Research On Wireless Resource Allocation Algorithm In OFDMA-based Cooperative Communication Systems

As a distributed virtual multiple antenna arrays transmission technology,cooperative communication combines the performance advantages of spatial diversityand relay transmission. In multi-user scenario, adjacent users cooperate to producespatial diversity gain to boost transmission performance without increasing the numberof antennas of any terminal. Meanwhile, OFDM has been selected as the coretechnology in physical layer of future wireless telecommunication system due to itsability to conquer multi-path fading and high utilization rate of frequency spectrum.Therefore, the validity and reliability of the wireless communication transmission willbe dramatically improved if OFDM and cooperative technology are combined together.Specific to OFDFA cooperative communications, the dissertation explores the resourceallocation strategies for OFDMA-based single-source multi-relay (SSMR) andmulti-source multi-relay (MSMR) cooperative communication systems. The maincontents and results achieved in the research go as follow:1) The technical foundation of OFDMA-based cooperative communication systemsand the corresponding resource allocation algorithms was discussed. Firstly, based onthe three-node model, the principles, characteristics and properties of the half-duplexamplified-and-forward and decoded-and-forward relaying were summarized. Then,principle of OFDMA system was introduced. Finally, the features and advantages ofvarious resource allocation algorithms for OFDMA-based cooperative communicationsystems were comparatively analyzed.2) Resource allocation algorithm for OFDMA-based SSMR cooperativecommunication systems was researched. Firstly, optimal power allocation and dual-hopsub-carrier matching problems of OFDMA-based single-source single-relay (SSSR)cooperative communication systems were analyzed. Based on these, the resourceallocation of multi-relay peer-to-peer communication systems was studied, and theoptimization problem was formulated as a mixed binary integer programming problemby jointly considering relay selection, dual-hop sub-carrier matching, and optimalpower allocation. Heuristic algorithms were proposed to decompose the originalproblem into two independent sub-problems for efficient solution. Finally, simulationsevaluated the performance improvement and the capacity enhancement respectively forthe proposed strategies. 3) Resource allocation algorithm for OFDMA-based MSMR cooperativecommunication systems was researched. Aiming at user fairness, a wireless resourceallocation model was established based on game theory and Nash Bargaining Solution(NBS), which insured certain QoS and fairness for users. A sub-optimal sub-carrierallocation algorithm was proposed in accordance with NBS, which could guarantee theminimum rate of each user, and allocate sub-carriers fairly to improve the systemcapacity at the same. According to residual power in relaying nodes, a water-fillingpower allocation scheme based on dichotomy was also studied after this sub-carrierallocation work. Simulations evaluated the resource allocation fairness and the systemthroughput respectively for the proposed strategies.