Algorithm Research Of Cooperative Relay Selection And Optimal Power Reallocation

With the development of society, users' requirements for wireless communication performance are also rising, so the next generation wireless communication systems need to provide user with higher transmission rates and transmission reliability. Cooperative relay communication as a key technology for wireless communication, not only can effectively reduce the channel fading and make the communication system more reliable but also effectively enhance the performance of wireless communication system. There are several cooperative relays in cooperative relay communication system, and how to select the reasonable relay stations has been a hot issue. The existing optimal relay selection algorithm has the best performance, while owns the highest complexity and limited application. In addition, under the condition of the system limited power, The unreasonable power distribution may lead to poor system performance.According to the above issues, this paper offers a novel scheme which performs close to the optimal algorithm with a low complexity. It selects the least number of relay stations to meet users' needs. Under the circumstances that the system power is limited, this paper also studied a power optimization method that can reduce the system outage probability and improve the system of rate. The main research work is as follows:(1) A study on relay selection algorithm based on threshold. Assuming that the power of source node and the relay nodes being equal, we firstly calculate the SNR based on CSI, and then calculate the threshold, finally we can select the relay comparing with the SNR and threshold SNR.(2) A study on power optimization method. It reduces the system outage probability and improve achievable rate. In this algorithm, the mathematical model is built first, then the convex optimization method and Newton method are used to find the cooperative relaying optimal allocation factor of source node which reduces system outage probability and improve the system of rate.According to the simulation results and theory analysis, the relay selection algorithm based on threshold greatly reduce the complexity while maintains the optimal performance. Besides, the proposed method selects a minimum number of relays to meet user's requirement and economizes the resource of system. Comparing to the average power allocation algorithm, the achievable rate and system outage probability of power optimization algorithm are obviously improved. Eventually, energy efficiency and reliability of system are promoted apparently.