamas, Apostolos1 aPrimpas, Dimitris  uhttp://telematics.upatras.gr/telematics/publications/framework-dynamic-and-demand-qos-videoconference-session?language=en02395nas a2200133   4500008004100000245010200041210006900143300001500212520182000227100002102047700002102068700001802089856015402107       2007                        eng d00aImprovements on IP - IAPP: A fast IP handoff protocol for IEEE 802.11 wireless and mobile clients0 aImprovements on IP IAPP A fast IP handoff protocol for IEEE 8021  a 497 - 5103 aOne of the most critical issues in introducingWireless
LAN (WLAN) real-time and delay sensitive applications,
such asVoice over IP (VoIP), is guaranteeing IP service
continuation during inter-subnet Basic Service Set (BSS)
transitions. Even though WLANs offer very high channel
bandwidth, they exhibit long network-layer handoff latency.
This is a restraining factor for mobile clients using interactive
multimedia applications such as VoIP or video streaming.
In a previous work, we presented a novel fast and efficient
IP mobility solution, called ?IP-IAPP?, which offers
constant IP connectivity to the 802.11 mobile users and successfully
preserves their ongoing sessions, even during subnet
handoffs (fast recovery of active connections). It is an
802.11-dependent IP mobility solution, which accelerates
the network reconfiguration phase after subnet handoffs and
significantly reduces the IP handoff latency. It restores L3
connectivity almost simultaneously to the L2 connectivity
after a subnet handoff, due to a zero-delay movement detection
method. As a result, even the most demanding next generation WLAN applications such as Voice over WLAN
(VoWLAN) suffer insignificant disruption. In this paper we
present an improved version of the IP-IAPP mobility mechanism
(new optimized protocol procedures). Certain extensions
have also been incorporated to the initial proposal, for
the provision of more advanced services: (a) secure inter-AP
IP-IAPP communications, (b) zero patching on the clients
s/w, and (c) support of clients which use a dynamic IP address.
Performance measurements out of further and more
complex testing verify that the proposed method outperforms
other existing mobility solutions, and still introduces the
lesser imperative amendments to the existing 802.11 wireless
LAN framework.1 aBouras, Christos1 aSampraku, Ioanna1 aKaroubalis, T  uhttp://telematics.upatras.gr/telematics/publications/improvements-ip-iapp-fast-ip-handoff-protocol-ieee-80211-wireless-and-mobile-clients?language=en01652nas a2200145   4500008004100000245006800041210006500109260001700174520110000191100002101291700002601312700002201338700002301360856012301383       2007                        eng d00aInput here - Execute there through networks: the case of gaming0 aInput here Execute there through networks the case of gaming  c10 - 13 June3 aAs the evolution of computer technology introduces
new advances in networks (among others), online gaming
becomes a new trend. Following the trends of our era, Games At
Large introduces an innovative platform for running interactive,
rich content multimedia applications over a WAN Network.
Games@Large project?s vision is to provide a new system
architecture for Interactive Multimedia which will enhance
existing CE devices such as, Set Top Boxes (STB) and other
devices, which are lacking both the CPU power and the graphical
performance to provide a rich user experience. This paper
presents the controllers? sub-system of the innovative mechanism
that will be implemented in the context of Games at Large
project. More specifically, it presents the general architecture of
the complete system and focuses on the “capturing” and
“execution of commands” modules at the client and server side.
The client software captures the input from the input devices,
sends the commands over a WAN and the server is responsible
for receiving and executing the commands to the correct
application.1 aBouras, Christos1 aPoulopoulos, Vassilis1 aTsogkas, Vassilis1 aSengounis, Ioannis  uhttp://telematics.upatras.gr/telematics/publications/input-here-execute-there-through-networks-case-gaming?language=en01587nas a2200193   4500008004100000245006100041210006100102260001100163300001300174520095800187653000901145653001801154653000901172100002101181700002201202700002401224700002201248856012301270       2007                        eng d00aMBMS Power Planning in Macro and Micro Cell Envirohments0 aMBMS Power Planning in Macro and Micro Cell Envirohments  c1 July  a 33 - 383 aMultimedia Broadcast Multicast Services (MBMS), introduced in Third Generation Partnership Project (3GPP) Release 6, is a point-to-multipoint downlink bearer service that addresses the need for the efficient usage of the expensive radio resources. Power control is one of the most important aspects in MBMS due to the fact that Node B?s transmission power is a limited resource and must be shared among all MBMS users in a cell. Consequently, the analysis of transmitted power plays a fundamental role in the planning and optimization process of Universal Mobile Telecommunications System (UMTS) radio access networks. This paper investigates several factors affecting Node B?s transmission power levels such as, cell deployment, propagation models, Quality of Service (QoS) requirements, users? distributions and mobility issues. Finally, different transport channels for the transmission of the multicast data over the UTRAN interfaces are considered.10aMBMS10aPower Control10aUMTS1 aBouras, Christos1 aAlexiou, Antonios1 aKokkinos, Vasileios1 aRekkas, Evangelos  uhttp://telematics.upatras.gr/telematics/publications/mbms-power-planning-macro-and-micro-cell-envirohments?language=en01201nas a2200169   4500008004100000245005100041210004800092260002200140300001500162520066100177653000900838653000900847100002100856700002200877700002200899856011000921       2007                        eng d00aMulticast in UMTS: Adopting TCP - Friendliness0 aMulticast in UMTS Adopting TCP Friendliness  c12 - 14 September  a 433 - 4443 aIn this paper, we present a novel mechanism for the multicast congestion control over UMTS networks. The proposed mechanism is based on the well known TCP-Friendly Multicast Congestion Control (TFMCC) scheme. The key challenge in the design of the new scheme lies in improving the TFMCC mechanism to cope with the packet losses caused by either the temporary or the permanent degradation of the wireless channels. The proposed scheme introduces minor modifications in the UMTS nodes with respect to the computing power of the mobile terminals. Finally, our approach is implemented in the ns-2 network simulator and is evaluated it under various conditions.10aMBMS10aUMTS1 aBouras, Christos1 aAlexiou, Antonios1 aPapazois, Andreas  uhttp://telematics.upatras.gr/telematics/publications/multicast-umts-adopting-tcp-friendliness?language=en01206nas a2200145   4500008004100000245008000041210006900121260001900190300001200209520062800221100002100849700002700870700002500897856013800922       2007                        eng d00aAn Object Driven Partitioning Approach for Distributed Virtual Environments0 aObject Driven Partitioning Approach for Distributed Virtual Envi  c3 - 6 December  a153-1543 aDistributed virtual environments tend to become a de facto solution for large-scale networked virtual environments. One of the key issues and problems that need to be handled in the design of a scalable and effective distributed virtual environment system is the partitioning problem, which refers to the efficient assignment of the system?s workload to the available resources of the system. This paper presents an object driven partitioning approach based on the partitioning algorithm of Lui & Chan, who proposed a three step technique for balancing the workload among the servers of the Distributed Virtual Environment.1 aBouras, Christos1 aTsiatsos, Thrasivoulos1 aGiannaka, Eleftheria  uhttp://telematics.upatras.gr/telematics/publications/object-driven-partitioning-approach-distributed-virtual-environments?language=en01241nas a2200145   4500008004100000245008200041210006900123260002000192300001300212520065700225100002100882700002700903700002500930856014000955       2007                        eng d00aPartitioning of Distributed Virtual Environments Based on Objects' Attributes0 aPartitioning of Distributed Virtual Environments Based on Object  c22 - 24 October  a 72 - 753 aThe partitioning constitutes one of the basic problems that need to be handled in Distributed Virtual Environments for maintaining consistency among users? view of the virtual scene and for optimizing the performance of the system. This paper presents an approach for handling the partitioning problem, which is based on objects? attributes. In particular, the approach proposes a technique, which takes into account the degree of interaction that the objects of the virtual environment carry for predicting future avatar behavior. This prediction of avatars? behavior based on objects? attributes defines the initial partitioning of the virtual space.1 aBouras, Christos1 aTsiatsos, Thrasivoulos1 aGiannaka, Eleftheria  uhttp://telematics.upatras.gr/telematics/publications/partitioning-distributed-virtual-environments-based-objects-attributes?language=en01526nas a2200121   4500008004100000245008800041210006900129300001500198520100500213100002101218700001901239856014601258       2007                        eng d00aPerformance Analysis of Adaptive Admission Control Algorithms for Bandwidth Brokers0 aPerformance Analysis of Adaptive Admission Control Algorithms fo  a 191 - 2183 aIn this paper, we propose a novel architecture for the admission control module of a Bandwidth Broker entity that aims at achieving a satisfactory balance between maximizing the resource utilization for the managed network and minimizing the overhead of the module. We also describe, analyze and evaluate mechanisms which aim at solving the additional problems of fairly prioritizing resubmitted requests and efficiently handling requests which do not specify ending times. We use the well known network simulator ns-2, as well as a custom simulation environment in order to study the performance characteristics of the proposed mechanisms and compare them with various alternatives for the admission control module of a Bandwidth Broker. We provide the results of the experimental evaluations and the conclusions they lead us to for the relative importance of the proposed solution and the various alternatives, their advantages and drawbacks, and the environments for which each one is best suited.1 aBouras, Christos1 aStamos, Kostas  uhttp://telematics.upatras.gr/telematics/publications/performance-analysis-adaptive-admission-control-algorithms-bandwidth-brokers?language=en01715nas a2200145   4500008004100000245006500041210006500106260001500171300001200186520117500198100002101373700002601394700002201420856012701442       2007                        eng d00aPersonalizing text summarization based on sentence weighting0 aPersonalizing text summarization based on sentence weighting  c3 - 8 July  a 3 - 103 aThe amount of data that exists on the Internet is enormous enough to distract users when trying to find useful information. In addition, the expansive use of small screen devices for browsing the World Wide Web generates huge problems when trying to find and read information. A solution to these problems is to personalize the web and try to reduce algorithmically the amount of text. Many text summarizers have been presented in order to reduce the valueless information that is presented to the users and many web sites, especially news portals, introduce personalization features for the users, though, still these techniques are not often used in combination in order to create more effective results. In this paper a mechanism for creating personalized summaries for the members of a news portal that reproduces articles collected from major portals is presented, together with evaluation both of the summarizer and the personalized summaries. The evaluators of the personalized summaries are members of the news portal. The personalized summary mechanism can also be utilized by users of small screen devices, for easier reading of less but inclusive information.1 aBouras, Christos1 aPoulopoulos, Vassilis1 aTsogkas, Vassilis  uhttp://telematics.upatras.gr/telematics/publications/personalizing-text-summarization-based-sentence-weighting?language=en01411nas a2200181   4500008004100000245007200041210006900113260001700182300001100199520079000210653000901000653001801009653000901027100002101036700002201057700002201079856012801101       2007                        eng d00aA Power Control Scheme for Efficient Radio Bearer Selection in MBMS0 aPower Control Scheme for Efficient Radio Bearer Selection in MBM  c18 - 21 June  a 1 - 83 aThis paper proposes a power control scheme for the efficient radio bearer selection in the Multimedia Broadcast/Multicast Service (MBMS) framework of Universal Mobile Telecommunications System (UMTS). The choice of the most efficient transport channel in terms of power consumption is a key point for the MBMS since a wrong transport channel selection for the transmission of the MBMS data could result to a significant decrease in the total capacity of the system. Different UMTS transport channels are examined and an algorithm that defines the switching point between dedicated and common radio bearers is proposed. The proposed MBMS power control scheme selects the transport channel that minimizes the Node B?s transmission power in every cell of the network with multicast users.10aMBMS10aPower Control10aUMTS1 aBouras, Christos1 aAlexiou, Antonios1 aRekkas, Evangelos  uhttp://telematics.upatras.gr/telematics/publications/power-control-scheme-efficient-radio-bearer-selection-mbms?language=en01875nas a2200193   4500008004100000245006600041210006600107260002000173300001500193520122000208653000901428653001801437653000901455100002101464700002201485700002401507700002201531856012801553       2007                        eng d00aPower Efficient Radio Bearer Selection in MBMS Multicast Mode0 aPower Efficient Radio Bearer Selection in MBMS Multicast Mode  c22 - 26 October  a 261 - 2683 aMultimedia Broadcast Multicast Services (MBMS) was
introduced in Third Generation Partnership Project (3GPP)
Release 6 in order to address the need for the efficient usage of
the expensive radio resources. The goal of this effort is to support
downlink streaming and download-and-play type services to large
groups of users. From the radio perspective, MBMS includes
point-to-point (PtP) and point-to-multipoint (PtM) modes. The
fact that Node B?s transmission power is a limited resource and
must be shared among all MBMS users in a cell indicates the need
for power control during an MBMS service. Consequently, the
analysis of the transmitted power plays a fundamental role in the
planning and optimization process of Universal Mobile
Telecommunications System (UMTS) radio access networks. In
this paper we investigate the factors that affect the Node B?s
transmission power levels during an MBMS session, such as, cell
deployment, propagation models, users? distributions and
mobility issues. To this direction, the transport channels in the
downlink, currently existing in UMTS which could be used to
transmit the multicast data over the UMTS Terrestrial Radio-
Access Network (UTRAN) interfaces are examined.10aMBMS10aPower Control10aUMTS1 aBouras, Christos1 aAlexiou, Antonios1 aKokkinos, Vasileios1 aRekkas, Evangelos  uhttp://telematics.upatras.gr/telematics/publications/power-efficient-radio-bearer-selection-mbms-multicast-mode?language=en01689nas a2200181   4500008004100000245005100041210005100092260001500143300001300158520112000171653000901291653001801300653000901318100002101327700002201348700002401370856011301394       2007                        eng d00aPower Saving Techniques in MBMS Multicast Mode0 aPower Saving Techniques in MBMS Multicast Mode  c26 October  a 62 - 693 aMultimedia Broadcast Multicast Services (MBMS) was
introduced in Third Generation Partnership Project (3GPP)
Release 6 in order to more efficiently use network and radio
resources for the transmission of multimedia services both in the
core network and, most importantly, in the air interface of
UTRAN (UMTS Terrestrial Radio Access Network). From the
radio perspective, MBMS includes point-to-point (PtP) and pointto-
multipoint (PtM) modes. The latter aims to overcome network
congestion when a large number of users request the same
content. One of the most important aspects in MBMS is power
control. The fact that Node B?s transmission power is a limited
resource and must be shared among all MBMS users in a cell
indicates the need for power control during an MBMS service.
Techniques, such us rate splitting and mixed usage of transport
channels can be used to reduce the power requirement of
delivering multicast traffic for MBMS users. To this direction,
this paper presents simulation results that will reinforce the need
for the usage of such techniques and will reveal the amount of
power that is saved.10aMBMS10aPower Control10aUMTS1 aBouras, Christos1 aAlexiou, Antonios1 aKokkinos, Vasileios  uhttp://telematics.upatras.gr/telematics/publications/power-saving-techniques-mbms-multicast-mode?language=en01485nas a2200157   4500008004100000245005900041210005900100300001700159520093300176653002301109653000901132100002101141700002201162700002301184856012001207       2007                        eng d00aScalable Rate Control for Video Transmission over UMTS0 aScalable Rate Control for Video Transmission over UMTS  a 1315 - 11313 aThis paper proposes a mechanism for the congestion control for video transmission over Universal Mobile
Telecommunications System (UMTS). Our scheme is applied when the mobile user experiences real time
multimedia content and adopts the theory of a widely accepted rate control method in wired networks,
namely equation-based rate control. In this approach, the transmission rate of the multimedia data is
determined as a function of the packet loss rate, the round trip time and the packet size and the server
explicitly adjusts its sending rate as a function of these parameters. Through a number of simulations and
experiments we validate the correctness and measure the performance and efficiency of the mechanism. A
first level of evaluation is carried out using the ns-2 simulator. A second level then validates the proposed
mechanism in real world traffic scenarios by performing experiments in a commercial UMTS network.10aCongestion Control10aUMTS1 aBouras, Christos1 aAlexiou, Antonios1 aIgglesis, Vaggelis  uhttp://telematics.upatras.gr/telematics/publications/scalable-rate-control-video-transmission-over-umts?language=en01314nas a2200133   4500008004100000245004000041210004000081260002200121520085900143100002101002700002501023700002701048856010501075       2007                        eng d00aSign Language Interpreters Training0 aSign Language Interpreters Training  c26 - 28 September3 aNowadays, the evolution of technology and the increasing use of computers gave the opportunity for developing new methods of education of deaf individuals and sign language interpreters. The e-learning environments that have been developed for the education of sign language provide web-based courses, designed to effectively teach to anyone the Sign Language. Recognizing the difficulties and barriers of sign language training as well as the importance of sign language interpreters for the community of deaf and hearing impaired, this paper presents the SIGN Learning Partnership, a project for sign language education. The objective of the partnership is to develop a new training method for sign language interpreter?s training together with a curriculum ready for accreditation, based on the outcome of the research in all previous-mentioned areas.1 aBouras, Christos1 aGiannaka, Eleftheria1 aAndriakopoulou, Eirini  uhttp://telematics.upatras.gr/telematics/publications/sign-language-interpreters-training?language=en01854nas a2200133   4500008004100000245008400041210006900125260002600194300001500220520130200235100002101537700001601558856014601574       2007                        eng d00aUsing Open Source to Building and Accessing Learning Objects and Online Courses0 aUsing Open Source to Building and Accessing Learning Objects and  bIDEA Group Publishing  a 268 - 2983 a<p>As e-learning continuously gains the interest of the scientific community, industry, and government, a wide variety of learning technology products have been incorporated into the marketplace. Advances in information and communication technologies are in favor of the incorporation of innovative services and functionalities in such systems, though content creation and delivery remain the two key factors in any e-learning system. Therefore, in this chapter, we present the design and implementation of a tool targeted at building and accessing learning objects and online courses through the Web. This tool aims to facilitate instructors and trainers to easily develop accessible, reusable, and traceable learning content that can meet their distant students? needs for anytime and anyplace learning. Learners are able to access learning content, in addition to consulting, at any time, reports on their interactions within a course and get support by subject experts. Furthermore, all users can request to upgrade their role in the system and, thus, actively participate in the learning process. Special attention has been paid on the utilization of reliable and qualitative open source technologies and Web standards so that the proposed solution can form an easily accessible system.</p>
1 aBouras, Christos1 aNani, Maria  uhttp://telematics.upatras.gr/telematics/publications/using-open-source-building-and-accessing-learning-objects-and-online-courses?language=en01614nas a2200145   4500008004100000245006900041210006700110260001000177300001500187520107700202100002101279700002301300700001601323856012901339       2007                        eng d00aA Web Content Manipulation Technique based on Page Fragmentation0 aWeb Content Manipulation Technique based on Page Fragmentation  cApril  a 563 - 5853 aWeb portals today offer a variety of content and services to their users. This content can be split into various categories and usually content semantically related is placed in the same area. In this paper, a software technique is presented that allows the viewers of web sites to build their own personalized portals, using speciﬁc areas of their preferred sites. This technique saves users? time and reduces the cost of browsing the web by minimizing the volume of data that has to be downloaded. It is based on an algorithm, which fragments a web page in discrete fragments using the page?s internal structure. Users utilize a web interface to deﬁne which parts of selected web pages they desire to appear in their personalized portal. No additional software needs to be installed on the users? personal computers, since this technique is designed to function centrally as a data source for a Web Server. In addition, usage of this technique reduces user perceived latency during browsing sessions, since less data must be transferred to users? personal computers.1 aBouras, Christos1 aMisedakis, Ioannis1 aKounenis, G  uhttp://telematics.upatras.gr/telematics/publications/web-content-manipulation-technique-based-page-fragmentation?language=en01886nas a2200145   4500008004100000245008100041210006900122260001700191520130200208100002101510700002701531700002601558700001401584856014201598       2007                        eng d00aX3D multi-user virtual environment platform for collaborative spatial design0 aX3D multiuser virtual environment platform for collaborative spa  c25 - 29 June3 aIt is well known that both space and the spatial organization play an important role in our work and learning environments as well as in everyday life. Space is neither innocent nor neutral, it has a performative aspect for whoever inhabits it and it works on its occupants. At the micro level, space prohibits, decides what may occur, lays down the law, implies a certain order, commands and locates bodies. Therefore, there is a definite need for many persons to design their space along with an expert and to preview it in order to test its functionality. Many times there is a need for the inhabitants and workers to collaborate in order to co-design their space from distance.
Multi-user three dimensional virtual environments are a powerful form of collaborative telecommunication applications, enabling the users to share a common three dimensional space and interact with each other as well as with the environment surrounding them, in order to collaboratively solve problems or aid learning processes. This paper presents the work done for extending a multi-user virtual environments platform, called EVE, in order to support collaborative spatial design applications. Furthermore, a usage scenario is presented concerning the collaborative design of a classroom for educational purposes.1 aBouras, Christos1 aTsiatsos, Thrasivoulos1 aTriglianos, Vasileios1 aTegos, Ch  uhttp://telematics.upatras.gr/telematics/publications/x3d-multi-user-virtual-environment-platform-collaborative-spatial-design?language=en01261nas a2200133   4500008004100000245005000041210005000091260002100141520078100162100002100943700002700964700002500991856011101016       2006                        eng d00aBest Practices Worldwide for Broadband Growth0 aBest Practices Worldwide for Broadband Growth  c11 - 14 December3 aThis paper investigates and analyses the best practices followed by various countries worldwide for supporting the broadband growth. The methodology used to locate the best practices is based on three main steps: (a) the presentation of the main factors that have a major impact on broadband growth; (b) the definition of what is a “best practice” based on quantitative criteria; (c) the calculation of a best practice index and a good practice index, which indicates that a country followed these best or good practices to support its broadband growth respectively. This methodology indicated that Denmark, United States, Japan, Canada and Rep. of Korea followed best practices for their broadband growth, while United Kingdom and the Netherlands followed good practices.1 aBouras, Christos1 aTsiatsos, Thrasivoulos1 aGiannaka, Eleftheria  uhttp://telematics.upatras.gr/telematics/publications/best-practices-worldwide-broadband-growth?language=en01293nas a2200133   4500008004100000245010500041210006900146260001700215300001500232520072000247100002100967700001900988856015201007       2006                        eng d00aComperative Evaluation of Adaptive Price-based Admission Control Algorithms for Bandwidth Allocation0 aComperative Evaluation of Adaptive Pricebased Admission Control   c19 - 21 July  a 339 - 3433 aIn this paper we analyze the performance
characteristics of various alternatives for the admission
control module of a Bandwidth Broker. In particular, we
study the metrics such as acceptance rate, fairness towards
requests and computation overhead and how they are
affected when comparing a simple admission control module
and an adaptive one. Furthermore, we examine the benefits
that can arise under various circumstances through usage of
adaptive price-based admission control and enhancements
such as the ability to handle the resubmission of previously
rejected requests. We describe the results of our
experimentation using a simulated environment and the
operating circumstances that benefit each solution.
1 aBouras, Christos1 aStamos, Kostas  uhttp://telematics.upatras.gr/telematics/publications/comperative-evaluation-adaptive-price-based-admission-control-algorithms-bandwidth?language=en01215nas a2200121   4500008004100000245007800041210006900119260001700188520071400205100002100919700002200940856013100962       2006                        eng d00aA delay - based analytical provisioning model for a QoS - enabled service0 adelay based analytical provisioning model for a QoS enabled serv  c11 - 15 June3 aCarefully designed and managed services are essential
for quality-demanding traffic, especially in large-scale IP
networks where the aggregation of flows and the variety of traffic
types are extensive. Although individual mechanisms have been
widely investigated, not much related work exists on integrated
approaches to QoS provisioning that are also feasible to
implement. This work presents a thorough approach to the
design, dimensioning and provisioning of a high priority service
for high-quality demanding traffic over an IP network. Our
approach employs efficient scheduling and a dynamic admission
control scheme while demonstrating novel characteristics in
terms of the quality offered to IP flows.
1 aBouras, Christos1 aSevasti, Afroditi  uhttp://telematics.upatras.gr/telematics/publications/delay-based-analytical-provisioning-model-qos-enabled-service?language=en01515nas a2200133   4500008004100000245005600041210005600097260002000153520102500173100002101198700002201219700002201241856011801263       2006                        eng d00aDesign Aspects of Open Municipal Broadband Networks0 aDesign Aspects of Open Municipal Broadband Networks  c4 - 6 September3 aThis paper presents the design principles that cover
the implementation of broadband infrastructure in the
region of Western Greece, by examining all the
necessary parameters that arise while implementing
such a critical developmental project. Furthermore, we
present as a case study, all issues of the designing of
the Metropolitan Area Network of Patras, the third
biggest city of Greece. The major target of the MAN of
Patras is to interconnect the buildings of the public
sector in the city and also deploy fibers that will create
conditions of competition in providing both access and
content services in advantage of the end consumer.
The usage of the broadband infrastructure by service
providers will be based on the open availability of the
fiber optics infrastructure in a cost effective way.
Finally, we present the main characteristics of a
proposed business plan that ensures financial viability
of the broadband infrastructure and guarantees the
administration, growth, and exploitation of
infrastructure.
1 aBouras, Christos1 aPrimpas, Dimitris1 aAlexiou, Antonios  uhttp://telematics.upatras.gr/telematics/publications/design-aspects-open-municipal-broadband-networks?language=en02459nas a2200157   4500008004100000245007100041210006900112260001200181300001000193520187200203100002102075700002702096700002502123700002902148856012402177       2006                        eng d00aDistribution and Partitioning Techniques for NVEs: the case of EVE0 aDistribution and Partitioning Techniques for NVEs the case of EV  c19 June  a73-823 aThe majority of the systems and platforms developed
for supporting Distributed Virtual Environments are based on the
concept of distribution from the early beginning of their
development. In this paper we present the migration to a
distributed virtual environment from a traditional client-server
architecture. In particular, this paper describes the case of EVE,
a Networked Virtual Environment originally aimed to support
small-scale applications. EVE started as a standard client-multi
server architecture, which could support multiple concurrent
virtual worlds with a maximum number of seventeen
simultaneous participants in each of these worlds. However, the
need to support larger-scale applications revealed that the
traditional architecture, upon which EVE was based, is
insufficient to meet the needs of these applications, which are
large both in the sense of virtual space and graphics and in regard
to the number of concurrent participants. This paper discusses
the migration of EVE to a distributed platform, which will be
able to support large-scale networked virtual environments. In
particular, the paper describes the modifications realized in the
architectural model of the initial platform for supporting
effectively large-scale applications. The basic entities of the
distributed model are presented, their operations, as well as the
interconnection among them. In addition, the paper presents an
initial approach of the algorithm that will be adopted for the
efficient partitioning of the virtual world and the assignment of
the clients to the entities and resources of the distributed
platform. The approach presented is space-object driven, in the
sense that both the actual size of the virtual space along with the
number of objects with which the user can interact is taken into
account during the partitioning.
1 aBouras, Christos1 aTsiatsos, Thrasivoulos1 aGiannaka, Eleftheria1 aPanagopoulos, Alexandros  uhttp://telematics.upatras.gr/telematics/publications/distribution-and-partitioning-techniques-nves-case-eve?language=en01545nas a2200133   4500008004100000245007200041210006900113260000900182300003100191520100500222100002101227700002701248856013601275       2006                        eng d00aEducational Virtual Environments: Design Rationale and Architecture0 aEducational Virtual Environments Design Rationale and Architectu  cJune  aVol. 29, No. 2,  153 - 1733 aThe use of collaborative virtual environments in e-learning is one of the
most promising uses of virtual reality technology. While much research has been
done in the area of networked virtual environments corresponding to the sharing of
events, very little research has been done on specific services and functionality.
However both the requirements and the kind of the offered services affect significantly
the design of a system. In this paper we present the design and implementation
of a platform suitable for educational virtual environments, which are
collaborative virtual environments aiming at offering collaborative e-learning services
to the users. Apart from the platform itself, we present the technological
choices, and a new method for sharing virtual environments. Furthermore, we
present an e-learning environment to support e-learning services using collaborative
virtual environments from both the technical and functional point of view, along
with the end-user evaluation results.1 aBouras, Christos1 aTsiatsos, Thrasivoulos  uhttp://telematics.upatras.gr/telematics/publications/educational-virtual-environments-design-rationale-and-architecture?language=en01326nas a2200169   4500008004100000245005900041210005600100260001600156520075800172653000900930653000900939100002100948700002200969700002600991700002201017856011701039       2006                        eng d00aAn Efficient Multicast Packet Delivery Scheme for UMTS0 aEfficient Multicast Packet Delivery Scheme for UMTS  c2-6 October3 aIn this paper we present an efficient scheme for the multicast transmission of the data in the Universal Mobile Telecommunications System (UMTS). We take advantage of the tree topology of the examined network and we introduce the use of Routing Lists (RLs) in the nodes of the UMTS. The adoption of these lists leads to the decrement of the transmitted packets and the efficient use of network resources during the multicast transmission of the data. We describe in detail the necessary steps for the successful multicast transfer of data. Furthermore, we analyze the handling of special cases such as user mobility scenarios. Especially, the various handover types are examined along with the Serving Radio Network Subsystem (SRNS) relocation procedure10aMBMS10aUMTS1 aBouras, Christos1 aAlexiou, Antonios1 aAntonellis, Dimitrios1 aPapazois, Andreas  uhttp://telematics.upatras.gr/telematics/publications/efficient-multicast-packet-delivery-scheme-umts?language=en01170nas a2200145   4500008004100000245005800041210005600099300001500155520064700170100002100817700002300838700002600861700002400887856011300911       2006                        eng d00aEnhancing a Web Based Community: the case of SIG-GLUE0 aEnhancing a Web Based Community the case of SIGGLUE  a 112 - 1303 aThe expansion of the web has reached outrageous proportions with
the number of web communities existing and the number of those being created
daily increasing dramatically. To parallel this phenomenon is the trend
nowadays of mobile phone services. One of the most representative is the case
of Greece, where in a period of five years about five million people subscribed
for a telephone number for mobile devices. The communities are not static any
more. The philosophy is: a universal community has to be mobile. This paper
analysed the expansion of the community of SIG-GLUE in order to support
mobile users with any necessary web service.1 aBouras, Christos1 aKapoulas, Vaggelis1 aPoulopoulos, Vassilis1 aAntonellis, Ioannis  uhttp://telematics.upatras.gr/telematics/publications/enhancing-web-based-community-case-sig-glue?language=en01542nas a2200169   4500008004100000245008100041210006900122260001800191300001500209520090500224653002301129653000901152100002101161700002201182700002601204856014201230       2006                        eng d00aEquation Based Congestion Control for Video Transmission over WCDMA Networks0 aEquation Based Congestion Control for Video Transmission over WC  c18 - 20 April  a 445 - 4503 a   The scheme of real time streaming video is one of
the newcomers in wireless data communication,
raising a number of new requirements in both
telecommunication and data communication systems.
This scheme is applied when the user experiences real
time multimedia content. Rate control is an important
issue in video streaming applications for both wired
and wireless networks. A widely accepted rate control
method in wired networks is equation based rate
control. In this work, we focus on a mechanism for
equation based congestion control for video
transmission over WCDMA networks. With our
mechanism, the sender explicitly adjusts its sending
rate as a function of the measured rate of loss events,
the round trip time and the packet size. Furthermore,
we examine the performance of UMTS air interface for
real time video transmission using real time protocols,
through a number of experiments.
10aCongestion Control10aUMTS1 aBouras, Christos1 aAlexiou, Antonios1 aAntonellis, Dimitrios  uhttp://telematics.upatras.gr/telematics/publications/equation-based-congestion-control-video-transmission-over-wcdma-networks?language=en01245nas a2200121   4500008004100000245009700041210006900138260001500207520070800222100002100930700001900951856015300970       2006                        eng d00aEvaluating Admission Control Modules for Bandwidth Brokers in DiffServ Networks Using ns - 20 aEvaluating Admission Control Modules for Bandwidth Brokers in Di  c9 - 12 May3 aIn this paper we use the well known network
simulator ns-2 in order to study the performance
characteristics of various alternatives for the admission
control module of a Bandwidth Broker. In particular, we
present the modifications that have to be made at the ns-2
architecture in order to simulate these architectures, the
metrics such as acceptance rate, fairness towards requests
and computation overhead and how they are affected
when comparing a simple admission control module and
more sophisticated ones. Furthermore, we examine the
benefits that can arise under various circumstances
through usage of enhancements such as the ability to
handle the resubmission of previously rejected requests.
1 aBouras, Christos1 aStamos, Kostas  uhttp://telematics.upatras.gr/telematics/publications/evaluating-admission-control-modules-bandwidth-brokers-diffserv-networks-using-ns-2?language=en01280nas a2200169   4500008004100000245007000041210006900111260001700180300001100197520068700208653000900895653000900904100002100913700002200934700002600956856012800982       2006                        eng d00aEvaluating Different One to Many Packet Delivery Schemes for UMTS0 aEvaluating Different One to Many Packet Delivery Schemes for UMT  c26 - 29 June  a 66-723 aIt is known that multicasting is an efficient method
of supporting group communication as it allows the
transmission of packets to multiple destinations using
fewer network resources. Thus, service providers are
increasingly interested in supporting multicast
communications over wireless networks and in
particular over UMTS. Multicasting is a more efficient
method of supporting group communication than
unicasting or broadcasting, as it allows transmission
and routing of packets to multiple destinations using
fewer network resources. In this paper the three above
mentioned      methods     of     supporting      group
communication are analyzed in terms of their
performance.10aMBMS10aUMTS1 aBouras, Christos1 aAlexiou, Antonios1 aAntonellis, Dimitrios  uhttp://telematics.upatras.gr/telematics/publications/evaluating-different-one-many-packet-delivery-schemes-umts?language=en01408nas a2200133   4500008004100000245007500041210006900116300001500185520086300200100002101063700002701084700002901111856013401140       2006                        eng d00aImplementation of 3D Mesh Streaming and Compression Techniques in NVEs0 aImplementation of 3D Mesh Streaming and Compression Techniques i  a 127 - 1403 a<p>In this paper, we present a framework that integrates three-dimensional (3D) mesh streaming and compression techniques and algorithms into our EVE-II Networked Virtual Environments platform, in order to offer support for large-scale environments as well as highly complex world geometry. This framework allows the partial and progressive transmission of 3D worlds as well as of separate meshes, achieving reduced waiting times for the end-user and improved network utilization. We also present a 3D mesh compression method focused on network communication, which is designed to support progressive mesh transmission, offering a fast and effective means of reducing the storage and transmission needs for geometrical data. This method is integrated in the above framework and utilizes prediction to achieve efficient lossy compression of 3D geometry.</p>
1 aBouras, Christos1 aTsiatsos, Thrasivoulos1 aPanagopoulos, Alexandros  uhttp://telematics.upatras.gr/telematics/publications/implementation-3d-mesh-streaming-and-compression-techniques-nves?language=en01697nas a2200157   4500008004100000245009700041210006900138260001700207300001300224520106900237100002101306700002601327700002201353700002201375856014201397       2006                        eng d00aThe importance of the difference in text types to keyword extraction: Evaluating a mechanism0 aimportance of the difference in text types to keyword extraction  c26 - 29 June  a 43 - 493 aInformation exists in every aspect of our life. The expansion of the web has helped to this direction. The web
feeds us with enormous information and the widespread use of computers and other hardware appliances has lead us to a
state where we have a lot of information in our hands, but many times it is useless. People are not able to find information
that they really need but already own. How many times have you tried to find a specific article that you have, or a specific
mail that you received, or even an SMS from someone saying something specific. For this reason many information
retrieval techniques have been proposed and many information extraction mechanisms have been created. In this paper we
will provide the experimental evaluation of a keyword extraction mechanism and how we treat different types of text (news
articles, publications, e-mails). This keyword extraction mechanism is a part of a complete system that includes information
retrieval, information extraction, categorization and publication of information to a personalized portal.
1 aBouras, Christos1 aPoulopoulos, Vassilis1 aDimitriou, Charis1 aTsogkas, Vassilis  uhttp://telematics.upatras.gr/telematics/publications/importance-difference-text-types-keyword-extraction-evaluating-mechanism?language=en01285nas a2200169   4500008004100000245006400041210006100105260002600166300001500192520066800207100002100875700002700896700002500923700002900948700001600977856012200993       2006                        eng d00aAn Integrated Platform for Educational Virtual Environments0 aIntegrated Platform for Educational Virtual Environments  bIDEA Group Publishing  a 291 - 3203 a<p>In this chapter, we present the design and implementation of an integrated platform for Educational Virtual Environments. This platform aims to support an educational community, synchronous online courses in multi-user three-dimensional (3D) environments, and the creation and access of asynchronous courses through a learning content management system. In order to offer synchronous courses, we have implemented a system called EVE-II, which supports stable event sharing for multi-user 3D places, easy creation of multi-user 3D places, H.323-based voice- over IP services fully integrated in a 3D space, as well as many concurrent 3D multi-user spaces.</p>
1 aBouras, Christos1 aTsiatsos, Thrasivoulos1 aGiannaka, Eleftheria1 aPanagopoulos, Alexandros1 aNani, Maria  uhttp://telematics.upatras.gr/telematics/publications/integrated-platform-educational-virtual-environments?language=en01309nas a2200133   4500008004100000245011000041210006900151260001700220300001000237520073100247100002100978700002200999856015401021       2006                        eng d00aInvestigating Bandwidth Broker's inter-domain operation for dynamic and automatic end to end provisioning0 aInvestigating Bandwidth Brokers interdomain operation for dynami  c11 - 14 July  a61-693 aThis paper deals with a distributed bandwidth broker that we try to extend in order to perform inter-domain
operation. The basic issues for inter-domain operation are discussed and we try to approach the most demanding
issues as the selection of the best inter domain routing path. Generally, we discuss three models for inter domain
routing through bandwidth broker, analyzing their advantages. Also, a very important point that affects the inter-
domain operation is the SLAs between adjacent domains and the capability that a bandwidth broker should have
to ask and perform dynamic negotiation. Finally, we analyze the best model and present how it should be
incorporated in the existing distributed implementation.
