Opportunistic Energy Harvesting for Multi-Antenna-Relay-Assisted Wireless Powered Communication Network

Abstract

This letter aims to maximize the achievable throughput of a multi-antenna-relay-assisted wireless powered communication network, where each transmission block starts with the wireless energy transfer (WET) from the energy-rich relay to the source in phase 1, follows the wireless information transmission from the source to the relay and the destination in phase 2, ends with the information forwarding from the relay to the destination in phase 3. Since that radio frequency signal can carry information and energy concurrently, WET also occurs from the relay to the source in phase 3. The closed-form expression of the optimal and suboptimal beamforming vectors at the relay in phase 3 with a fixed time split (TS) is obtained based on which the complexity of achieving the optimal TS is large. Hence, we further design a heuristic beamforming vector in phase 3, then the closed-form expression of the optimal TS is obtained, which yields near optimal performance. Moreover, the expected average throughput is analyzed.