Publications

@conference{3007,

title = {A Simulation Framework for LTE-A Systems with Femtocell Overlays},

author = {Christos Bouras and Andreas Papazois and Vasileios Kokkinos and Konstantinos Kontodimas},

url = {https://telematics.upatras.gr/wp-content/uploads/2024/01/3407p85-bouras.pdf},

year  = {2012},

date = {2012-10-01},

urldate = {2012-10-01},

booktitle = {ACM PM2HW2N 2012 Workshop, Paphos, Cyprus, pp. 85-90},

pages = {85 - 90},

abstract = {The 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.},

keywords = {Femtocell, LTE},

pubstate = {published},

tppubtype = {conference}

}

@conference{3010,

title = {Genetic Optimization for Spectral Efficient Multicasting in LTE Systems},

author = {Christos Bouras and Andreas Papazois and Vasileios Kokkinos and Konstantinos Asimakis},

url = {https://telematics.upatras.gr/wp-content/uploads/2024/01/Proceedings_WMNC_2012.pdf},

year  = {2012},

date = {2012-09-01},

urldate = {2012-09-01},

booktitle = {Fifth IFIP Wireless and Mobile Networking Conference, Bratislava, Slovakia, pp. 54-59},

pages = {54-59},

abstract = {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.},

keywords = {LTE, MBMS, MBSFN},

pubstate = {published},

tppubtype = {conference}

}

@conference{3008,

title = {A Performance Study of Fractional Frequency Reuse in OFDMA Networks},

author = {Christos Bouras and Andreas Papazois and Vasileios Kokkinos and Georgia Tseliou and Dimitrios Bilios},

url = {https://telematics.upatras.gr/wp-content/uploads/2024/01/WMNC_20121.pdf},

year  = {2012},

date = {2012-09-01},

urldate = {2012-09-01},

booktitle = {Fifth IFIP Wireless and Mobile Networking Conference, Bratislava, Slovakia, pp. 38-43},

pages = {38 - 43},

abstract = {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.},

keywords = {FFR, LTE},

pubstate = {published},

tppubtype = {conference}

}

@conference{2999,

title = {Evaluating RaptorQ FEC over 3GPP Multicast Services},

author = {Christos Bouras and Andreas Papazois and Vasileios Kokkinos and Nikos Kanakis},

url = {https://telematics.upatras.gr/wp-content/uploads/2024/01/4189046_7137.pdf},

year  = {2012},

date = {2012-08-01},

urldate = {2012-08-01},

booktitle = {The 8th International Wireless Communications & Mobile Computing Conference (IWCMC 2012), Limassol, Cyprus, pp. 257-262},

pages = {257 - 262},

abstract = {Third 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. troducing 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.},

keywords = {FEC, LTE, MBMS},

pubstate = {published},

tppubtype = {conference}

}

@conference{3000,

title = {Enhaning Reliable Mobile Multicasting with RaptorQ FEC},

author = {Christos Bouras and Andreas Papazois and Vasileios Kokkinos and Nikos Kanakis},

url = {https://telematics.upatras.gr/4588is041/},

year  = {2012},

date = {2012-07-01},

urldate = {2012-07-01},

booktitle = {17th IEEE Symposium on Computers andCommunication (ISCC), Cappadocia, Turkey, pp. 82-87},

pages = {82-87},

abstract = {A 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.},

keywords = {FEC, LTE, MBMS},

pubstate = {published},

tppubtype = {conference}

}

@conference{2997,

title = {Interference Management in LTE Femtocell Systems Using an Adaptive Frequency Reuse Scheme},

author = {Christos Bouras and Andreas Papazois and Vasileios Kokkinos and Georgios Kavourgias},

url = {https://telematics.upatras.gr/wp-content/uploads/2024/01/5956WTS.pdf},

year  = {2012},

date = {2012-04-01},

urldate = {2012-04-01},

booktitle = {Wireless Telecommunications Symposium (WTS 2012), London, UK, pp. 1-7},

pages = {1 - 7 },

abstract = {Long 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.},

keywords = {Femtocell, FFR, LTE},

pubstate = {published},

tppubtype = {conference}

}

@conference{2995,

title = {Optimization of Fractional Frequency Reuse in Long Term Evolution Networks},

author = {Christos Bouras and Andreas Papazois and Vasileios Kokkinos and Georgia Tseliou and Dimitrios Bilios},

url = {https://telematics.upatras.gr/3709p1875-bilios/},

year  = {2012},

date = {2012-04-01},

urldate = {2012-04-01},

booktitle = {2012 IEEE Wireless Communications and Networking Conference (WCNC 2012), Paris, France, pp. 1875-1879},