1 aBouras, Christos1 aPrimpas, Dimitris  uhttp://telematics.upatras.gr/telematics/publications/investigating-bandwidth-brokers-inter-domain-operation-dynamic-and-automatic-end-end?language=en01435nas a2200145   4500008004100000245006000041210005900101300003300160520088800193100002101081700002201102700001901124700002201143856012401165       2006                        eng d00aIPv6 Deployment: Real Time Applications and QoS Aspects0 aIPv6 Deployment Real Time Applications and QoS Aspects  aVol. 29, No. 9,  1393 - 14013 aThis paper gives an overview of the issues related to the QoS mechanisms under IPv6 and the transition of applications to the new Internet protocol. We describe the implementation and testing of a QoS service on IPv6 networks, which is based on the DiffServ architecture (expedited forwarding) and provides strict priorities to packets that are produced from real time applications. The service was implemented and tested at the 6NET large-scale IPv6 network, and additional advanced testing was performed in a local testbed. We present and analyze the results from our tests under a number of different scenarios. In addition, we focus on issues regarding application transition to IPv6 and we briefly discuss as a case study the transition of OpenH323 protocol stack to support IPv6. We also discuss the usage and the expected impact of the new Flow Label field in the IPv6 header.1 aBouras, Christos1 aGkamas, Apostolos1 aStamos, Kostas1 aPrimpas, Dimitris  uhttp://telematics.upatras.gr/telematics/publications/ipv6-deployment-real-time-applications-and-qos-aspects?language=en01220nas a2200133   4500008004100000245004400041210004400085260001500129520077400144100002100918700001900939700002200958856010600980       2006                        eng d00aIPv6 QoS Testing on Dual Stack Networks0 aIPv6 QoS Testing on Dual Stack Networks  c10 October3 aThis paper presents our work regarding the testing
and evaluation of DiffServ QoS mechanisms over IPv6
and IPv4 in dual stack software based platforms. IPv6
introduces some additional features (like flow label)
and the current support for QoS mechanisms in IPv6
implementations approaches the corresponding QoS
support in IPv4. Therefore, a number of tests with
DiffServ QoS mechanisms applied on IPv6 traffic have
been carried out on a testbed created specifically for
this purpose, in order to validate the mechanisms and
evaluate the router?s overall performance. Our
evaluations cover the load incurred to the routing
devices from the implementation of the mechanisms,
the level of support for QoS IPv6 features and the
comparison of performance over IPv4 and IPv6.1 aBouras, Christos1 aStamos, Kostas1 aPrimpas, Dimitris  uhttp://telematics.upatras.gr/telematics/publications/ipv6-qos-testing-dual-stack-networks?language=en00538nam a2200145   4500008004100000245005800041210005600099100002100155700002200176700001900198700002200217700001800239700001800257856011700275       2006                        eng d00aIPv6: The protocol, transition and porting mechanisms0 aIPv6 The protocol transition and porting mechanisms1 aBouras, Christos1 aGkamas, Apostolos1 aStamos, Kostas1 aPrimpas, Dimitris1 aKaraliotas, A1 aGanos, Petros  uhttp://telematics.upatras.gr/telematics/publications/ipv6-protocol-transition-and-porting-mechanisms?language=en01237nas a2200169   4500008004100000245005500041210005200096260001600148300001500164520069000179653000900869653000900878100002100887700002200908700002600930856011100956       2006                        eng d00aA Multicast Approach for UMTS: A Performance Study0 aMulticast Approach for UMTS A Performance Study  c15 - 19 May  a 1086-10913 aIn this paper, a multicast scheme for UMTS which only requires in-
significant modifications in the current UMTS network infrastructure is ana-
lyzed. We analytically present the multicast routing mechanism behind our
scheme as well as the multicast group management functionality of it. Further-
more, we present an evaluation of our scheme in terms of its performance. The
critical parameters for the evaluation of the scheme are the number of multicast
users within the multicast group, the amount of data sent to the multicast users,
the density of the multicast users within the cells and the type of transport
channel used for the transmission of the multicast data over the air.10aMBMS10aUMTS1 aBouras, Christos1 aAlexiou, Antonios1 aAntonellis, Dimitrios  uhttp://telematics.upatras.gr/telematics/publications/multicast-approach-umts-performance-study?language=en01729nas a2200169   4500008004100000245008300041210006900124260001400193300001300207520111000220653000901330653000901339100002101348700002201369700002601391856014201417       2006                        eng d00aA Multicast Packet Forwarding Mechanism for WCDMA Networks using Routing Lists0 aMulticast Packet Forwarding Mechanism for WCDMA Networks using R  c6 October  a 27 - 343 aThis paper proposes a multicast scheme for the packet forwarding mechanism in the Universal Mobile Telecommunications System (UMTS). This scheme relies on the introduction of the Permanent Multicast Routing List (PMRL) and Temporary Multicast Routing List (TMRL) in each node of the network except UEs. In the PMRL we record the nodes of the next level that the messages for every multicast group should be forwarded. The TMRL is useful for the temporary record of information from the path from the mobile users to the GGSN. Additionally, a Multicast Group List (MGL) is kept in the GGSN which records the members of each multicast group. These lists lead to the decrement of the transmitted packets and the more efficient use of the network resources in the multicast routing in UMTS. We analyze the exact steps that the multicast packets are transmitted to the members of each multicast group. Furthermore, special issues such as joining/leaving a multicast service are described. Our simulation results show that the proposed mechanism for the multicast packet forwarding in UMTS performs efficiently.10aMBMS10aUMTS1 aBouras, Christos1 aAlexiou, Antonios1 aAntonellis, Dimitrios  uhttp://telematics.upatras.gr/telematics/publications/multicast-packet-forwarding-mechanism-wcdma-networks-using-routing-lists?language=en01217nas a2200133   4500008004100000245007300041210006900114260002200183300001300205520068800218100002100906700002200927856013400949       2006                        eng d00aPathfinding architectures for interdomain Bandwidth Broker operation0 aPathfinding architectures for interdomain Bandwidth Broker opera  c13 - 15 September  a 21 - 263 aThis paper deals with bandwidth brokers and their
inter-domain operation. The basic issues for inter-domain operation are discussed and we try to approach the most demanding issues as the selection of the best inter domain routing path (pathfinding). Generally, we discuss two models for inter domain routing through bandwidth broker, analyzing their advantages and comparing them. Also, we simulated the second one (generalized distributed pathfinding) trying to evaluate its performance. Finally, we discuss the simulation?s results and present how this model should be incorporated in normal operation routing of commercial ISPs or academic networks that works on a federated way.1 aBouras, Christos1 aPrimpas, Dimitris  uhttp://telematics.upatras.gr/telematics/publications/pathfinding-architectures-interdomain-bandwidth-broker-operation?language=en01338nas a2200145   4500008004100000245007400041210006900115260002000184300001500204520076300219100002100982700002601003700002401029856013901053       2006                        eng d00aPersonalized News Categorization through Scalable Text Classification0 aPersonalized News Categorization through Scalable Text Classific  c16 - 18 January  a 391 - 4013 aExisting news portals on the WWW aim to provide users with numerous articles that are categorized into specific topics. Such a categorization procedure improves presentation of the information to the end-user. We further improve usability of these systems by presenting the architecture of a personalized news classification system that exploits user?s awareness of a topic in order to classify the articles in a ?per-user? manner. The system?s classification procedure bases upon a new text analysis and classification technique that represents documents using the vector space representation of their sentences. Traditional ?term-to-documents? matrix is replaced by a ?term-to-sentences? matrix that permits capturing more topic concepts of every document.1 aBouras, Christos1 aPoulopoulos, Vassilis1 aAntonellis, Ioannis  uhttp://telematics.upatras.gr/telematics/publications/personalized-news-categorization-through-scalable-text-classification?language=en01285nas a2200145   4500008004100000245009300041210006900134300003100203520065900234100002100893700002700914700002500941700002900966856014400995       2006                        eng d00aA Platform for Virtual Collaboration Spaces and Educational Communities: The case of EVE0 aPlatform for Virtual Collaboration Spaces and Educational Commun  aVol. 11, No. 3,  290 - 3033 a<p>This paper presents the design, implementation and evaluation of EVE Community Prototype, which is an educational virtual community aiming to meet the requirements of a Virtual Collaboration Space and to support e-learning services. Furthermore, this paper describes the design and implementation of an integrated platform for Networked Virtual Environments, called EVE Platform, which supports the afore-mentioned educational community. This platform supports stable event sharing and creation of multi-user three dimensional (3D) places, H.323-based voice over IP services integrated in 3D spaces as well as multiple concurrent virtual worlds.</p>
1 aBouras, Christos1 aTsiatsos, Thrasivoulos1 aGiannaka, Eleftheria1 aPanagopoulos, Alexandros  uhttp://telematics.upatras.gr/telematics/publications/platform-virtual-collaboration-spaces-and-educational-communities-case-eve?language=en01251nas a2200121   4500008004100000245011100041210006900152260001800221520070200239100002100941700001900962856014800981       2006                        eng d00aResubmissions and Partly Defined Requests in an Adaptive Admission Control Algorithm for Bandwidth Brokers0 aResubmissions and Partly Defined Requests in an Adaptive Admissi  c23 - 27 April3 aThe purpose of this paper is to examine the issues
related to the efficiency and adaptability of the
admission control module of a Bandwidth Broker. The
proposed architecture is able to handle situations such
as the resubmission of previously rejected requests and
offer a fair treatment for requests in an environment
where a subset of these requests do not specify their
ending time. We describe the proposed mechanisms for
such cases which aim at solving the additional
problems of fairly prioritizing resubmitted requests
and efficiently handle requests which do not specify
ending times. We also provide experimental
evaluations of the proposed algorithms and the
conclusions they lead us to.1 aBouras, Christos1 aStamos, Kostas  uhttp://telematics.upatras.gr/telematics/publications/resubmissions-and-partly-defined-requests-adaptive-admission-control-algorithm?language=en01554nas a2200157   4500008004100000245003900041210003900080260001800119300001500137520104800152100002101200700002601221700002401247700002401271856010101295       2006                        eng d00aScalability of text classification0 aScalability of text classification  c19 - 22 April  a 408 - 4133 aWe explore scalability issues of the text classification problem where using (multi)labeled training
documents we try to build classifiers that assign documents into classes permitting classification in multiple
classes. A new class of classification problems, called ?scalable? is introduced that models many problems
from the area of Web mining. The property of scalability is defined as the ability of a classifier to adjust
classification results on a ?per-user? basis. Furthermore, we investigate on different ways to interpret
personalization of classification results by analyzing well known text datasets and exploring existent
classifiers. We present solutions for the scalable classification problem based on standard classification
techniques and present an algorithm that relies on the semantic analysis using document decomposition into
its sentences. Experimental results concerning the scalability property and the performance of these
algorithms are provided using the 20newsgroup dataset and a dataset consisting of web news.
1 aBouras, Christos1 aPoulopoulos, Vassilis1 aAntonellis, Ioannis1 aZouzias, Anastasios  uhttp://telematics.upatras.gr/telematics/publications/scalability-text-classification?language=en01670nas a2200169   4500008004100000245005300041210005300094260002200147300001300169520111600182653000901298653000901307100002101316700002201337700002601359856011501385       2006                        eng d00aSupporting Group Communication in WCDMA Networks0 aSupporting Group Communication in WCDMA Networks  c20 - 22 September  a 13 - 243 aIt is known that multicast is an efficient method of supporting group communication as it allows the transmission of the packets to multiple destinations using fewer network resources. Along with the widespread deployment of the third generation cellular networks and the fast-improving capabilities of the mobile devices, content and service providers are increasingly interested in supporting multicast communications over wireless networks and in particular over Universal Mobile Telecommunications System (UMTS). In this paper, a multicast scheme for UMTS is analyzed. We analytically present the multicast routing mechanism behind our scheme as well as the multicast group management functionality of the scheme. Furthermore, we present an evaluation of our scheme in terms of its performance. The critical parameters for the evaluation of the scheme are the number of users within the multicast group, the amount of data sent to the multicast users, the density of the multicast users within the cells and finally the type of transport channel used for the transmission of the multicast data over the air.10aMBMS10aUMTS1 aBouras, Christos1 aAlexiou, Antonios1 aAntonellis, Dimitrios  uhttp://telematics.upatras.gr/telematics/publications/supporting-group-communication-wcdma-networks?language=en01509nas a2200157   4500008004100000245009200041210006900133260001600202300001500218520088600233100002101119700001901140700002201159700002001181856015001201       2006                        eng d00aUsing the ns-2 simulation environment to implement and evaluate Bandwidth Broker models0 aUsing the ns2 simulation environment to implement and evaluate B  c3 - 5 April  a 285 - 2913 aIn this paper we present and compare four different
models of implementing a Bandwidth Broker in a DiffServ
network. We describe the relevant implementation aspects in the
well-known ns-2 simulator and present a number of experiments
that were conducted in order to verify our implementation,
analyze the performance characteristics of the various
alternatives and evaluate the usefulness of the ns-2 simulation
environment for similar purposes. We present our experiments
that aim at investigating a number of issues related to the
operation of Bandwidth Broker modules, and in particular how
the acceptance rate, the network overhead and the response time
for each Bandwidth Broker model are affected by the network
topology, the available buffers for incoming requests and the
advance time from the moment a request is submitted to the
moment the reservation should take place.
1 aBouras, Christos1 aStamos, Kostas1 aPrimpas, Dimitris1 aPappas, Ioannis  uhttp://telematics.upatras.gr/telematics/publications/using-ns-2-simulation-environment-implement-and-evaluate-bandwidth-broker-models?language=en01186nas a2200133   4500008004100000245013900041210006900180260001800249300001500267520057800282100002100860700002200881856014900903       2005                        eng d00aAn admission control and deployment optimization algorithm for an implemented distributed Bandwidth Broker in a simulation environment0 aadmission control and deployment optimization algorithm for an i  c17 - 21 April  a 766 - 7733 aThis paper describes and tests a distributed bandwidth broker that has
been implemented in NS simulator. It focuses on the admission control
algorithm, its advantages and drawbacks. Also, the bandwidth broker is tested,
managing the IP Premium service and we compare 2 different implementations
of the service. Finally it approaches the problem of the optimal location of a
bandwidth broker in a backbone network. For this purpose, a new model is
proposed that evaluates each node and finally selects the most capable node
where the base bandwidth broker should be located.1 aBouras, Christos1 aPrimpas, Dimitris  uhttp://telematics.upatras.gr/telematics/publications/admission-control-and-deployment-optimization-algorithm-implemented-distributed?language=en01267nas a2200145   4500008004100000245005400041210005200095260002100147300001500168520074700183100002100930700002700951700002900978856011401007       2005                        eng d00aAdvances in X3D multi - user virtual environments0 aAdvances in X3D multi user virtual environments  c12 - 14 December  a 136 - 1423 aThis paper presents the current state of the art in web3d multi-user technologies and more specifically networked virtual environment platforms that support the X3D standard, which are currently limited in number, and also the existing X3D browsers that enable these applications. Furthermore, this paper presents the architecture of a platform, called EVE, which was developed to support multi-user virtual environments and was initially based on VRML, as well as the implementation regarding the process of upgrading this platform in order to fully support the X3D standard, using the open-source Xj3D library. Finally, the benefits of shifting to the X3D standard are presented, and some of the problems that currently exist are discussed.1 aBouras, Christos1 aTsiatsos, Thrasivoulos1 aPanagopoulos, Alexandros  uhttp://telematics.upatras.gr/telematics/publications/advances-x3d-multi-user-virtual-environments?language=en01853nas a2200205   4500008004100000245005100041210005100092260001100143300001500154520123200169100002101401700002201422700001901444700002201463700001201485700001301497700001401510700001401524856010901538       2005                        eng d00aApplication on Demand System over the Internet0 aApplication on Demand System over the Internet  cAugust  a 209 - 2323 aThis paper describes the design and implementation of the ASP-NG system. The main modules of
the ASP-NG system are the AoD service and the Web Portal. The ASP-NG Portal is a portal for
providing the user with the necessary interface in order to access an Application on Demand (AoD)
service. The ASP-NG portal is responsible for the interaction with the user of the AoD service. Using
the AoD service the user rents an application for a limited time period at a fraction of the actual cost of
the application. The AoD service is responsible for downloading the appropriate parts of the
application according to the user’s actions, while enforcing the mutually agreed frame between the
user and the Application Service Provider (ASP). The implementation of the ASP-NG portal is based
on the Web Services of the Java 2, Enterprise Edition platform and the implementation of the AoD
module is based onCCCprogramming language. The ASP-NG portal offers to its users the capability
to select and customize the language of the user interface in order to present information in their
preferred language. Moreover the ASP-NG portal offers to the portal administrator the capability to
customise the look and feel of the ASP-NG portal.1 aBouras, Christos1 aGkamas, Apostolos1 aStamos, Kostas1 aPrimpas, Dimitris1 aNave, I1 aShani, A1 aSheory, O1 aTzruya, Y  uhttp://telematics.upatras.gr/telematics/publications/application-demand-system-over-internet?language=en02111nas a2200157   4500008004100000245010500041210006900146260001200215300001400227520147700241100002101718700002201739700001901761700001801780856015501798       2005                        eng d00aArchitecture and Performance Evaluation for Redundant Multicast Transmission Supporting Adaptive QoS0 aArchitecture and Performance Evaluation for Redundant Multicast   cJanuary  a 85 - 1103 a<p>In this paper we describe the architecture of an application that was developed for the transmission of multimedia data, using the multicast mechanism, over the Internet. There are two major issues that have to be considered when designing and implementing such a service, the fairness and the adaptation schemes. The fairness problem results from the fact that Clients with different capabilities have to be served. In our application we use a mechanism that categorizes the Clients into a number of groups according to each Client’s capabilities and (the mechanism) serves each group of Clients with a different multicast stream. With the term “capabilities” we do not only mean the processing power of the Client, but also the capacity and the condition of the network path towards that Client. Because of today’s Internet heterogeneity and the lack of Quality of Service (QoS) support, the Server cannot assume that the Clients will permanently be able to handle a specific bit rate.We have therefore implemented an additional mechanism for the intra-stream bit rate adaptation. The proposed mechanism uses a “friendly” to the network users congestion control policy to control the transmission of the data. We evaluate the adaptive multicast transmission mechanism through a number of experiments and a number of simulations in order to examine its behaviour to a heterogeneous group of Clients and its behaviour against TCP and UDP data streams.</p>
1 aBouras, Christos1 aGkamas, Apostolos1 aStamos, Kostas1 aKaraliotas, A  uhttp://telematics.upatras.gr/telematics/publications/architecture-and-performance-evaluation-redundant-multicast-transmission-supporting-0?language=en01349nas a2200181   4500008004100000245008700041210006900128260002100197520064800218100002100866700002300887700002700910700002200937700002300959700002400982700002401006856013701030       2005                        eng d00aThe Broadband Status in the Region of Western Greece: Overview and Recommendations0 aBroadband Status in the Region of Western Greece Overview and Re  c12 - 14 December3 aThis paper presents a study conducted in the Region of Western Greece, in order to propose an overall planning for the development of broadband infrastructure in the Region of Western Greece. The current broadband status in the region is being described, while the results of a survey on broadband usage and demand are being presented.
The paper proposes some Recommendations that should be adopted in the region of Western Greece in order for the appropriate broadband infrastructures to be developed and adopted so as to contribute to economic growth and to tackle any possible cases of “digital gap” between the citizens of our country.1 aBouras, Christos1 aKapoulas, Vaggelis1 aTsiatsos, Thrasivoulos1 aAlexiou, Antonios1 aIgglesis, Vaggelis1 aParaskevas, Mixalis1 aPapagiannopoulos, J  uhttp://telematics.upatras.gr/telematics/publications/broadband-status-region-western-greece-overview-and-recommendations?language=en01531nas a2200145   4500008004100000245006500041210006500106260002000171300001500191520099000206100002101196700002601217700001401243856012801257       2005                        eng d00aCreating a Polite Adaptive and Selective Incremental Crawler0 aCreating a Polite Adaptive and Selective Incremental Crawler  c19 - 22 October  a 307 - 3143 aThe expansion of the World Wide Web has led to a chaotic state where the users of the internet have to face and overcome the major problem of discovering information. For the solution of this problem, many mechanisms were created based on crawlers who are browsing the www and downloading pages. In this paper we will describe a crawling mechanism which is created in order to support data mining and processing systems and to obtain a history of the web’s content. A crawler has to be efficient and polite, trying not to harm or overload the pages it is visiting. Therefore, it is extremely important to follow specific rules when crawling. In addition to these rules, the mechanism we created includes a selective incremental algorithm, which is used to make the crawler more efficient and more polite in parallel. The structure and design of the mechanism is simple, but the experimental results showed us that this simplicity makes our crawler a very strong and stable mechanism.1 aBouras, Christos1 aPoulopoulos, Vassilis1 aThanou, A  uhttp://telematics.upatras.gr/telematics/publications/creating-polite-adaptive-and-selective-incremental-crawler?language=en01778nas a2200169   4500008004100000245008300041210006900124260001600193300001500209520115800224653000901382653000901391100002101400700002201421700002301443856014201466       2005                        eng d00aA Decision Feedback Scheme for Multimedia Transmission Over 3G Mobile Networks0 aDecision Feedback Scheme for Multimedia Transmission Over 3G Mob  c6 - 9 March  a 357 - 3613 aUMTS, the successor of GSM, is evolving toward a
future wireless all-IP network. In this paper we present how it
supports real-time IP multimedia services, as these services are
expected to drive the adoption of wireless all-IP networks. The
scheme of real time streaming video is one of the newcomers in
wireless data communication and in particular in UMTS, raising
a number of novel requirements in both telecommunication and
data communication systems. This scheme applies when the
mobile user is experiencing real time multimedia content. In this
paper, we describe the design and the implementation of a
decision feedback scheme, which is based on real time protocols
and it is used for streaming video over UMTS transport
channels. The decision feedback scheme uses a friendly, to the
mobile users, congestion control mechanism to control the
transmission rate of the real time video sequence. Furthermore,
we evaluate this mechanism through a number of experiments.
During these experiments we demonstrate the friendly behavior
of the decision feedback scheme to TCP and UDP data streams
that coexist in the same channel with the video sequence.10aMBMS10aUMTS1 aBouras, Christos1 aAlexiou, Antonios1 aIgglesis, Vaggelis  uhttp://telematics.upatras.gr/telematics/publications/decision-feedback-scheme-multimedia-transmission-over-3g-mobile-networks?language=en01198nas a2200193   4500008004100000245007500041210006900116260001400185300001500199520050900214100002100723700002300744700002200767700002300789700002400812700001700836700002400853856012700877       2005                        eng d00aDeployment of Broadband Infrastructure in the Region of Western Greece0 aDeployment of Broadband Infrastructure in the Region of Western   c7 October  a 588 - 5933 aThis paper presents the work that is taking place in the Region of Western Greece in order to develop state-of-the-art broadband infrastructure. The current status of broadband infrastructure in the region is being analyzed and the main principles on which the deployment of the networks will be based on is being described, by presenting the Metropolitan Area Networks and the Wireless access networks that will be developed. Two case studies of such municipal networks are also presented in this paper.1 aBouras, Christos1 aKapoulas, Vaggelis1 aAlexiou, Antonios1 aIgglesis, Vaggelis1 aParaskevas, Mixalis1 aScopoulis, I1 aPapagiannopoulos, J  uhttp://telematics.upatras.gr/telematics/publications/deployment-broadband-infrastructure-region-western-greece?language=en01713nas a2200157   4500008004100000245007300041210006900114260002100183300001500204520110900219100002101328700002301349700002601372700002401398856013301422       2005                        eng d00aDesign and Implementation of a Game Based Learning Related Community0 aDesign and Implementation of a Game Based Learning Related Commu  c23 - 25 February  a 215 - 2223 aA web-based community aims at providing communication and collaboration tools to a special interest group. This paper describes the functionality and architecture issues of a community which aims to bring together users who are interested in the field of game based learning and lifelong learning. The architecture and implementation issues of the platform developed are analyzed and their exact use is explained. More specifically the members of the community are provided with tools in order to share their knowledge and experience in game based learning through enhanced forums and chats, to read news or receive a newsletter concerning the aforementioned issue, arrange meetings, and make use of shared spaces. All these services are enhanced in order to meet the needs of this special interest group which is unique as it includes the collaboration of game developers, pedagogues and simple users. Furthermore, we describe a methodology to build a fully functional community with tools for communication and collaboration starting from a simple template and using core content management techniques.1 aBouras, Christos1 aKapoulas, Vaggelis1 aPoulopoulos, Vassilis1 aAntonellis, Ioannis  uhttp://telematics.upatras.gr/telematics/publications/design-and-implementation-game-based-learning-related-community?language=en01329nas a2200145   4500008004100000245008300041210006900124260001500193300001500208520074400223100002100967700002700988700002501015856014301040       2005                        eng d00aDesigning Virtual Spaces to Support Learning Communities and e - Collaboration0 aDesigning Virtual Spaces to Support Learning Communities and e C  c5 - 8 July  a 328 - 3323 aIn this paper, we present the design principles for
virtual spaces and two different tools as solutions for
supporting e-collaboration and multi-user
communication in web-based learning communities.
The first solution, called Virtual Conference, is
designed and implemented in the framework of the
VirRAD European project. It is a two-dimensional
space where participants represented by their photos
can use various e-collaboration tools. The second
solution, called EVE Training Area, is a threedimensional
space where participants, represented by
3D humanoid avatars, can use a variety of ecollaboration
tools. This paper describes the
functionality provided by both tools, compares them,
and proposes cases for exploiting each solution.1 aBouras, Christos1 aTsiatsos, Thrasivoulos1 aGiannaka, Eleftheria  uhttp://telematics.upatras.gr/telematics/publications/designing-virtual-spaces-support-learning-communities-and-e-collaboration?language=en01829nas a2200133   4500008004100000245009600041210006900137260001000206300001400216520126800230100002101498700002001519856015601539       2005                        eng d00aEstimating and Eliminating Redundant Data Transfers Over the Web: A Fragment Based Approach0 aEstimating and Eliminating Redundant Data Transfers Over the Web  cMarch  a 119- 1423 a<p>Redundant data transfers over the Web, can be mainly attributed to the repeated transfers of unchanged data. Web caches and Web proxies are some of the solutions that have been proposed, to deal with the issue of redundant data transfers. In this paper we focus on the efficient estimation and reduction of redundant data transfers over the Web. We first prove that a vast amount of redundant data is transferred in Web pages that are considered to carry fresh data. We show this by following an approach based on Web page fragmentation and manipulation. Web pages are broken down to fragments, based on specific criteria. We then deal with these fragments as independent constructors of the Web page and study their change patterns independently and in the context of the whole Web page. After the fragmentation process, we propose solutions for dealing with redundant data transfers. This paper has been based on our previous work on ‘Web Components’ but also on related work by other researchers. It utilises a proxy based, client/ server architecture, and imposes changes to the algorithms executed on the Proxy server and on clients. We show that our proposed solution can considerably reduce the amount of redundant data transferred on the Web.</p>
1 aBouras, Christos1 aKonidaris, Agis  uhttp://telematics.upatras.gr/telematics/publications/estimating-and-eliminating-redundant-data-transfers-over-web-fragment-based-approach-0?language=en01134nas a2200133   4500008004100000245008600041210006900127260001600196300001500212520059500227100002100822700001900843856013800862       2005                        eng d00aExamining the Benefits of a Hybrid Distributed Architecture for Bandwidth Brokers0 aExamining the Benefits of a Hybrid Distributed Architecture for   c7 - 9 April  a 491 - 4983 aIn this paper the issue of the architectural organization of a Bandwidth Broker with respect to the distribution of functionalities among separate entities is examined. We discuss the benefits of a distributed versus a centralized architecture and study some of the most important implementations. We also present a novel design proposal that builds on our earlier work on the admission control module of a Bandwidth Broker and introduces it in the framework of a distributed Bandwidth Broker architecture. Our conclusions are supported by a series of simulated experiments that we analyze.1 aBouras, Christos1 aStamos, Kostas  uhttp://telematics.upatras.gr/telematics/publications/examining-benefits-hybrid-distributed-architecture-bandwidth-brokers?language=en01411nas a2200145   4500008004100000245008100041210006900122260001700191300001500208520084400223100002101067700002101088700001801109856013801127       2005                        eng d00aFast IP handoff support for VoIP and multimedia applications in 802.11 WLANs0 aFast IP handoff support for VoIP and multimedia applications in   c13 - 16 June  a 332 - 3373 aWireless LANs (WLANs) have edged into numerous mobile and wireless users’ daily experience worldwide as a mainstream connectivity solution for a broad range of applications. Even though WLANs offer very high channel bandwidth, they show long network-layer handoff latency. This is a restraining factor for mobile clients using interactive multimedia applications such as voice over IP (VoIP) or video streaming. This paper presents an 802.11-dependent fast IP handoff method which quickly restores IP connectivity for mobile clients running next generation WLAN applications such as Voice over WLANs (VoWLAN). This method outperforms other existing proposed IP mobility solutions in 802.11 WLANs as verified from real performance testing, while introduces insignificant compulsory additions to the existing 802.11 wireless LAN framework.1 aBouras, Christos1 aSampraku, Ioanna1 aKaroubalis, T  uhttp://telematics.upatras.gr/telematics/publications/fast-ip-handoff-support-voip-and-multimedia-applications-80211-wlans?language=en01456nas a2200133   4500008004100000245004100041210004100082260001700123520100900140100002101149700002601170700002401196856010201220       2005                        eng d00aGame Based learning for Mobile Users0 aGame Based learning for Mobile Users  c27 - 30 July3 aGame based learning has been studied as an important alternative or supplement to traditional teaching. Existing web based platforms that utilize the power of the Internet in order to provide efficient access to information regarding computer learning games aim to create online communities. However, such attempts target only on traditional Internet users, excluding an ongoing population of people that access World Wide Web using mobile devices. In this paper, the restrictions of web browsing using personal digital assistants (PDAs) or smart mobile phones are considered and a methodology for the expansion of a preexisting community for game based learning in universities and lifelong is described in order to also attract mobile users. New, device-specific services are deployed so as to take advantage of game based learning opportunities that mobile phones offer and structural as well as design changes are described in order to fulfill requirements of web browsing using small screen devices.1 aBouras, Christos1 aPoulopoulos, Vassilis1 aAntonellis, Ioannis  uhttp://telematics.upatras.gr/telematics/publications/game-based-learning-mobile-users?language=en01546nas a2200133   4500008004100000245012000041210006900161260001700230300001300247520094900260100002101209700002501230856015701255       2005                        eng d00aThe Grid Framework as a Suitable Infrastructure for Supporting Large - Scale Desktop Networked Virtual Environments0 aGrid Framework as a Suitable Infrastructure for Supporting Large  c20 - 23 June  a 76 - 823 aThe maturation of the Internet, the familiarization of the users with this powerful means of communication and mainly the increment of the available bandwidth, which is presented the last few years, led to the idea of extending small scale virtual environments to larger applications that could support a tremendous number of concurrent users. However, the introduction of Large Scale Virtual Environments brings along a series of problems that are mainly related to the serious increment of the transmitted information. Neither the traditional architectures, algorithms originally designed for the NVEs, nor the improvement of the network seem sufficient to support this new kind of applications. A solution to this problem seems to be the adoption of the GRID. In this paper we present an approach, which describes the way that a Desktop Networked Virtual Environment could be efficiently supported and maintained under a GRID infrastructure.1 aBouras, Christos1 aGiannaka, Eleftheria  uhttp://telematics.upatras.gr/telematics/publications/grid-framework-suitable-infrastructure-supporting-large-scale-desktop-networked-virtual?language=en01334nas a2200121   4500008004100000245006200041210006000103260001700163520087000180100002101050700002201071856011901093       2005                        eng d00aA host selection model for a distributed bandwidth broker0 ahost selection model for a distributed bandwidth broker  c18 - 20 July3 aThis paper deals with a distributed bandwidth broker that we try to evaluate and therefore propose a model that will improve its operation in a backbone network. Such a distributed bandwidth broker has been implemented and tested in NS simulator. Its operation is affected very much by the network condition and the responding time is proportional to the delay of packets in the network. Therefore, the paper presents a model (heuristic) that evaluates each node and finally selects the most important node where the base bandwidth broker should be located. This model is also associated with the general model that describes the operation of the bandwidth broker, and we propose an adaptation module of the Bandwidth broker that optimizes its operation. Finally, the model is simulated in order to evaluate its performance and indicate points that can be improved.1 aBouras, Christos1 aPrimpas, Dimitris  uhttp://telematics.upatras.gr/telematics/publications/host-selection-model-distributed-bandwidth-broker?language=en01568nas a2200133   4500008004100000245007400041210006900115260001900184300001500203520104500218100002101263700002201284856012801306       2005                        eng d00aImplementation issues of Managed Bandwidth Service: The case of GRNET0 aImplementation issues of Managed Bandwidth Service The case of G  c14 - 17 August  a 293 - 2983 aThis paper describes the design and the implementation of the Managed Bandwidth Service (MBS) in a high speed backbone network as well as a management tool for the service. The service was designed taking advantage of features provided by the MPLS technology and also using the DiffServ architecture. So, it uses L2 MPLS VPNs to provide point to point connection and also marks the traffic in order to pass from certain priority queues (to provide guaranteed bandwidth). It also enables traffic engineering characteristics in order to provide load balancing on the network as well as fast rerouting in case of link failure. In addition we implemented a management tool for the service. The scope of this tool is to allow the users to manage their MBS requests (make a new one, edit, delete or view a request). Also the tool performs admission control and produces the necessary configuration that must be applied on the network in order to implement every service’s request. This service was designed and implemented on GRNET’s network.1 aBouras, Christos1 aPrimpas, Dimitris  uhttp://telematics.upatras.gr/telematics/publications/implementation-issues-managed-bandwidth-service-case-grnet?language=en01213nas a2200145   4500008004100000245012400041210006900165260001800234300001500252520056800267100002100835700002700856700002900883856015500912       2005                        eng d00aIntegration of 3D Mesh Streaming and Compression Techniques for Adaptive progressive Virtual World Transmission in NVEs0 aIntegration of 3D Mesh Streaming and Compression Techniques for   c20 - 22 April  a 235 - 2443 aIn this paper, we present a framework for exploiting three-dimensional (3D) mesh streaming and compression techniques and algorithms in order to improve the performance of our EVE-II Networked Virtual Environments platform. These improvements are related to the progressive transmission of 3D worlds or separate meshes. We also present a 3D mesh compression method focused on network communication, which is designed to support progressive mesh transmission, offering a fast and effective means of reducing the storage and transmission needs for geometrical data.1 aBouras, Christos1 aTsiatsos, Thrasivoulos1 aPanagopoulos, Alexandros  uhttp://telematics.upatras.gr/telematics/publications/integration-3d-mesh-streaming-and-compression-techniques-adaptive-progressive-virtual?language=en01269nas a2200169   4500008004100000245006800041210006800109260001900177300001300196520067300209653000900882653000900891100002100900700002200921700002300943856013300966       2005                        eng d00aMultimedia Transmission over Third Generation Cellurar Networks0 aMultimedia Transmission over Third Generation Cellurar Networks  c25 - 27 August  a 317 3243 a<p>The scheme of real time streaming video is one of the newcomers in wireless data communication, raising a number of new requirements in both telecommunication and data communication systems. This scheme applies when the user is experiencing real time multimedia content. This paper has as main target to study the performance of video transmission over the third generation cellular networks. In particular, we examine the performance of UMTS Dedicated Channels (DCHs) for real time MPEG-4 video transmission in Downlink direction. Finally, we examine if real time video transmission in conjunction with Internet traffic is applicable in UMTS radio interface.</p>
10aMBMS10aUMTS1 aBouras, Christos1 aAlexiou, Antonios1 aIgglesis, Vaggelis  uhttp://telematics.upatras.gr/telematics/publications/multimedia-transmission-over-third-generation-cellurar-networks?language=en00429nam a2200121   4500008004100000245003500041210003500076100002100111700002300132700002700155700002500182856010000207       2005                        eng d00aNetworked Virtual Environments0 aNetworked Virtual Environments1 aBouras, Christos1 aKapoulas, Vaggelis1 aTsiatsos, Thrasivoulos1 aGiannaka, Eleftheria  uhttp://telematics.upatras.gr/telematics/publications/networked-virtual-environments?language=en01189nas a2200133   4500008004100000245009000041210006900131260001700200300001500217520062500232100002100857700002200878856015500900       2005                        eng d00aPerformance enhancement of an AF service using TCP – aware marking and dynamic WRED0 aPerformance enhancement of an AF service using TCP aware marking  c27 - 30 June  a 642 - 6473 aThe implementation of successful Assured
