Multi-relay Selection And Power Allocation Scheme Based On Decode-and-Forward Protocol

With the development of wireless communication, more and more people are concerning about the higher quality wireless data transmission and quality of service (QoS).Wireless communication are moving towards the direction of high-speed, wide-coverage. However, multipath fading effect is always the severest problem in wireless communication. Because of above, people put forward the concept of cooperative diversity inspired by the relay channel theory. The results of the current study show that as a new space diversity ,the cooperative diversity can effectively reduce channel fading,improve the coverage,increase the system capacity and enhance the data rate and service of quality as the MIMO(multiple input multiple output) technique.The thesis first takes consider of the basic concepts of diversity technology,and summarizes the classification of diversity technology and the forms of the received combination. Next we analysis and compare these different protocols of cooperative diversity in detail.Based on the Decode-and-Forward protocol,we focous on the case of multi-node relays in which the mutual information and the system outage probability is analysised by utilizing repetition coded and space-time-coded.Based on the analysis above, we proposed a method in the scene of a given arbitrary source-destination pair and multi-node relays. These methods of the multi-relay selection are based on the channel capacity gain and only the partial channel state information is required. The simulation results indicate that the proposed scheme can obtain the similar performance with only half relays selected compared with the optimal selection. Moreover the proposed scheme can improve the performance of the outage probability compared with another relay selection schemes in which same number of relays are selected.The thesis then proposes a scheme of optimal power allocation with multi-relay under the channel fading model of Nakagami-m. This method aims to maximize the mutual information under the assumption that each transmitting node has limited energy. Convex optimization method is used to implement the algorithm, which optimally distributes power among the source and relay nodes. Both theoretical analysis and simulation results indicate that the proposed strategy notably improves system performance and energy efficiency.