Self-Energy Recycling for RF Powered Multi-Antenna Relay Channels

We investigate self-energy recycling (S-ER)-based RF powered multi-antenna relay channels (RCs) for the coverage extension in sensor networks or small cells. In the S-ER-based RF powered RC, the power used at the relay station for data transmission depends only on the energy from the access point and the recycled energy from its own transmission. We propose an optimal beamforming scheme with associated protocols and study their behaviors for both cases of downlink only and joint up-down link. Strategies for the power allocation between data transmission and RF powering are provided and a comparison with the conventional RF powered RC is made. For the proposed power allocation strategies, the performance of the conventional RC is achieved by the proposed RF powered RC only when infinite RF power is available. A high value of S-ER helps the proposed systems to reach the performance of conventional relay systems. In the joint up-down link protocol, we show that the up-down rate region can simply be constructed with easy power allocation strategy.