Forwarding (AF) services according to the DiffServ
framework remains a challenging problem today,
despite the numerous proposals for AF PHB
mechanisms and AF-based service implementations. In this work, we propose two modules, the TCP-Window
Aware Marker (TWAM) and the Dynamic WRED
(DWRED) mechanism for implementing the DiffServ
AF PHB. We provide analytical models and an
experimental evaluation in order to demonstrate how
they succeed in enhancing the quality, increasing
fairness, improving the performance and easing the
deployment of a production- level AF-based service.1 aBouras, Christos1 aSevasti, Afroditi  uhttp://telematics.upatras.gr/telematics/publications/performance-enhancement-af-service-using-tcp-%E2%80%93-aware-marking-and-dynamic-wred?language=en01536nas a2200133   4500008004100000245008300041210006900124260001500193300001500208520099900223100002101222700002201243856013701265       2005                        eng d00aPerformance of Adaptive Multimedia Transmission: The case of Unicast Technique0 aPerformance of Adaptive Multimedia Transmission The case of Unic  c5 - 7 July  a 121 - 1283 aUnicast mechanisms for the adaptive transmission of multimedia data can be used for the transmission of multimedia data over heterogeneous networks, like the Internet with the use of one unicast stream for each receiver. Those mechanisms have the capability to adapt the transmission of the multimedia data to network changes. In this paper, we describe a unicast mechanism for adaptive transmission of multimedia data, which is based on real time protocols. The proposed mechanism can be used for unicast transmission of multimedia data over heterogeneous networks, like the Internet, and has the capability to adapt the transmission of the multimedia data to network changes. Moreover, the proposed mechanism uses a “friendly” to the network users congestion control policy to control the transmission of the multimedia data. We evaluate the adaptive multicast transmission mechanism and we compare it with a number of similar mechanisms available to the literature (LBA, RAP, and TFRCP).1 aBouras, Christos1 aGkamas, Apostolos  uhttp://telematics.upatras.gr/telematics/publications/performance-adaptive-multimedia-transmission-case-unicast-technique?language=en01604nas a2200145   4500008004100000245007600041210006900117300001500186520104800201100002101249700002201270700001901292700002201311856012501333       2005                        eng d00aPorting and performance aspects from IPv4 to IPv6: The case of OpenH3230 aPorting and performance aspects from IPv4 to IPv6 The case of Op  a 847 - 8663 aThis paper is a summary of our experiences on a case study for porting applications to IPv6. We present the
results of the effort to port OpenH323, an open-source H.323 platform to IPv6, which we believe can serve
as guidelines for other projects with similar goals. We briefly present the structure of the OpenH323
platform. We also discuss a number of issues arising during the porting of a platform to IPv6, like which
would be the easiest approach to the porting procedure, how compatibility with earlier, IPv4-only versions
of the platform could be retained, if there are any useful tools for assisting this task, how and when one
could be positive that the necessary modifications had been made, and which testing procedures should be
followed. We then present a variety of experiments that we conducted in order to comparatively evaluate
the IPv4 and IPv6 protocol stacks. We also present the results of some initial experiments comparing IPv4
and IPv6 performance under congested network links and the conclusions that they lead us to.1 aBouras, Christos1 aGkamas, Apostolos1 aStamos, Kostas1 aPrimpas, Dimitris  uhttp://telematics.upatras.gr/telematics/publications/porting-and-performance-aspects-ipv4-ipv6-case-openh323?language=en01638nas a2200169   4500008004100000245005900041210005900100260002100159300001500180520105700195100002101252700002201273700001901295700001601314700001701330856012101347       2005                        eng d00aQoS experiences in native IPv6 GRNET and 6NET networks0 aQoS experiences in native IPv6 GRNET and 6NET networks  c17 - 20 November  a 284 - 2923 aAdoption of IPv6 technology has been accelerated in the last few years but there is limited experience in the deployment of Quality of Service (QoS) for IPv6 traffic in backbone networks. As available software and hardware is designed to handle IPv4 packets, there is a need to accurately measure the performance of QoS mechanisms in an IPv6 environment. This paper discusses tests in the deployment of IPv6 QoS in core networks, namely the production dual stack GRNET and the IPv6-only 6NET networks, using both hardware and software platforms. In either case, we succeeded in delivering advanced transport services to IPv6 traffic and provided different performance guarantees to portions of traffic. The deployed QoS schema was common for IPv6 and IPv4; in most cases both v4 and v6 traffic exhibited comparable performance per class while imposing no significantly different overhead on network elements. A major conclusion of our tests is that the IPv6 QoS mechanisms are efficiently supported with state-of-the-art router cards at gigabit speeds.1 aBouras, Christos1 aPrimpas, Dimitris1 aLiakopoulos, A1 aMaglaris, B1 aKalogeras, D  uhttp://telematics.upatras.gr/telematics/publications/qos-experiences-native-ipv6-grnet-and-6net-networks?language=en01392nas a2200145   4500008004100000245004700041210004500088260001700133300001500150520091400165100002101079700001901100700002201119856010501141       2005                        eng d00aQoS issues in a large - scale IPv6 network0 aQoS issues in a large scale IPv6 network  c23 - 28 July  a 406 - 4153 a<p>This paper presents our work in the framework of the 6NET project, regarding the design, implementation and testing of a QoS service in a large-scale IPv6 network. The DiffServ mechanism for providing QoS guarantees, is generally preferred over IntServ. However, the current support for QoS mechanisms in IPv6 implementations still lags behind QoS support in IPv4. Furthermore, the new Internet Protocol introduces a different network environment in many aspects and therefore the QoS services should be specifically designed and evaluated for IPv6. In order to evaluate this different behaviour, large-scale experiments have been carried out within the scope of the 6NET project. This paper describes the results from the experimentation with the DiffServ mechanism on a large-scale native IPv6 network that aims to service aggregates of real time traffic with minimum delay, jitter and packet loss.</p>
1 aBouras, Christos1 aStamos, Kostas1 aPrimpas, Dimitris  uhttp://telematics.upatras.gr/telematics/publications/qos-issues-large-scale-ipv6-network?language=en01427nas a2200169   4500008004100000245007200041210006900113260002000182520081300202100002101015700002201036700001801058700002401076700001901100700001601119856012201135       2005                        eng d00aQoS issues in the Research and Academic Networks: The case of GRnet0 aQoS issues in the Research and Academic Networks The case of GRn  c23 - 28 October3 a<p>This paper describes the design and the implementation of QoS services in a high speed backbone network as well as a management tool for the service. The services were designed taking advantage of features provided by the MPLS technology and also by using the DiffServ architecture. The supported QoS services include the IP Premium that tries to provide zero packet loss as well as minimum delay and jitter and the Less Than Best Effort service. In addition we implemented a management tool for the service. The scope of this tool is to allow the users to manage their QoS requests (make a new one, edit, delete or view a request). Also the tool performs admission control and produces the necessary configuration that must be applied on the network in order to implement every service’s request.</p>
1 aBouras, Christos1 aPrimpas, Dimitris1 aKaraliotas, A1 aParaskevas, Mixalis1 aOikonomakos, M1 aSintoris, C  uhttp://telematics.upatras.gr/telematics/publications/qos-issues-research-and-academic-networks-case-grnet?language=en01348nas a2200169   4500008004100000245008600041210006900127260002200196300001500218520071500233653002300948653000900971653000900980100002100989700002201010856014601032       2005                        eng d00aRate and Loss Control for Video transmission over UMTS using Real -Time Protocols0 aRate and Loss Control for Video transmission over UMTS using Rea  c27 - 29 September  a 333 - 3363 aUMTS is evolving toward a future wireless all-IP network. In this paper we present how it supports real-time IP multimedia services, as these services are expected to drive the adoption of wireless all-IP networks. The scheme of real time streaming video is one of the newcomers in wireless data communication and in particular in UMTS, raising a number of novel requirements in both telecommunication and data communication systems. This scheme applies when the mobile user is experiencing real time video content. In this work we focus on the design and implementation of a rate and loss control mechanism for monitoring the UMTS network state and estimating the appropriate rate of the streaming video data.10aCongestion Control10aMBMS10aUMTS1 aBouras, Christos1 aAlexiou, Antonios  uhttp://telematics.upatras.gr/telematics/publications/rate-and-loss-control-video-transmission-over-umts-using-real-time-protocols?language=en01404nas a2200133   4500008004100000245004500041210004500086260001700131300001500148520095900163100002101122700001901143856010801162       2005                        eng d00aSecuring a Bandwidth Broker Architecture0 aSecuring a Bandwidth Broker Architecture  c27 - 30 June  a 474 - 4803 aIn this paper we discuss the topic of the security in the context of a Bandwidth Broker?s operation based on the existing literature on this issue and new techniques and methods. We propose mechanisms to enhance the security of the communications during the Bandwidth Broker operation both within a single domain and across different domains. The message exchanges for the operation of a distributed Bandwidth Broker architecture are enumerated. The purpose is to examine the main security risks for a distributed Bandwidth Broker architecture operating in a real-world environment and address them using the PKI architecture mechanisms. We also present a proposal for identifying misbehaving flows that intends to be both simple and effective. We finally evaluate the performance impact that our solution incurs to the operation of the Bandwidth Broker and show that it offers an advantageous trade-off in most cases where security considerations exist.1 aBouras, Christos1 aStamos, Kostas  uhttp://telematics.upatras.gr/telematics/publications/securing-bandwidth-broker-architecture?language=en01219nas a2200133   4500008004100000245007100041210006900112260001300181300001500194520070300209100002100912700002200933856013000955       2005                        eng d00aService Level Agreement for DiffServ - based services provisioning0 aService Level Agreement for DiffServ based services provisioning  cNovember  a 285 - 3023 aThe evolution of mechanisms for providing Quality-of-Service (QoS) over the contemporary
network infrastructures has introduced the need for regulation and management of the emerging QoS
services with the use of Service Level Agreements (SLAs). SLAs define the qualitative and
quantitative characteristics of the services provided from a network provider to peering networks or
customers. In this work, we define a template for the SLA structure to support the provision of a QoS
service between two peering domains and then we proceed with the definition of an end-to-end SLA
across consecutive domains, based on the bilateral ones. We also propose a model for the service
provisioning procedures.1 aBouras, Christos1 aSevasti, Afroditi  uhttp://telematics.upatras.gr/telematics/publications/service-level-agreement-diffserv-based-services-provisioning?language=en01472nas a2200133   4500008004100000245010400041210006900145260001000214300001500224520090700239100002101146700002201167856014901189       2005                        eng d00aSRAMT: A hybrid sender and receiver-based adaptation scheme for TCP friendly multicast transmission0 aSRAMT A hybrid sender and receiverbased adaptation scheme for TC  cMarch  a 551 - 5753 aIn this paper,we describe a hybrid sender and receiver-based adaptation scheme for multicast transmission of multimedia
data,which we call SRAMT (Sender–Receiver based Adaptation scheme for Multicast Transmission). The most
prominent features of SRAMT are its distributed (to sender and receivers) transmission rate estimation algorithm and
its innovative RTT (Round Trip Time) estimation algorithm based on one-way delay measurements. With the use of
SRAMT,we ensure that sender will transmit TCP friendly traffic and receivers with different capabilities (in terms of
available bandwidth) are able to receive the multimedia information. We evaluate SRAMT through a number of simulations
and compare it with other schemes available to the literature. Main target of the simulations was the examination
of SRAMT behavior to a heterogeneous group of receivers and its behavior against TCP connections.1 aBouras, Christos1 aGkamas, Apostolos  uhttp://telematics.upatras.gr/telematics/publications/sramt-hybrid-sender-and-receiver-based-adaptation-scheme-tcp-friendly-multicast?language=en00533nas a2200133   4500008004100000245006800041210006800109100002100177700001900198700002200217700001600239700001700255856012700272       2005                        eng d00aSurvey of IPv4 Dependencies in Global Grid Forum Specifications0 aSurvey of IPv4 Dependencies in Global Grid Forum Specifications1 aBouras, Christos1 aStamos, Kostas1 aPrimpas, Dimitris1 aSofia, Rute1 aJiang, Sheng  uhttp://telematics.upatras.gr/telematics/publications/survey-ipv4-dependencies-global-grid-forum-specifications?language=en01457nas a2200169   4500008004100000245009800041210006900139260002200208520079800230100002101028700002201049700001901071700002001090700001301110700001601123856014801139       2005                        eng d00aTechniques for DiffServ - based QoS in Hierarchically Federated MAN Networks - the GRNET Case0 aTechniques for DiffServ based QoS in Hierarchically Federated MA  c18 - 21 September3 aDiffServ is the basis of contemporary QoS-enabled networks. Setting up DiffServ QoS requires extensive engineering effort in dimensioning and provisioning, especially for adjacent networks under different administrations linked in a “federated” hierarchy. In this paper we present a case study for QoS techniques employed in the GRNET MAN networks of Athens and Crete. After introducing the supported QoS mechanisms and service types, we discuss our dimensioning methodology and present two algorithms for worst-case dimensioning. We explain the provisioning mechanisms of GRNET and we present in brief our new automated provisioning ANS tool. Finally, we deal with the extension of our mechanisms and tools in hierarchically federated networks and give some future directions of our work.1 aBouras, Christos1 aPrimpas, Dimitris1 aLiakopoulos, A1 aVarvitsiotis, A1 aSiris, V1 aFotiadis, G  uhttp://telematics.upatras.gr/telematics/publications/techniques-diffserv-based-qos-hierarchically-federated-man-networks-grnet-case?language=en01346nas a2200181   4500008004100000245007000041210006600111260002000177300001500197520069500212100002100907700002700928700002500955700002600980700001601006700001501022856012701037       2005                        eng d00aA Unified Framework for Political Support e - Democracy Practices0 aUnified Framework for Political Support e Democracy Practices  c19 - 22 October  a 119 - 1233 ae-Government and e-Democracy constitute a central theme in information society policy at all levels: local, regional, national, European and even globally. To this direction, a variety of efforts have been made and many systems have been developed. This paper proposes a methodology for designing and implementing web-based services that can support e-Democracy practices. Furthermore, the paper presents and describes the effort made by a Greek political party to this direction, for the design and development of a unified framework for providing, supporting and managing e-Democracy services. The paper describes the actions taken and the work done according to the proposed methodology.1 aBouras, Christos1 aTsiatsos, Thrasivoulos1 aGiannaka, Eleftheria1 aPoulopoulos, Vassilis1 aKarounos, T1 aPriftis, A  uhttp://telematics.upatras.gr/telematics/publications/unified-framework-political-support-e-democracy-practices?language=en00818nas a2200145   4500008004100000245003600041210003200077300001500109520035700124100002100481700002300502700002700525700002300552856009700575       2005                        eng d00aA web - based virtual community0 aweb based virtual community  a 127 - 1393 aThis paper describes functionality and architectural issues in the design of a web-based virtual community. This virtual community aims to meet the requirements of a virtual collaboration system with both autonomous and collaborative e-learning services, by supporting communities whose members interact and form groups based on their common interests.1 aBouras, Christos1 aKapoulas, Vaggelis1 aTsiatsos, Thrasivoulos1 aIgglesis, Vaggelis  uhttp://telematics.upatras.gr/telematics/publications/web-based-virtual-community?language=en01491nas a2200145   4500008004100000245006400041210006000105260001700165520094400182100002101126700002601147700002301173700001601196856013301212       2005                        eng d00aA Web Clipping Service’s Information Extraction Mechanism0 aWeb Clipping Service s Information Extraction Mechanism  c22 - 27 July3 aInformation overload is one of the most important problems of today’s WWW. Users are often lost in a wealth of information when searching about a topic. Although they have specific information needs, using a search engine or regularly browsing in popular news sites for updates can lead them to search in tens or hundreds of possibly relevant pages or loose some updates that were interesting for them. One promising solution for this problem is ‘web-clipping’ services. A service like this continuously searches the Web and whenever it finds a web page that might interest some users, it informs these users that they should visit this specific page. This paper describes the information extraction mechanism of a web-clipping service that is being designed as part of a larger project for information search and manipulation. This mechanism is used to extract information from web pages and find out which links should be followed.1 aBouras, Christos1 aPoulopoulos, Vassilis1 aMisedakis, Ioannis1 aKounenis, G  uhttp://telematics.upatras.gr/telematics/publications/web-clipping-service%E2%80%99s-information-extraction-mechanism?language=en01400nas a2200133   4500008004100000245006600041210006300107260002800170300001500198520088900213100002101102700001901123856012401142       2004                        eng d00aAn Adaptive Admission Control Algorithm for Bandwidth Brokers0 aAdaptive Admission Control Algorithm for Bandwidth Brokers  c30 August - 1 September  a 243 - 2503 aThis paper focuses on the operation of the Bandwidth Broker, an entity that is responsible for managing the bandwidth within a network domain and for the communication with Bandwidth Brokers of neighboring domains. A very important aspect of the Bandwidth Broker is its admission control module that determines whether the bandwidth reservation requests are going to be accepted or not. We summarize the status of the current research in this field and propose a novel architecture for the admission control module that aims at achieving a satisfactory balance between maximizing the resource utilization for the network provider and minimizing the overhead of the module. This is achieved by gathering and examining sets of book-ahead requests and by adapting the size of the set to be examined so that the network utilization and the computation overhead are appropriately balanced.1 aBouras, Christos1 aStamos, Kostas  uhttp://telematics.upatras.gr/telematics/publications/adaptive-admission-control-algorithm-bandwidth-brokers?language=en00506nam a2200133   4500008004100000245005400041210005400095100002100149700002300170700002200193700001900215700002200234856011600256       2004                        eng d00aAdvanced Issues on Computer Networks and Services0 aAdvanced Issues on Computer Networks and Services1 aBouras, Christos1 aKapoulas, Vaggelis1 aGkamas, Apostolos1 aStamos, Kostas1 aPrimpas, Dimitris  uhttp://telematics.upatras.gr/telematics/publications/advanced-issues-computer-networks-and-services?language=en01486nas a2200157   4500008004100000245005700041210005700098260001800155300001900173520093300192100002101125700002201146700001901168700002201187856011901209       2004                        eng d00aApplication on Demand Portal using J2EE technologies0 aApplication on Demand Portal using J2EE technologies  c23 - 26 March  a I.551 - I.5583 aA Web Based Virtual Community is an example of a Collaborative Virtual Environment, which focalizes in providing collaborative functionalities and both synchronous and asynchronous interaction services. This paper describes a virtual community, which aims to meet the requirements of a virtual collaboration space and support autonomous and collaborative e-learning services. In particular, a web-based platform is described, which is able to support communities whose members are able to interact and form groups based on their common interests. The community provides its members with the ability to communicate through enhanced forums and chats, but also, to interact in the social interaction spaces. The users can arrange events, which occur in virtual meeting centers, where 3D avatars represent the users. In these multi-user spaces, extended functionalities are offered, while system agents assist and consult the users.1 aBouras, Christos1 aGkamas, Apostolos1 aStamos, Kostas1 aPrimpas, Dimitris  uhttp://telematics.upatras.gr/telematics/publications/application-demand-portal-using-j2ee-technologies?language=en01428nas a2200145   4500008004100000245008000041210006900121260002900190520085100219100002101070700001901091700002201110700001501132856013501147       2004                        eng d00aDesign and implementation of a Bandwidth Broker in a simulation environment0 aDesign and implementation of a Bandwidth Broker in a simulation   c29 November - 1 December3 aA Bandwidth Broker is an entity that has been proposed in order to provide end-to-end
QoS. For this purpose it manages the bandwidth (the QoS services) within a network
domain and it is also responsible for the communication with Bandwidth Brokers of
adjacent domains. In this paper, we present a Bandwidth Broker implementation in the
widely used NS-2 simulation environment. We describe the Bandwidth Broker architecture
that was our model for the simulation implementation. Furthermore, we illustrate the
experiments that we conducted that examined the Bandwidth Broker functionality as well
as its performance. All the experiments demonstrated that with this implementation we can
achieve end-to-end QoS and that our implementation can be used in order to model the
behavior of a Bandwidth Broker in the widely popular NS-2 network simulator.1 aBouras, Christos1 aStamos, Kostas1 aPrimpas, Dimitris1 aStathis, N  uhttp://telematics.upatras.gr/telematics/publications/design-and-implementation-bandwidth-broker-simulation-environment?language=en01312nas a2200133   4500008004100000245007800041210006900119260001000188300001400198520078300212100002100995700002701016856013501043       2004                        eng d00aDistributed Virtual Reality:Building a Multi - User Layer in EVE Platform0 aDistributed Virtual RealityBuilding a Multi User Layer in EVE Pl  cApril  a 91 - 1113 aIn this paper, we present the design and implementation of a VRML97 multi-user layer, which is
introduced in the EVE distributed virtual reality platform. Though other approaches use a VRML
node insertion mechanism, such as VSPLUS, or a substitution mechanism, such as SPIN-3D, our
approach uses a removal mechanism. Main consideration of our multi-user extension is the ease of
transforming single-user virtual worlds into multi-user virtual worlds, as well as the conformity with
any standard VRML97 browser. Furthermore, we present the EVE’ s communication platform,
which can be used in order to support Collaborative Virtual Environments. Main issues regarding the
effective network communication as well as the initialization of the 3D scene are discussed in this
paper.1 aBouras, Christos1 aTsiatsos, Thrasivoulos  uhttp://telematics.upatras.gr/telematics/publications/distributed-virtual-realitybuilding-multi-user-layer-eve-platform?language=en01022nas a2200157   4500008004100000245007200041210006900113260002100182300001300203520042300216100002100639700002700660700002900687700002100716856012700737       2004                        eng d00aEVE - II: An Integrated Platform for Networked Virtual Environments0 aEVE II An Integrated Platform for Networked Virtual Environments  c8 - 10 September  a 81 - 853 aIn this paper, we present the design and implementation of an integrated platform for Networked Virtual Environments. This platform called EVE-II is an enhancement of the EVE distributed virtual reality platform, supporting stable event sharing for multi-user 3D places, easy creation of 3D multi-user3D places, H.323-based Voice over IP services integrated in a 3D spaces well as many concurrent 3D multi-user spaces.1 aBouras, Christos1 aTsiatsos, Thrasivoulos1 aPanagopoulos, Alexandros1 aTheoxaris, Nikos  uhttp://telematics.upatras.gr/telematics/publications/eve-ii-integrated-platform-networked-virtual-environments?language=en01740nas a2200145   4500008004100000245006400041210006300105260001700168300001500185520120900200100002101409700002101430700001801451856012501469       2004                        eng d00aFast and Efficient IP Handover in IEEE 802.11 Wireless LANs0 aFast and Efficient IP Handover in IEEE 80211 Wireless LANs  c21 - 24 June  a 249 - 2553 aThis paper presents an effective and simple solution to the problem of Layer 3 (L3) handover in IEEE 802.11 wireless LANs (WLANs), so as to extend the IP mobility area of 802.11 wireless Stations (STAs). The IEEE 802.11f Inter-Access Point Protocol (IAPP), handles the Layer 2 (L2) mobility of STAs during L2 (intra-network) handovers, and offers IP connectivity via L2 specific methods. Instead of using a different protocol for the L3 mobility management of STAs, such as Mobile IP (MIP) [4] or a MIP-variant, the IAPP protocol is extended so as to also support the inter-network (L3) movements of 802.11 STAs. The proposed IAPP-based mechanism supports host mobility and offers substantial uninterrupted wireless IP-connectivity, even after L3 movements. The cornerstones of this mechanism are the zero-delay IP movement detection and the zero over-the-air IP signaling during IP handover establishment, which lead to seamless (very fast) and smooth IP handoffs. This fast IP-handoff method is especially suitable to 802.11 systems, as it has better performance than traditional MIP-based methods (shorter handover delays, near zero packet loss), while makes IP roaming transparent to the mobile STAs.1 aBouras, Christos1 aSampraku, Ioanna1 aKaroubalis, T  uhttp://telematics.upatras.gr/telematics/publications/fast-and-efficient-ip-handover-ieee-80211-wireless-lans?language=en01970nas a2200193   4500008004100000245004700041210004700088300001300135520136900148100002101517700002301538700002301561700002301584700001701607700001401624700001301638700001301651856011201664       2004                        eng d00aGame Based Learning Using Web Technologies0 aGame Based Learning Using Web Technologies  a 67 - 843 aGame-based learning has been recognized as an
important alternative or supplement to traditional
in-class, face-to-face teaching. It can help both
adults and children in learning new concepts,
acquiring expertise and practicing knowledge.
Although game-based learning has been applied
mainly for teaching children, it can be quite
helpful for adult vocational or university learning.
In this paper, a web-based game is presented,
which has been developed for enhancing the
learning experience of university students. Its goal
is to serve as a complement to classes, although it
can be used independently. It provides the students
with many ways of synchronous or asynchronous
communication and knowledge acquisition.
Through the game, students have to search for
information, understand it and use it in discussions
with the members of other teams. Many users are
able to play the game simultaneously, while many
teachers may run different game themes.
Microsoft’s ASP.NET scripting environment was
used for creating the game’s website and its
rationale. The website utilizes also Macromedia’s
communication technology (Flash Communication
Server MX) for enabling real-time communication
by several means (voice, text, etc). Flash was used
in the website for building the real-time
communication modules as well as for creating a
more elegant user interface.1 aBouras, Christos1 aKapoulas, Vaggelis1 aIgglesis, Vaggelis1 aMisedakis, Ioannis1 aDziabenko, O1 aKoubek, A1 aPivec, M1 aSfiri, A  uhttp://telematics.upatras.gr/telematics/publications/game-based-learning-using-web-technologies?language=en01037nas a2200133   4500008004100000245009200041210006900133260002000202300001500222520047400237100002100711700002500732856014600757       2004                        eng d00aMonitoring and Analyzing Performance of Networked Virtual Environments: the case of EVE0 aMonitoring and Analyzing Performance of Networked Virtual Enviro  c21 - 23 October  a 218 - 2213 aThis paper focuses on the performance monitoring of a networked virtual environment, called EVE, in order to identify the elements that degrade its network performance. In particular, based both on the architectural and communication model that EVE adopts in order to cope with the dynamic behavior of the network, we performed a series of experiments, taking into account the number of the connected users, the network load as well as the connection type of the users.1 aBouras, Christos1 aGiannaka, Eleftheria  uhttp://telematics.upatras.gr/telematics/publications/monitoring-and-analyzing-performance-networked-virtual-environments-case-eve?language=en01368nas a2200133   4500008004100000245007500041210006900116260002000185300001200205520084600217100002101063700002201084856012801106       2004                        eng d00aA new pricing mechanism for a high - priority DiffServ - based service0 anew pricing mechanism for a high priority DiffServ based service  c9 - 11 February  a585-5903 aQoS provisioning according to the DiffServ framework has raised the requirements for pricing mechanisms that preserve the potential and flexibility of DiffServ. At the same time, such mechanisms should reflect resource usage, allocate resources efficiently, reimburse costs or maximize service provision profits and lead customers to requesting services that will maximize their revenue. This work proposes a policy for pricing based on resource allocation by a particular category of DiffServ-based services for aggregated traffic in the case of transport networks. Our research takes into account the particularities that apply to the case of DiffServ services’ provision over transport networks while imposing minimal overload and a-priori estimation of costs. The detailed pricing methodology is presented and experimentally evaluated.1 aBouras, Christos1 aSevasti, Afroditi  uhttp://telematics.upatras.gr/telematics/publications/new-pricing-mechanism-high-priority-diffserv-based-service?language=en01164nas a2200145   4500008004100000245007700041210006900118260001800187300001400205520060800219100002100827700002100848700001800869856013100887       2004                        eng d00aAn optimized handoff scheme for IP mobility support in IEEE 802.11 WLANs0 aoptimized handoff scheme for IP mobility support in IEEE 80211 W  c4 - 6 October  a 99 - 1083 aThis paper presents an 802.11-dependent IP mobility solution which ac-
celerates the network reconfiguration phase after subnet handoffs and
significantly reduces the IP handoff latency. The proposed fast IP hand-
off method offers the next generation WLAN applications such as Voice
over WLANs (VoWLAN) complete freedom of movement without expe-
riencing any connectivity problems. The performance results verify that
this method outperforms other existing proposed IP mobility solutions
inWLANs, in a way which introduces the lesser imperative amendments
to the existing 802.11 wireless LAN framework.1 aBouras, Christos1 aSampraku, Ioanna1 aKaroubalis, T  uhttp://telematics.upatras.gr/telematics/publications/optimized-handoff-scheme-ip-mobility-support-ieee-80211-wlans?language=en01080nas a2200157   4500008004100000245006500041210006300106260001800169300001500187520051400202100002100716700002200737700001900759700002200778856012200800       2004                        eng d00aPerformance Evaluation of an IPv6 - capable H323 Application0 aPerformance Evaluation of an IPv6 capable H323 Application  c29 - 31 March  a 470 - 4753 aOpenH323 is an open source H.323 implementation that has been ported to IPv6. In this paper we briefly introduce the library architecture and the performance citeria with which the ported version should be evaluated. We then present a variety of experiments that we conducted in order to comparatively evaluate the IPv4 and IPv6 protocol stacks. We also present the results of some initial experiments comparing IPv4 and IPv6 performance under congested network links and the conclusions that they lead us to.1 aBouras, Christos1 aGkamas, Apostolos1 aStamos, Kostas1 aPrimpas, Dimitris  uhttp://telematics.upatras.gr/telematics/publications/performance-evaluation-ipv6-capable-h323-application?language=en01562nas a2200145   4500008004100000245006300041210006300104260002900167520102000196653000901216100002101225700002201246700002301268856012501291       2004                        eng d00aPerformance Evaluation of TCP over UMTS Transport Channels0 aPerformance Evaluation of TCP over UMTS Transport Channels  c29 November - 1 December3 aUniversal Mobile Telecommunications System
(UMTS) is a third-generation cellular network that
enables high-speed wireless Internet access. It can
provide maximum data-rates ranging from 64kb/s to
2Mb/s in different environmental types. UMTS is
designed to provide access to the existing Internet
services as well as to UMTS specific services. It will
augment the existing capabilities of 2G mobile
networks and GPRS, and one often envisaged strategy
is to offer a richer set of multimedia services. It is
widely known that TCP does not perform efficiently in
wireless links where the bit error rate is high enough.
This paper has as main target to evaluate the
performance of TCP data transfer over the UMTS air
interface, by means of a rather detailed simulation
model. We examine the performance of TCP over
UMTS Dedicated Channels (DCHs) with different bit
rates and Transmission Time Intervals (TTIs) and we
represent some simulation experiments for UMTS
High Speed Downlink Packet Access (HSDPA)
transmissions.10aUMTS1 aBouras, Christos1 aAlexiou, Antonios1 aIgglesis, Vaggelis  uhttp://telematics.upatras.gr/telematics/publications/performance-evaluation-tcp-over-umts-transport-channels?language=en01478nas a2200157   4500008004100000245013500041210006900176260001300245300001500258520080600273100002101079700002201100700001901122700002201141856015701163       2004                        eng d00aPerformance Evaluation of the Impact of Quality of Service mechanisms in an IPv6 network for IPv6 - capable real time applications0 aPerformance Evaluation of the Impact of Quality of Service mecha  cDecember  a 463 - 4833 aThis paper describes a Quality of Service (QoS) service on an IPv6 domain that aims
to service aggregates of real-time traffic with minimum delay, jitter, and packet loss. It
contains results from the tests that were performed in order to configure and evaluate the
QoSmechanisms.As an actual example of real-time traffic, we have used theOpenH323
project, an open source H.323 implementation that has been ported to IPv6. The QoS
mechanisms in IPv6 networks is still a field that has not been researched adequately,
and we therefore present the results from the experiments in our IPv6 network that
took advantage of the QoS mechanisms. This QoS service uses the Modular QoS CLI
(MQC) mechanism and especially the Low Latency Queue feature (LLQ) in order to
treat packets from real-time applications.1 aBouras, Christos1 aGkamas, Apostolos1 aStamos, Kostas1 aPrimpas, Dimitris  uhttp://telematics.upatras.gr/telematics/publications/performance-evaluation-impact-quality-service-mechanisms-ipv6-network-ipv6-capable-real?language=en01238nas a2200157   4500008004100000245006200041210006200103260001800165300001100183520069100194653000900885100002100894700002200915700002300937856012000960       2004                        eng d00aPerformance Evaluation of UMTS for Mobile Internet Access0 aPerformance Evaluation of UMTS for Mobile Internet Access  c5 - 7 October  a 1 - 43 aUMTS constitutes the third generation of cellular wireless
networks which aims to provide high-speed data access
along with real time voice calls (Holma & Toskala, 2001).
Wireless data is one of the major boosters of wireless
communications and one of the main challenges of next
generation standards (Chaudhury & Mohr, 1999).
It can provide maximum data-rates ranging from 64kb/s
to 2Mb/s in different environmental types. UMTS is
designed to provide access to the existing Internet services
as well as to UMTS specific services. It will augment the
existing capabilities of 2G mobile networks and GPRS, and
one often envisaged strategy is to offer a richer set of
multimedia services.10aUMTS1 aBouras, Christos1 aAlexiou, Antonios1 aIgglesis, Vaggelis  uhttp://telematics.upatras.gr/telematics/publications/performance-evaluation-umts-mobile-internet-access?language=en00937nas a2200133   4500008004100000245006100041210006100102260001700163300001500180520043900195100002100634700002500655856012300680       2004                        eng d00aPerformance Monitoring on Networked Virtual Environments0 aPerformance Monitoring on Networked Virtual Environments  c21 - 24 June  a 302 - 3083 aAs networked virtual environments gain increasing interest and acceptance in the field of Internet applications, a lot of effort is drawn in the optimization of their performance, which will result in the wide adaptation of this evolving mean of communication. This paper focuses on the performance monitoring of such a networked virtual environment, called EVE, in order to identify the elements that degrade its network performance.1 aBouras, Christos1 aGiannaka, Eleftheria  uhttp://telematics.upatras.gr/telematics/publications/performance-monitoring-networked-virtual-environments?language=en01335nas a2200121   4500008004100000245009700041210006900138260002100207520079100228100002101019700002201040856015101062       2004                        eng d00aPerformance of Adaptive Multimedia Transmission: The case of One Multicast Stream techniques0 aPerformance of Adaptive Multimedia Transmission The case of One   c18 - 20 February3 aA “one multicast stream” mechanism is a mechanism, which
can be used for multicast multimedia data with the use of one multicast
stream over heterogeneous networks, like the Internet, and has the
capability to adapt the transmission oft he multimedia data to network
changes. In this paper, we describe a “one multicast stream” mechanism
for adaptive transmission of multimedia data, which is based on real time
protocols. In addition, the proposed mechanism uses an inter-receiver
fairness function in order to treat the group of receivers with fairness in
a heterogeneous environment. We evaluate the adaptive multicast transmission
mechanism through a number ofsim ulations and compare it with
a number ofsimilar schemes available to the literature (LBA+, TFMCC,
PGM, TBRCA).1 aBouras, Christos1 aGkamas, Apostolos  uhttp://telematics.upatras.gr/telematics/publications/performance-adaptive-multimedia-transmission-case-one-multicast-stream-techniques?language=en02183nas a2200145   4500008004100000245008000041210006900121260000900190300001500199520162700214100002101841700002001862700002401882856013101906       2004                        eng d00aPredictive Prefetching on the Web and its Potential Impact in the Wide Area0 aPredictive Prefetching on the Web and its Potential Impact in th  cJune  a 143 - 1793 aThe rapid increase of World Wide Web users and the development of services with high bandwidth requirements
have caused the substantial increase of response times for users on the Internet. Web latency would be significantly
reduced, if browser, proxy or Web server software could make predictions about the pages that a user is
most likely to request next, while the user is viewing the current page, and prefetch their content.
In this paper we study Predictive Prefetching on a totally new Web system architecture. This is a system
that provides two levels of caching before information reaches the clients. This work analyses prefetching on a
Wide Area Network with the above mentioned characteristics. We first provide a structured overview of predictive
prefetching and show its wide applicability to various computer systems. TheWAN that we refer to is the GRNET
academic network in Greece. We rely on log files collected at the network’s Transparent cache (primary caching
point), located at GRNET’s edge connection to the Internet. We present the parameters that are most important for
prefetching on GRNET’s architecture and provide preliminary results of an experimental study, quantifying the
benefits of prefetching on theWAN. Our experimental study includes the evaluation of two prediction algorithms:
an “n most popular document” algorithm and a variation of the PPM (Prediction by Partial Matching) prediction
algorithm. Our analysis clearly shows that Predictive prefetching can improve Web response times inside the
GRNET WAN without substantial increase in network traffic due to prefetching.1 aBouras, Christos1 aKonidaris, Agis1 aKostoulas, Dionisis  uhttp://telematics.upatras.gr/telematics/publications/predictive-prefetching-web-and-its-potential-impact-wide-area?language=en01493nas a2200121   4500008004100000245004000041210004000081300001500121520108700136100002101223700002201244856010501266       2004                        eng d00aPricing QoS over transport networks0 aPricing QoS over transport networks  a 167 - 1743 aIn recent years, a number of alternatives for service
differentiation and QoS provision have been proposed and
standardized in communication networks. In the case of backbone
networks the DiffServ architecture has prevailed, due to its
scalability and deployment feasibility. The provisioning of
differentiated services has raised the requirements for
interdependent controlled resource allocation and service
pricing, with particular needs for pricing mechanisms that
preserve the potential and flexibility of the DiffServ framework.
