Energy Harvesting Wireless Communications With Energy Cooperation Between Transmitter and Receiver

Energy harvesting is an increasingly attractive source of power for wireless communications devices. In this paper, we consider a point-to-point (P2P) wireless communications system, where both the practical transmitter and receiver, whose hardware circuits consume non-zero power when active, are powered solely by the energy harvested from external sources. An energy cooperation save-then-transmit (EC-ST) scheme is proposed: both the transmitter and receiver go into sleep mode to save energy for a proportion of time while their passive energy harvester units collect energy for later operations, and then become active to communicate for the remaining time proportion (referred to as the active-ratio), during which energy is allowed to flow between the transmitter and receiver. We first consider additive white Gaussian noise one-way channels with two-way energy transfer under a deterministic energy arrival rate. In this case, the optimal active-ratio and the energy cooperation power are obtained in closed form to achieve the maximum throughput. Next, for Rayleigh block fading channels with a stochastic energy arrival rate, we find the optimal energy cooperation power for minimizing the outage probability. Finally, numerical and simulation results are presented to validate the analytical findings.