Key Technologial Issues In Optimization Of Multi-Cell Transmission System For Interference Mitigation In Next Generation Cellular Networks

Mobile telecommunication systems have experienced tremendous growth during last few decades. Data traffic in wireless cellular networks has been increasing on an exponential rate. Traditional cellular networks and wireless technologies are facing unprecedented challenges to meet the increasing demand of data traffic. The evolution of next generation wireless cellular networks is characterized to meet the requirements of high data rates, decreased latency and high capacity.The key to increase the data rates is to improve the spectral efficiency of cellular networks. Multiple-input multiple-output (MIMO) technique can significantly increase the system throughput and spectrum efficiency in cellular networks. This technique has been adopted in next generation wireless cellular networks. However, the gains of MIMO technique are degraded in a multi-cell environment due to severe inter-cell interference. Moreover, the next generation wireless cellular networks uses Orthogonal Frequency Division Multiple Access (OFDMA) for its scalability and flexibility. The use of OFDMA ideally eliminates the intra-cell interference but the environment is still limited by inter-cell interference. In addition to that, universal frequency reuse in next generation wireless cellular networks also results in severe inter-cell interference. So the performance of next generation wireless cellular networks is fundamentally limited by inter-cell interference, especially affecting the users at the cell-edge. Advance interference mitigation techniques are therefore required to improve the performance of next generation wireless cellular networks.Multi-cell transmission also referred to as coordinated multi-point transmission has emerged as a key promising technique in next generation wireless cellular networks to effectively mitigate inter-cell interference and has a great potential to increase the cell-edge user throughput, spectral efficiency and coverage. However, multi-cell transmission faces various critical challenges and key technological issues for its implementation in practical systems. Feedback overhead, backhaul overhead, system complexity and the compromise between average cell throughput and cell-edge throughput are the critical issues in multi-cell transmission. This research work focuses to improve and optimize the performance of multi-cell transmission for effective inter-cell interference mitigation in next generation wireless cellular networks. We develop a variety of novel, spectrally efficient, multi-cell transmission schemes that effectively mitigate the inter-cell interference with minimal increase in feedback and backhaul overhead. The developed schemes significantly improve the cell-edge user performance. Moreover the developed solutions significantly reduce the computational and system complexities. In the next stage, this research work focuses to further improve and optimize the system performance by developing a variety of spectrally efficient, low complexity schemes that effectively mitigate the inter-cell interference and simultaneously improve the cell-edge performance as well as average cell-performance. The developed solutions also reduce the feedback and backhaul overhead as well as system complexity. The developed solutions significantly improve average system throughput, cell-edge user throughput, average spectral efficiency and cell-edge user spectral efficiency. In addition to that, the use of linear precoding schemes further reduces the system computational complexity. The developed solutions provide a very good tradeoff between system performance improvement and system complexity and also increase the fairness of the system.In the last stage of our work we extend our research to effectively mitigate the cross-tier interference in multi-tier heterogeneous network deployment. We present a variety of novel, spectrally efficient multi-cell transmission schemes that effectively mitigate the cross-tier interference in multi-tier heterogeneous networks. This research exploits multi-cell transmission in a unique way to significantly improve and optimize the performance of heterogeneous networks with reduced feedback and backhaul overhead and system complexity. It effectively mitigates the cross-tier interference and significantly improves the performance of cell-edge users. Moreover, we further improve and optimize the system performance by developing spectrally efficient, low complexity transmission techniques that effectively mitigate the cross-tier interference and simultaneously improve the cell-edge performance as well as average cell-performance in multi-tier heterogeneous networks. The developed solutions also reduce the feedback and backhaul overhead as well as system complexity.