At the same time, such mechanisms should reflect resource
usage, allocate resources efficiently, reimburse costs or maximize
service provision profits and lead customers to requesting
services that will maximize their revenue. Presents the key issues
involved in the area of pricing DiffServ-based services and the
research work carried out in this field, while at the same time
outlining the basic principles that such a pricing infrastructure
should obey with respect to the particularities that apply to the
case of DiffServ services provision.1 aBouras, Christos1 aSevasti, Afroditi  uhttp://telematics.upatras.gr/telematics/publications/pricing-qos-over-transport-networks?language=en01889nas a2200145   4500008004100000245010300041210006900144300001500213520128100228100002101509700002201530700001901552700001601571856015601587       2004                        eng d00aProviding and verifying advanced IP services in hierarchical DiffServ networks - the case of GEANT0 aProviding and verifying advanced IP services in hierarchical Dif  a 321 - 3363 aThe differentiated services (DiffServ) framework is widely proposed as an efficient method for providing
advanced IP services to large-scale networks, with QoS requirements. However, the provisioning of such
services in production networks has proved to be more difficult than initially expected, in defining, setting
and verifying appropriate Service Level Agreements (SLAs). GEANT, the Gigabit core pan-European
research network, on a pilot basis introduced ‘Premium IP’ service, offering bounded delay and negligible
packet loss to the European National Research & Education Networks (NRENs) that it interconnects.
However, large scale provisioning of this new service requires the definition of efficient interaction
procedures between administrative domains involved and methods for SLA monitoring. This paper focuses
on these issues and presents the experience acquired from the early experiments in GEANT, as an example
of hierarchical Gigabit multi-domain environment, enabled with QoS provisioning to its constituent
NRENs. This model scales more efficiently than the common peering Internet Service provider (ISP)
commercial paradigm. Finally, we outline other options that promise QoS, such as Layer 2 VPNs in MPLS
backbones, with non-standard (yet) mechanisms.1 aBouras, Christos1 aSevasti, Afroditi1 aLiakopoulos, A1 aMaglaris, B  uhttp://telematics.upatras.gr/telematics/publications/providing-and-verifying-advanced-ip-services-hierarchical-diffserv-networks-case-geant?language=en01510nas a2200157   4500008004100000245004900041210004900090260001700139300001500156520099200171100002101163700002201184700001901206700002201225856010501247       2004                        eng d00aQuality of Service aspects in an IPv6 domain0 aQuality of Service aspects in an IPv6 domain  c25 - 29 July  a 238 - 2453 aDuring the last years 2 Quality of Service architectures (IntServ and DiffServ) have been proposed and evaluated. The DiffServ architecture has proved its ascendancy and some services have already been proposed and deployed on IPv4 domains. But the usage of IPv6 protocol creates new challenges, as the QoS mechanisms that are currently supported for IPv6 in most implementations are fewer (or different) compared to IPv4 and in addition the whole network’s behaviour is different. So, as a result the QoS services should be designed and evaluated again. This paper describes a QoS service on an IPv6 domain that aims to service aggregates of real time traffic with minimum delay, jitter and packet loss. In addition, it contains results from the experiments in our IPv6 network that took advantage of the QoS mechanisms. This QoS service uses the Modular QoS CLI (MQC) mechanism and especially the Low Latency Queue feature (LLQ) in order to treat packets from real time applications.1 aBouras, Christos1 aGkamas, Apostolos1 aStamos, Kostas1 aPrimpas, Dimitris  uhttp://telematics.upatras.gr/telematics/publications/quality-service-aspects-ipv6-domain?language=en01917nas a2200133   4500008004100000245004900041210004700090260001300137300001700150520146400167100002101631700002201652856010901674       2004                        eng d00aSLA - based QoS pricing in DiffServ networks0 aSLA based QoS pricing in DiffServ networks  cDecember  a 1868 - 18803 aThe availability of high-speed transmission media and networking equipment in contemporary networks, as well as the evolution of
quality-demanding applications has focused research interest on the provision of advanced qualitative services in addition to the traditional
best-effort model of the Internet. A number of alternatives for service differentiation and QoS provisioning have been proposed and
standardized, but in the case of backbone, transport networks the DiffServ architecture has prevailed, due to its scalability and deployment
feasibility. The provisioning of services according to the DiffServ framework has in turn raised the requirements for interdependent,
controlled resource allocation and service pricing, with particular needs for pricing mechanisms that preserve the potential and flexibility of
DiffServ. At the same time, such mechanisms should reflect resource usage, allocate resources efficiently, reimburse costs or maximize
service provision profits and lead customers to requesting services that will maximize their revenue. In this work, after reviewing related
research, the principles that a pricing scheme for DiffServ-based services should follow are presented, stressing the differences form
traditional Internet pricing. Based on these principles, an analytical approach to pricing a particular class of DiffServ-based services and a
methodology for applying this approach in a real network are proposed and evaluated.1 aBouras, Christos1 aSevasti, Afroditi  uhttp://telematics.upatras.gr/telematics/publications/sla-based-qos-pricing-diffserv-networks?language=en01281nas a2200181   4500008004100000245008900041210006900130260001800199300001500217520058900232100002100821700002300842700002700865700002500892700002200917700001600939856014400955       2004                        eng d00aUsing VR technology to Support e - Learning: The 3D Virtual Radiopharmacy Laboratory0 aUsing VR technology to Support e Learning The 3D Virtual Radioph  c23 - 26 March  a 268 - 2733 aIn this paper, we present a virtual laboratory, which is designed and implemented in the framework of the VirRAD European project. This laboratory represents a 3D simulation of a radio-pharmacy laboratory, where learners, represented by 3D avatars, can experiment on radio-pharmacy equipment by carrying out specific learning scenarios. This paper describes the functionality provided by this laboratory, the motivation factors which led to its formation, the technological decisions that were made for the optimization of the system as well as the envisioned steps to be carried out.1 aBouras, Christos1 aKapoulas, Vaggelis1 aTsiatsos, Thrasivoulos1 aGiannaka, Eleftheria1 aAlexiou, Antonios1 aNani, Maria  uhttp://telematics.upatras.gr/telematics/publications/using-vr-technology-support-e-learning-3d-virtual-radiopharmacy-laboratory?language=en01756nas a2200145   4500008004100000245013500041210006900176260001900245300001300264520110900277100002101386700002501407700002201432856015601454       2004                        eng d00aVirtual Laboratories in Education: A cheap way for schools to obtain laboratories for all courses by using the Computer Laboratory0 aVirtual Laboratories in Education A cheap way for schools to obt  c22 - 27 August  a 19 - 283 aPractical experience is an important component of the educational process. However, the time and economical resources often required for the setting up and construction of scientific laboratories is outside the scope of many institutions. A solution to this problem could be found in the adaptation of the Virtual Reality technology, which could allow the creation of Virtual Laboratories, which will simulate the processes and actions that could take place in real laboratories. In particular, this paper, based on the expertise and motivation gained by the VirRAD-IST project, proposes and describes such an educational virtual laboratory, which aims to meet the requirements of a real laboratory and furthermore to support communication and collaboration services. We propose a web-based system, which allows users to perform experiments on educational fields, such as Physics or Chemistry in 3D multi-user worlds where users are represented by avatars and they are offered a wide range of communication and collaboration services in order to simulate efficiently a real learning experimental process.1 aBouras, Christos1 aGiannaka, Eleftheria1 aAlexiou, Antonios  uhttp://telematics.upatras.gr/telematics/publications/virtual-laboratories-education-cheap-way-schools-obtain-laboratories-all-courses-using?language=en01306nas a2200169   4500008004100000245008000041210006900121300001500190520066300205100002100868700002300889700002700912700002500939700002200964700001600986856013401002       2004                        eng d00aThe Virtual Radiopharmacy Laboratory: A 3D Simulation for Distance Learning0 aVirtual Radiopharmacy Laboratory A 3D Simulation for Distance Le  a 307 - 3223 aThis article presents Virtual Radiopharmacy Laboratory (VR
LAB), a virtual laboratory accessible through the Internet.
VR LAB is designed and implemented in the framework of
the VirRAD European project. This laboratory represents a
3D simulation of a radio-pharmacy laboratory, where learners,
represented by 3D avatars, can experiment on radiopharmacy
equipment by carrying out specific learning scenarios.
This article describes the functionality provided by
this laboratory, the motivation factors which led to its formation,
the technological decisions that were made for the optimization
of the system, as well as the envisioned steps to be
carried out.1 aBouras, Christos1 aKapoulas, Vaggelis1 aTsiatsos, Thrasivoulos1 aGiannaka, Eleftheria1 aAlexiou, Antonios1 aNani, Maria  uhttp://telematics.upatras.gr/telematics/publications/virtual-radiopharmacy-laboratory-3d-simulation-distance-learning?language=en01186nas a2200133   4500008004100000245008600041210006900127260002800196300001500224520063300239100002100872700001600893856014300909       2004                        eng d00aA Web - based Tool for Building and Accessing Learning Objects and Online Courses0 aWeb based Tool for Building and Accessing Learning Objects and O  c30 August - 1 September  a 645 - 6473 aIn this paper we present a web-based tool that facilitates instructors and trainers to easily develop learning objects and online courses so as to serve their distant learners? needs. Additionally, we present the way content created using that tool can be delivered to the learners during a learning process. We therefore present a sample content management and delivery system that exploits the potential of the above-mentioned web-based tool. The resultant e-learning content can be easily searched and retrieved, tracked in terms of the learners? interactions with it and reused within different learning objects and courses.1 aBouras, Christos1 aNani, Maria  uhttp://telematics.upatras.gr/telematics/publications/web-based-tool-building-and-accessing-learning-objects-and-online-courses?language=en01532nas a2200157   4500008004100000245007200041210006900113260001800182300001300200520093300213100002101146700002301167700002701190700002301217856013401240       2004                        eng d00aA Web Based Virtual Community: Funcionality and Architecture Issues0 aWeb Based Virtual Community Funcionality and Architecture Issues  c23 - 26 March  a 59 - 663 aA Web Based Virtual Community is an example of a Collaborative Virtual Environment, which focalizes in providing collaborative functionalities and both synchronous and asynchronous interaction services. This paper describes a virtual community, which aims to meet the requirements of a virtual collaboration space and support autonomous and collaborative e-learning services. In particular, a web-based platform is described, which is able to support communities whose members are able to interact and form groups based on their common interests. The community provides its members with the ability to communicate through enhanced forums and chats, but also, to interact in the social interaction spaces. The users can arrange events, which occur in virtual meeting centers, where 3D avatars represent the users. In these multi-user spaces, extended functionalities are offered, while system agents assist and consult the users.1 aBouras, Christos1 aKapoulas, Vaggelis1 aTsiatsos, Thrasivoulos1 aIgglesis, Vaggelis  uhttp://telematics.upatras.gr/telematics/publications/web-based-virtual-community-funcionality-and-architecture-issues?language=en01287nas a2200145   4500008004100000245009000041210006900131260001800200300001500218520069000233100002100923700002300944700002300967856015100990       2004                        eng d00aWeb page fragmentation and content manipulation for constructing personalized portals0 aWeb page fragmentation and content manipulation for constructing  c14 - 17 April  a 744 - 7543 aThis paper presents a web page fragmentation technique, which is
utilized for extracting specific parts of web pages and building personalized
portals using these fragments. It is based on an algorithm, which fragments a
web page in discrete fragments using the page’s internal structure. A training
and update procedure is used for identifying the specific fragments of a web
page in different time points. Using this technique a service provider can offer
Web users a system for building personalized pages based on the content of
their favorite sites. This technique, besides providing a convenient way for
browsing, saves time and reduces the cost of browsing in different sites.1 aBouras, Christos1 aKapoulas, Vaggelis1 aMisedakis, Ioannis  uhttp://telematics.upatras.gr/telematics/publications/web-page-fragmentation-and-content-manipulation-constructing-personalized-portals?language=en01228nas a2200145   4500008004100000245006400041210006400105260001600169300001500185520069000200100002100890700002300911700002300934856012500957       2004                        eng d00aWeb Page Fragmentation for Personalized Portal Construction0 aWeb Page Fragmentation for Personalized Portal Construction  c5 - 7 April  a 332 - 3363 aWeb portals offer many services and wealth of content
to Web users. However, most users do not find interest in
all the content present in these sites. Most of them visit
some specific sites and browse in specific thematic areas of
them. In this paper, a software technique is presented that
allows the viewers of web sites to build their own
personalized portals, using specific thematic areas of their
preferred sites. This transcoding technique is based on an
algorithm, which fragments a web page in discrete
fragments using the page’s internal structure. A training
and update procedure is used for identifying the different
instances of thematic areas in different time points.1 aBouras, Christos1 aKapoulas, Vaggelis1 aMisedakis, Ioannis  uhttp://telematics.upatras.gr/telematics/publications/web-page-fragmentation-personalized-portal-construction?language=en01184nas a2200145   4500008004100000245006700041210006300108260001800171300001700189520064100206100002100847700002300868700002300891856012400914       2004                        eng d00aA Web - page fragmentation technique for personalized browsing0 aWeb page fragmentation technique for personalized browsing  c14 - 17 March  a 1146 - 11473 aIn this paper, a technique is presented that allows web sites
viewers to build personalized web pages, using specific thematic
areas of their preferred sites. This technique, besides saving from
the trouble of having to browse in different sites in order to find
the desired content, saves users time and reduces the cost of
browsing the web by minimizing the data that have to be
downloaded. It is based on an algorithm, which fragments a web
page in discrete fragments using the page’s internal structure. A
training and update procedure is utilized for recognizing the
instances of the web page components in different time points.1 aBouras, Christos1 aKapoulas, Vaggelis1 aMisedakis, Ioannis  uhttp://telematics.upatras.gr/telematics/publications/web-page-fragmentation-technique-personalized-browsing?language=en00917nas a2200157   4500008004100000245005900041210005800100260001900158300001500177520037100192100002100563700002200584700001900606700001400625856012000639       2003                        eng d00aAdding IPv6 support to H323 Gnomemeeting/openH323 port0 aAdding IPv6 support to H323 GnomemeetingopenH323 port  c7 - 10 October  a 458 - 4623 aThis article deals with the port towards the new IPv6
Internet network of voice and multi-media over IP applications.
We explain in detail our experience in porting Gnomemeeting,
the well-known Linux based videoconference software, and
more particularly the H323 library which implements the
signaling protocols (call establishment, transfer, codec
negotiation,…).1 aBouras, Christos1 aGkamas, Apostolos1 aStamos, Kostas1 aJosset, S  uhttp://telematics.upatras.gr/telematics/publications/adding-ipv6-support-h323-gnomemeetingopenh323-port?language=en01323nas a2200133   4500008004100000245008200041210006900123260001700192300001300209520077600222100002100998700002201019856014801041       2003                        eng d00aAnalytical approach and verification of a DiffServ – based priority service0 aAnalytical approach and verification of a DiffServ based priorit  c23 - 25 July  a 11 - 203 aThe provision of Quality of Service (QoS) in a seamless way over the
dominating internetworking protocol of our times (IP), has been a challenge for
many researchers in the past years. Strict qualitative guarantees have proven
difficult to provide in a way that has discouraged efforts in the area. The lack of
a coherent provisioning methodology has been identified as the main reason for
this. In this work, we are attempting an analytical yet straightforward approach
to the provisioning methodology proposed for premium service of high-quality
demanding traffic in the wide-area. Our approach is based on a series of wellknown
results of queuing theory but is proven to provide good approximations
to experimental results as well as worthwhile qualitative guarantees.1 aBouras, Christos1 aSevasti, Afroditi  uhttp://telematics.upatras.gr/telematics/publications/analytical-approach-and-verification-diffserv-%E2%80%93-based-priority-service?language=en01239nas a2200157   4500008004100000245008800041210006900129260001800198300001500216520063700231100002100868700001800889700001900907700001300926856014200939       2003                        eng d00aAn approach to methodology and implementation of a Network Monitoring Analysis Tool0 aapproach to methodology and implementation of a Network Monitori  c14 - 16 April  a 125 - 1293 aIn this paper we describe the design and implementation of a
network monitoring analysis tool. The network resources
were configured to support SNMP under various operating
systems, thresholds definitions and events. The data were
collected by a network monitoring system and handled
according to the values of the variables or the event type. A
real- time report to a database was established via adaptive
scripts. A Network Node Manager (NNM) will inform an
external, remote database about the network status by
sending real time data containing alerts and events. The
whole tool is called Network Management Analysis Tool
(NMAT).1 aBouras, Christos1 aGanos, Petros1 aAravantinos, E1 aIlias, A  uhttp://telematics.upatras.gr/telematics/publications/approach-methodology-and-implementation-network-monitoring-analysis-tool?language=en00869nas a2200169   4500008004100000245006000041210005500101260001400156300000900170520028500179100002100464700002300485700002700508700002500535700001600560856012300576       2003                        eng d00aBuilding e – learning communities: The case of VirRAD0 aBuilding e learning communities The case of VirRAD  c9-11 July  a 4523 aThis paper discusses the development of virtual
communities and especially e-learning communities. In
particular, this paper is inspired by VirRAD European
project, and presents the intermediate results that have
raised from the definition of this virtual radiopharmacy
community.1 aBouras, Christos1 aKapoulas, Vaggelis1 aTsiatsos, Thrasivoulos1 aGiannaka, Eleftheria1 aNani, Maria  uhttp://telematics.upatras.gr/telematics/publications/building-e-%E2%80%93-learning-communities-case-virrad?language=en01232nas a2200145   4500008004100000245006700041210006600108260001900174300001500193520068200208100002100890700002700911700001600938856013200954       2003                        eng d00aBuilding reusable and interactive e-learning content using Web0 aBuilding reusable and interactive elearning content using Web  c18 - 20 August  a 497 - 5083 aThis paper presents the design of a web-based learning content
authoring tool as well as the way learners can access courseware material,
within the scope of a personalized, yet social, learning environment for
vocational training. The authoring tool is intended to be part of the instructional
component of the VirRAD European project, where the learning process is
inspired by the principles of the Mindful Learning theory and supported by an
intelligent learner modelling system. It will enable the creation of
Radiopharmacy-related learning content that can be easily accessed and reused.
In addition, it will facilitate the monitorship of the users’ learning activities.1 aBouras, Christos1 aTsiatsos, Thrasivoulos1 aNani, Maria  uhttp://telematics.upatras.gr/telematics/publications/building-reusable-and-interactive-e-learning-content-using-web?language=en01600nas a2200133   4500008004100000245010200041210006900143260001700212300001500229520102200244100002101266700002201287856015701309       2003                        eng d00aComparing performance of SRAMT – LE vs other Layerd encoding schemes regarding TCP friendliness0 aComparing performance of SRAMT LE vs other Layerd encoding schem  c23 - 25 July  a 493 - 5023 aIn this paper we describe a hybrid sender and receiver-based
adaptation scheme for multicast transmission of multimedia data using layered
encoding, which we call SRAMT-LE (Sender-Receiver based Adaptation
scheme for Multicast Transmission using Layered Encoding). The most
prominent features of SRAMT-LE are its distributed (to sender and receivers)
transmission rate estimation algorithm and its innovative RTT (Round Trip
Time) estimation algorithm based on one-way delay measurements. SRAMTLE
is using both a TCP model and an AIMD (Additive Increase Multiplicative
Decrease) algorithm in order to estimate a TCP friendly bandwidth share. We
evaluate SRAMT-LE and compare it with a number of similar layered encoding
schemes available to the literature (PLM, RLC, MLDA). Main conclusion of
this evaluation was that SRAMT-LE has friendly behavior against the dominant
traffic types of today’s Internet and has a relative good behavior comparing
with the other layered encoding schemes available to the literature.1 aBouras, Christos1 aGkamas, Apostolos  uhttp://telematics.upatras.gr/telematics/publications/comparing-performance-sramt-%E2%80%93-le-vs-other-layerd-encoding-schemes-regarding-tcp?language=en01491nas a2200145   4500008004100000245006200041210006200103300001600165520096300181100002101144700002301165700001901188700001601207856012201223       2003                        eng d00aCompetitive Video on Demand Schedulers for Popular Movies0 aCompetitive Video on Demand Schedulers for Popular Movies  aPP. 49 - 613 a<p>In this paper we investigate the online video on demand problem, namely having to accept or reject a request for a movie without knowing the future requests. We present online movie-scheduling schemes that implement the principles of refusal by choice and delayed noti- 4cation. A novel way to schedule movies that exploits the knowledge of the distribution of the preference of requests for movies, is shown to have a competitive ratio that outperforms all the previously knownschemes inpractical situations. Infact, our scheduler has a competitive ratio bounded above by a constant, independent of the number of the users, channels, or movies, in the case that a large fraction of the requests tends to concentrate in a small number of movies. We extend our approach by presenting an “adaptive” randomized scheduler which initially is not aware of the movie popularities but it adapts to it, and achieves the same asymptotic competitive ratio.</p>
1 aBouras, Christos1 aKapoulas, Vaggelis1 aSpirakis, Paul1 aPantziou, G  uhttp://telematics.upatras.gr/telematics/publications/competitive-video-demand-schedulers-popular-movies-0?language=en02050nas a2200193   4500008004100000245007900041210006900120260001600189300001500205520135600220100002101576700002301597700002301620700002001643700001401663700001801677700001401695856014701709       2003                        eng d00aDelivering Interactive Enhanced Sports Content to Thin – Client DTV STBs0 aDelivering Interactive Enhanced Sports Content to Thin Client DT  c30 - 31 May  a 193 - 2043 aDigital Television (DTV) was the first major advance in the television industry
since the establishment of color TV sets in the 50’s. However, despite the
ambitious anticipations, most DTV operators offering subscriber TV services
are facing serious economic problems. Many believe that significantly
increasing the DTV operator revenues is closely linked to the provision of
advanced interactive TV applications which, on one-hand, based on content
enhancements will attract more subscribers, and on the other hand will also
generate indirect revenues through services like TV-commerce or on-line
betting. In this paper an end-to-end interactive TV application is presented.
The application has been developed for accompanying sport broadcasts, given
that sports content is very attractive for the majority of subscribers. This
application enhances sport broadcasts with relevant content (statistics, news,
information) appearing on user-demand, as well as with an innovative
interactive entertaining game of predictions challenging users to make
predictions and to prove their anticipatory skills and sport knowledge. The
application supports multiple types of forward and return channels and STB
middleware systems. Furthermore, its components can be used in content
distribution networks targeting multiple network-enabled information
appliances1 aBouras, Christos1 aKapoulas, Vaggelis1 aMisedakis, Ioannis1 aKarathanasis, H1 aTzovla, V1 aVrahliotis, G1 aMakris, M  uhttp://telematics.upatras.gr/telematics/publications/delivering-interactive-enhanced-sports-content-thin-%E2%80%93-client-dtv-stbs?language=en01316nas a2200133   4500008004100000245007900041210006900120260001800189300001300207520078800220100002101008700002201029856013101051       2003                        eng d00aDeployment of a DiffServ - based priority service in a MAN/WAN environment0 aDeployment of a DiffServ based priority service in a MANWAN envi  c27 - 29 March  a 27 - 323 aThe increased need for Quality of Service (QoS) in
today?s networks has concentrated a lot of research and
implementation efforts. Particular interest exists for the
exploitation of the DiffServ framework towards the
provision of qualitative services in MANs and WANs
worldwide. Although individual mechanisms have been
widely investigated, not many references to studies
combining all levels of priority and QoS provisioning
exist. This work aims at presenting a thorough and
unified approach to the dimensioning and provisioning of
a high priority service for high-quality demanding traffic
over a MAN/WAN environment. Our approach anticipates
for bounds in specific quality metrics and is demonstrated
by the experimental case-study of a high-priority service
over a MAN topology.1 aBouras, Christos1 aSevasti, Afroditi  uhttp://telematics.upatras.gr/telematics/publications/deployment-diffserv-based-priority-service-manwan-environment?language=en01297nas a2200133   4500008004100000245007000041210006600111300001300177520079400190100002100984700001801005700001801023856012201041       2003                        eng d00aThe deployment of IPv6 in an IPv4 world and Transition Mechanisms0 adeployment of IPv6 in an IPv4 world and Transition Mechanisms  a 86 - 933 aIt is stated that the new version of the IP protocol, IPv6, is
the answer to the majority of the problems that were raised
during the enormous expansion of the Internet and its
transformation to a global communication platform with
commercial scope. At the same time it is also stated that
IPv6 dominance will not be easy and there will be a period
when the two versions of the protocol will co-exist. In this
paper we describe some of the main transition mechanisms
that can be deployed in order to facilitate the transition
process to the new version of the IP protocol. Furthermore,
the presented mechanisms are discussed regarding their
usability, usefulness and manageability. Describes the way
some of these mechanisms were applied to the Greek
Research & Technology Network (GRNET).1 aBouras, Christos1 aKaraliotas, A1 aGanos, Petros  uhttp://telematics.upatras.gr/telematics/publications/deployment-ipv6-ipv4-world-and-transition-mechanisms?language=en01312nas a2200133   4500008004100000245007200041210006900113260001500182300001500197520079200212100002101004700002401025856012901049       2003                        eng d00aEducational Information Society in Greece: The Greek School Network0 aEducational Information Society in Greece The Greek School Netwo  c3 - 6 June  a 179 - 1863 aIn this paper, we present the Greek School Network. This project is financed by the Second and Third Community Support
Framework of the European Union. Research and Academic Computer Technology Institute (CTI) has the responsibility for
the design, coordination and the implementation of the project. The main object of the project is the implementation of a
network infrastructure for the interconnection of school laboratories and educational administration offices and the provision
of network services in a wide range. It forms a closed educational network, which is based on the Greek educational and
research backbone network (GRNET). The Greek School Network statistics show that teachers and students have adopted the
services of GSN in their school life and learning activities.1 aBouras, Christos1 aParaskevas, Mixalis  uhttp://telematics.upatras.gr/telematics/publications/educational-information-society-greece-greek-school-network?language=en01336nas a2200145   4500008004100000245007900041210006900120260001900189300001300208520076800221100002100989700002001010700002401030856013601054       2003                        eng d00aEfficient Reduction of Web Latency through Predictive Prefetching on a WAN0 aEfficient Reduction of Web Latency through Predictive Prefetchin  c17 - 19 August  a 25 - 363 aThis paper studies Predictive Prefetching on a Web system that provides
two levels of caching before information reaches the clients. We analyze
prefetching on a Wide Area Network with the above mentioned characteristics.
First, we provide a structured overview of predictive prefetching and show its
wide applicability to various computer systems. The WAN that we refer to is
the GRNET academic network in Greece. We rely on log files collected at the
network’s Transparent cache (primary caching point), located at GRNET’s edge
connection to the Internet. We present the parameters that are most important
for prefetching on GRNET’s architecture and provide preliminary results of an
experimental study, quantifying the benefits of prefetching on the WAN.1 aBouras, Christos1 aKonidaris, Agis1 aKostoulas, Dionisis  uhttp://telematics.upatras.gr/telematics/publications/efficient-reduction-web-latency-through-predictive-prefetching-wan?language=en02261nas a2200133   4500008004100000245008000041210006900121300001500190520172400205100002101929700002701950700001401977856013601991       2003                        eng d00aAn electronic voting service to support decision making in Local Government0 aelectronic voting service to support decision making in Local Go  a 255 - 2743 aThis paper presents details of a web-based, database-oriented ‘‘electronic voting service’’.
Rapid world-wide growth in Internet and Web use has stimulated many initiatives aimed at
applying information and communication innovations to create what has been called a
‘‘digital’’ or ‘‘electronic democracy’’. Internet voting is already widespread in a variety of
forms, some serious, most not. A new set of opportunities is offered to facilitate closer links
among citizens, between citizens and politicians and direct democratic participation through
online voting and interactive polling. Local government decision-making procedures can be
enhanced by the application of a electronic voting service to evaluate citizens responses to
certain issues and to canvass the possible solutions they have in mind.
The main characteristics of this electronic voting service were developed on the basis of
strong lengthy experience of and a good deal of consultation with local authorities. This interaction
revealed a demand for an easy to use (for novice users) and administer tool, low cost
with a minimum set of security mechanisms, but still able to provide valid results. The systems
services were planned and implemented to be easily expandable. The application is based on
state-of-the-art software platform, integrating WWW and database. The system aims to become
a pilot for implementing efforts to support on line voting procedures. The service provides
the capability to create a questionnaire/poll, view the subject and participate in the
voting procedure. Only authorised users can use the system to vote or create a questionnaire.
All users can view results from previous voting procedures.1 aBouras, Christos1 aTriantafillou, Vasilis1 aKatris, N  uhttp://telematics.upatras.gr/telematics/publications/electronic-voting-service-support-decision-making-local-government?language=en01404nas a2200145   4500008004100000245006500041210006500106300001200171520085500183100002101038700002301059700002201082700002701104856012701131       2003                        eng d00aEvaluation of Teleteaching Services over ATM and IP Networks0 aEvaluation of Teleteaching Services over ATM and IP Networks  a 1 - 183 aThis paper presents the components of a synchronous teleteaching application, their underlying
technology and their interaction with network services. In addition, it presents the
architecture and design of a synchronous teleteaching application used over the public ATM
network in Greece. This paper presents various teleteaching scenarios over an ATM network
infrastructure with the use of native ATM and IP over ATM. In each scenario we present the
standards used, the logical components, the resource demands (network and equipment) and
its special characteristics. For each scenario we give detailed information about the transmission
and frame rates and the video delay. The main result of our experiments is that
broadband networks offer many capabilities for high quality teleteaching, and generally
speaking, high quality telematic services.1 aBouras, Christos1 aKapoulas, Vaggelis1 aGkamas, Apostolos1 aTsiatsos, Thrasivoulos  uhttp://telematics.upatras.gr/telematics/publications/evaluation-teleteaching-services-over-atm-and-ip-networks?language=en01098nas a2200145   4500008004100000245005200041210005100093260002000144300001500164520061000179100002100789700002200810700001900832856010100851       2003                        eng d00aFrom IPv4 to IPv6: The Case of OpenH323 Library0 aFrom IPv4 to IPv6 The Case of OpenH323 Library  c27 - 31 January  a 196 - 1993 aIn this paper, we discuss our experience form porting
the OpenH323 platform to IPv6. We briefly discuss the
structure of the platform, and we present the various
problems we faced and choices we made, regarding the
easiest approach to the porting procedure, the
compatibility with earlier, IPv4-only versions of the
platform, the existence of tools that could aid us with the
porting task and the verification of result. We believe
that the results of our effort can serve as guidelines for
other similar projects and we present a general
methodology which might be applicable to similar
porting projects.1 aBouras, Christos1 aGkamas, Apostolos1 aStamos, Kostas  uhttp://telematics.upatras.gr/telematics/publications/ipv4-ipv6-case-openh323-library?language=en01365nas a2200169   4500008004100000245014200041210006900183260001700252300001500269520064800284100002100932700002200953700001900975700002200994700001801016856016101034       2003                        eng d00aIssues for the Performance Monitoring of an Open Source H.323 Implementation Ported to IPv6 – Enabled Networks with QoS Characteristics0 aIssues for the Performance Monitoring of an Open Source H323 Imp  c23 - 26 June  a 765 - 7713 aOpenH323 is an open source H.323 implementation
that has been ported to IPv6. It therefore presents an
opportunity to perform experiments and compare the
performance of an H.323 application when using the
IPv4 stack and when using the IPv6 stack. In this
paper we initially introduce briefly the porting
procedure and the methodology we used in order to
achieve it. We then present the appropriate
experiments that have to be performed in order to
comparatively evaluate the IPv4 and IPv6 protocol
stacks. We also present the results of some initial
experiments comparing IPv4 and IPv6 performance
and the conclusions that they can lead us to.1 aBouras, Christos1 aGkamas, Apostolos1 aStamos, Kostas1 aPrimpas, Dimitris1 aKaraliotas, A  uhttp://telematics.upatras.gr/telematics/publications/issues-performance-monitoring-open-source-h323-implementation-ported-ipv6-%E2%80%93-enabled?language=en01285nas a2200145   4500008004100000245007600041210006900117260001700186300001500203520071800218100002100936700002700957700002500984856013001009       2003                        eng d00aIssues for the Performance Monitoring on Networked Virtual Environments0 aIssues for the Performance Monitoring on Networked Virtual Envir  c11 - 13 June  a 725 - 7283 aThe wide expansion and increasing demand for
Networked Virtual Environments resulted in efforts for the
optimization of these environments with the enhancement of
advanced features, which offered extended functionality and
created an improved sense of realism. However, the added
functionality often creates resource overhead both in the system
as well as in the network host, which results in performance
reduction. This paper presents such a networked virtual
environment and based on the system?s architecture tries to trace
down with the time and recourse consuming parameters and
proposes models on which a networked virtual environment, like
the one presented, could achieve optimization of its performance.1 aBouras, Christos1 aTsiatsos, Thrasivoulos1 aGiannaka, Eleftheria  uhttp://telematics.upatras.gr/telematics/publications/issues-performance-monitoring-networked-virtual-environments?language=en00985nas a2200133   4500008004100000245004700041210004700088260001700135520052400152100002100676700002300697700002200720856010900742       2003                        eng d00aManagement Bandwidth Sevice on MPLS domain0 aManagement Bandwidth Sevice on MPLS domain  c7 - 10 April3 aThis paper describes an efficient way to implement managed bandwidth services. The
proposed solution is based on MPLS technology and especially with the creation of
virtual private networks. The virtual private networks will be layer 3 VPNs (IP VPNs)
and are described all the mechanisms and the MPLS features that are necessary for the
MBS service implementation. The paper also describes how the service will interact
with the users and finally presents a schema for the interconnection with the MBS
service of Geant.1 aBouras, Christos1 aKapoulas, Vaggelis1 aPrimpas, Dimitris  uhttp://telematics.upatras.gr/telematics/publications/management-bandwidth-sevice-mpls-domain?language=en00532nas a2200133   4500008004100000245007000041210006800111260002100179300001500200100002100215700001600236700001600252856013000268       2003                        eng d00aManaging users and services using an LDAP based web - application0 aManaging users and services using an LDAP based web application  c10 - 13 February  a 773 - 7781 aBouras, Christos1 aSintoris, C1 aLimperis, A  uhttp://telematics.upatras.gr/telematics/publications/managing-users-and-services-using-ldap-based-web-application?language=en01221nas a2200133   4500008004100000245008500041210006900126260002600195300001500221520066500236100002100901700002000922856014500942       2003                        eng d00aModeling Data Intensive Web Sites for Personalisation, Integrity and Performance0 aModeling Data Intensive Web Sites for Personalisation Integrity   bIDEA Group Publishing  a 259 - 2763 a<p>This chapter presents a step-by-step approach to the design, implementation and management of a Data-Intensive Web Site (DIWS). The approach introduces five data formulation and manipulation graphs that are presented analytically. The core concept behind the modeling approach is that of “Web fragments,” that is an information decomposition technique that aids design, implementation and management of DIWS. We then present the steps that must be followed in order to “build” a DIWS based on Web fragments. Finally, we show how our approach can be used to ensure the basic DIWS user requirements of personalization, integrity and performance.</p>
1 aBouras, Christos1 aKonidaris, Agis  uhttp://telematics.upatras.gr/telematics/publications/modeling-data-intensive-web-sites-personalisation-integrity-and-performance?language=en01220nas a2200145   4500008004100000245010500041210006900146260002000215300001500235520060200250100002100852700002000873700002400893856015700917       2003                        eng d00aA Most Popular Approach of Predictive Prefetching on a WAN to Efficiently Improve WWW Response Times0 aMost Popular Approach of Predictive Prefetching on a WAN to Effi  c7 - 10 Devember  a 344 - 3513 aThis paper studies Predictive Prefetching on a Wide Area Network
with two levels of caching. The WAN that we refer to is the GRNET academic
network in Greece. We rely on log files collected at the network’s Transparent
cache (primary caching point), located at GRNET’s edge connection to the
Internet. Our prefetching model bases its predictions on popularity ranking of
passed requests. We present a “n-next most popular” approach used for prefetching
on GRNET’s architecture and provide preliminary results of our experimental
study, quantifying the benefits of prefetching on the WAN.1 aBouras, Christos1 aKonidaris, Agis1 aKostoulas, Dionisis  uhttp://telematics.upatras.gr/telematics/publications/most-popular-approach-predictive-prefetching-wan-efficiently-improve-www-response-times?language=en01216nas a2200157   4500008004100000245007300041210006900114260001600183300001500199520062400214100002100838700002700859700001800886700001700904856013700921       2003                        eng d00aMulti – User Layer in the EVE Distributed Virtual Reality Platform0 aMulti User Layer in the EVE Distributed Virtual Reality Platform  c19 - 22 May  a 602 - 6073 aIn this paper, we present the design and
implementation of a VRML97 multi-user layer, which is
introduced in the EVE distributed virtual reality platform.
