A Genetic Algorithm For Multiple Relay Selection In Cooperative And Cognitive Wireless Networks

With the development of wireless communications, consumer's requirements for high data rate and service quality promote the wireless communication technology to develop towards the direction of speed and communication quality. Cooperative communication is a cooperative transmission with the help of relay stations and adjacent users, this method can improve system capacity, overcome multipath fading and reduce outage probability. However, the performance of the system will vary greatly because of different relay cooperative mode, selection strategy and power allocation. Therefore, the relay selection and power allocation in cooperative communication has become a study hotspot in the field of wireless communication.This thesis focuses on the research of multi relay selection strategy in cognitive cooperative wireless networks. This paper firstly introduces the background and significance of relay selection in cooperative communication. Then describes the current research in relay cooperation mode, selection strategy and cooperative cognitive wireless network. Next introduces the key technologies at the area of cooperative communication, cognitive radio and genetic algorithm. At last we propose a sub optimal multi relay selection strategy which is based on the combination of sum rate and energy efficiency with the help of genetic algorithm, this strategy is reasonable to use the advantage of genetic algorithm in optimize search, and quickly obtain the joint optimal relay cooperation program with better sum rate and energy efficiency in current population. Simulation results show that the proposed scheme can obtain more than 50% system energy efficiency gain at the price of 10% sum rate loss.According to the sub optimal multi relay selection strategy we propose a relay selection strategy which is based on system energy efficiency under QoS constraint. If the sum rate is not satisfied with QoS constraint, we increase transmission power to guarantee the system operation normally. Otherwise choose relay cooperation program with best energy efficiency. Simulation results show that the proposed scheme not only ensure the relay system performance, but also improve the system energy efficiency.