Full-duplex amplify-and-forward relay system with direct link: Performance analysis and optimization

In this paper, we analyze the performance of a full-duplex (FD) amplify-and-forward (AF) relay system under various cases of relaying gains and channel state information conditions. Specifically, we consider the case that the FD relay node uses either fixed or variable gain for relaying under perfect and imperfect channel state information (CSI). For the case of imperfect CSI (I-CSI), we derive the exact expressions for the outage probability (OP), throughput, and symbol error probability (SEP) of the considered system. For the case of perfect CSI (P-CSI), we can provide approximate expressions of OP, throughput, SEP, and ergodic capacity. We also propose an effective power allocation scheme for the FD relay node to reduce the effect of residual self-interference (RSI). Both analytical and simulation results show a significant impact of RSI on the system performance. In particular, when RSI is small the variable-gain relaying can provide better performance than the fixed gain. However, when RSI becomes large these two relaying schemes have similar performance. In this situation, using the proposed optimal power allocation scheme can improve the system performance, especially for the case with weak direct link. © 2019 Elsevier B.V.