Researchon Resource Allocation Technologyin Cooperative OFDM Communication Systems

OFDM communication systems is the necessary part of LTE and LTE-A systems in the future. It has a lot of advantages, for example, the modulation of subcarriers in the symbol is flexibility, the anti-fading ability is strong and large amounts of data can be sent under the narrow band condition, so OFDM is a key technology in the communication systems. Relay cooperative technology is one of the key technologies in cooperative communication systems. It could improve thetotal system rate and expand the coverage of the edge cell while not need to add base station and more spectrum. Combining OFDM technology and cooperative technology could effectively anti-multipath interference and fading, enhance total systemrate and the communication quality using space diversity, improve the system performances and power utilization, and also could support the difference quality of service requirement. The resource allocation is a hotspot in combining OFDM technology and Cooperative technology, and the efficient subcarrier allocation algorithm and bit loading algorithm of thecooperative OFDM communication system’s resource allocation has become increasingly important research significance.In this thesis, we research the resource allocation techniques of the cooperative OFDM communication systems, and focus on the resource allocation problem of the cooperative communication system with relay nodes and multiuser without relay nodes. Under different constraints, we discuss the corresponding optimization objectives and find the optimal resource allocation scheme.In the systems with relay nodes, we consider maximizing the total system rate as the goal under the condition that the system model is power limited, and discuss the resource allocation problem of the OFDM systems in Decode-and-Forward (DF) model. Based on channel gain of every subcarrier, we use relay selection algorithm to choose relay node for each subcarrier, and then calculate the equal channel gain. In bit allocation part, Genetic Algorithm (GA) is used. Optimal solution will be gotten, using the strong global search ability of Genetic Algorithm. The simulation result shows that in the communication systems with relay node, using the relay node and appropriate relay selection algorithm, the data rate of the systems with relay node will be higher than the system without relay node. Under the same relay node condition in the power limited systems, compared with the adaptive Genetic Algorithm and the Equal Bit Allocation Algorithm (EBA), the total rate of GA will be higher than that of EBA and the power utilization is also better.In the systems without relay node, we consider power limited systems with data rate proportional of multi-user, and focus on the subcarrier allocation and bit allocation of OFDM systems. We propose the secondary allocation algorithm mixed greedy and genetic algorithm, and compare with other different resource allocation algorithms. The simulation shows that in the communication systems without relay node, the system’s total data rate of proposed algorithm is much better than that of the traditional genetic algorithm, and also could meet the data rate requirement of multi-user data rate proportional. In the bit error ratio, the signal noise ratio (SNR) of the proposed algorithm is smaller than that ofthe genetic algorithm under the same bit error ratio (BER) condition.