Diversity Theory And Resource Scheduling In Wireless Cooperative Relay Communication Systems

With the cooperation between wireless network nodes, wireless cooperative communication can fully utilize the advantages of MIMO (Multiple Input Multiple Output) techniques without requiring multiple antennas at each node. It can efficiently cope with the capacity bottleneck and coverage issues encountered by traditional cellular networks. The concept of wireless cooperative communication has become one of the major research topics, and also has gained widely interest in the telecommunication industry, which is believed to be one of key techniques in next generation wireless communication systems.This dissertation focuses on the diversity theory in the wireless cooperative relay communication system, arming at perfecting the related theoretical framework. Based on this, the dissertation further presents a comprehensive study on the resource allocation and transmission strategy design with the goal of optimizing the system performance. First, the capacity study on the sing-antenna cooperative relay system in fading channels is presented, followed by the diversity performance analysis in multi-antenna cooperative relay networks. Then, the multiuser diversity theory is discussed in cooperative relay systems. Based on these theoretical analysis, the dissertation further presents various power allocation strategies with different optimization objectives under different channel state information (CSI) assumptions; finally, joint power and bandwidth allocation strategies aiming at providing heterogeneous services in orthogonal frequency division multiplexing (OFDM) cooperative relay systems are investigated. The major work and contributions of this dissertation consist in:1. Capacity study of single antenna cooperative relay systems in fading channelsCooperative relay system with multiple single-antenna relay nodes is the classical model for wireless cooperative communications. The dissertation first investigates the capacity issue of this classical model, which is the basic issue for any communication system. We theoretically analyze the ergodic capacity and outage capacity performance, based on which we further study the impact on the system capacity regarding the number of relay and the cooperation protocol. It shows that the capacity of cooperative relay systems decreases with the increasing of relay. Regarding two classical protocols, amplify-and-forward performs better than decode-and-forward at low SNR regions, while decode-and-forward performs better in high SNR regions. 2. Diversity performance of multi-antenna wireless cooperative relay systemsMIMO is one of key techniques in the next generation wireless communication. We present the theoretical diversity performance study in MIMO cooperative relay networks, with specially focus on the space-time coding strategy in obtaining the spatial diversity gain. By deriving the statistics of the harmonic mean of Chi-square distributed random variables and using the related theory in Probability Theory, we present closed form expressions regarding key system performance metrics, including symbol error probability, outage probability and system capacity, by which we further study the impact of various system configurations on the system performance, including cooperation protocols, antenna configurations etc. It shows that by adopting multiple antennas, the system can achieve higher diversity order, while the space-time coding discussed in this dissertation can obtain the full diversity gain. The cooperative diversity and antenna diversity can be efficiently combined.3. Multiuser diversity in multiuser wireless cooperative relay networksMultiuser diversity is an inherent diversity in multiuser wireless systems. A theoretical framework to analyze the multiuser diversity in cooperative relay networks is presented, based on which the performance of multiuser diversity in cooperative multi-relay networks is presented. We first derive asymptotic expressions of outage probability and symbol error probability for various cooperation protocols with joint multiuser and cooperative diversity. Both the theoretical analysis and simulations demonstrate that the multiuser diversity can be readily combined with the cooperative diversity, while the multiuser diversity dependent scheduling can efficiently exploit such gain to improve the system performance.4. Power allocation in the cooperative relay system with different optimization objectivesEfficient and adaptive radio resource management (RRM) is very important for wireless systems. This dissertation discusses the optimizing power allocation in wireless cooperative relay systems. We specifically study power allocation problems in MIMO cooperative relay networks adopting space-time coding. With different CSI assumptions at the transmitter, both optimal power allocation strategies aiming at maximizing the system capacity and at minimizing the system outage probability are proposed. The study shows that the proposed schemes can allocate power adaptively according to channel conditions. All schemes perform far better than the traditional methods, while the gain depends on antenna configurations and channel conditions. 5. Joint power and bandwidth allocation in wireless cooperative relay networks with heterogeneous servicesOFDM has been recognized as one of the key techniques for the next generation wireless communications. We discuss RRM strategies in OFDM cooperative relay networks with heterogeneous services. The optimal power and subcarrier allocation scheme for point-to-point transmission of heterogeneous sservices is derived, based on which a sub-optimal algorithm with linear complexity is proposed for the practical implementation. Then, the idea is extended to multiuser scenario. Optimal solution is provided, and two fastest-power-descending based power and subcarrier allocation algorithms are proposed. Simulation result shows that the proposed schemes improve the spectral efficiency while guaranteeing the QoS of each service. And it also demonstrates that the proposed algorithms in multiuser scenario can efficiently exploit multiuser diversity gain to improve the system performance.The research outputs related to this dissertation have been accepted as papers in IEEE journals and conferences.