Performance of Multiple Relay Selection System Based on a Novel Selection Scheme Combined Precoding Design

Abstract

In this paper we propose a novel multiple relay selection scheme based on the log-likelihood ratio (LLR). In this scheme, the joint design of precoding matrices at both the source and relay nodes in a multiple relay system based on perfect channel information is considered, which is based on the maximum signal-to-noise ratio. Using eigen-decomposition of matrices and monotonicity of functions, the joint design problem is transformed into two kinds of independent sub-problems and a fast algorithm is proposed. Compared with the traditional scheme based on signal-to-noise ratio (SNR), the proposed scheme is better in the symbol error rate (SER) performance. Simulation results show that the scheme based on LLR is superior to SNR in the SER performance. Meanwhile the multi-relay system with the proposed scheme can improve the SER performance effectively compared with only space-time coding or only precoding system.