Main consideration of our multi-user extension is the ease
of transforming single-user virtual worlds to multi-user
virtual worlds, as well as the conformity with any standard
VRML97 browser. Furthermore, we present the EVE' s
communication platform, which can be used in order to
support Collaborative Virtual Environments (CVEs). Main
issues regarding the effective network communication as
well as the initialization of the 3D scene are discussed in
this paper.1 aBouras, Christos1 aTsiatsos, Thrasivoulos1 aPsaltoulis, D1 aPsaroudis, C  uhttp://telematics.upatras.gr/telematics/publications/multi-%E2%80%93-user-layer-eve-distributed-virtual-reality-platform?language=en01539nas a2200121   4500008004100000245007500041210006900116300001500185520104200200100002101242700002201263856013201285       2003                        eng d00aMultimedia Transmission with Adaptive QoS based on Real Time Protocols0 aMultimedia Transmission with Adaptive QoS based on Real Time Pro  a 225 - 2483 aIn this paper, we describe a mechanism for adaptive transmission of multimedia data, which is based on
real-time protocols. The proposed mechanism can be used for unicast or multicast transmission of
multimedia data over heterogeneous networks, like the Internet, and has the capability to adapt the
transmission of the multimedia data to network changes. In addition, the implemented mechanism uses an
inter-receiver fairness function in order to treat the group of clients with fairness during the multicast
transmission in a heterogeneous environment. The proposed mechanism uses a ‘friendly’ to the network
users congestion control policy to control the transmission of the multimedia data. We implement a
prototype application based on the proposed mechanism and we evaluate the proposed mechanism both in
unicast and multicast transmission through a number of experiment and a number of simulations in order
to examine its fairness to a group of clients and its behaviour against transport protocols (TCP) and UDP
data streams.1 aBouras, Christos1 aGkamas, Apostolos  uhttp://telematics.upatras.gr/telematics/publications/multimedia-transmission-adaptive-qos-based-real-time-protocols?language=en01269nas a2200133   4500008004100000245008900041210006900130260001800199300001500217520072300232100002100955700002200976856013700998       2003                        eng d00aPerformance Analysis for a DiffServ - enabled network : the case of Relative Service0 aPerformance Analysis for a DiffServ enabled network the case of   c16 - 18 April  a 381 - 3873 aA lot of research work has recently focused on the exploitation of the DiffServ framework towards building reliable networking services that provide deterministic quality guarantees. In this work we are attempting to devise a DiffServ-based service model for relative differentiation of traffic in a network serving aggregated traffic. The service model proposed aims at providing a minimum capacity during congestion and a bounded average end-to-end delay to profile-conforming traffic, obtaining thus a relatively better performance when compared to the best-effort service. We provide the framework on which the proposed service model is based and we present results from its deployment in a simulation environment.1 aBouras, Christos1 aSevasti, Afroditi  uhttp://telematics.upatras.gr/telematics/publications/performance-analysis-diffserv-enabled-network-case-relative-service?language=en01925nas a2200133   4500008004100000245009500041210006900136260001000205300001300215520137100228100002101599700002001620856015101640       2003                        eng d00aPerformance Evaluation of a Hybrid Run-time Management Policy for Data intensive Web Sites0 aPerformance Evaluation of a Hybrid Runtime Management Policy for  cMarch  a 23 - 473 aThe issues of performance, response efficiency and data consistency are among the most important for data
intensive Web sites. In order to deal with these issues we analyze and evaluate a hybrid run-time management
policy that may be applied to data intensive Web sites. Our research relies on the performance evaluation of
experimental client/server configurations. We propose a hybrid Web site run-time management policy that may
apply to differentWeb site request patterns and data update frequencies. A run-time management policy is viewed
as a Web page materialization policy that can adapt to different conditions at run-time. We define a concept
that we have named the Compromise Factor (CF), to achieve the relationship between current server conditions
and the materialization policy. The issue of Web and database data consistency is the driving force behind our
approach. In some cases though, we prove that certain compromises to consistency can be beneficial to Web
server performance and at the same time be unnoticeable to users. We first present a general a comparative cost
model for the hybrid management policy and three other related and popular Web management policies. We then
evaluate the performance of all the approaches. The results of our evaluation show that the concept of the CF may
be beneficial to Web servers in terms of performance.1 aBouras, Christos1 aKonidaris, Agis  uhttp://telematics.upatras.gr/telematics/publications/performance-evaluation-hybrid-run-time-management-policy-data-intensive-web-sites?language=en01693nas a2200145   4500008004100000245008000041210006900121260002000190300001400210520112400224100002101348700002301369700002201392856013301414       2003                        eng d00aPerformance Evaluation of the Managed Bandwidth Service with QoS guarantees0 aPerformance Evaluation of the Managed Bandwidth Service with QoS  c23 - 25 October  a 93 - 1003 aThis paper describes a solution to extend the Managed Bandwidth Service (MBS), which is provided on a backbone network using MPLS VPNs, to non-MPLS domains and also evaluates it. It is based on the Class Based Weighted Fair Queueing mechanism (CBWFQ) [4] and describes the way it should be implemented to provide guaranteed bandwidth connections. In particular, CBWFQ can provide assured bandwidth connections when simultaneously leads to efficient bandwidth utilization. In addition, the proposed solution is being tested on simulation environment (using the Network Simulator) in order to evaluate its performance characteristics. On the simulation tests had been reserved specific amount of bandwidth for specific flows and their throughput was measured in order to understand if the proposed solution works well. Finally, the results are very well and prove that this method can guarantee bandwidth for every flow in all network conditions (congested or un-congested). At last, the paper presents a technical example of router configuration for implementing the MBS service according to the basic proposed solution.1 aBouras, Christos1 aKapoulas, Vaggelis1 aPrimpas, Dimitris  uhttp://telematics.upatras.gr/telematics/publications/performance-evaluation-managed-bandwidth-service-qos-guarantees?language=en02195nas a2200169   4500008004100000245006300041210006300104300001500167520158500182100002101767700002301788700002901811700002201840700002001862700002101882856012201903       2003                        eng d00aPerformance issues of bandwidth management in ATM networks0 aPerformance issues of bandwidth management in ATM networks  a 151 - 1693 aIn our days, efficient management of the available network resources becomes a critical issue, both from a
functional point of view (so that users can be provided with the bandwidth they need), and an economical
point of view (so that carriers can satisfactorily and efficiently serve as many customers as possible and at
the same time increase their revenue). In this paper we consider a bandwidth control scheme (i.e. managed
bandwidth service) for an ATM network infrastructure which is applied to the Greek research and
technology network (GRNET). We present some methods that we have tested (in a simulation setting) in
order to increase the efficiency of the system and the utilization of the available bandwidth. More
specifically, we consider a bandwidth-resizing algorithm for virtual paths, in order to keep the allocated
bandwidth very close to the bandwidth actually used. This leads to an increased number of accepted
requests and better network utilization. We, also, use the simulation results in order to get an estimation of
the effective bandwidth for VBR paths that can be used in call admission. Finally, we consider a semioffline
scheme where requests are gathered and considered for acceptance in regular intervals. Simulation
results show an increase in the utilization of resources. As a further improvement, we allow connections to
be allocated a little before or after the time initially requested. This leads to further improvement in
network utilization. All the improvement schemes were tested with the ATM-TN simulator and the results
look promising.1 aBouras, Christos1 aKapoulas, Vaggelis1 aPanagopoulos, Alexandros1 aSevasti, Afroditi1 aChantzi, Chrysa1 aSampraku, Ioanna  uhttp://telematics.upatras.gr/telematics/publications/performance-issues-bandwidth-management-atm-networks?language=en01121nas a2200145   4500008004100000245007900041210006900120300001100189520055700200100002100757700002000778700002400798700002200822856013100844       2003                        eng d00aPolicies for Content Filtering in Educational Networks: The case of Greece0 aPolicies for Content Filtering in Educational Networks The case   a 71-953 aThe Internet removes all barriers to sending and receiving information. An increasing
number of nations connect their schools on the Internet as an acknowledgment of its importance
in education. Despite its undeniable usefulness, it also has certain perils. This study
specifies and evaluates these, finding the technologies that are currently available to address
filtering issues and comparing them. We present our proposed solution for the Greek School
Network, and illustrate to what extent our solution successfully addresses the issues discussed.1 aBouras, Christos1 aAvgoulea, Maria1 aParaskevas, Mixalis1 aStathakopoulos, G  uhttp://telematics.upatras.gr/telematics/publications/policies-content-filtering-educational-networks-case-greece-0?language=en01238nas a2200157   4500008004100000245008000041210006900121260001300190300001300203520064500216100002100861700002200882700001800904700001800922856014000940       2003                        eng d00aQoS and SLA aspects across multiple management domains: The SEQUIN approach0 aQoS and SLA aspects across multiple management domains The SEQUI  cFebruary  a 313-3263 aThe aim of this work is to define and implement an end-to-end approach to quality of service (QoS), operating across
multiple management domains and exploiting a combination of link layer technologies. The architecture for the Premium IP
service is presented, which aims at offering the equivalent of an end-to-end virtual leased line service at the IP layer across
multiple domains. Also, the results of the initial testing performed for the validation of the service and the provisioning
model for Premium IP are described. The work presented has been carried out in the framework of SEQUIN, a European
Commission-funded research project.1 aBouras, Christos1 aSevasti, Afroditi1 aCampanella, M1 aPrzybylski, M  uhttp://telematics.upatras.gr/telematics/publications/qos-and-sla-aspects-across-multiple-management-domains-sequin-approach?language=en01023nas a2200145   4500008004100000245003100041210002500072260001700097300001300114520058600127100002100713700002700734700001600761856010000777       2003                        eng d00aA SCORM – conformant LMS0 aSCORM conformant LMS  c23 - 28 June  a 10 - 133 aIn this paper we propose a sample Learning Management System (LMS) that
will be conformant with the SCORM v1.3 Specification. In particular, the sample LMS
we propose will make use of both, the SCORM Run Time Environment, in order to
communicate with the learning content, and a sequencing engine so as to sequence
discrete learning activities in a consistent way, based on the learners’ interactions with
the content. Even if the SCORM v1.3 Specification is not yet finalized, the proposed
LMS intends to be an attempt to test and evaluate the specification in its present form.1 aBouras, Christos1 aTsiatsos, Thrasivoulos1 aNani, Maria  uhttp://telematics.upatras.gr/telematics/publications/scorm-%E2%80%93-conformant-lms?language=en01940nas a2200133   4500008004100000245013000041210006900171260002000240300001300260520133800273100002101611700002201632856015201654       2003                        eng d00aSRAMT-LE: A Hybrid Sender And Receiver-Based Adaptation Scheme For TCP friendly multicast transmission using layered encoding0 aSRAMTLE A Hybrid Sender And ReceiverBased Adaptation Scheme For   c19 - 23 January  a 71 - 763 aIn this paper we describe a hybrid sender and receiver-based adaptation
scheme for multicast transmission of multimedia data using layered
encoding, which we call SRAMT-LE (Sender-Receiver based Adaptation
scheme for Multicast Transmission using Layered Encoding). The most
prominent features of SRAMT-LE are its distributed (to sender and
receivers) transmission rate estimation algorithm and its innovative RTT
(Round Trip Time) estimation algorithm based on one-way delay
measurements. In addition, SRAMT-LE adjusts the transmission rates of the
layers in order to service better the group of the receivers. SRAMT-LE is
using both a TCP model and an AIMD (Additive Increase Multiplicative
Decrease) algorithm in order to estimate a TCP friendly bandwidth share.
With the use of SRAMT-LE, we ensure that sender will transmit TCP
friendly traffic and receivers with different capabilities (in terms of
available bandwidth) are able to receive the multimedia information. We
evaluate SRAMT-LE through a number of simulations in order to examine
its behaviour to a heterogeneous group of receivers and its behaviour against
TCP connections. Main conclusion of the simulations was that SRAMT-LE
has friendly behaviour against the dominant traffic types of today’s Internet
and treats a heterogeneous group of receivers with fairness.1 aBouras, Christos1 aGkamas, Apostolos  uhttp://telematics.upatras.gr/telematics/publications/sramt-le-hybrid-sender-and-receiver-based-adaptation-scheme-tcp-friendly-multicast?language=en01341nas a2200157   4500008004100000245008600041210006900127260002100196300001300217520073500230100002100965700002200986700001901008700002201027856013401049       2003                        eng d00aUsing J2EE Web Services for the Implementation of an Application on Demand Portal0 aUsing J2EE Web Services for the Implementation of an Application  c13 - 14 December  a 72 - 833 aThis paper describes the design of the ASP-NG portal, which is a portal for providing the user with the
necessary interface in order to access an Application on Demand (AoD) service. The ASP-NG portal is
responsible for the interaction with the user of the Application on Demand service. The implementation of
the ASP-NG portal is going to be based on the Web Services of the Java 2, Enterprise Edition (J2EE)
platform. The ASP-NG portal will offer to its users the capability to select and customize the language of
the user interface in order to present information in their preferred language. Moreover the ASP-NG
portal will offer to the portal administrator the capability to customise the look and feel of the ASP-NG
portal.1 aBouras, Christos1 aGkamas, Apostolos1 aStamos, Kostas1 aPrimpas, Dimitris  uhttp://telematics.upatras.gr/telematics/publications/using-j2ee-web-services-implementation-application-demand-portal?language=en01585nas a2200145   4500008004100000245005200041210005100093260002000144300001300164520107700177100002101254700002701275700002501302856011201327       2003                        eng d00aVirtual Collaboration Spaces: The EVE Community0 aVirtual Collaboration Spaces The EVE Community  c27 - 31 January  a 48 - 553 aAn Educational Virtual Environment (EVE) is an
instance of a Collaborative Virtual Environment (CVE),
which focalises in providing collaborative, as well as
educational, functionalities, such as synchronous and
asynchronous e-learning services. This paper describes
such an educational virtual community, which aims to
meet the requirements of a virtual collaboration space
and furthermore to support e-learning services. In
particular, we are developing a web-based system, which
allows users to communicate with the other members of
the community through forums, chat, e-mail, to schedule
events which take place in the learning environment and
to join, and even create, courses, which are held in 3D
multi-user worlds where users are represented by avatars.
These characteristics offer extended functionalities such
as support of application sharing and voice chat,
transmission of the educational material as well as
transmission of the users’ profiles to the other community
members. We describe the model of this community and
the functionalities that it provides.1 aBouras, Christos1 aTsiatsos, Thrasivoulos1 aGiannaka, Eleftheria  uhttp://telematics.upatras.gr/telematics/publications/virtual-collaboration-spaces-eve-community?language=en01255nas a2200169   4500008004100000245007500041210006900116260002000185300001500205520062300220100002100843700002300864700002700887700002500914700001600939856013000955       2003                        eng d00aVirtual Learning Communities - Theory and Practice: The case of VirRAD0 aVirtual Learning Communities Theory and Practice The case of Vir  c7 - 11 November  a 495 - 4983 aIn this paper we discuss the development of virtual communities and especially virtual learning communities, taking into account basic community requirements as well as social factors of e-learning. This paper has been inspired by the VirRAD European project and presents the intermediate results that have raised form the definition of a virtual community for the vocational training of radiopharmacists. We therefore present the user requirements that form the functional specification of such an environment along with the role model that provides a mindful but solid distribution of the access level in the system.1 aBouras, Christos1 aKapoulas, Vaggelis1 aTsiatsos, Thrasivoulos1 aGiannaka, Eleftheria1 aNani, Maria  uhttp://telematics.upatras.gr/telematics/publications/virtual-learning-communities-theory-and-practice-case-virrad?language=en02138nas a2200181   4500008004100000245005600041210005200097260002100149300001500170520153600185100002101721700002301742700002301765700002301788700001701811700001301828856011501841       2003                        eng d00aA web-based game for supporting game-based learning0 awebbased game for supporting gamebased learning  c19 - 21 November  a 111 - 1183 aGame-based learning has been recognized as an important
alternative or supplement to traditional in-class, face-to-face
teaching. It can help both adults and children in learning new
concepts, acquiring expertise and practicing knowledge.
Although game-based learning has been applied mainly for
teaching children, it can be quite helpful for adult vocational
or university learning. In this paper, a web-based game is
presented, which has been developed for enhancing the
learning experience of university students. Its goal is to
serve as a complement to classes, although it can be used
independently. It provides the students with many ways for
communicating (synchronously or asynchronously) and
acquiring information. Through the use of the game, the
students gain easily new knowledge, since they have to
search for it, understand it and use it in discussions with
other students, who are members of other teams. The game
is played by many users simultaneously. Microsoft’s
ASP.NET scripting environment was used for creating the
game’s website. The website utilizes also Macromedia’s
communication technology (Flash Communication Server
MX) for enabling real-time communication by several means
(voice, text, etc). Flash was used in the website for building
the real-time communication modules as well as for creating
a more elegant user interface. The game platform can be
used by many teachers simultaneously for running different
game themes. It also gives the opportunity to visitors to
watch games as spectators.1 aBouras, Christos1 aKapoulas, Vaggelis1 aIgglesis, Vaggelis1 aMisedakis, Ioannis1 aDziabenko, O1 aPivec, M  uhttp://telematics.upatras.gr/telematics/publications/web-based-game-supporting-game-based-learning?language=en02040nas a2200169   4500008004100000245002800041210002800069260001000097520155000107100002101657700001801678700002401696700001701720700002101737700001901758856009301777       2003                        eng d00aWireless School Network0 aWireless School Network  cApril3 aThe architecture of the wireless network consists of 3 main parts. The wireless infrastructure, the connection of the
wireless island to the rest network and the interconnection between the neighboring schools a near one participating in
the wireless network. The wireless connection supports Point-to-Multipoint technology [3] and uses the frequency band
2,4 Ghz to 2,4835 Ghz. The reserved bandwidth of this wireless LAN is order of magnitude 11 Mbps. In each school the
bridge device is connected to a newly equipped Fast Ethernet switch interconnecting the internal schools network to the
wireless network. Between the schools a fast Ethernet network is built using copper and Fiber optic cabling. The
interconnection of the wireless network upstream to the backbone is achieved with the use of the link between the E.A.O
and the local main distribution node of the EDUNET network. This link had to be upgrade because it will carry the
traffic from the wireless network too. The selected solution was the VDSL technology by engaging the appropriate
modems over a two-wire leased line between the E.A.O and the main node. We have a selected point in each school unit
that wireless bridge and antenna will be installed. The wireless bridge must stand near to antenna because long cabling
distances will produce noise in the transmission signal. The wireless bridge will be housed at waterproof cabinet, which
offers all the necessary specifications for protection and electric feeding. The waterproof cabinet is installed at the
antenna pylon.1 aBouras, Christos1 aKaraliotas, A1 aParaskevas, Mixalis1 aPapoutsis, V1 aNtokos, Christos1 aDrosopoulos, N  uhttp://telematics.upatras.gr/telematics/publications/wireless-school-network?language=en01508nas a2200157   4500008004100000245008000041210006900121300001200190520091700202100002101119700002301140700001901163700001401182700001601196856013801212       2002                        eng d00aAn Architecture for Interactive Distributed Multimedia Information Services0 aArchitecture for Interactive Distributed Multimedia Information   a 3 - 103 aIn this work, we present an architecture for interactive distributed multimedia information services. The service
consists of three basic parts, the clients, the access servers, and the content servers. Clients manage the
presentation of the requested multimedia documents, while also ensure the synchronization among various
involved media. Special policies for the synchronized presentation of multimedia documents and user
interactions management are discussed. Access servers authorize the users for legitimate use of the service,
while also provide various searching capabilities Content servers manage the transportation of multimedia
documents over a broadband network and the user interactions. The proposed architecture preserves
scalability, flexibility and modularity due to the distributed nature of the architecture, while also results in good
performance due to the dynamic allocation of resources.1 aBouras, Christos1 aKapoulas, Vaggelis1 aSpirakis, Paul1 aMoiras, D1 aOuzounis, V  uhttp://telematics.upatras.gr/telematics/publications/architecture-interactive-distributed-multimedia-information-services?language=en01585nas a2200157   4500008004100000245010600041210006900147260001900216300001500235520094300250100002101193700002201214700001901236700001801255856015401273       2002                        eng d00aBehaviour Investigation using Simulation for Redundant Multicast Transmission Supporting Adaptive QoS0 aBehaviour Investigation using Simulation for Redundant Multicast  c27 - 30 August  a 112 - 1173 aIn this paper we describe a mechanism for redundant multicast
transmission of multimedia data supporting adaptive QoS over
the Internet and we investigate its behaviour using simulation.
There are two major issues that have to be considered when
designing and implementing such a mechanism, the fairness,
which is the ability to cope with receiver heterogeneity, and the
adaptation schemes. The proposed mechanism uses a friendly to
the network users congestion control policy to control the
transmission of the data. We evaluate the adaptive multicast
transmission mechanism through a number of simulations in
order to examine its behaviour to a heterogeneous group of
receivers and its behaviour against TCP and UDP data streams.
Main conclusion of the simulation was that the proposed
mechanism has friendly behaviour against the dominant traffic
types of today’s Internet and treats a heterogeneous group of
receivers with fairness.1 aBouras, Christos1 aGkamas, Apostolos1 aStamos, Kostas1 aKaraliotas, A  uhttp://telematics.upatras.gr/telematics/publications/behaviour-investigation-using-simulation-redundant-multicast-transmission-supporting?language=en00807nas a2200133   4500008004100000245004600041210004600087260002100133300001500154520034500169100002100514700002700535856011100562       2002                        eng d00aBuilding Educational Virtual Environments0 aBuilding Educational Virtual Environments  c9 - 12 September  a 547 - 5483 aThe collaborative virtual environments have become a
good media for supporting collaborative e-learning
services. In this paper we present the Educational Virtual
Environments (EVE) platform, which integrates a variety
of communication a collaboration tools to support
collaborative virtual environments focused on
collaborative e-learning.1 aBouras, Christos1 aTsiatsos, Thrasivoulos  uhttp://telematics.upatras.gr/telematics/publications/building-educational-virtual-environments?language=en01333nas a2200157   4500008004100000245010500041210006900146260001700215300001700232520068900249100002100938700002300959700002200982700001901004856015201023       2002                        eng d00aDesktop Synchronous Distance Learning Application Enhanced with Efficient Chair Control Capabilities0 aDesktop Synchronous Distance Learning Application Enhanced with   c24 - 27 June  a 1158 - 11643 aThe use of multimedia in Telematics
and new services has been greatly improved by the
introduction of new systems and techniques. These
new systems and techniques made the implementation
of many telematic applications like Synchronous
Distance Learning possible. In this paper, we present
design, functionality and implementation issues, which
concern a Synchronous Distance Learning
application. The described application is a networkbased
application, which can be used over IP and
ISDN networks. In addition the implemented
Synchronous Distance Learning application uses an
innovative chair control module, which does not
require any support from the MCU (Multipoint
Control Unit).1 aBouras, Christos1 aKapoulas, Vaggelis1 aGkamas, Apostolos1 aStamos, Kostas  uhttp://telematics.upatras.gr/telematics/publications/desktop-synchronous-distance-learning-application-enhanced-efficient-chair-control?language=en01209nas a2200157   4500008004100000245007000041210006700111260001900178300001500197520062400212100002100836700002700857700001800884700001700902856013200919       2002                        eng d00aAn Educational Community Using Collaborative Virtual Environments0 aEducational Community Using Collaborative Virtual Environments  c17 - 19 August  a 180 - 1913 aThe use of Collaborative Virtual Environments in e-learning is one of
the most promising uses of the virtual reality technology. While a lot of
research has been done in the area of collaborative virtual environments
corresponding to the sharing of events, very little research has been done on
specific services and functionality. However both the requirements and the kind
of the offered services affect significantly the design of a system. In this paper
we present an Educational Community to support e-learning services using
Collaborative Virtual Environments from both the technical and functional
point of view.1 aBouras, Christos1 aTsiatsos, Thrasivoulos1 aPsaltoulis, D1 aPsaroudis, C  uhttp://telematics.upatras.gr/telematics/publications/educational-community-using-collaborative-virtual-environments?language=en01569nas a2200133   4500008004100000245007700041210006900118260001900187300001500206520103700221100002101258700002001279856013601299       2002                        eng d00aEfficient Materialization of Dynamic Web Data to Improve Web Performance0 aEfficient Materialization of Dynamic Web Data to Improve Web Per  c11 - 14 August  a 866 - 8793 aThe issues of performance, response efficiency and data consistency
are among the most important ones for data intensive Web sites on the Internet
today. In order to deal with these issues we analyze and evaluate a
materialization policy that may be applied to data intensive Web sites. Our
research relies on the performance evaluation of experimental client/server
configurations. We propose a materialization policy that applies to different
Web site request patterns and data update frequencies. The issue of Web and
database data consistency is the driving force behind our approach. In some
cases though, we prove that certain compromises to consistency can be
beneficial to Web server performance and at the same time be unnoticeable to
users. We evaluate the performance of our approach and compare it with other
popular materialization approaches. The results of our evaluation show that the
concept of “acceptable inconsistencies” between Web and Database data may
be beneficial to Web servers in terms of performance.1 aBouras, Christos1 aKonidaris, Agis  uhttp://telematics.upatras.gr/telematics/publications/efficient-materialization-dynamic-web-data-improve-web-performance?language=en01262nas a2200145   4500008004100000245006800041210006800109260002000177300001500197520071500212100002100927700002200948700002200970856012400992       2002                        eng d00aEnhancing the DiffServ Architecture of a Simulation Environment0 aEnhancing the DiffServ Architecture of a Simulation Environment  c11 - 13 October  a 108 - 1183 aSimulation has always been a valuable tool for
experimentation and validation of models, architectures
and mechanisms in the field of networking. In the case of
the DiffServ framework, simulation is even more valuable,
due to the fact that an analytical approach of mechanisms
and services is infeasible because of the aggregation and
multiplexing of flows. In this work, we have extended the
functionality of a widely used simulation environment
towards the direction of realistic traffic generation and a
series of mechanisms defined by the DiffServ architecture.
The modules created are being presented and a case
study of a simulation scenario that exploits the
functionality provided by them is described.1 aBouras, Christos1 aPrimpas, Dimitris1 aSevasti, Afroditi  uhttp://telematics.upatras.gr/telematics/publications/enhancing-diffserv-architecture-simulation-environment?language=en01280nas a2200133   4500008004100000245008100041210006900122300001500191520074600206100002100952700002200973700002200995856012901017       2002                        eng d00aAn environment for the annotation of multimedia material by younger children0 aenvironment for the annotation of multimedia material by younger  a 363 - 3853 aThe exceptional advent of interactive multimedia applications
has led to the need for their exploitation for educational
purposes. In this article, the design and implementation of a
multimedia annotation environment for young children is
presented. This environment was developed to provide children
aged 4 - 8 with the opportunity to reflect upon and annotate
episodes from their everyday life. The aim was to exploit
the latest technological developments in the field of
multimedia, to build an annotation environment where children
would be able to add multimedia annotations to videos.
Apart from the environment itself, design choices, interface
realization, as well as media handling methods and performance
issues are also presented.1 aBouras, Christos1 aGkamas, Apostolos1 aSevasti, Afroditi  uhttp://telematics.upatras.gr/telematics/publications/environment-annotation-multimedia-material-younger-children?language=en01453nas a2200133   4500008004100000245009600041210006900137260001700206300001400223520088700237100002101124700002001145856015401165       2002                        eng d00aEstimating and Eliminating Redundant Data Transfers Over the Web: A Fragment Based Approach0 aEstimating and Eliminating Redundant Data Transfers Over the Web  c24 - 27 June  a 95 - 1023 aRedundant data transfers over the Web, can mainly be attributed to repeated transfers of unchanged data. Web caches and Web proxies are some of the solutions that have been proposed, to deal with the issue of redundant data transfers. In this paper we focus on the efficient estimation and reduction of redundant data transfers over the Web. We first prove that a vast amount of redundant data is transferred in Web pages that are considered to carry fresh data. We show this by following an approach based on Web page fragmentation and manipulation. Web pages are broken-down into fragments, based on specific criteria. We then deal with these fragments as independent constructors of the Web page and study their change patterns independently and in the context of the whole Web page. After the fragmentation process we propose solutions for dealing with redundant data transfers.1 aBouras, Christos1 aKonidaris, Agis  uhttp://telematics.upatras.gr/telematics/publications/estimating-and-eliminating-redundant-data-transfers-over-web-fragment-based-approach?language=en01382nas a2200133   4500008004100000245007900041210006900120260002100189300001500210520084100225100002101066700002701087856013401114       2002                        eng d00aExtending the Limits of CVEs to Support Collaborative e-Learning Scenarios0 aExtending the Limits of CVEs to Support Collaborative eLearning   c9 - 12 September  a 420 - 4243 aThis paper proposes the use of collaborative virtual
environments in order to provide collaborative e-learning
services in an efficient and cost effective way. On the one
hand, we present the transformation of well known
collaborative learning techniques to collaborative elearning
scenarios. The collaborative learning
techniques, which are discussed in this paper, are
brainstorming/roundtable, think pair share, jigsaw,
quickwrites/microthemes, and structured academic
controversies. On the other hand, we describe the
necessary modifications of the collaborative virtual
environments in order to support collaborative e-learning
services and scenarios. Main proposals are the
integration of more media to offer more awareness, the
support of more people with different roles, and the
definition of an integrated system architecture.1 aBouras, Christos1 aTsiatsos, Thrasivoulos  uhttp://telematics.upatras.gr/telematics/publications/extending-limits-cves-support-collaborative-e-learning-scenarios?language=en00936nas a2200133   4500008004100000245010100041210006900142300001300211520035600224100002100580700002700601700002700628856014700655       2002                        eng d00aA Framework for Intelligent Virtual Training Environment: The steps from specification to design0 aFramework for Intelligent Virtual Training Environment The steps  a 11 - 263 aThe growing need for communication, visualization and organization technologies in the field of e-learning
environments has led to the application of virtual reality and the use of collaborative virtual environments.
This paper presents a system architecture to support such environments, defined by user needs and using
state of the art technologies.1 aBouras, Christos1 aTsiatsos, Thrasivoulos1 aTriantafillou, Vasilis  uhttp://telematics.upatras.gr/telematics/publications/framework-intelligent-virtual-training-environment-steps-specification-design?language=en01472nas a2200157   4500008004100000245008300041210006900124260001800193300001300211520087600224100002101100700001801121700001901139700001601158856014001174       2002                        eng d00aHTTP Traffic Simulation and Evaluation for multiple Users in Intranet Network 0 aHTTP Traffic Simulation and Evaluation for multiple Users in Int  c14 - 17 April  a 63 - 673 aIn this paper we describe the architecture and design of a network-stressing tool developed to simulate and evaluate the HTTP requests and responses of hundreds of users. There are two major issues that have to be considered when designing and implementing such a simulation tool, the reliability evaluation and the user “friendly” environment. In our application we use a mechanism exploiting Intranet technology to stress the tested network and confirm the performance, proper operation and delay issues. We have also implemented an easy interaction with the user considering the creation of the scenarios and the presentation of the simulation results, pointing out the problems and the network’s status. Finally, we examined through a number of experiments using different simulation scenarios the behavior of the Intranet by load balancing the simulated users.1 aBouras, Christos1 aGanos, Petros1 aAravantinos, E1 aKokkinos, P  uhttp://telematics.upatras.gr/telematics/publications/http-traffic-simulation-and-evaluation-multiple-users-intranet-network?language=en01153nas a2200169   4500008004100000245004800041210004600089260001700135300001200152490000600164520062000170100002100790700002300811700002200834700002000856856010700876       2002                        eng d00aA Managed Bandwidth Service for IP Networks0 aManaged Bandwidth Service for IP Networks  c23 - 26 June  a644-6480 v13 aThe work presented here attempts to face the problem of bandwidth management in IP networks, especially in cases where the available resources have to be shared among many users with demanding and conflicting needs. We have designed a Managed Bandwidth Service (MBS) that allows users to make bandwidth reservations throughout the topology of the network infrastructure to which they have access based on the establishment of Virtual Private Networks (VPNs) using the Multiprotocol Label Switching (MPLS) technology. In this paper we present the MBS developed along with our on-going and future work on the subject.1 aBouras, Christos1 aKapoulas, Vaggelis1 aSevasti, Afroditi1 aChantzi, Chrysa  uhttp://telematics.upatras.gr/telematics/publications/managed-bandwidth-service-ip-networks?language=en01743nas a2200181   4500008004100000245007300041210006900114260002000183300001500203520107800218100002101296700002301317700002901340700002201369700002001391700002101411856012901432       2002                        eng d00aPerformance Analysis of a Managed Bandwidth Service for ATM Networks0 aPerformance Analysis of a Managed Bandwidth Service for ATM Netw  c27 - 31 January  a 220 - 2253 aIn this paper we are considering methods to improve the performance
of a bandwidth control scheme (i.e. Managed Bandwidth
Service) for an ATM network infrastructure (with application to the
Greek Research and Technology Network - GRNET). These methods
try to increase the efficiency of the system and the utilisation of
the available bandwidth. More specifically, we consider: a) a
bandwidth-resizing algorithm for virtual paths in order to (constantly)
keep the allocated bandwidth very close to the bandwidth
actually used, b) a simple method to estimate the effective bandwidth
for VBR paths that can be used in call admission, and c) a
semi-offline call admission scheme where requests are gathered and
considered for acceptance in regular intervals (with a further improvement,
of allowing connections to be allocated a little before or
after the time initially requested). All these methods were tested in
a simulation setting (with the ATM-TN simulator), and results indicate
that they lead to an increased number of accepted requests and
better network utilisation.1 aBouras, Christos1 aKapoulas, Vaggelis1 aPanagopoulos, Alexandros1 aSevasti, Afroditi1 aChantzi, Chrysa1 aSampraku, Ioanna  uhttp://telematics.upatras.gr/telematics/publications/performance-analysis-managed-bandwidth-service-atm-networks?language=en01834nas a2200145   4500008004100000245005200041210005000093260001900143300001500162520133600177100002101513700002301534700002301557856010801580       2002                        eng d00aA platform for gaming in Digital Interactive TV0 aplatform for gaming in Digital Interactive TV  c9 - 11 October  a 105 - 1093 aDigital Television has increased its popularity the last
years. Its’ main advantage over traditional analogue TV is that
it offers the viewers the ability to use their TV system in order to
view or search for information in a way that is impossible with
analogue TV. The next important step is the offer of
interactivity with Service Providers, exchanging information,
with the use of a return channel. Modern Set-Top-Boxes are not
just decoders of the transmitted digital signals, but can be
programmed to execute complex applications that can interact
with the user through the use of the remote control and with
Service Providers using a built-in modem and the PSTN
network. Applications can be downloaded from satellite, loaded
and executed dynamically, multiplexed with video and audio
streams, along with the data needed, while a viewer changes the
channel he/she watches. Using these types of applications the
viewer becomes a user, using the provided services, despite of
passively watching TV channels.
