Optimal Time Allocation for Wireless Powered Relay Systems with Joint S-D Energy Transfer

In this paper, time-switching based wireless powered relay systems, where the source and destination jointly transfer energy to the relay, is studied. Given a certain transmission duration, there is a time trade-off between wireless energy transfer and information cooperative transmission. Although more time for energy harvesting causes more available power at the relay, it shrinks the duration of information transmission and may incur less system throughput. To obtain the optimal time allocation, we derive the information outage probability of the relay system. And then we solve the optimization problem of time allocation to achieve the maximum system throughput. Finally, simulation results verify our derived theoretical results. And it is also shown that the proposed time allocation scheme indeed achieves maximum average throughput.