Dual-hop full duplex relay networks over composite fading channels: Power and location optimization

This paper investigates schemes for improving the outage performance of dual-hop full duplex (FD) and half duplex (HD) decode and forward (DF) based relay networks over composite Nakagami-m/log-normal fading channels. First of all, we derive new analytical expression for the outage probability of dual-hop FDR network considering the effects of interference caused by direct link from source-to-destination and the residual self-interference (RSI) at the full duplex relay (FDR). We also provide the asymptotic outage probability expression. We then investigate optimal power allocation (OPA); optimal relay location (ORL) and joint optimization of transmit power and relay location that minimizes the outage probability. We show that the first two problems are convex and devise modified Polak-Ribiere Conjugate Gradient Method to determine the OPA and ORL. Since the joint optimization problem is non convex, we devise an efficient, low complex and fast converging iterative algorithm based on alternating optimization technique. We repeat the investigations for dual-hop HDR networks as well assuming composite fading model. The results demonstrate that both OPA and ORL can improve the outage probability; however joint optimization leads to superior performance as compared to OPA, ORL and un-optimized cases.