In this paper, we describe an Interactive Digital TV platform
being developed for delivering statistical and interactive services
to the public. In particular, we use it for offering statistical data
and an interactive game in which the users of the platform can
compete by answering questions and making predictions.1 aBouras, Christos1 aKapoulas, Vaggelis1 aMisedakis, Ioannis  uhttp://telematics.upatras.gr/telematics/publications/platform-gaming-digital-interactive-tv?language=en01131nas a2200157   4500008004100000245008000041210006900121260001700190300001300207520053700220100002100757700002000778700002400798700002200822856012900844       2002                        eng d00aPolicies for Content Filtering in Educational Networks : the Case of Greece0 aPolicies for Content Filtering in Educational Networks the Case   c24 - 29 June  a 57 - 623 aAn increasing number of nations connect their schools on the Internet as an
acknowledgment to its extreme importance in the education area. Our study specifies the
perils that arise from its use when the users are minors and evaluates the technologies that are
currently available to address the filtering issues. The thoughts presented in this paper outline
our proposed solution for the Greek School Network. By no means the thoughts that are
presented here, apply for adults or people who pay to establish access to the Internet.1 aBouras, Christos1 aAvgoulea, Maria1 aParaskevas, Mixalis1 aStathakopoulos, G  uhttp://telematics.upatras.gr/telematics/publications/policies-content-filtering-educational-networks-case-greece?language=en01488nas a2200133   4500008004100000245007500041210006900116260002000185300001300205520094700218100002101165700002201186856014601208       2002                        eng d00aPricing priority services over DiffServ – enabled transport networks0 aPricing priority services over DiffServ enabled transport networ  c13 - 16 October  a 25 - 373 aThe rapid evolution of the DiffServ framework in our days has provided the means for efficient QoS provisioning over contemporary IP networks. The provisioning of services according to the DiffServ framework has in turn raised the requirements for pricing mechanisms that preserve the potential and flexibility of the DiffServ framework. At the same time, such mechanisms should reflect resource usage, allocate resources efficiently, reimburse costs or maximize service provision profits and lead customers to requesting services that will maximize their revenue. This work proposes a policy for pricing based on resource allocation of a particular category of DiffServ-based services for aggregated traffic in the case of transport networks. Our research takes into account the particularities that apply to the case of DiffServ services’ provision over transport networks while imposing minimal overload and a-priori estimation of costs.1 aBouras, Christos1 aSevasti, Afroditi  uhttp://telematics.upatras.gr/telematics/publications/pricing-priority-services-over-diffserv-%E2%80%93-enabled-transport-networks?language=en00744nas a2200109   4500008004100000245002700041210002600068260001500094520041500109100002200524856008800546       2002                        eng d00aSEQUIN: Results on QoS0 aSEQUIN Results on QoS  c3 - 6 June3 aSEQUIN has defined and implemented an end-to-end
approach to Quality of Service (QoS), operating across
multiple management domains based on IP protocol and
independent of link layer technology
&#149; The project has specified the implementation architecture
for the Premium IP service, which aims at offering the
equivalent of an end-to-end virtual leased line service at
the IP layer across multiple domains.1 aSevasti, Afroditi  uhttp://telematics.upatras.gr/telematics/publications/sequin-results-qos?language=en01672nas a2200145   4500008004100000245006000041210005900101260001600160300001300176520116500189100002101354700002201375700001801397856011101415       2002                        eng d00aSLA definition for the provision of an EF-based service0 aSLA definition for the provision of an EFbased service  c14 - 16 May  a 17 - 213 aThe evolution of mechanisms for providing
Quality-of-Service (QoS) over the contemporary network
infrastructures has introduced the need for regulation and
management of the emerging QoS services with the use of
Service Level Agreements (SLAs). SLAs for QoS-enabled
networks move one step forward in the direction of
traditional ones, in the sense that they do not only have to
specify availability, security, quantity of allocated resources
and a number of other quantitative values but also have to
specify the values of appropriate quality parameters. This
paper deals with the particular cases of introduction of QoS
mechanisms to large transport networks according to the
DiffServ architecture. In these cases, the extensive level of
aggregation of flows and the connectionless nature of QoS
services’ provisioning makes the definition of QoS
parameters and the engineering of QoS metrics in the
traditional SLA specification a demanding task. Due to the
fact that strictly bounded deterministic guarantees are not
realistic, usually only upper bounds for the relevant
parameters can be defined and the corresponding SLAs have
to be defined accordingly.1 aBouras, Christos1 aSevasti, Afroditi1 aCampanella, M  uhttp://telematics.upatras.gr/telematics/publications/sla-definition-provision-ef-based-service?language=en01232nas a2200121   4500008004100000245008000041210006900121260002100190520072400211100002100935700002000956856013400976       2002                        eng d00aSpeeding-up, filtering and manipulating the web to meet specific user needs0 aSpeedingup filtering and manipulating the web to meet specific u  c18 - 21 December3 aIn our days the Web has become a large
repository of information. This information is constantly
updated and altered. In this work we describe a software
architecture that has been used to implement a tool that
may potentially aid individual Web users but also
groups of users, to upgrade their browsing sessions and
make these sessions more productive. The software that
is presented here, uses documented and widely accepted
techniques to improve users’ browsing sessions. It also
utilizes new experimental and emerging techniques. The
software can be used in various client/server
configurations. We present the software modules and
their configuration, as well as the interaction that is
carried out between them.1 aBouras, Christos1 aKonidaris, Agis  uhttp://telematics.upatras.gr/telematics/publications/speeding-filtering-and-manipulating-web-meet-specific-user-needs?language=en01563nas a2200133   4500008004100000245013100041210006900172260002000241300001500261520095900276100002101235700002201256856015101278       2002                        eng d00aSRAMT-S: A hybrid sender and receiver-based adaptation scheme for TCP friendly multicast transmission using simulcast approach0 aSRAMTS A hybrid sender and receiverbased adaptation scheme for T  c10 - 11 October  a 105 - 1223 aIn this paper, we describe a hybrid sender and receiver-based adaptation
scheme for multicast transmission of multimedia data using the simulcast
approach, which we call SRAMT-S (Sender-Receiver based Adaptation
scheme for Multicast Transmission using Simulcast). The most prominent
features of SRAMT-S are its distributed (to sender and receivers) transmission
rate estimation algorithm and its innovative RTT (Round Trip Time)
estimation algorithm based on one-way delay measurements. SRAMT-S is
using both an AIMD algorithm and a TCP model in order to estimate a TCP
friendly bandwidth share. We evaluate SRAMT-S through a number of
simulations in order to examine its behaviour to a heterogeneous group of
receivers and its behaviour against TCP connections. Main conclusion of the
simulation was that SRAMT-S has friendly behaviour against the dominant
traffic types of today’s Internet and treats a heterogeneous group of receivers
with fairness.1 aBouras, Christos1 aGkamas, Apostolos  uhttp://telematics.upatras.gr/telematics/publications/sramt-s-hybrid-sender-and-receiver-based-adaptation-scheme-tcp-friendly-multicast?language=en01499nas a2200145   4500008004100000245009600041210006900137260001000206300001500216520091000231100002101141700001901162700001501181856015701196       2002                        eng d00aSTEPS: Supporting Traditional Education ProcedureS-A TCP/IP Multimedia Networks-Based Model0 aSTEPS Supporting Traditional Education ProcedureSA TCPIP Multime  cMarch  a 251 - 2763 aThis paper describes an integrated model for the realization of an Open and Distance Learning (ODL)
environment supporting traditional learning procedures, through collaborative learning and active participation
of the involved group of students. Internet technologies are used as a vehicle for distribution of interactive multimedia
at the user’s desktop. We also present off-the-shelf solutions for the architecture and implementation of
an Educational Network necessary to support the ODL environment. An Educational Entity (specially shaped
part of a legal educational authority) is also prescribed as the central point for the Educational Network, being
the content provider and the learning procedure evaluator. It is mainly intended to be used in a higher education
setting, aspiring to be an efficient solution for the common educational needs of a group of students and teachers or
researchers.1 aBouras, Christos1 aSpirakis, Paul1 aLampsas, P  uhttp://telematics.upatras.gr/telematics/publications/steps-supporting-traditional-education-procedures-tcpip-multimedia-networks-based-model?language=en00965nas a2200145   4500008004100000245006300041210006200104260001700166300001300183520045400196100002100650700001800671700001800689856011200707       2002                        eng d00aTransition Strategies from IPv4 to IPv6: The case of GRNET0 aTransition Strategies from IPv4 to IPv6 The case of GRNET  c16 - 18 July  a 89 - 963 aIn this paper we describe the results that came out from the project of employing the IPv6 protocol over the Greek Research & Technology Network (GRNET). In the way of this process one of the big issues that had to be considered was the transition strategy that would be deployed. The main goals of a transition strategy are to be smooth enough and therefore to put the less of configuration overhead to the end users and the network administrators.1 aBouras, Christos1 aKaraliotas, A1 aGanos, Petros  uhttp://telematics.upatras.gr/telematics/publications/transition-strategies-ipv4-ipv6-case-grnet?language=en01624nas a2200157   4500008004100000245010500041210006900146260001900215300001500234520098400249100002101233700002201254700001901276700001801295856015301313       2001                        eng d00aArchitecture and Performance Evaluation for Redundant Multicast Transmission Supporting Adaptive QoS0 aArchitecture and Performance Evaluation for Redundant Multicast   c9 - 12 October  a 585 - 5923 a<p>In this paper we describe the architecture of an application that was developed for the transmission of multimedia data, using the multicast mechanism, over the Internet. There are two major issues that have to be considered when designing and implementing such a service, the fairness and the adaptation schemes. In our application we use a mechanism that categorizes the receivers into a number of groups according to each receiver’s capabilities and (the mechanism) serves each group of users with a different multicast stream. We have also implemented an additional mechanism for the intra-stream bit rate adaptation. The proposed mechanism uses a “friendly” to the network users congestion control policy to control the transmission of the data. We evaluate the adaptive multicast transmission mechanism through a number of experiments in order to examine its behaviour to a heterogeneous group of receivers and its behaviour against TCP and UDP data streams.</p>
1 aBouras, Christos1 aGkamas, Apostolos1 aStamos, Kostas1 aKaraliotas, A  uhttp://telematics.upatras.gr/telematics/publications/architecture-and-performance-evaluation-redundant-multicast-transmission-supporting?language=en01727nas a2200157   4500008004100000245008100041210006900122260001900191300001500210520112500225100002101350700002201371700001901393700001801412856013901430       2001                        eng d00aAn Architecture for Redundant Multicast Transmission Supporting Adaptive QoS0 aArchitecture for Redundant Multicast Transmission Supporting Ada  c7 - 9 November  a 133 - 1423 aIn this paper we describe the architecture and the implementation of an application that was
developed for the transmission of multimedia data, using the multicast mechanism, over the
Internet. There are two major issues that have to be considered when designing and implementing
such a service, the fairness and the adaptation schemes. The fairness problem results from the fact
that receivers with different capabilities have to be served. In our application we use a mechanism
that categorizes the receivers into a number of groups according to each receiver’s capabilities and
(the mechanism) serves each group of users with a different multicast stream. With the term
“capabilities” we do not only mean the processing power of the client, but also the capacity and the
condition of the network path towards that client. Because of today’s Internet heterogeneity and the
lack of Quality of Service (QoS) support, the sender cannot assume that the receivers will
permanently be able to handle a specific bit rate. We have therefore implemented an additional
mechanism for the intra-stream bit rate adaptation.1 aBouras, Christos1 aGkamas, Apostolos1 aStamos, Kostas1 aKaraliotas, A  uhttp://telematics.upatras.gr/telematics/publications/architecture-redundant-multicast-transmission-supporting-adaptive-qos?language=en01380nas a2200133   4500008004100000245006900041210006900110260001900179300001700198520085300215100002101068700002701089856013001116       2001                        eng d00aArchitectures and Protocols for Educational Virtual Environments0 aArchitectures and Protocols for Educational Virtual Environments  c22 - 25 August  a 1107 - 11103 aShared or networked virtual environments are one of the most
promising uses of the virtual reality technology. While a lot of
research has been done in the area of multi-user virtual
environments corresponding to the sharing of events very few
research has been done on specific services and functionality.
However both the requirements and the kind of the offered
services affect significantly the design of a system. In this paper
we present the main issues in the design of a platform to support
the distant education process using networked virtual
environments. We also introduce the term Educational Virtual
Environments and their basic requirements. According to these
requirements of the educational virtual environments we propose
both a suitable architecture and a protocol for the interaction
between the components of this architecture.1 aBouras, Christos1 aTsiatsos, Thrasivoulos  uhttp://telematics.upatras.gr/telematics/publications/architectures-and-protocols-educational-virtual-environments?language=en00999nas a2200157   4500008004100000245010300041210006900144260001700213300001300230520035600243100002100599700002700620700002700647700001400674856015300688       2001                        eng d00aArchitectures Supporting e-Learning Through Collaborative Virtual Environments: The Case of INVITE0 aArchitectures Supporting eLearning Through Collaborative Virtual  c6 - 8 August  a 13 - 163 aThe growing need for communication, visualization and
organization technologies in the field of e-learning
environments has led to the application of virtual reality
and the use of collaborative virtual environments. This
paper presents a system architecture to support such
environments, defined by user needs and using state of the
art technologies.1 aBouras, Christos1 aTsiatsos, Thrasivoulos1 aTriantafillou, Vasilis1 aHornig, G  uhttp://telematics.upatras.gr/telematics/publications/architectures-supporting-e-learning-through-collaborative-virtual-environments-case?language=en01383nas a2200145   4500008004100000245008900041210006900130260001700199300001500216520078000231100002101011700002701032700002701059856015101086       2001                        eng d00aAspects of collaborative learning environment using distributed virtual environments0 aAspects of collaborative learning environment using distributed   c25 - 30 June  a 173 - 1783 aA decisive factor for new technologies is always the added value with respect to
the efficiency and capacity of traditional technologies. This also is true when considering the
impact of new technologies in training applications. New types of applications have been
developed along the last few years to incorporate information technology in the learning
environment. The growing need for communication, visualisation and organisation features in
the field of learning and training environments, the e-learning approach, has led to the
application of virtual reality and the use of multi-user real-time communication platforms to
support these needs. This paper presents the first approach of such a system as well as useful
technologies and standards for its implementation.1 aBouras, Christos1 aTsiatsos, Thrasivoulos1 aTriantafillou, Vasilis  uhttp://telematics.upatras.gr/telematics/publications/aspects-collaborative-learning-environment-using-distributed-virtual-environments?language=en01608nas a2200121   4500008004100000245006600041210006600107300001300173520113300186100002101319700002301340856012301363       2001                        eng d00aBasic Internet Services Environment for the Education Society0 aBasic Internet Services Environment for the Education Society  a 35 - 443 aComputer-based, networking learning environments play a signif-
icant role in the improvement of the learning procedure. Elec-
tronic communication and collaboration services provide tutors and
trainees with continual, close, and eácient cooperation. An increase
in the use of the Internet as a repository of resources for learning,
and also as a means for delivery of specially prepared teaching
materials, is a particularly signißcant innovation in the ßeld of
education. Educational applications are increasingly based on the
World Wide Web, combining simplißed access to the application
and integration into a Web-based learning environment. This work
presents a àexible communication and collaboration environment,
developed within the framework of the ODYSSEAS project, that
may be used by educators. The basic services environment presented
in this paper is built upon the well-known and popular standards
HTTP, SMTP, and POP3 and is accessible to the potential user
through a web browser and connection to a user authentication
server that will handle the user's private information, with minimal
installation cost.1 aBouras, Christos1 aKapoulas, Vaggelis  uhttp://telematics.upatras.gr/telematics/publications/basic-internet-services-environment-education-society?language=en01281nas a2200121   4500008004100000245007400041210006900115300001500184520079200199100002100991700001801012856012901030       2001                        eng d00aCost of implementing Banyan networks for use in ATM switching fabrics0 aCost of implementing Banyan networks for use in ATM switching fa  a 771 - 7913 aIn this paper, we present a model for computing the cost of implementing Banyan
networks. We limit our interest in Banyan networks which are used in ATM switching fabrics
and are build in VLSI. The cost is given as a function of the characteristics of the network (i.e.
length of buffers, speed of links, etc.). It is well-known that the implementation cost must be
related to the performance of the network. The choices, that the designer may have, impact both
the performance and the cost. We demonstrate the case where a slight increase in performance
implies a great increase in cost (in that case it is not cost effective to build a better switching
network), and of course the reverse, i.e., the case where a decrease in cost implies a degradation
of the performance of the switch.1 aBouras, Christos1 aGkantsidis, C  uhttp://telematics.upatras.gr/telematics/publications/cost-implementing-banyan-networks-use-atm-switching-fabrics?language=en01422nas a2200145   4500008004100000245005600041210005500097260000900152300001500161520091200176100002101088700002701109700001901136856012101155       2001                        eng d00ae-Learning through Distributed Virtual Environments0 aeLearning through Distributed Virtual Environments  cJuly  a 175 - 1993 ae-learning is one of the emerging needs of the information age. Access to education
is going to become crucial for the success of our information society, and therefore
a lot of potential is seen in distance learning and distributed virtual environments. The
communicative character of the distributed virtual environments would allow students and
staff to meet in social shared spaces and engage in on-line real-time seminars and tutorials.
Such technologies may mitigate some of the problems of isolation that distance learning
brings. This paper presents our work in multi-user distributed virtual environments which
are designed and implemented for educational uses in the bounds of the VES project.
Furthermore, it presents our proposal for the extensions and reconstruction of the current
system in order to create a more efficient system, which can be characterized as a learning
virtual environment.1 aBouras, Christos1 aTsiatsos, Thrasivoulos1 aPhilopoulos, A  uhttp://telematics.upatras.gr/telematics/publications/e-learning-through-distributed-virtual-environments?language=en01301nas a2200145   4500008004100000245008500041210006900126260001700195300001500212520072200227100002100949700002700970700001400997856014401011       2001                        eng d00aAn Electronic Polling Service to support Public Awareness using Web Technologies0 aElectronic Polling Service to support Public Awareness using Web  c27 - 29 June  a 935 - 9463 aThis paper presents a Web-based, database-oriented application called “Electronic Polling”, a smart
way to support voting on common subjects in which all people of a Local Authority are interested. The
systems services were planned and implemented to be easily expandable. The application is based on
state-of-the-art software platform, integrating WWW and database. The system aims to become a pilot
in future efforts relative with “on line Democracy”. The system provides the capability to create a
poll, view the subject and participate to the voting procedure. Only authorised users can participate to
use the system to vote or create a poll but all users can view results from previous voting procedures.1 aBouras, Christos1 aTriantafillou, Vasilis1 aKatris, N  uhttp://telematics.upatras.gr/telematics/publications/electronic-polling-service-support-public-awareness-using-web-technologies?language=en01416nas a2200157   4500008004100000245008100041210006900122260001600191300001500207520082000222100002101042700002001063700002201083700001601105856013701121       2001                        eng d00aIntroducing Navigation Graphs as a Technique for Improving WWW User Browsing0 aIntroducing Navigation Graphs as a Technique for Improving WWW U  c9 - 11 July  a 249 - 2563 aIn this paper we show that users move from page to page, in the
WWW, by following similar browsing patterns when they have similar
browsing experience. Similar browsing patterns do not absolutely imply that the
same URL’s are visited. They only mean that users react in similar ways to
similar web sites and follow almost foreseen routes. In order to prove this
conclusion we introduce the Navigation Graph technique to trace users’ web
browsing patterns. We also categorize sites according to their structure by using
a commercial tool. Having done these, we analyze the results of the navigation
graphs and present them, pointing out the problems that users may encounter.
Finally, in order to answer to these problems, we propose enhancements that
can improve the performance of web browsers and web servers.1 aBouras, Christos1 aKonidaris, Agis1 aSevasti, Afroditi1 aKonidari, E  uhttp://telematics.upatras.gr/telematics/publications/introducing-navigation-graphs-technique-improving-www-user-browsing?language=en01387nas a2200133   4500008004100000245008000041210006900121260002000190300001300210520085300223100002101076700002201097856013401119       2001                        eng d00aA Mechanism for Multicast Multimedia Data With Adaptive QoS Characteristics0 aMechanism for Multicast Multimedia Data With Adaptive QoS Charac  c17 - 19 October  a 74 - 883 aIn this paper, we describe a mechanism for adaptive transmission of
multimedia data, which is based on real time protocols. The proposed
mechanism can be used for multicast multimedia data over heterogeneous
networks, like the Internet, and has the capability to adapt the transmission of
the multimedia data to network changes. In addition, the adaptive multicast
transmission mechanism uses an inter-receiver fairness function in order to treat
the group of receivers with fairness in a heterogeneous environment. The
proposed mechanism uses a “friendly” to the network users congestion control
policy to control the transmission of the data. We evaluate the adaptive
multicast transmission mechanism through a number of simulations in order to
examine its fairness to the group of receivers and its behavior against TCP and
UDP data streams.1 aBouras, Christos1 aGkamas, Apostolos  uhttp://telematics.upatras.gr/telematics/publications/mechanism-multicast-multimedia-data-adaptive-qos-characteristics?language=en01767nas a2200169   4500008004100000245005800041210005400099260001500153300001500168520119400183100002101377700002301398700002201421700002001443700002101463856011301484       2001                        eng d00aAn On-line Managed Bandwidth Service for ATM Networks0 aOnline Managed Bandwidth Service for ATM Networks  c4 - 7 June  a 315 - 3203 aIn our days, the number of demanding, in terms of
network bandwidth, applications increases dramatically
as the number of users that obtain access to networking
facilities augments. As a result, efficient management of
the available network resources becomes a critical issue
both from a functional point of view, so that users can be
provided with the bandwidth they need, and an
economical point of view, so that carriers can
satisfactorily and efficiently serve as many customers as
possible. The work presented here attempts to face from
a practical point of view the problem of bandwidth
management in ATM networks, especially in cases
where the available resources have to be shared among
many users with conflicting needs. We have designed
and implemented a Managed Bandwidth Service (MBS)
that allows users to make multiple bandwidth
reservations throughout the topology of the network
infrastructure to which they have access. This MBS also
provides an administrative module for configuring and
monitoring the service’s operation. In this paper we
present the MBS developed and all the implementation
issues related to it, as well as our on-going and future
work on the service.1 aBouras, Christos1 aKapoulas, Vaggelis1 aSevasti, Afroditi1 aChantzi, Chrysa1 aSampraku, Ioanna  uhttp://telematics.upatras.gr/telematics/publications/line-managed-bandwidth-service-atm-networks?language=en01380nas a2200157   4500008004100000245006000041210005800101260001900159300001500178520082700193100002101020700002701041700001801068700001701086856011901103       2001                        eng d00aA Platform for Sharing Educational Virtual Environments0 aPlatform for Sharing Educational Virtual Environments  c9 - 12 October  a 659 - 6663 aIn recent years, a lot of work has been done on multi-user virtual environments. This
work led to platforms that aim to support 3D virtual communities. However, little research has
been done on specific services and functionality, which affect significantly the design of a system.
The growing need for communication, visualisation and organisation technologies in the field of
e-learning environments, has led to the application of virtual reality and the use of multi-user
real-time communication platforms to support these needs. In this paper we present the design
and implementation of a platform, suitable for educational virtual environments. Apart from the
platform itself, we present the technological choices, a new method for sharing virtual
environments and a new protocol for educational virtual environments.1 aBouras, Christos1 aTsiatsos, Thrasivoulos1 aPsaltoulis, D1 aPsaroudis, C  uhttp://telematics.upatras.gr/telematics/publications/platform-sharing-educational-virtual-environments?language=en01241nas a2200145   4500008004100000245006200041210006100103260001400164300001000178490000800188520073500196100002100931700002000952856012300972       2001                        eng d00aRun-time Management Policies for Data Intensive Web sites0 aRuntime Management Policies for Data Intensive Web sites  c3 January  a61-700 v7013 aWeb developers have been concerned with the issues of Web latency and Web data consistency
for many years. These issues have become more important in our days since the accurate and
imminent dissemination of information is vital to businesses and individuals that rely on the
Web. In this paper, we evaluate different run-time management policies against real Web site
data. We first define the meaning of data intensive Web sites and categorize them according to
their hit patterns. Our research relies on real world Web data collected from various popular Web
sites and proxy log files. We propose a Web site run-time management policy that may apply to
various real Web site hit patterns and Web data update frequencies.1 aBouras, Christos1 aKonidaris, Agis  uhttp://telematics.upatras.gr/telematics/publications/run-time-management-policies-data-intensive-web-sites?language=en01314nas a2200133   4500008004100000245010800041210006900149260001000218300001300228520074800241100002100989700002201010856014801032       2001                        eng d00aSchool Networks and Telematics Services:perspectives of international co-operation in the Mediterranean0 aSchool Networks and Telematics Servicesperspectives of internati  cMarch  a 17 - 183 aThe forthcoming ‘Information Society’ is expected to transform radically the way of
communicating knowledge and expertise. The application of ICT for educational purposes
should be aimed to improve the education process in terms of pedagogical methodologies,
school infrastructure, human resources development and organisational restructuring, in order
to efficiently absorb and utilise the technological developments. New learning paradigms
have already emerged giving emphasis to the communication and collaborative aspects of the
learning process. Self-supported and collaborative learning is expected to transform the
traditional educational activities (teacher-centred model) and promote flexibility, reflection
and group interaction.1 aBouras, Christos1 aTsakarissianos, G  uhttp://telematics.upatras.gr/telematics/publications/school-networks-and-telematics-servicesperspectives-international-co-operation?language=en01257nas a2200133   4500008004100000245011800041210006900159260001700228300001500245520066800260100002100928700002000949856015400969       2001                        eng d00aWeb Components: A Concept for Improving Personalization and Reducing User Perceived Latency on the World Wide Web0 aWeb Components A Concept for Improving Personalization and Reduc  c25 - 28 June  a 238 - 2443 aIn this paper we address one of the
performance problems of the World Wide Web, known
as User Perceived Latency (UPL). We begin by
presenting a new definition of UPL. Next we present a
concept that may benefit the WWW and reduce UPL.
This is the concept of Web Components. We show how
Web Components can work together with other
concepts for efficient Web Data manipulation and
delivery, in order to reduce UPL. We then show how
Web Components can also be used to support Web
personalization as a means for reducing latency. After
that we present the operation of the WWW model (Web
Servers, Web Proxies and Web Browsers) for
supporting the Web Component concept.1 aBouras, Christos1 aKonidaris, Agis  uhttp://telematics.upatras.gr/telematics/publications/web-components-concept-improving-personalization-and-reducing-user-perceived-latency?language=en01193nas a2200133   4500008004100000245010000041210006900141260001500210300001500225520062500240100002100865700001900886856015400905       2000                        eng d00aAccounting management system enhancement supporting automated monitoring and storing facilities0 aAccounting management system enhancement supporting automated mo  c3 - 6 July  a 117 - 1243 aIn this work we present the design, development and implementation of a set of tools embedded
in a network management system used in the University of Patras Network (UPatrasnet),
providing advanced accounting management services. These tools help the critical network
parameters monitoring and storing procedure in order to provide the information needed for
efficient management. We defined which resources to be watched and what kind of information
to be collected by the management system in order to deploy the specifications of the
processing and analyzing tools. Finally, we used HP OpenView as a network manager.1 aBouras, Christos1 aKastaniotis, S  uhttp://telematics.upatras.gr/telematics/publications/accounting-management-system-enhancement-supporting-automated-monitoring-and-storing?language=en01842nas a2200145   4500008004100000245006100041210006100102260001500163300001700178520130800195100002101503700002701524700001901551856012601570       2000                        eng d00aCitizen information services using Internet technologies0 aCitizen information services using Internet technologies  c3 - 5 July  a 1123 - 11303 aThis paper presents a Web-based, database-oriented
set of applications, namely “Public Information” and “Electronic
Voting”, to support information services (exchange and
sharing) between Local Government authorities (Region, Prefecture
and Municipalities) and the citizens. The whole set of
services developed exploits Internet and Extranet technologies
enabling asynchronous cooperation, manipulation of information
from heterogeneous sources, security and easy administration,
providing in parallel advanced telecommunication facilities.
We propose an innovating approach for submitting questions,
remarks and comments from citizen to Local authorities
(prefecture) and receiving response/correspondence in a reasonable
period of time (Public Information) and, on the other hand,
a smart way to support voting on common subjects in which all
local community is interested in. The system included applications
and services were planned and implemented to be easily
expandable to any organizational chart of any Local Administration.
Both applications are based on state-of-the-art software
platforms, integrating WWW and database. The system
aims to become a pilot in future efforts relative with distribution
and management information between and within different
types of local authorities.1 aBouras, Christos1 aTriantafillou, Vasilis1 aKastaniotis, S  uhttp://telematics.upatras.gr/telematics/publications/citizen-information-services-using-internet-technologies?language=en01494nas a2200133   4500008004100000245009100041210006900132260002000201300002000221520093100241100002101172700001801193856014901211       2000                        eng d00aCost/Performance evaluation of Banyan networks which are used in ATM switching fabrics0 aCostPerformance evaluation of Banyan networks which are used in   c26 - 28 January  a 1A-2.1/1.A-2.83 aIn this paper, we present a model for computing the cost
of implementing Banyan networks. We limit our interest in
Banyan networks which are used in ATM switching fabrics
and are build in VLSI. The cost is given as a function of the
characteristics of the network (ie. length of buffers, speed
of links, etc). We are focusing in this area because such
networks have been used extensively in the design of large
ATM switches, which are the core elements of broadband
networks. It is well-known that the cost of implementing
must be related to the performance of the network. The
choices, that the designer may have, impact both the per-
formance and the cost. We will show when a slight increase
in performance implies a great increase in cost, in which case
it is not cost effective to build a better switching network,
and of course the reverse, when a decrease in cost implies a
degradation of the performance of the switch.1 aBouras, Christos1 aGkantsidis, C  uhttp://telematics.upatras.gr/telematics/publications/costperformance-evaluation-banyan-networks-which-are-used-atm-switching-fabrics?language=en00365nam a2200085   4500008004100000245005200041210005000093100002100143856011500164       2000                        eng d00aData Communication and Computer Networks I & II0 aData Communication and Computer Networks I II1 aBouras, Christos  uhttp://telematics.upatras.gr/telematics/publications/data-communication-and-computer-networks-i-ii?language=en01363nas a2200133   4500008004100000245006700041210006500108260002000173300001300193520085400206100002101060700001901081856012901100       2000                        eng d00aDistributed Virtual Learning Environment: A Web-Based Approach0 aDistributed Virtual Learning Environment A WebBased Approach  c4 - 7 September  a 50 - 553 aIn this paper, we present a web-based Distributed
Virtual Learning Environment (DVLE) that could be used
as a sophisticated tool for distance education and
collaboration between teachers and students. We design
and develop this application and the corresponding
Graphical User Interface (GUI) as a proposal that aims
at providing an integrated communicational environment
which supplies the communicative needs of an
educational community, using the latest
telecommunication and multimedia information
processing technology. The environment that we propose
can be used for virtual lectures, virtual conferences, and
exchange of useful material and experiences among
teachers and students. It is a web-based application that
is being developed as client/server architecture using
standard protocols and technologies such as HTTP,
HTML, Java and VRML.1 aBouras, Christos1 aPhilopoulos, A  uhttp://telematics.upatras.gr/telematics/publications/distributed-virtual-learning-environment-web-based-approach?language=en01681nas a2200157   4500008004100000245005000041210004800091260001800139300001500157520115500172100002101327700002301348700002001371700002201391856011001413       2000                        eng d00aA Dynamic Distributed Video on Demand Service0 aDynamic Distributed Video on Demand Service  c10 - 13 April  a 496 - 5033 aIn our days, the use of Internet services has become a part of every day life. The need
for more advanced applications is increasing and solutions have to be provided in
order to meet it. Multimedia information is constantly getting more popular. The
connections’ bandwidth though is not ready yet to cope with the rising expectations of
applications such as Video on Demand (VoD), which are very consuming in terms of
bandwidth. In this paper we propose a way to implement such a service over a limited
bandwidth/best effort Internet based network. Our proposal consists of the
implementation of algorithms and the attempt to introduce Quality of Service features
on a network such as the Internet that inherently does not support such features. In this
paper we propose two techniques that can serve in the implementation of an Internet
based Video on Demand service. The first deals with the distribution of video titles on
the several Video Servers and is called Disk Manipulation Algorithm (DMA). The
second gives a dynamic nature to the service, imposes a virtual routing procedure to
the system and is called Virtual Routing Algorithm (VRA).1 aBouras, Christos1 aKapoulas, Vaggelis1 aKonidaris, Agis1 aSevasti, Afroditi  uhttp://telematics.upatras.gr/telematics/publications/dynamic-distributed-video-demand-service?language=en01675nas a2200169   4500008004100000245006100041210005900102260001900161300001400180520110800194100002101302700002001323700001601343700002201359700001201381856011201393       2000                        eng d00ae-DEDALUS: A dynamic tool for data publishing on the web0 aeDEDALUS A dynamic tool for data publishing on the web  c5 - 8 November  a 98 - 1053 aTheWorld WideWeb (WWW) provides a great
opportunity for companies and individuals to publish their
ideas, products and everything they would like other peo-
ple to view. Since the Internet community and the Web
are expanding every day, the demand for user friendly Web
publishing applications is rising. The procedures that could
be followed by Internet users in order to publish content on
the web till now, were to either buy and read some books
on HTML and have some basic knowledge on Web Servers,
or pay an ISP a quite substantial amount of money to do
it for them. In this paper we rst justify the necessity of
the existence of an alternative method for online web pub-
lishing. We then describe the method and a tool, called
e-DEDALUS, which can be used by many diverse Internet
user groups. An Internet user that has no previous expe-
rience in programming, or desktop design, will be able to
create his/her own Web site, online. The e-DEDALUS tool
that will be described in this paper aims at oering simplic-
ity, customisability and multilingual support to a substantial
number of WWW users.1 aBouras, Christos1 aKonidaris, Agis1 aSintoris, C1 aApostolopoulos, A1 aKhan, V  uhttp://telematics.upatras.gr/telematics/publications/e-dedalus-dynamic-tool-data-publishing-web?language=en01680nas a2200145   4500008004100000245007700041210006900118260002000187300001500207520112900222100002101351700001901372700001401391856012901405       2000                        eng d00aAn efficient algorithm to improve handoff in mobility for IP v6 protocol0 aefficient algorithm to improve handoff in mobility for IP v6 pro  c11 - 14 October  a 505 - 5113 aThis paper describes an extension of the mobility support for the IPv6 protocol, which
is currently an Internet Draft. We argue that by processing geographical data information a
mobile node can efficiently switch between different LANs without disturbance to ongoing data
sessions. Furthermore the number of location update messages diminishes as the mobile node
transmits them only when switching to a new LAN. This extension requires that each router of
the foreign networks the mobile node visits, advertises the GPS coordinates of x points that
describe its region. It also requires that the mobile node is capable of receiving GPS signals.
Once having collected this information the mobile node can safely figure whether it will continue
to be served by the same LAN or it has to switch to a different one because soon it will be out of
the old LAN’s range. Furthermore using this information the mobile node can also decide to
which LAN it is preferable to switch. Lower-layer information, when it is available, such as
signal strength or signal quality can be used as auxiliary indications for the switch decision.1 aBouras, Christos1 aSpirakis, Paul1 aSiahos, Y  uhttp://telematics.upatras.gr/telematics/publications/efficient-algorithm-improve-handoff-mobility-ip-v6-protocol?language=en02348nas a2200193   4500008004100000245006000041210005900101300001500160520169800175100002101873700002201894700002701916700001701943700001901960700001501979700001801994700001702012856012502029       2000                        eng d00aEfficient Web-Based Open and Distance Learning Services0 aEfficient WebBased Open and Distance Learning Services  a 213 - 2373 aIn this paper, we present data management issues faced during the design and development
of an open distance learning system for the University of Patras, Greece. In order to handle
data e&#129;ciently, as required in a web tele-training application, for each type of information
maintained, di&#128;erent strategies must be deployed according to their behaviour and structure.
The diversity and complexity of data, the network aspect of the application and web de®-
ciencies impose an architecture design incorporating a plethora of technologies and tools that
must be integrated in such a fashion that they e&#129;ciently organise these data preserving their
relationships. This presents a software engineering challenge requiring coherence of solutions
at all levels: structures, consistency, security, models, and protocols. The paper presents the
data components of an open and distance learning (ODL) system that access the information
stored in a database and the ®le system, their underlying technology, their interaction with the
network services, and features regarding the ways they address issues faced in an open vendorindependent
distance learning environment and outlines the system's overall architecture. In
addition, this paper presents the architecture, the design and the services of a network-based
information system that supports open and distance learning activities. The open and distance
learning information system (ODLIS) o&#128;ers synchronous and asynchronous distance learning
and management of information system (MIS) services to support the educational procedure.
The ODLIS is a web-based application, which runs over the Internet using real time protocols.1 aBouras, Christos1 aGkamas, Apostolos1 aTsiatsos, Thrasivoulos1 aDestounis, P1 aGarofalakis, J1 aSakalis, G1 aSakopoulos, B1 aTsaknakis, J  uhttp://telematics.upatras.gr/telematics/publications/efficient-web-based-open-and-distance-learning-services?language=en01020nas a2200145   4500008004100000245007400041210006900115260001800184300001500202520045800217100002100675700002700696700001900723856013200742       2000                        eng d00aInformation services using Internet technologies in the Public Sector0 aInformation services using Internet technologies in the Public S  c23 - 25 March  a 112 - 1193 aThis work presents a Web-based, database-oriented set of applications,
which include an asynchronous Open Distance Learning tool (without the presence of
a tutor), an application for retrieving information about work safety issues and allows
information exchange between the public and different departments of Greek Power
Company (GPC). All applications offer secure and easy administration, providing in
parallel advanced telecommunication facilities.1 aBouras, Christos1 aTriantafillou, Vasilis1 aKastaniotis, S  uhttp://telematics.upatras.gr/telematics/publications/information-services-using-internet-technologies-public-sector?language=en01387nas a2200145   4500008004100000245005700041210005700098260002000155300001300175520086500188100002101053700002201074700002701096856011801123       2000                        eng d00aInternet Protocols for Synchronous Distance Learning0 aInternet Protocols for Synchronous Distance Learning  c4 - 8 September  a 46 - 503 aThe use of multimedia in telematics and new services
has been greatly improved by the introduction of new
systems and techniques. These new systems and techniques
made the implementation of many telematic applications
like tele-teaching, collaborative or tele-medicine
applications possible. In this paper, we present design,
protocols and implementation issues, which concern an
Internet based synchronous distant learning application.
We describe in detail the design and the implementation of
each application’s module and we appose the protocols,
which control the communication among the application's
components. The described application is a network-based
application, which follows the client-server model. The
application runs over the Internet and more specifically
over the web. The users of the application access its
services through web pages.1 aBouras, Christos1 aGkamas, Apostolos1 aTsiatsos, Thrasivoulos  uhttp://telematics.upatras.gr/telematics/publications/internet-protocols-synchronous-distance-learning?language=en00324nam a2200085   4500008004100000245003700041210003700078100002100115856010200136       2000                        eng d00aMultimedia and Computer Networks0 aMultimedia and Computer Networks1 aBouras, Christos  uhttp://telematics.upatras.gr/telematics/publications/multimedia-and-computer-networks?language=en00496nas a2200133   4500008004100000245005100041210005000092260002100142300001300163100002100176700002200197700002700219856011600246       2000                        eng d00aNetwork-Based Distributed Learning Environment0 aNetworkBased Distributed Learning Environment  cJuly - September  a 29 - 371 aBouras, Christos1 aGkamas, Apostolos1 aTsiatsos, Thrasivoulos  uhttp://telematics.upatras.gr/telematics/publications/network-based-distributed-learning-environment?language=en01001nas a2200145   4500008004100000245008600041210006900127260002600196300001500222520040100237100002100638700002700659700001900686856015000705       2000                        eng d00aA Networked Intelligent Distributed Virtual Training Environmnet:A First Approach0 aNetworked Intelligent Distributed Virtual Training EnvironmnetA   c27 February - 3 March  a 604 - 6073 aCollaborative livelong learning is one of the emerging
needs of the information age. Access to education is going
to become crucial for the success of our information
society. Therefore a lot of potential is seen in distance
learning and online collaborative environments. This paper
proposes an intelligent distributed virtual training
environment for distance education through shared 3D
spaces1 aBouras, Christos1 aTsiatsos, Thrasivoulos1 aPhilopoulos, A  uhttp://telematics.upatras.gr/telematics/publications/networked-intelligent-distributed-virtual-training-environmneta-first-approach-0?language=en01109nas a2200145   4500008004100000245007600041210006900117260002100186520055500207100002100762700001900783700001400802700001600816856013100832       2000                        eng d00aThe Performance of Simple Queueing Theoretic Video On Demand Algorithms0 aPerformance of Simple Queueing Theoretic Video On Demand Algorit  c14 - 17 February3 aVideo On Demand (VOD) Systems comprise an
emerging new technology, which is expected to
significantly affect everyday life. The implementation of
effective commercial VOD systems has to overcome some
technical limitations, such as the low bandwidth offered
by the existing communication channels. In our work we
present some simple queuing theoretic algorithms for the
optimal use of a limited number of communication
channels keeping a fair policy for the users requests. We
compare our algorithms with well-known algorithms, by
means of simulation.1 aBouras, Christos1 aGarofalakis, J1 aTzimas, J1 aPetridis, P  uhttp://telematics.upatras.gr/telematics/publications/performance-simple-queueing-theoretic-video-demand-algorithms?language=en01126nas a2200133   4500008004100000245009200041210006900133260001900202300001300221520055700234100002100791700002700812856015300839       2000                        eng d00apLVE: Suitable Network Protocol Supporting Multi-User Virtual Environments in Education0 apLVE Suitable Network Protocol Supporting MultiUser Virtual Envi  c6 - 9 December  a 73 - 813 aVirtual Reality Modeling Language (VRML) and the broad use of communication networks provide
the users with realistic virtual environments. However these environments need and a pioneer
application such as distance learning. In order to realize suitable educational virtual environments
the desired functionality should be collected, a general architecture should be specified and a
suitable communication protocol between the components of the system should be designed. In this
paper we present the design rationale for such a communication protocol.1 aBouras, Christos1 aTsiatsos, Thrasivoulos  uhttp://telematics.upatras.gr/telematics/publications/plve-suitable-network-protocol-supporting-multi-user-virtual-environments-education?language=en01236nas a2200133   4500008004100000245006400041210006400105260002000169300001500189520073100204100002100935700002200956856012400978       2000                        eng d00aStreaming multimedia data with adaptive QoS characteristics0 aStreaming multimedia data with adaptive QoS characteristics  c22 - 25 October  a 129 - 1393 aIn this paper, we describe the design and the
implementation of an adaptive streaming architecture,
which is based on real time protocols. The adaptive
streaming application, which we have developed, can
be used for streaming multimedia data over
heterogeneous networks like the Internet and has the
capability to adapt the streaming of multimedia data to
network changes. The adaptive streaming application
uses a friendly to the network users congestion control
mechanism to control the transmission of the media.
