Joint optimal power allocation and relay selection scheme in energy harvesting asymmetric two-way relaying system

Energy harvesting, which is an emerging technology to prolong the lifetime of energy-constrained wireless networks, has received significant attention. In this study, the authors consider an amplify-and-forward-based asymmetric two-way relaying system, where two source nodes exchange information through an energy-constrained relay node. The relay node scavenges energy from the received signals and uses the harvested energy to forward the received signals to the two terminal nodes. The signal power splitting ratio, depicting the trade-off between the harvesting energy and the forward signals' power, is a crucial factor for the system outage probability. Therefore, an optimal power allocation (OPA) scheme, which jointly takes into consideration the optimisation of signal power splitting ratio and the transmission power allocation, is proposed to minimise the outage probability. In addition, a close-form solution for the OPA scheme is obtained. Finally, a joint OPA and relay selection schemes are presented to further improve the system performance. Simulation results highlight the superiority of the author's proposed scheme.