Optimal Power Splitting for Simultaneous Wireless Information and Power Transfer in Amplify-and-Forward Multiple-Relay Systems

In this paper, we investigate simultaneous wireless information and power transfer (SWIPT) amplify-and-forward relay systems, in which multiple relay nodes support communication between a source node and a destination node. Relay node transceivers are equipped with radio frequency energy harvesters for a power source to retransmit the signals from the source to the destination node. Both the power splitting (PS) ratio and adaptive power control are jointly optimized for SWIPT multiple-relay systems. We prove that the optimal power allocation strategy in our joint solution is to fully use the harvested power, which is contrary to conventional non-SWIPT multiple-relay systems. Based on this result, we propose an optimal centralized PS scheme and suboptimal distributed PS methods. Simulation results demonstrate that the proposed schemes outperform the naive PS schemes in terms of the average rate and the bit-error rate.