We evaluate the adaptive streaming application
through a number of experiments. During these
experiments, we demonstrate the friendly behaviour of
the adaptive streaming application to TCP and UDP
data streams.1 aBouras, Christos1 aGkamas, Apostolos  uhttp://telematics.upatras.gr/telematics/publications/streaming-multimedia-data-adaptive-qos-characteristics?language=en01017nas a2200157   4500008004100000245006700041210006600108260002200174300001300196520043300209100002100642700002300663700002200686700002700708856012400735       2000                        eng d00aTelematic Services over ATM Networks: The case of Teleteaching0 aTelematic Services over ATM Networks The case of Teleteaching  c13 - 15 September  a 26 - 313 aIn this paper we present various tele-teaching scenarios over ATM network infrastructure.
In each scenario we present the standards which we use, the logical components, the demand in
resources (network resources and equipment) and its special characteristics. Main result of our
experiments is that broadband networks offer many capabilities for high quality Teleteaching and
generally speaking high quality Telematic services.1 aBouras, Christos1 aKapoulas, Vaggelis1 aGkamas, Apostolos1 aTsiatsos, Thrasivoulos  uhttp://telematics.upatras.gr/telematics/publications/telematic-services-over-atm-networks-case-teleteaching?language=en00974nas a2200157   4500008004100000245005200041210005100093260001500144300001300159520043400172100002100606700002300627700002200650700002700672856011700699       2000                        eng d00aTele-teaching Scenarios over Broadband Networks0 aTeleteaching Scenarios over Broadband Networks  c5 - 6 June  a 64 - 663 aIn this paper we present various tele-teaching scenarios over ATM
network infrastructure. In each scenario we present the standards
which we use, the logical components, the demand in resources
(network resources and equipment) and its special characteristics.
Main result of our experiments is that broadband networks offer many
capabilities for high quality tele-teaching and generally speaking high
quality Telematic services.1 aBouras, Christos1 aKapoulas, Vaggelis1 aGkamas, Apostolos1 aTsiatsos, Thrasivoulos  uhttp://telematics.upatras.gr/telematics/publications/tele-teaching-scenarios-over-broadband-networks?language=en00540nas a2200121   4500008004100000245008300041210006900124260002800193300001500221100002100236700002200257856013900279       2000                        eng d00aUsing Java to implement a multimedia annotation environment for young children0 aUsing Java to implement a multimedia annotation environment for   c30 October - 3 November  a 187 - 1941 aBouras, Christos1 aSevasti, Afroditi  uhttp://telematics.upatras.gr/telematics/publications/using-java-implement-multimedia-annotation-environment-young-children?language=en01250nas a2200181   4500008004100000245007700041210006900118260002100187300001500208520059200223100002100815700002300836700002000859700002200879700001500901700002000916856013200936       2000                        eng d00aUsing Multimedia to Support Reflection on Past Events for Young Children0 aUsing Multimedia to Support Reflection on Past Events for Young   c26 June - 1 July  a 105 - 1103 aThe work presented in this paper focuses on software tools that act as video explorers
and annotation platforms and more specifically as diary composers for younger children. Through
such tools, children can have as their raw material video recordings from everyday life and they are
given the opportunity to review this material, reflect upon it and annotate it, thus creating the
stories of everyday life from their own perspective. The specific tool proposed, focuses on multiperspective
capture of events by one or more children and their cooperation during the annotation
procedure.1 aBouras, Christos1 aKapoulas, Vaggelis1 aKonidaris, Agis1 aSevasti, Afroditi1 aRamalho, M1 aVan de Velde, W  uhttp://telematics.upatras.gr/telematics/publications/using-multimedia-support-reflection-past-events-young-children?language=en01226nas a2200145   4500008004100000245006700041210006600108260002800174300001300202520066900215100002100884700002700905700001900932856012900951       2000                        eng d00aUsing Multi-user Distributed Virtual Environments in Education0 aUsing Multiuser Distributed Virtual Environments in Education  c30 October - 4 November  a 56 - 623 aOn-line learning is one of the emerging needs of the information age. Access to
education is going to become crucial for the success of our information society. Therefore a lot of
potential is seen in distance learning and distributed virtual environments. The communicative
character of the distributed virtual environments would allow for students and stuff to meet in
social shared spaces and engage in on-line real-time seminars and tutorials. Such technologies may
mitigate some of the problems of isolation that distance learning brings. This paper presents multiuser
distributed virtual environments, which are designed and implemented for educational uses.1 aBouras, Christos1 aTsiatsos, Thrasivoulos1 aPhilopoulos, A  uhttp://telematics.upatras.gr/telematics/publications/using-multi-user-distributed-virtual-environments-education?language=en01189nas a2200145   4500008004100000245004900041210004900090260003100139300001500170520068400185100002100869700002000890700002200910856011100932       2000                        eng d00aVirtual Environments in Educational Networks0 aVirtual Environments in Educational Networks  bKluwer Academic Publishers  a 195 - 2033 a<p>The field of Virtual Environments (VEs) is rapidly evolving into a new means of communication and accessing information, likely to overcome many existent technologies. However, being a new field makes the design and implementation of educational VEs an important aspect for scientific research in their educational potentials and the exploitation of existent technologies. New technologies in the field of VEs have appeared the establishment and combination of which, is yet to be investigated. This paper makes an effort to approach the issue of developing educational VEs introducing new aspects in the issues of interface, interaction with the user and functionality.</p>
1 aBouras, Christos1 aKonidaris, Agis1 aSevasti, Afroditi  uhttp://telematics.upatras.gr/telematics/publications/virtual-environments-educational-networks?language=en01521nas a2200145   4500008004100000245008000041210006900121260001500190300001500205520095200220100002101172700002701193700001901220856013601239       2000                        eng d00aA Web Based open distance learning tool for tutors of special social groups0 aWeb Based open distance learning tool for tutors of special soci  c8 - 10 May  a 189 - 1933 aThis work presents an integrated information system to
support Open Distance Learning activities for tutors of
special social groups. All applications and services are
implemented based on Internet Technologies that allow
the asynchronous cooperation between users, flexible
and secure data management, offering advanced
communication facilities. We propose an ODL tool that
will be able to support tutors and professionals working
at different institutions and organizations, especially
those unable to attend long term training courses. The
system includes a Database where all relevant data
about organizations in Greece offering vocational and
lifelong training programs can be found and
individuals professionally involved in such activities as
trainers. The user can attend asynchronous lessons
(with video or sound), communicate with the
responsible tutor and at the same time consult a library,
the glossary or fill in a evaluation report.1 aBouras, Christos1 aTriantafillou, Vasilis1 aKastaniotis, S  uhttp://telematics.upatras.gr/telematics/publications/web-based-open-distance-learning-tool-tutors-special-social-groups?language=en01805nas a2200169   4500008004100000245006300041210006200104260002000166300001300186520121800199100002101417700002401438700001801462700001901480700001901499856011701518       2000                        eng d00aWinds of Aiolos: How connect the Greek Schools in Internet0 aWinds of Aiolos How connect the Greek Schools in Internet  c19 - 20 October  a 27 - 373 aIn this paper, we present the first Greek School Network, which is implemented by the project
"Winds of Aiolos”. This project is subsumed in the framework of the European Community
Action "Operational Program for the Education and Initial Vocational Training - Odysseia".
Computer Technology Institute (CTI) has the responsibility for the design and the
implementation of the project. On the basis of the influence of the networking technologies to
the educational activities and according to the international experience, the usage of the
network to the educational procedure acts as knowledgeable object, information source,
learning tool and communication tool. The main object of the project is the implementation of
a network infrastructure for the interconnection of school laboratories and educational
administration offices and the provision of network services in a wide range. It forms a closed
educational network, which is based on the Greek educational and research backbone network
(GRNET). The Greek school network statistics show that the students prefer the Greek
Domain. The educational units of the Greek School Network still act more as consumers than
as creators in the information society.1 aBouras, Christos1 aParaskevas, Mixalis1 aGanos, Petros1 aAdamopoulos, N1 aKaraiskakis, D  uhttp://telematics.upatras.gr/telematics/publications/winds-aiolos-how-connect-greek-schools-internet?language=en01693nas a2200169   4500008004100000245008600041210006900127300001300196520105200209100002101261700002701282700001701309700001901326700001401345700001701359856014701376       1999                        eng d00aA Cooperative Environment for Local Government: An Internet – Intranet Approach0 aCooperative Environment for Local Government An Internet Intrane  a 75 - 893 a<p>In this paper we present a Web-based, database oriented CSCW system to support information dispersal between di€erent Local Government authorities (Region, Prefecture and Municipalities) and the citizens. The system is implemented around the `shared workspace' notion, a group of directories and ®les controlled by the users of the workspace. Intranet and Extranet technologies are exploited to enable asynchronous and synchronous co-operation, manipulation of information from heterogeneous sources, security and easy administration, providing in parallel advanced communication facilities. We propose an innovative approach for the development of shared workspaces over WWW, based on state-of-the-art software platforms, integrating WWW and database technologies. The whole system was developed under a project funded by the Greek General Secretariat of Research and Technology and aims in the ecient distribution and management of information between and within di€erent types of local authorities (Municipalities, Prefectures).</p>
1 aBouras, Christos1 aTriantafillou, Vasilis1 aDestounis, P1 aGarofalakis, J1 aTzimas, J1 aZarafidis, P  uhttp://telematics.upatras.gr/telematics/publications/cooperative-environment-local-government-internet-%E2%80%93-intranet-approach?language=en01489nas a2200181   4500008004100000245006600041210006600107260001800173300001500191520086300206100002101069700002701090700001701117700001901134700001401153700001701167856012301184       1999                        eng d00aCooperative Information Systems over the Internet and the WWW0 aCooperative Information Systems over the Internet and the WWW  c25 - 28 April  a 232 - 2363 aIn this paper we present a WWW-based approach for the
development of a system supporting information sharing
within an organizational environment. The system developed
is exploiting Intranet and Extranet technologies enabling
asynchronous and synchronous cooperation, manipulation of
information from heterogeneous sources, security and easy
administration, providing in parallel advanced communication
facilities. We propose an innovative approach for the
development of shared workspaces over WWW, based on
state-of-the-art software platforms, integrating WWW and
database technologies. The whole system was developed
under a project funded by the Greek General Secretariat of
Research and Technology and aims in the efficient
distribution and management of information between and
within different types of local authorities (Municipalities,
Prefectures).1 aBouras, Christos1 aTriantafillou, Vasilis1 aDestounis, P1 aGarofalakis, J1 aTzimas, J1 aZarafidis, P  uhttp://telematics.upatras.gr/telematics/publications/cooperative-information-systems-over-internet-and-www?language=en00942nas a2200157   4500008004100000245004600041210004600087260001700133300001500150520044300165100002100608700002300629700001400652700001300666856010500679       1999                        eng d00aDeployment scenarios of Dves in Education0 aDeployment scenarios of Dves in Education  c19 - 24 June  a 317 - 3223 aDVEs, along with the Internet in general, offer a number of attractive features for the
education sector. However deployment in traditional educational environments, such as
secondary schools, has not been achieved on a noticeable scale so far. In this contribution, we
discuss technical and pedagogical issues, and specifically define possible scenarios of how this
technology can be introduced to the school sector in a sustainable way.1 aBouras, Christos1 aKapoulas, Vaggelis1 aKoubek, A1 aMayer, H  uhttp://telematics.upatras.gr/telematics/publications/deployment-scenarios-dves-education?language=en01363nas a2200145   4500008004100000245007900041210006900120260002000189300001500209520078300224100002101007700002201028700002701050856014001077       1999                        eng d00aDistributed Learning Environment using Advanced Services over the Internet0 aDistributed Learning Environment using Advanced Services over th  c18 - 21 October  a 182 - 1863 aMultimedia and hypermedia had and still have a
tremendous impact on the evolution of educational
software. In this paper we propose an Integrated
Distributed Learning Environment (IDLE) for the
implementation of the services of an educational network
over TCP/IP networks such as the Internet. Our proposal
aims at providing an integrated communicational
environment, which supplies the communicative needs of
an educational community, using the latest
telecommunication and multimedia information
processing technology. The environment that we
implemented can be used for virtual lectures, virtual
conferences, collaborative work on projects, which are
shared among institutions, exchange of useful material
and experiences among teachers, and creation of
educational material.1 aBouras, Christos1 aGkamas, Apostolos1 aTsiatsos, Thrasivoulos  uhttp://telematics.upatras.gr/telematics/publications/distributed-learning-environment-using-advanced-services-over-internet?language=en01873nas a2200193   4500008004100000245006400041210006400105260002000169520120800189100002101397700002201418700002701440700001701467700001901484700001501503700001801518700001701536856012601553       1999                        eng d00aEfficient Data Management to support Educational Activities0 aEfficient Data Management to support Educational Activities  c7 - 8 September3 aIn this paper we present data management issues faced during the design and
development of an Open Distance Learning system for the University of Patras,
Greece. In order to handle data efficiently, as required in a Web Tele-training
Application, for each type of information maintained different strategies must be
deployed according to their behaviourand structure.
The diversity and complexity of data, the network aspect of the application and web
deficiencies impose an architecture design incorporating a plethora of technologies
and tools that must be integrated in such a fashion that they efficiently organise these
data preserving their relationships. This presents a software engineering challenge
requiring coherence of solutions at all levels: structures, consistency, security, models,
and protocols.
The paper presents the data components of a open and distance learning system that
access the information stored in a database and the file system, their underlying
technology, their interaction with the network services, and features regarding the
ways they address issues faced in a open vendor-independent distance learning
environment and outlines the system’s overall architecture.1 aBouras, Christos1 aGkamas, Apostolos1 aTsiatsos, Thrasivoulos1 aDestounis, P1 aGarofalakis, J1 aSakalis, G1 aSakopoulos, B1 aTsaknakis, J  uhttp://telematics.upatras.gr/telematics/publications/efficient-data-management-support-educational-activities?language=en01238nas a2200157   4500008004100000245005500041210005500096260001700151300001200168520069400180100002100874700002300895700002000918700002200938856012000960       1999                        eng d00aImproving and Utilizating Web and Data Interaction0 aImproving and Utilizating Web and Data Interaction  c3 - 4 August  a 7 - 123 aWeb and Database Interaction is one of the growing trends in Web-site creation. This
interaction can facilitate the needs of the online community in various ways. Until now
databases were only used to hold large amounts of information needed for certain
applications. Many of these applications are nowadays Web-based. The constant interaction
that is needed by them is very demanding in terms of computer resources. In this paper we
propose a technique that can reduce the amount of resources needed to run these demanding
applications. We also introduce an alternative model according to which databases can be
used for many other purposes in the process of Web and Database interaction.1 aBouras, Christos1 aKapoulas, Vaggelis1 aKonidaris, Agis1 aSevasti, Afroditi  uhttp://telematics.upatras.gr/telematics/publications/improving-and-utilizating-web-and-data-interaction?language=en01399nas a2200145   4500008004100000245006400041210006000105260001800165300001300183520088000196100002101076700001901097700001501116856012201131       1999                        eng d00aThe Information and Communication Technologies in Education0 aInformation and Communication Technologies in Education  c25 - 26 March  a 27 - 313 aIn the majority of the advanced countries there are many educational school networks and even more and
more schools are getting equipped with multimedia computers and connected to the Internet. Through the
advancements of the personal computer and the Internet, the school of the future will find new strengths
in both personalised and community learning environments. The prevailing perspective for the
introduction of the Information and Communication Technologies can be characterised as the “computer
as a tool”. However, as with all tools, effective use of the technology is embedded within practices and
activities that realise its functionality for specific purposes and situations. On the other hand, the
investigation of the relationship between practices, purposes, and situations and computer-based
learning technologies is a major topic on pedagogic research.1 aBouras, Christos1 aPhilopoulos, A1 aFotakis, D  uhttp://telematics.upatras.gr/telematics/publications/information-and-communication-technologies-education?language=en00478nam a2200121   4500008004100000245005900041210005700100100002100157700002300178700001900201700001700220856011900237       1999                        eng d00aIntroduction to graphs: Theory, problems and solutions0 aIntroduction to graphs Theory problems and solutions1 aBouras, Christos1 aKirousis, Lefteris1 aSpirakis, Paul1 aStamatiou, G  uhttp://telematics.upatras.gr/telematics/publications/introduction-graphs-theory-problems-and-solutions?language=en01069nas a2200169   4500008004100000245006300041210006300104260001600167300001500183520046300198100002100661700002300682700002200705700002700727700002000754856012500774       1999                        eng d00aNetwork Based Information System to support ODL Activities0 aNetwork Based Information System to support ODL Activities  c8 - 11 June  a 117 - 1253 aThis paper presents the architecture, the design and the services of a network based
Information System that supports ODL (Open and Distance Learning) activities. The ODLIS
(Open and Distance Learning Information System) offers synchronous and asynchronous
distance learning and MIS (Management of Information System) services to support the
educational procedure. The ODLIS is a web-based application, which runs over the Internet
using real time protocols.1 aBouras, Christos1 aKapoulas, Vaggelis1 aGkamas, Apostolos1 aTsiatsos, Thrasivoulos1 aKontogiannis, S  uhttp://telematics.upatras.gr/telematics/publications/network-based-information-system-support-odl-activities?language=en02429nas a2200145   4500008004100000245004600041210004500087260001700132520193500149100002102084700002302105700002202128700002702150856010602177       1999                        eng d00aODL services and PTTs: The Greek PTT case0 aODL services and PTTs The Greek PTT case  c20 - 24 June3 aDuring the last years Open and Distance Learning (ODL) methods that utilise network resources and
services are gaining wide acceptance. An increasingly number of enterprises uses ODL for training
their employees. Interestingly enough not all the enterprises that want to and can use ODL are doing
so. The role of PTTs is important in here. PTTs can provide not only the connections necessary for
the implementation of ODL services but the ODL services themselves, thus making the process of
adopting ODL easier for the enterprises. In Greece the main PTT organisation, as part of its strategy
to offer integrated telematics services in various areas, designed and currently operates a pilot
network offering ODL services. The services offered include among others Synchronous Distance
Education, Asynchronous Distance Education, Co-operative Learning etc.The network utilises ISDN
links to connect the users of the ODL services (either trainers or trainees) to a central site. This site is
used to interconnect the users among themselves, and to host the services and any educational
material needed. The ODL services can be offered either over ISDN services or over the Internet
(using TCP/IP services and applications). In the first case the central site utilises a Multipoint Control
Unit (MCU). In the second case the ISDN lines are used to the implement the connections to the
Internet, and the central site utilises a powerful server. Each user may access the ODL service using
an ISDN enabled personal computer. Small groups of users that wish to participate from the same
location can be accommodated using larger displays. The ODL services (and the network that
supports them) are currently being used and evaluated by a variety of organisations and enterprises
including schools, hospitals, vocational training centres, etc. The results of the evaluation will be
used to guide the deployment of the system in full scale.1 aBouras, Christos1 aKapoulas, Vaggelis1 aGkamas, Apostolos1 aTsiatsos, Thrasivoulos  uhttp://telematics.upatras.gr/telematics/publications/odl-services-and-ptts-greek-ptt-case?language=en01305nas a2200169   4500008004100000245009300041210006900134300001500203520065900218100002100877700002300898700001900921700001400940700001600954700001500970856015000985       1999                        eng d00aOn-Demand Hypermedia/Mutimedia Service using Pre-Orcestrated Scenarios over the Internet0 aOnDemand HypermediaMutimedia Service using PreOrcestrated Scenar  a 741 - 7623 aIn this paper we present a unified approach for delivering hypermedia/multimedia
objects over broadband networks. The described service consists of several multimedia servers
and a set of functions that intend to present to the end user interactive information in real-time.
The hypermedia documents are structured using a hypermedia markup language that keeps information
of the spatiotemporal relationships among document’s media components. In order to
deal with the variant network behavior, buffering manipulation mechanisms and grading of the
transmitted media quality techniques are proposed to smooth presentation and synchronization
anomalies.1 aBouras, Christos1 aKapoulas, Vaggelis1 aSpirakis, Paul1 aMoiras, D1 aOuzounis, V1 aTatakis, A  uhttp://telematics.upatras.gr/telematics/publications/demand-hypermediamutimedia-service-using-pre-orcestrated-scenarios-over-internet?language=en02397nas a2200145   4500008004100000245004500041210004400086260001800130300001300148520193000161100002102091700002302112700001502135856010102150       1999                        eng d00aTele-working services from the Greek PTT0 aTeleworking services from the Greek PTT  c18 - 19 March  a 17 - 223 aDuring the last years tele-working methods that utilise network resources and
services are gaining wide acceptance. Interestingly enough not all the enterprises
that want to and can use tele-working are doing so. The main obstacles in adopting
and implementing tele-working techniques are lack of technical knowledge, poor
infrastructure, and lack of support. In Greece the main PTT organisation, as part of
its strategy to offer integrated Telematic services in various areas, designed and is
currently testing under several tele-working scenarios various services that will be
offered in suitable packages. The services offered include telephony services, basic
and advanced network services etc. The packages to be offered cover a wide area of
tele-workers, including tele-workers from home, mobile tele-workers, telecommuters
etc. The packages also cover the need to establish suitable infrastructure
for the tele-workers in the enterprise’s premises, and the establishment of
telecentres/telecottages or satellite centres.In order to effectively test all the
proposed services a pilot network has been established. The network is based on
ISDN links and it consists of a few central nodes (i.e. representing enterprises’
premises) and several remote nodes (some of them mobile) representing for the teleworkers.
The central nodes are equipped with an ISDN PBX, an enterprise server,
and a router. These nodes are connected to the public ISDN network via a few
Primary Rate Interface (PRI) ISDN links. The tele-workers’ nodes are equipped
with communication devices, such as telephones and facsimiles, and with personal
computers. The nodes are connected to the public ISDN network via one or a few
Basic Rate Interface (BRI) ISDN links. The initial tests show very promising
results. The offered integrated services are easy to use and very reliable. As a
consequence the tele-workers exhibit improved performance.1 aBouras, Christos1 aKapoulas, Vaggelis1 aMamalis, B  uhttp://telematics.upatras.gr/telematics/publications/tele-working-services-greek-ptt?language=en01886nas a2200313   4500008004100000245002100041210001900062260002000081300001300101520110300114100002101217700002301238700002001261700002201281700001401303700001101317700001501328700001301343700001301356700001601369700001301385700001401398700001601412700001301428700001401441700001401455700001901469856008401488       1999                        eng d00aToday's Stories 0 aTodays Stories  c22 - 24 October  a 88 - 943 aResearch frameworks are being developed that involve very
young children in the process of development of future technologies. Children,
their teachers and parents from schools in Israel and Denmark are coming together
with researchers, educationalists, psychologists, designers and technologists
to develop a wearable technology for educational use- the KidsCam.
This example of a hyper-camera will facilitate and support the development of
social, communicative and emotional skills in the context of the everyday activities
of children. It is envisioned that such digital technology will become
embedded in educational culture and create opportunities for shared reflection
on early life experiences. Integral to the work is the development of an ethically
theorized and ethically led practical framework to consider the issues that
surround the development and deployment of new technology by and for children.
These will include issues of appropriateness, need and value. A series of
interactive presentations will be used to illustrate both the work in progress
and the vision of the project.1 aBouras, Christos1 aKapoulas, Vaggelis1 aKonidaris, Agis1 aSevasti, Afroditi1 aPanayi, M1 aRoy, D1 aBernsen, N1 aVelde, W1 aKlaff, J1 aCakmakci, O1 aPaepe, K1 aLassbo, G1 aHakvoort, I1 aBeach, D1 aBarlev, Y1 aAviram, A1 aNeofotistos, G  uhttp://telematics.upatras.gr/telematics/publications/todays-stories?language=en01094nas a2200145   4500008004100000245008700041210006900128260002000197300001500217520051700232100002100749700002000770700002200790856013600812       1999                        eng d00aThe transition from contemporary to virtual user interfaces for Web-based Services0 atransition from contemporary to virtual user interfaces for Webb  c25 - 30 October  a 125 - 1303 aComputer and Internet based services are increasingly provided to users in our
days. The users are also increasing exponentially and it is obvious that they are not
experienced in the use of computers. This paper examines the problem of user friendly web
based service interfaces and proposes a new kind of interface. This interface is called a
Virtual Interface and is thoroughly presented. The Virtual Interface is compared to
contemporary User Interfaces and the results of this comparison are also presented.1 aBouras, Christos1 aKonidaris, Agis1 aSevasti, Afroditi  uhttp://telematics.upatras.gr/telematics/publications/transition-contemporary-virtual-user-interfaces-web-based-services?language=en01443nas a2200181   4500008004100000245003200041210003100073260001600104300001700120520092200137100002101059700002301080700001401103700001501117700001301132700001901145856009701164       1999                        eng d00aVirtual European School-VES0 aVirtual European SchoolVES  c7 - 11 June  a 1055 - 10573 aThe Virtual European School (VES) is an ongoing
European project - funded by the Educational Multimedia
Task Force Initiative of the European Union - with the
aim to develop a comprehensive on-line resource of
teaching material for secondary school education. The
system will be fed by a group of smaller publishing houses
from different European countries (Austria, Italy, Greece,
Great Britain) specialised in educational material. The
offer will contain multimedia material, CBT products, and
also additional background materials, such as passages
from schoolbooks, or Internet resources. The technical
structure of the VES system will be based on Internet
technologies, with interconnected VES servers in each
participating region. The multimedia material will be
stored in a database, with multi-lingual annotations for
each project. There exist three user groups within the
VES: publishers, teachers and pupils.1 aBouras, Christos1 aKapoulas, Vaggelis1 aKoubek, A1 aFotakis, D1 aMayer, H1 aRehatscheck, H  uhttp://telematics.upatras.gr/telematics/publications/virtual-european-school-ves?language=en01165nas a2200145   4500008004100000245009900041210006900140260002000209300001500229520055400244100002100798700002200819700002700841856015100868       1999                        eng d00aA Web-based distributed environment to support teleteaching: Design and Implementations issues0 aWebbased distributed environment to support teleteaching Design   c1 - 2 September  a 906 - 9113 aWeb based systems have been shown to be useful tools
for supporting educational communication for teachers
and students. In this paper we present such a system,
which is an Integrated Distributed Learning Environment
(IDLE). We present the technical description of this IDLE
and we discuss its main characteristics like the
transmission of multimedia data over the network, the
manipulation of the educational procedure and the
management of the users. In addition we list the
functionalities of the IDLE and also discuss some
implementation issues.1 aBouras, Christos1 aGkamas, Apostolos1 aTsiatsos, Thrasivoulos  uhttp://telematics.upatras.gr/telematics/publications/web-based-distributed-environment-support-teleteaching-design-and-implementations?language=en01358nas a2200157   4500008004100000245007200041210006900113260002000182300001700202520078500219100002101004700002001025700001501045700001301060856012701073       1999                        eng d00aA Web-enabled Communication Environment for the Education Community0 aWebenabled Communication Environment for the Education Community  c25 - 30 October  a 1198 - 11993 aThe research and development of computer-based, networked learning
environments will be built around electronic communication and collaboration services that
will play a significant role in the improvement of the learning procedure. Applications of this
kind provide tutors and trainees with the ability of continual, close and efficient cooperation,
en masse as well as individually. The goal of this work is the presentation of a communication
environment that was developed in the framework of Odysseas project. The flexible design
and implementation of basic communication services, accompanied with a friendly user
interface, comprise an ergonomic environment and ensure the introduction of information
technology in education as a daily communication and collaboration tool.1 aBouras, Christos1 aKontogiannis, S1 aBazaios, A1 aZoura, A  uhttp://telematics.upatras.gr/telematics/publications/web-enabled-communication-environment-education-community?language=en01364nas a2200145   4500008004100000245012000041210006900161300001500230520073200245100002100977700001900998700002701017700001901044856015501063       1998                        eng d00aAnalytical Performance Models for Multistage Interconnection Networks with finite, infinite and zero length buffers0 aAnalytical Performance Models for Multistage Interconnection Net  a 169 - 1823 aMultistage Interconnection Networks (MINs) with crossbar switches have been used
to interconnect processors and memory modules in parallel multiprocessor systems.
They also play an increasingly important role in the development of ATM networks.
In this paper we analyze the general case of MINs, made of kxk switches with
finite, infinite or zero length buffers (unbuffered). The exact solution of the steady
state distribution of the first stage is derived for all cases. We use this to get an
approximation for the steady state distributions in the second stage and beyond. In
the case of unbuffered switches we reach the known exact solution for all the stages
of the MIN. Our results are validated by extensive simulations.1 aBouras, Christos1 aSpirakis, Paul1 aTriantafillou, Vasilis1 aGarofalakis, J  uhttp://telematics.upatras.gr/telematics/publications/analytical-performance-models-multistage-interconnection-networks-finite-infinite-and?language=en00916nas a2200145   4500008004100000245007300041210006900114260002100183300001500204520036300219100002100582700001900603700001600622856013200638       1998                        eng d00aOn Demand Delivery of Multimedia Documents using Distributed Objects0 aDemand Delivery of Multimedia Documents using Distributed Object  c14 - 16 December  a 357 - 3603 aIn this paper, we propose an architecture for the ondemand
delivery of multimedia documents over
broadband networks using distributed objects. The basic
components of our model are the network agents and the
presentation agents. Our model preserves flexibility,
transparency and modularity and value added opportunity
due to the usage of distributed objects.1 aBouras, Christos1 aSpirakis, Paul1 aOuzounis, V  uhttp://telematics.upatras.gr/telematics/publications/demand-delivery-multimedia-documents-using-distributed-objects?language=en01196nas a2200145   4500008004100000245005600041210005400097260002100151300001500172520069200187100002100879700001900900700001500919856011600934       1998                        eng d00aA Distributed Virtual Learning Center in Cyberspace0 aDistributed Virtual Learning Center in Cyberspace  c18 - 20 November  a 410 - 4153 aIn this paper, we present a user-friendly 3D Distributed Virtual
Environment (DVE) that would be used for on-line access to educational multimedia
material over the Internet. We design and develop this application and the
corresponding Graphical User Interface (GUI) in the framework of the European
project “Virtual European School” (VES) whose aim is to develop a comprehensive
resource of teaching material for secondary school education and to provide access
to this material over Internet. It is a web-based application that is being developed as
a client/server architecture using standard protocols and technologies such as
TCP/IP, HTTP, HTML, Java and appropriate 3D formats.1 aBouras, Christos1 aPhilopoulos, A1 aFotakis, D  uhttp://telematics.upatras.gr/telematics/publications/distributed-virtual-learning-center-cyberspace?language=en01446nas a2200133   4500008004100000245007700041210006900118260001700187300001500204520091500219100002101134700001901155856013801174       1998                        eng d00aDistributed Virtual Reality Environments Over Web for Distance Education0 aDistributed Virtual Reality Environments Over Web for Distance E  c24 - 26 June  a 481 - 4843 aVirtual Environments for education have been discussed in various ways. While advanced multi-user
educational VEs are still speculation, simpler VEs based on standard technologies have been in
existence for some time. On the other hand, there is a great enthusiasm for promoting Virtual Reality
as a major factor in future (and present) environments for training and education. In this paper, we
discuss the concept of the Distributed Virtual Environments and the use of them in distance education
applications. Next, we consider VRML technology as the key technology for building such
environments and we present the basic features and functionalities of it that make it suitable for
delivering VEs over the Web. In addition to this, we present some of the roles of VRML in education.
Finally, we conclude with some recommendations on the construction of Virtual Reality
Environments for educational purposes.1 aBouras, Christos1 aPhilopoulos, A  uhttp://telematics.upatras.gr/telematics/publications/distributed-virtual-reality-environments-over-web-distance-education?language=en01612nas a2200157   4500008004100000245010900041210006900150260002000219300001500239520097100254100002101225700002301246700001401269700001601283856015501299       1998                        eng d00aA Framework for a Distributed Information Service Using Hypermedia/Multimedia Pre-Orchestrated Scenarios0 aFramework for a Distributed Information Service Using Hypermedia  c28 - 31 October  a 226 - 2293 aReal time delivery of multimedia objects based on preorchestrated
scenarios, seems to have several difficulties
due to presentation deadlines that should be satisfied, and
network’s unpredictable behavior which may lead to synchronization
anomalies among related media streams. Beyond
these, a structural model that represents such scenarios
is required. In this paper, we present a general framework
that addresses the above mentioned issues, and we
attempt to describe a unified approach for delivering hypermedia/
multimedia objects over network connections
preserving their timing constraints. We mainly concentrate
on the study and development of a markup language that
models the presentational structure of a multimedia object
and provides primitives that assure playout synchronization
of the different media streams that compose these
hypermedia objects. Methods for keeping a constant quality
level of presentation in times of network load are discussed.1 aBouras, Christos1 aKapoulas, Vaggelis1 aMoiras, D1 aOuzounis, V  uhttp://telematics.upatras.gr/telematics/publications/framework-distributed-information-service-using-hypermediamultimedia-pre-orchestrated?language=en01193nas a2200169   4500008004100000245010000041210006900141260001100210520054100221100002100762700002300783700001900806700001400825700001600839700001500855856015300870       1998                        eng d00aImplementing spatio-temporal relations for hypermedia presentations using an HTML-like language0 aImplementing spatiotemporal relations for hypermedia presentatio  c13 May3 aHypermedia is currently the trend in delivering information composed of various
forms of media. Up to now most systems lack the ability to present the user with
hypermedia information containing various media that have specific spatio-temporal
relations. In this paper we propose and describe a model that can describe such kinds
of hypermedia presentations. The core of the model is an HTML-like language that
supports tags for the description of timing relations between the information objects
that compose a hypermedia presentation.1 aBouras, Christos1 aKapoulas, Vaggelis1 aSpirakis, Paul1 aMoiras, D1 aOuzounis, V1 aTatakis, A  uhttp://telematics.upatras.gr/telematics/publications/implementing-spatio-temporal-relations-hypermedia-presentations-using-html-language?language=en01237nas a2200181   4500008004100000245009800041210006900139260002000208300001500228520054100243100002100784700002700805700001700832700001900849700001400868700001700882856015600899       1998                        eng d00aAn Intranet and Internet based Information System for Administration and Information purposes0 aIntranet and Internet based Information System for Administratio  c29 - 30 October  a 211 - 2153 aThis work presents a system developed within a project funded by the Greek Government.
The system deals with the distribution of information and the exchange of documents within,
from and towards (region, municipalities, citizens, various groups etc.) the prefecture of
Corfu. It is exploiting Intranet and Extranet technologies in order to enable asynchronous
and synchronous cooperation, manipulation of information from heterogeneous sources,
security and easy administration, providing in parallel advanced communication facilities.1 aBouras, Christos1 aTriantafillou, Vasilis1 aDestounis, P1 aGarofalakis, J1 aTzimas, J1 aZarafidis, P  uhttp://telematics.upatras.gr/telematics/publications/intranet-and-internet-based-information-system-administration-and-information-purposes?language=en01420nas a2200181   4500008004100000245007300041210006900114260002000183300001500203520075500218100001900973700001900992700002701011700002901038700001501067700001801082856013801100       1998                        eng d00aMRP II-based Production Management Using Intelligent Decision Making0 aMRP IIbased Production Management Using Intelligent Decision Mak  bSpringer Verlag  a 379 - 4123 a<p>This paper presents an extended MRP II-based production management system (PMS), which improves the traditional MRP II paradigm by attaching an intelligent decision supporting system (IDSS) to it. The IDSS is attached to the lowest level of the PMS, namely the production activity control (PAC) subsystem, and includes a simulator, that imitates real system behaviour, a knowledge-based component, that imitates expert reasoning, and a real-time database manager, that acts as the data pool and the communication gate between them. The IDSS is capable of performing off-line and on-line rescheduling, thus resulting in more realistic short-term plans. Analysis of the related case problem and implementation of the system are also discussed.</p>
1 aSofotassios, D1 aSpirakis, Paul1 aTriantafillou, Vasilis1 aHatzilygeroudis, Ioannis1 aDendris, N1 aTsakalidis, A  uhttp://telematics.upatras.gr/telematics/publications/mrp-ii-based-production-management-using-intelligent-decision-making?language=en01568nas a2200181   4500008004100000245008300041210006900124260001700193300001500210520091300225100002101138700001901159700001501178700001701193700001501210700001301225856014801238       1998                        eng d00aMultimedia Architecture offering Open Distance Learning Services over Internet0 aMultimedia Architecture offering Open Distance Learning Services  c22 - 25 June  a 145 - 1493 aThe increase in the use of the Internet not only as a
repository of resources for learning but also as a
means for the delivery of courses and specially
prepared teaching material is a particularly
significant innovation in the range of education.
