Resource Allocation And Performance Analysis In Wireless Relay Communication Systems

With the emergence of mobile phone and mobile Internet, the requirement for high speed data communication is more and more huge. Due to the features, such as high spectrum efficiency, resistance to multipath fading, and supporting adaptive modulation, OFDM has become the most popular modulation scheme and key technology. OFDMA, which is the combination of OFDM modulation and FDMA multiple access technology, has been the mainstream of the new generation’s mobile communication. Wireless relay technology can improve the weak signal at the cell edge and expand the cell coverage at low cost. The thesis investigates resource allocation in OFDMA-based wireless relay systems, as well as diversity performance in traditional multiple relay networks.First, common methods of resource allocation in wireless communication are introduced, mainly including convex optimization and heuristic algorithms. Then some common resource allocation problems in OFDMA systems are introduced, which also exist in OFDMA-based relay systems.Afterwards, joint subcarrier and power allocation in the downlink transmission of a specific OFDMA-based wireless relay network is considered, where the goal is maximize the weighted system capacity. Multipath greedy algorithm is proposed as a centralized method, which is a generalization of traditional greedy algorithm. Different from resource allocation methods in the literatures, whose weighted system capacity often extremely approach the optimal value but with the suboptimal allocation, it achieves the optimal resource allocation exactly at high probability. Besides, its complexity is polynomial and acceptable.To alleviate the uplink transmission of the CSI feedback from the relay stations, a semi-distributed method for resource allocation is proposed. Only the sort information of subchannel strength, not CSI itself, is transmitted to the base station. Then the base station allocates subcarriers to the microcells only with the operation of table lookup and compare. Its complexity is linear and lower, compared with the common algorithms in the literatures. Moreover its performance is close to the optimal centralized method.In the last part, a wireless relay network, which consists of a source node, multiple relay nodes and a destination node, is considered. The relation between DSTBC and the SER/diversity performance is analyzed. Starting with the case of a deterministic channel, the upper and lower bounds of SER in Rayleigh channels are given through rigorous derivation, which leads to the diversity gain in the case without a direct path and the case with a direct path.