pages = {1875-1879},

abstract = {In 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.},

keywords = {FFR, LTE},

pubstate = {published},

tppubtype = {conference}

}

@conference{2990,

title = {AL-FEC for Streaming Services over LTE Systems},

author = {Christos Bouras and Andreas Papazois and Vasileios Kokkinos and Nikos Kanakis},

url = {https://telematics.upatras.gr/4760pid1999633/},

year  = {2011},

date = {2011-10-01},

urldate = {2011-10-01},

booktitle = {14th International Symposiumon Wireless Personal Multimedia Communications, Brest, France, pp. 284-288},

pages = {284-288},

abstract = {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.},

keywords = {FEC, LTE, MBMS},

pubstate = {published},

tppubtype = {conference}

}

@conference{2991,

title = {Interference Behavior of Integrated Femto and Macrocell Environments},

author = {Christos Bouras and Antonios Alexiou and Andreas Papazois and Vasileios Kokkinos and Konstantinos Kontodimas},

url = {https://telematics.upatras.gr/25171569481919/},

year  = {2011},

date = {2011-10-01},

urldate = {2011-10-01},

booktitle = {IFIP Wireless Days 2011, Niagara Falls, Ontario, Canada, pp. 1-5},

pages = {1 - 5},

abstract = {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 stimates the cross-tier interference and the throughput in every point of an integrated femtocell/macrocell Long Term Evolution-Advanced (LTE-A) network.},

keywords = {Femtocell, LTE},

pubstate = {published},

tppubtype = {conference}

}

@conference{2983,

title = {Reliable Multicasting over LTE: A Performance Study},

author = {Christos Bouras and Antonios Alexiou and Andreas Papazois and Vasileios Kokkinos and Konstantinos Asimakis and Georgia Tseliou},

url = {https://telematics.upatras.gr/2179cc_070/},

year  = {2011},

date = {2011-06-01},

urldate = {2011-06-01},

booktitle = {16th IEEE Symposioum  on Computers and Communications (ISCC 2011), Kerkyra, Greece, pp. 603-608},

pages = {603 - 608},

abstract = {With 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.},

keywords = {FEC, LTE, MBMS, MBSFN},

pubstate = {published},

tppubtype = {conference}

}

@conference{2982,

title = {Optimizing the Combination of MBSFN and PTM Transmissions in LTE Systems},

author = {Christos Bouras and Antonios Alexiou and Andreas Papazois and Vasileios Kokkinos and Georgia Tseliou},

url = {https://telematics.upatras.gr/41721569411933/},

year  = {2011},

date = {2011-04-01},

urldate = {2011-04-01},

booktitle = {Tenth Annual Wireless Telecommunications Symposium (WTS 2011), New York, USA, pp. 1-7},

pages = {1 - 7},

abstract = {The 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.},

keywords = {LTE, MBMS, MBSFN},

pubstate = {published},

tppubtype = {conference}

}

@conference{2984,

title = {Combining MBSFN and PTM Transmissions Schemes for Resource Efficiency in LTE Networks},

author = {Christos Bouras and Antonios Alexiou and Andreas Papazois and Vasileios Kokkinos and Konstantinos Asimakis},

url = {https://telematics.upatras.gr/1517alexiou_wwic_2011_cr/},

year  = {2011},

date = {2011-01-01},

urldate = {2011-01-01},

booktitle = {9th International Conference on Wired/Wireless Internet Communications, Vilanova I la Geltru, Barcelona, Spain, June 15 - 17, 2011, pp. 56-67},

pages = {56 - 67},

abstract = {Long 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.},

keywords = {LTE, MBMS, MBSFN},

pubstate = {published},

tppubtype = {conference}

}

@conference{2979,

title = {Enhancing FEC Application in LTE Cellular Networks},

author = {Christos Bouras and Antonios Alexiou and Andreas Papazois and Vasileios Kokkinos and Georgia Tseliou},

url = {https://telematics.upatras.gr/3883wd_2/},

year  = {2010},

date = {2010-10-01},

urldate = {2010-10-01},

booktitle = {IFIP Wireless Days 2010, Venice, Italy, pp. 1-5},

pages = {1 - 5},

abstract = {3rd 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.},

keywords = {FEC, LTE, MBMS, MBSFN},

pubstate = {published},

tppubtype = {conference}

}

@conference{2978,

title = {Efficient MCS Selection for MBSFN Transmissions over LTE Networks},

author = {Christos Bouras and Antonios Alexiou and Andreas Papazois and Vasileios Kokkinos and George Tsichritzis},

url = {https://telematics.upatras.gr/3975wd_1/},

year  = {2010},

date = {2010-10-01},

urldate = {2010-10-01},

booktitle = {IFIP Wireless Days 2010, Venice, Italy, pp. 1-5},

pages = {1 - 5},

abstract = {Long 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.},

keywords = {LTE, MBMS, MBSFN, MCS},

pubstate = {published},

tppubtype = {conference}

}