The main concept here is a Virtual class, which is
based on the principles of CSCL (Computer
Supported Collaborative Learning) systems. This
paper describes an integrated, WWW based
platform for the development of web enabled
environments over TCP/IP networks, such as
Internet. This platform is designated through a
Teletraining and Collaborative Learning
Application. The proposed platform aspires to be
an efficient solution for a group of students and
teachers that need a shared workspace, supporting
remote interactive lectures, flexible exchange of
teaching material and various communication
utilities, with focus on transparent and secure
interaction.1 aBouras, Christos1 aSpirakis, Paul1 aLampsas, P1 aZarafidis, P1 aBazaios, A1 aZoura, A  uhttp://telematics.upatras.gr/telematics/publications/multimedia-architecture-offering-open-distance-learning-services-over-internet?language=en01209nas a2200169   4500008004100000245008000041210006900121260002800190300001500218520057600233100002100809700002300830700002200853700002700875700001500902856012200917       1998                        eng d00aA platform for the implementation of the services of an Educational Network0 aplatform for the implementation of the services of an Educationa  c31 August - 4 September  a 159 - 1693 aMultimedia and hypermedia had and still have a tremendous impact on the evolution of educational
software. In this paper we propose a platform for the implementation of the services of an
educational network over TCP/IP networks such as the Internet. Our proposal aims at providing an
integrated communicational environment which supplies the communicative needs of one
educational community, using the latest telecommunication and multimedia information processing
technology. We propose various kinds of communication forms for the interaction between the
participants.1 aBouras, Christos1 aKapoulas, Vaggelis1 aGkamas, Apostolos1 aTsiatsos, Thrasivoulos1 aLampsas, P  uhttp://telematics.upatras.gr/telematics/publications/platform-implementation-services-educational-network?language=en02201nas a2200193   4500008004100000245014800041210006900189300001300258520143500271100002101706700001901727700001501746700002201761700001901783700001501802700001401817700002001831856015601851       1998                        eng d00aResults and experience from the application of a common methodology for Users Requirements Specification in Distance Education using Telematics0 aResults and experience from the application of a common methodol  a 61 - 743 aThe cooperation of the Information and Communications Technologies (ICT) and the Educational communities, is
recognised as a necessity that must result in the adaptation and tuning of the education processes in terms of
pedagogical methodologies, school infrastructure, human resources development and organisational restructuring, in
order to efficiently absorb and utilize technological developments. The ICT community has to realize the significance
of the users’ needs, the difficulties of the intervention to an old and traditional process. And the need to view their
technology applications not only as a technical exercise. The initial phases of the TRENDS project, which are
described in this paper, resulted in an agreed common methodology for carrying out the necessary investigation of
the user needs in secondary education. This methodology, which was followed more or less in all participating
countries, produced answers to questions concerning the role of the educators and their basic training, their
familiarity with technology, education policies from a trans-European perspective, the content, forms and aims of
further training, the distance training of teachers in the use of new technologies, the motives, incentives and
organisational schemes for enhancing re-education, the needs of the educational environment and technology-based
training, the needs of the educators in practical didactic methods, etc.1 aBouras, Christos1 aSpirakis, Paul1 aLampsas, P1 aTsakarissianos, G1 aGarofalakis, J1 aAntonis, K1 aKastis, N1 aKontogiannis, S  uhttp://telematics.upatras.gr/telematics/publications/results-and-experience-application-common-methodology-users-requirements-specification?language=en01286nas a2200145   4500008004100000245011800041210006900159260001800228300001500246520066700261100002100928700001900949700001500968856015700983       1998                        eng d00aTraining Centres: An Architecture for the Realisation of Open and Distance Learning Environments using Telematics0 aTraining Centres An Architecture for the Realisation of Open and  c10 - 14 March  a 118 - 1203 aIn this paper, we are describing an architecture for the realisation of Open and Distance
Learning (ODL) Environments using Telematics. The approach of using Training Centres as
dedicated education services providers, located at the premises of an educational authority is
discussed. These Training Centres may be Points of Presence of an international educational network
(as is the case in the TRENDS Project in the context of which Training Centres were studied).
Crucial aspects of the feasibility study, aiming to investigate the operational and organisational
conditions of the Centres, that must precede the implementation of a Training Centre, are cited.1 aBouras, Christos1 aSpirakis, Paul1 aLampsas, P  uhttp://telematics.upatras.gr/telematics/publications/training-centres-architecture-realisation-open-and-distance-learning-environments-using?language=en01030nas a2200157   4500008004100000245004700041210004600088260002000134300001300154520052500167100002100692700001500713700001500728700001700743856011200760       1998                        eng d00aWeb-Enabled Distance Education Environment0 aWebEnabled Distance Education Environment  c7 - 12 November  a 80 - 853 aAs the new network computer technology forces into every aspect of daily life,
many things change in a rather rapid way, compared to what we were used to until recently.
One of the most important aspects in the social activity of people, Education, could not be an
exception. Advances in network infrastructures and telematics services, combined with
multimedia techniques and powerful personal computers provide the opportunity to make a
network-based multimedia system for distance learning (teletraining) a real fact.1 aBouras, Christos1 aLampsas, P1 aBazaios, A1 aTsindilas, G  uhttp://telematics.upatras.gr/telematics/publications/web-enabled-distance-education-environment?language=en01004nas a2200157   4500008004100000245006300041210006200104260002000166300001500186520045100201100002100652700001500673700001700688700001300705856012800718       1998                        eng d00aWeb-Enabled Distributed Collaborative Learning Environment0 aWebEnabled Distributed Collaborative Learning Environment  c14 - 17 October  a 489 - 4933 aThis paper describes, in design, architecture and implementation
level, a web based environment for co-operative teleworking and
collaborative learning over TCP/IP networks, such as Internet. The
implemented tool claims to be an efficient solution for a group of
users/students that need a shared workspace containing various
communication utilities, including on-line and off-line communication,
with focus on transparent and secure interaction.1 aBouras, Christos1 aLampsas, P1 aZarafidis, P1 aZoura, A  uhttp://telematics.upatras.gr/telematics/publications/web-enabled-distributed-collaborative-learning-environment?language=en01488nas a2200145   4500008004100000245006200041210006200103260001700165520096100182100002101143700002301164700001901187700001601206856012001222       1997                        eng d00aCompetitive Video on Demand Schedulers for Popular Movies0 aCompetitive Video on Demand Schedulers for Popular Movies  c11 - 12 July3 a<p>In this paper we investigate the online video on demand problem, namely having to accept or reject a request for a movie without knowing the future requests. We present online movie-scheduling schemes that implement the principles of refusal by choice and delayed notication. A novel way to schedule movies that exploits the knowledge of the distribution of the preference of requests for movies, is shown to have a competitive ratio that outperforms all the previously known schemes in practical situations. In fact, our scheduler has a competitive ratio bounded above by a constant, independent of the number of the users, channels, or movies, in the case that a large fraction of the requests tends to concentrate in a small number of movies. We extend our approach by presenting an \adaptive" randomized scheduler which initially is not aware of the movie popularities but it adapts to it, and achieves a similar asymptotic competitive ratio.</p>
1 aBouras, Christos1 aKapoulas, Vaggelis1 aSpirakis, Paul1 aPantziou, G  uhttp://telematics.upatras.gr/telematics/publications/competitive-video-demand-schedulers-popular-movies?language=en01631nas a2200205   4500008004100000245010300041210006900144260001700213300001300230520089300243100002101136700001901157700001501176700002201191700001901213700001501232700001401247700002001261856014401281       1997                        eng d00aConclusions on the Analysis of User Requirements concerning the use of ICT in the Didactic Process0 aConclusions on the Analysis of User Requirements concerning the   c14 - 19 June  a 13 - 183 aThe co-operation of the Information and Communications Technologies (ICT)
and the Educational Society, is deemed necessary for the adaptation and tuning of the
didactic process in terms of pedagogical methodologies, school infrastructure, human
resources utilisation and organisational restructuring. The use of ICT in the classroom
should be viewed as a highly influencing tool that will support the educators’ effort for
interaction with their students, rather than as a technical exercise. The initial phases of the
TRENDS project, which are described in this paper, resulted in a widely accepted common
methodology, that complies with the international standards for determining the User
Requirements in the Secondary Education. The major results emerged from this survey are
presented here, as well as some common axes that deal with the application of ICT in the
didactic process.1 aBouras, Christos1 aSpirakis, Paul1 aLampsas, P1 aTsakarissianos, G1 aGarofalakis, J1 aAntonis, K1 aKastis, N1 aKontogiannis, S  uhttp://telematics.upatras.gr/telematics/publications/conclusions-analysis-user-requirements-concerning-use-ict-didactic-process?language=en01843nas a2200241   4500008004100000245010200041210006900143260001900212300001500231520099200246100002101238700001901259700002701278700001901305700001701324700001401341700001801355700001601373700002401389700001801413700001401431856015601445       1997                        eng d00aThe Design and Development of Advanced Network Services over the Patras University Campus Network0 aDesign and Development of Advanced Network Services over the Pat  c2 - 6 December  a 420 - 4273 aThis paper presents some results of the initial phases of a big internal
project running at the University of Patras. In this project - which is co-funded by the
European Union - our team is responsible for the development of the Advanced
Network Services over the Campus Network, which is being established during the
project. In the following chapters we first present the general perspective and the
architecture of the integrated system which offers the set of advanced services to the
University community. We then describe in detail the different services (WWW and
Intranet, On-line teletraining, Computer supported cooperative work, and Off-line
teletraining). A key characteristic of the system is the integration of existing
commercial tools, with tools that we are developing for the specific needs of the
foreseen users. It is evident that this system can be considered as a pilot project for
large and demanding user communities, as is the case with the University of Patras.1 aBouras, Christos1 aSpirakis, Paul1 aTriantafillou, Vasilis1 aGarofalakis, J1 aTsaknakis, J1 aTzimas, J1 aTsakalidis, A1 aAntoniou, I1 aKarageorgopoylos, D1 aBasiliadis, B1 aKappos, P  uhttp://telematics.upatras.gr/telematics/publications/design-and-development-advanced-network-services-over-patras-university-campus-network?language=en01241nas a2200145   4500008004100000245005600041210005600097260002800153520072600181100002100907700001900928700001500947700001600962856011700978       1997                        eng d00aEnabling Distance Education over the World Wide Web0 aEnabling Distance Education over the World Wide Web  c31 Octiber - 5 November3 aThe recent advancements in the field of the information and communication technology
resulted in a revolution comparable to the industrial revolution. The basis of this revolution
is the information and the value it has as the pure expression of human knowledge. The
technological advancements offer us the ability to process, store, retrieve and transmit
information in multiple formats (text, sound, image, video) independently of time, volume
and distance. In this paper we present the technology that is required and an architecture for
the realization of distance education over the World Wide Web. We also address some basic
aspects of the users’ needs that every software tool for distance education should meet.1 aBouras, Christos1 aSpirakis, Paul1 aLampsas, P1 aAntoniou, I  uhttp://telematics.upatras.gr/telematics/publications/enabling-distance-education-over-world-wide-web?language=en01295nas a2200157   4500008004100000245007200041210006900113260001900182300001600201520070300217100002100920700001900941700002700960700001900987856013101006       1997                        eng d00aA General Performance Model for Multistage Interconnection Networks0 aGeneral Performance Model for Multistage Interconnection Network  c25 - 29 August  a 993 - 10003 aMultistage Interconnection Networks (MINs) with crossbar
switches are used to interconnect processors and memory modules in
parallel multiprocessor systems. In this paper we analyze the general case
of MINs, made of kk switches with nite, innite or zero length buers
(unbuered). The exact solution of the steady state distribution of the
rst stage is derived for all cases. We use this to get an approximation
for the steady state distributions in the second stage and beyond. In the
case of unbuered switches we reach the known exact solution for all the
stages of the MIN. Our results are validated by extensive simulations.
Keywords: analytical models, queueing theory models, evaluation.1 aBouras, Christos1 aSpirakis, Paul1 aTriantafillou, Vasilis1 aGarofalakis, J  uhttp://telematics.upatras.gr/telematics/publications/general-performance-model-multistage-interconnection-networks?language=en01559nas a2200193   4500008004100000245007400041210006900115260001600184300001300200520088400213100002101097700002301118700001901141700001401160700001601174700001601190700002401206856013501230       1997                        eng d00aHermes Service: Distributed Hypermedia Educational Services on Demand0 aHermes Service Distributed Hypermedia Educational Services on De  c14 - 19 Jne  a 19 - 243 aIn this paper we present a distributed HypERMEdia SERVICE
(HERMES SERVICE) which supports integrated capabilities for distance
education and learning purposes. Hermes service consists of hermes servers
and hermes browsers. The users are connected with the service using hermes
browsers and retrieve hypermedia lessons organised in thematical units. The
lessons are stored in various distributed Hermes servers which retrieve the
requested lesson and transmit it to the corresponding browser on on-demand
basis. The requested lesson is presented to the user according to a well defined
presentation scenario. The media objects are rendered in a synchronized
manner according to the spatio-temporal relationships existing among them.
Finally, special monitoring mechanism controls the state of the network and
adjusts the presentation process so as to improve presentation quality.1 aBouras, Christos1 aKapoulas, Vaggelis1 aSpirakis, Paul1 aMoiras, D1 aOuzounis, V1 aAntoniou, I1 aKarageorgopoylos, D  uhttp://telematics.upatras.gr/telematics/publications/hermes-service-distributed-hypermedia-educational-services-demand?language=en00549nas a2200133   4500008004100000245007800041210006900119260001700188100002100205700002300226700001900249700001500268856013200283       1997                        eng d00aAn HTML like language supporting time-depended transmission of hypermedia0 aHTML like language supporting timedepended transmission of hyper  c6 - 11 April1 aBouras, Christos1 aKapoulas, Vaggelis1 aSpirakis, Paul1 aTatakis, A  uhttp://telematics.upatras.gr/telematics/publications/html-language-supporting-time-depended-transmission-hypermedia?language=en01071nas a2200169   4500008004100000245006100041210005900102260001700161300001300178520050300191100002100694700001900715700001400734700001600748700001600764856012100780       1997                        eng d00aHY-MOST: HYpermedia MOdel for Synchronised presenTations0 aHYMOST HYpermedia MOdel for Synchronised presenTations  c6 - 11 April  a 18 - 233 aA brief abstract. In this paper we present a new model for
hypermedia presentations. This model is based on an
HTML-like language which provides the necessary modules
for the intermedia synchronisation of the inline media that
comprise the hypermedia document. The model also enables
a distributed approach in the storage of the hypermedia
documents. Additionally, it is capable of incorporating the
necessary protocols needed for the real-time delivery of
continuous media such as audio and video.1 aBouras, Christos1 aSpirakis, Paul1 aMoiras, D1 aOuzounis, V1 aAntoniou, I  uhttp://telematics.upatras.gr/telematics/publications/hy-most-hypermedia-model-synchronised-presentations?language=en00576nas a2200133   4500008004100000245009400041210006900135260001600204300001500220100002100235700001900256700001500275856015200290       1997                        eng d00aIn-Service Training through ODL Environments:From User Needs To Functional Specifications0 aInService Training through ODL EnvironmentsFrom User Needs To Fu  c1 - 5 April  a 519 - 5221 aBouras, Christos1 aSpirakis, Paul1 aLampsas, P  uhttp://telematics.upatras.gr/telematics/publications/service-training-through-odl-environmentsfrom-user-needs-functional-specifications?language=en01925nas a2200193   4500008004100000245006100041210006100102260002200163300001500185520128800200100002101488700002001509700002201529700002001551700001501571700001501586700001701601856011301618       1997                        eng d00aMajor Principles on the Design of an Educational Network0 aMajor Principles on the Design of an Educational Network  c17 - 19 September  a 359 - 3663 aThe modern communication networks, apart from the specialized applications that they
offer depending on the nature of their target groups, they support a set of general purpose elementary
network services, that provide some essential communication facilities to the end users.
Regarding an educational network, these facilities include collaboration, navigation into the
information resources, as well as interpersonal communication, to the members of the Education
Society. In the sequel the major principles on providing these elementary network services are
presented. On-lline/off-line contact over an alternative means of communication among the members
of the trans-European Education Society could be an adequate reason for the deployment of an
educational communication network. This category of services will offer the members of the
Education Society the ability of exchanging opinions on educational and social matters, as well as
interpersonal messages, and collaborating. These facilities should be provided by already existing
network services, enhanced where necessary by supporting multimedia information exchange (mostly
off-line). In the latter case external media players of attachment viewers may be used for the
presentation of the multiple media of information.1 aBouras, Christos1 aKonidaris, Agis1 aSevasti, Afroditi1 aKontogiannis, S1 aFotakis, D1 aKatanou, A1 aStephanou, E  uhttp://telematics.upatras.gr/telematics/publications/major-principles-design-educational-network?language=en01166nas a2200157   4500008004100000245006800041210006700109260001900176520059800195100002100793700001900814700001800833700001500851700001800866856012400884       1997                        eng d00aODYSSEAS: The Greek Educational Network for Secondary Education0 aODYSSEAS The Greek Educational Network for Secondary Education  c5 - 7 November3 aThe purpose of this paper is the description of the project
ODYSSEAS. The aim of the project is the design, development, and
pilot operation of an integrated network of schools in secondary
education in the Greek areas of Achaia, Thrace and Aegean Islands. A
special network infrastructure will be created and network software and
services (containing a WWW server, network software for teaching the
Greek language, applications of administrative support and so on) will
be developed. Training of the teachers and pupils and evaluation of the
project results will be the final project actions.1 aBouras, Christos1 aSpirakis, Paul1 aHatzilakos, A1 aKoutlis, M1 aPanopoulos, N  uhttp://telematics.upatras.gr/telematics/publications/odysseas-greek-educational-network-secondary-education?language=en01156nas a2200121   4500008004100000245007600041210006900117300001500186520065800201100001900859700002700878856012900905       1997                        eng d00aPure greedy Hot-Potato routing in the 2-d mesh with random destinations0 aPure greedy HotPotato routing in the 2d mesh with random destina  a 249 - 2583 aWe analyze here a pure greedy hot-potato routing strategy on a two-dimensional
mesh of n^2 nodes. We specifically study the case of n^
2 packets, originating one per
node, to be delivered at random uniform destinations. Each packet attempts to follow
the shortest path leading first to the destination row/column (whichever is closest) and
then to the actual destination node. A de
ection policy is adopted to solve con
icts. We prove that all packets are delivered to the destinations in average time O(nlogn). The
average is taken over all possible destination functions. No average case analysis of pure
greedy hot-potato routing was known up to now.1 aSpirakis, Paul1 aTriantafillou, Vasilis  uhttp://telematics.upatras.gr/telematics/publications/pure-greedy-hot-potato-routing-2-d-mesh-random-destinations?language=en01712nas a2200145   4500008004100000245004900041210004900090260001700139300001300156520123200169100002101401700001901422700001501441856011001456       1997                        eng d00aSuperhighways for Open and Distance Learning0 aSuperhighways for Open and Distance Learning  c23 - 25 June  a 32 - 363 aAn educational information network, is a multimedia network with a centralized architecture for the
provision of educational services. The educational services comprise basic network applications (such
as multimedia e-mail, fora for debates on educational subjects, access to already existing
information), video distribution of multimedia lessons and a custom developed teletraining tool for
the conduction of lessons over a broadband networking infrastructure.
The suitability of the widely available broadband networking technologies (ATM, ISDN), as opposed
to the alternative of using already existing networking infrastructure (Internet, CATV), for the
implementation of educational networks for the realization of an Open and Distance Learning
Environment will be examined. More specifically the types of educational services that can be best
hosted by each technology and the costs as opposed to the maturity for the deployment of each
networking technology will be cited.
Finally, a proposal for an implementation scheme of an educational information network, concerning
the appropriate (and cost effective) networking infrastructure that can best accommodate the
aforementioned educational services will be elaborated.1 aBouras, Christos1 aSpirakis, Paul1 aLampsas, P  uhttp://telematics.upatras.gr/telematics/publications/superhighways-open-and-distance-learning?language=en01882nas a2200193   4500008004100000245008800041210006900129260001100198300001300209520119000222100002101412700002301433700001901456700001501475700001501490700002001505700001501525856014801540       1997                        eng d00aUsing Multimedia/Hypermedia Tools over Networks for Distance Education and Training0 aUsing MultimediaHypermedia Tools over Networks for Distance Educ  cSummer  a 20 - 263 aThe rapid developments in the Information Technology sector as well as the
deployment of faster networks brings us to the era of the New Information
Technology (NIT). The citizen of the near future must be able to use them else he will
be seriously handicapped in his everyday life. Thus NIT becomes part of the
educational process while on the other hand offers the tools and the infrastructure for
the establishment of the distance education process. The educators are one of the first
professions that must learn to use NIT and its tools. Multimedia/hypermedia tools
offer solutions to the problems posed by the distance education process. They can be
user-friendly and enticing and they can cover most, if not all, the needs of their users.
A lot of prototype systems (tools) for distance education have been developed, each
offering a number of functions that aid the process of distance education. The rapid
growth of World Wide Web is adding another factor that can lead to the wider
deployment of distance education systems. Although the value of distance education
is unquestionable there is still a lot of work to be done before a wide spread
implementation platform emerges.1 aBouras, Christos1 aKapoulas, Vaggelis1 aSpirakis, Paul1 aLampsas, P1 aTatakis, A1 aKontogiannis, S1 aFotakis, D  uhttp://telematics.upatras.gr/telematics/publications/using-multimediahypermedia-tools-over-networks-distance-education-and-training?language=en00744nas a2200205   4500008004100000245008700041210006900128260001700197300001300214100002100227700002300248700001900271700001500290700001500305700001700320700001600337700001900353700002400372856014200396       1996                        eng d00aFINE:Implementation of a Distributed Telematics Environment for Clinical Engineers0 aFINEImplementation of a Distributed Telematics Environment for C  c10 -12 April  a 56 - 601 aBouras, Christos1 aKapoulas, Vaggelis1 aSpirakis, Paul1 aTatakis, A1 aFotakis, D1 aBalaouras, P1 aChadelis, L1 aPalikarakis, N1 aSandalatzopoulos, R  uhttp://telematics.upatras.gr/telematics/publications/fineimplementation-distributed-telematics-environment-clinical-engineers?language=en01376nas a2200205   4500008004100000245007900041210007500120260001700195300001300212520061800225100002100843700002300864700001900887700001500906700001500921700002000936700001500956700001600971856018300987       1996                        eng d00aAn Interactive Cooperative Teleworking Environment-Tηλεµάθεια ∗0 aInteractive Cooperative Teleworking EnvironmentTηλεµάθεια ∗  c17 - 22 June  a 37 - 423 a<p>In this paper we present the design and the implementation of an interactive environment for cooperative teleworking. Telemathea offers tools that support the communication and the teleworking between tutor and trainee, who may reside in remote geographical regions. This environment offers audio communication over the network as well as support for joint editing of text documents and still images. It supports different audio coding techniques so as to adjust to the available bandwidth, and makes use of the RTP protocol in order to facilitate the exchange of audio and, in the future, video packets.</p>
1 aBouras, Christos1 aKapoulas, Vaggelis1 aSpirakis, Paul1 aLampsas, P1 aTatakis, A1 aKontogiannis, S1 aFotakis, D1 aKyriakou, K  uhttp://telematics.upatras.gr/telematics/publications/interactive-cooperative-teleworking-environment-t%CE%B7%CE%BB%CE%B5%C2%B5%CE%AC%CE%B8%CE%B5%CE%B9%CE%B1-%E2%88%97?language=en01637nas a2200181   4500008004100000245006800041210006600109260001800175300001500193520101000208100002101218700002301239700001901262700001401281700001601295700001501311856012901326       1996                        eng d00aOn-Demand Hypermedia/Multimedia Service over Broadband Networks0 aOnDemand HypermediaMultimedia Service over Broadband Networks  c6 - 9  August  a 224 - 2313 aIn this paper we present a unied approach for de-
livering hypermedia/multimedia objects over broadband
networks. Documents are stored in various multimedia
servers, while the inline data may reside in their own
media servers, attached to the multimedia servers. The
described service consists of several multimedia servers
and a set of functions that intend to present to the
end user interactive information in real-time. Users
interact with the service requesting multimedia docu-
ments on demand. Various media streams are trans-
mitted over dierent parallel connections according to
their transmission requirements. The hypermedia doc-
uments are structured using a hypermedia markup lan-
guage that keeps information of the spatiotemporal re-
lationships among document's media components.
In order to deal with the variant network behavior,
buering manipulation mechanisms and grading of the
transmitted media quality techniques are proposed to
smooth presentation and synchronization anomalies.1 aBouras, Christos1 aKapoulas, Vaggelis1 aSpirakis, Paul1 aMoiras, D1 aOuzounis, V1 aTatakis, A  uhttp://telematics.upatras.gr/telematics/publications/demand-hypermediamultimedia-service-over-broadband-networks?language=en01606nas a2200133   4500008004100000245008900041210006900130260001000199300001500209520105800224100002101282700001901303856015001322       1996                        eng d00aPerformance Modeling of Distributed Timestamp Ordering: Perfect and Imperfect Clocks0 aPerformance Modeling of Distributed Timestamp Ordering Perfect a  cApril  a 105 - 1303 aThis work presents a model of a distributed database system which provides the framework to study the performance of timestamp ordering concurrency control. Locking and timestamping are two popular approaches to concurrency control in database systems. Timestamp-based algorithms have been proposed to protect distributed databases from inconsistencies during concurrent access. In these algorithms, transactions may reach a particular site in different order than their timestamps, due to unexpected network delays. This causes conflicts which the distributed concurrency control mechanism has to cope with. We exhibit an analytical solution, which has been tested with extensive simulation. The accuracy seems to be very high. We assume perfect and also imperfect clocks for synchronization and quantify the way in which local clock inaccuracies affect the phenomenon of transaction conflicts. In particular, we derive a lot of interesting performance measures such as probability of abort, mean waiting time, throughput, mean queue length and others.1 aBouras, Christos1 aSpirakis, Paul  uhttp://telematics.upatras.gr/telematics/publications/performance-modeling-distributed-timestamp-ordering-perfect-and-imperfect-clocks?language=en00444nas a2200133   4500008004100000245004000041210004000081300000800121100002100129700002300150700001900173700001600192856010200208       1996                        eng d00aRandomized adaptive video on demand0 aRandomized adaptive video on demand  a1791 aBouras, Christos1 aKapoulas, Vaggelis1 aSpirakis, Paul1 aPantziou, G  uhttp://telematics.upatras.gr/telematics/publications/randomized-adaptive-video-demand?language=en02056nas a2200169   4500008004100000245007200041210006900113260001600182300001500198520143800213100002101651700002301672700001901695700002201714700001401736856013601750       1996                        eng d00aTRENDS: Training Educators through Networks and Distributed Systems0 aTRENDS Training Educators through Networks and Distributed Syste  c8 - 10 July  a 195 - 1993 aThe TRENDS project aims at the in-service, distance training of 2,400 school teachers in Secondary Education,
and the use of Information Technology and Telematics in the learning process, by six countries (Greece, Italy,
Spain, Portugal, France, and United Kingdom). The training process will be implemented by flexible and
distance learning methods, through the development and use of an in-service school-based training system,
which will be based on multimedia telematics and existing mature network technologies, and the establishment
and operation of a European Teacher’s Training Network, consisted of six interconnected National Sites
(Training Centre, schools and teachers per country). Each Training Centre in the Network will act as service
provider to the schools and the teachers. The major aspect of the project is to provide the educator and their
trainers, with various services including : e-mail contact with other educators and trainers, access to multimedia
information, forums for the discussion and debate on educational projects, access to curriculum-related
information for the educators, and multimedia teletraining for the conduction of lessons over the network. Due
to the nature of the planned services and applications, the network infrastructure that will be used for the
realization of the TRENDS, must offer high speed, multicasting, trans-European interoperability and certified
quality of services.1 aBouras, Christos1 aKapoulas, Vaggelis1 aSpirakis, Paul1 aTsakarissianos, G1 aKastis, N  uhttp://telematics.upatras.gr/telematics/publications/trends-training-educators-through-networks-and-distributed-systems?language=en01746nas a2200193   4500008004100000245005800041210005700099260001700156300001500173520111800188100002101306700002301327700001901350700001501369700001501384700001501399700002201414856011601436       1995                        eng d00aHIPPOCRATES: A multimedia tool for distance education0 aHIPPOCRATES A multimedia tool for distance education  c17 - 21 June  a 103 - 1083 aIn this paper we present a software tool for the realisation of the distance education
service, that is the conduction of classes through the use of computers. The classes
are directed towards personnel in various areas and aim at the retraining and update
of the personnel in subjects of special interest in their line of work. The conduction of
classes takes place, from and towards, remote regions with the aid of a computer network.
Hippocrates is a flexible and easy-to-use application, which permits students, who sit in
front of remotely situated workstations, to attend classes or seminars given by a teacher
or expert, who can also be located in some remote geographical area. Hippocrates can be
thought of as a distributed transparency projector. The teacher can project transparencies
on the screens of the students’ workstations and can emphasize or indicate regions of
interest on them by using the graphical tools offered by Hippocrates. Immediate results
of the use of Hippocrates are the fast updating of the personnel in remote areas and the
upgrading of the quality of the services they offer.1 aBouras, Christos1 aKapoulas, Vaggelis1 aSpirakis, Paul1 aLampsas, P1 aTatakis, A1 aFotakis, D1 aPapoutsopoulos, G  uhttp://telematics.upatras.gr/telematics/publications/hippocrates-multimedia-tool-distance-education?language=en00981nas a2200193   4500008004100000245005300041210005300094260002800147300001500175520035400190100002100544700002300565700001900588700001500607700001500622700002000637700001500657856011500672       1995                        eng d00aMultilingual Implementations of OSI Applications0 aMultilingual Implementations of OSI Applications  c30 October - 1 November  a 367 - 3743 aIn this work the problem of supporting multilingual environments over
OSI applications is addressed. Initially a solution based on the idea of using
multilingual structures and transcription techniques is presented. Another
solution based on the major principles of the former follows, which exploits
the coding of all of character sets uniformally.1 aBouras, Christos1 aKapoulas, Vaggelis1 aSpirakis, Paul1 aLampsas, P1 aTatakis, A1 aKontogiannis, S1 aFotakis, D  uhttp://telematics.upatras.gr/telematics/publications/multilingual-implementations-osi-applications?language=en00468nas a2200097   4500008004100000245008000041210006900121100002300190700001900213856013800232       1995                        eng d00aRandomized Competitive Algorithms for Admission Control in General Networks0 aRandomized Competitive Algorithms for Admission Control in Gener1 aKapoulas, Vaggelis1 aSpirakis, Paul  uhttp://telematics.upatras.gr/telematics/publications/randomized-competitive-algorithms-admission-control-general-networks?language=en00455nam a2200121   4500008004100000245004900041210004800090100002100138700002300159700001900182700001900201856011300220       1994                        eng d00aDiscrete Mathematics: Problems and Solutions0 aDiscrete Mathematics Problems and Solutions1 aBouras, Christos1 aKirousis, Lefteris1 aSpirakis, Paul1 aVoutsadakis, G  uhttp://telematics.upatras.gr/telematics/publications/discrete-mathematics-problems-and-solutions?language=en01483nas a2200133   4500008004100000245012300041210006900164260001600233300001500249520089200264100002101156700001901177856015301196       1993                        eng d00aThe perfect and imperfect clocks approach to performance analysis of basic timestamp ordering in distributed databases0 aperfect and imperfect clocks approach to performance analysis of  c27 - 29 May  a 403 - 4073 aLocking and timestamping are two popular approaches
to concurrency control in databases systems.
Although more than a dozen analytic performance
studies of locking techniques have recently appeared
in the literature, analytic performance study
of timestamp–based concurrency algorithms largely remains
an unexplored area. This work presents a model
of a distributed database system which provides the
framework to study the performance of timestamp ordering
concurrency control. We exhibit an analytical
solution, which has been tested with extensive simulation.
The accuracy seems to be very high. We assume
perfect and also imperfect clocks for synchronization
and quantify the way in which local clock inaccuracies
affect the phenomenon of transaction conflicts. In
particular, we derive a lot of interesting performance
measures such as probability of abort, throughput and
others.1 aBouras, Christos1 aSpirakis, Paul  uhttp://telematics.upatras.gr/telematics/publications/perfect-and-imperfect-clocks-approach-performance-analysis-basic-timestamp-ordering?language=en01018nas a2200133   4500008004100000245010300041210006900144260002000213300001500233520044800248100002100696700001900717856014800736       1993                        eng d00aPerformance Models for Perfect and Imperfect Clocks on Timestamp Ordering in Distributed Databases0 aPerformance Models for Perfect and Imperfect Clocks on Timestamp  c17 - 20 January  a 243 - 2463 aThis work presents a model of a distributed
database system which provides the framework to
study the performance of timestamp ordering concurrency
control. We exhibit an analytical solution, which
has been tested with extensive simulation. The accuracy
seems to be very high. We assume perfect and
also imperfect clocks for synchronization and quantify
the way in which local clock inaccuracies affect the
phenomenon of transaction conflicts.1 aBouras, Christos1 aSpirakis, Paul  uhttp://telematics.upatras.gr/telematics/publications/performance-models-perfect-and-imperfect-clocks-timestamp-ordering-distributed?language=en00354nam a2200109   4500008004100000245002500041210002500066100002100091700002300112700001900135856009000154       1992                        eng d00aDiscrete Mathematics0 aDiscrete Mathematics1 aBouras, Christos1 aKirousis, Lefteris1 aSpirakis, Paul  uhttp://telematics.upatras.gr/telematics/publications/discrete-mathematics?language=en00571nas a2200157   4500008004100000245006200041210006100103260001700164300001500181100002100196700002300217700001900240700001800259700001400277856012200291       1992                        eng d00aMIPL:An Image Processing Library for Medical Applications0 aMIPLAn Image Processing Library for Medical Applications  c14 - 17 June  a 519 - 5251 aBouras, Christos1 aKapoulas, Vaggelis1 aSpirakis, Paul1 aGeorgantas, T1 aGoutis, K  uhttp://telematics.upatras.gr/telematics/publications/miplan-image-processing-library-medical-applications?language=en01271nas a2200133   4500008004100000245008400041210006900125260002100194300001300215520073700228100002100965700001900986856013201005       1991                        eng d00aThe effect of clock drifts on the performance of distributed timestamp ordering0 aeffect of clock drifts on the performance of distributed timesta  c12 - 14 December  a 69 - 853 aTimestamp–based algorithms have been proposed to protect distributed
database from inconsistencies during concurrent access. In such algorithms,
transactions may reach a paricular site out of the order of their timestamps,
due to unexpected network delays. This causes conflicts which the distributed
concurrency control mechanism has to cope with. In this paper we analyze
the essential features of the conflict phenomenon under the realistic assumption
of the local site clocks out of total synchrony. We quantify the way in
which local clock inaccuracies affect the phenomenon of transaction conflicts.
In particular, we express the probability of order–reverse as a particular increasing
function of the maximum clock drift.1 aBouras, Christos1 aSpirakis, Paul  uhttp://telematics.upatras.gr/telematics/publications/effect-clock-drifts-performance-distributed-timestamp-ordering?language=en00594nas a2200157   4500008004100000245007100041210006900112260001400181300001300195100002100208700001900229700001900248700002200267700001800289856012900307       1991                        eng d00aRECPHONE: A new environment for medical remote expert consultation0 aRECPHONE A new environment for medical remote expert consultatio  c2 -3 July  a 22 - 231 aBouras, Christos1 aSpirakis, Paul1 aGarofalakis, J1 aPapoutsopoulos, G1 aBasiroglou, P  uhttp://telematics.upatras.gr/telematics/publications/recphone-new-environment-medical-remote-expert-consultation?language=en00595nas a2200121   4500008004100000245012500041210006900166260002800235300001500263100002100278700001900299856015500318       1990                        eng d00aSimplified performance models of the reordering issue in timestamp ordering concurrency control in distributed databases0 aSimplified performance models of the reordering issue in timesta  c30 October - 2 November  a 719 - 7271 aBouras, Christos1 aSpirakis, Paul  uhttp://telematics.upatras.gr/telematics/publications/simplified-performance-models-reordering-issue-timestamp-ordering-concurrency-control?language=en00570nas a2200145   4500008004100000245006800041210006800109260001600177300001500193100002100208700001900229700002700248700001900275856013000294       1987                        eng d00aQueueing Delays in Buffered Multistage Interconnection Networks0 aQueueing Delays in Buffered Multistage Interconnection Networks  c11 - 14 May  a 111 - 1211 aBouras, Christos1 aSpirakis, Paul1 aTriantafillou, Vasilis1 aGarofalakis, J  uhttp://telematics.upatras.gr/telematics/publications/queueing-delays-buffered-multistage-interconnection-networks?language=en