Wireless Powered Spatially Correlated MIMO AF Relaying Systems with Energy Beamforming

This paper analyzes the performance of energy beamforming in spatially correlated multiple-input multiple-output (MIMO) relaying systems, where the source and destination nodes are equipped with multiple spatially correlated antennas and communicating via a dual-hop amplify-and-forward (AF) single antenna energy-constrained relay. To maximize the overall harvested energy so as to enable long-distance wireless power transfer, the wirelessly powered relay scavenge energy from the source radio-frequency (RF) signal through energy beamforming, then uses the harvested energy to forward the source message to the destination. To facilitate wireless information and power transfer at the relay, time-switching receiver (TSR) protocol is considered. To this end, tight lower and upper bound expressions for the outage probability and ergodic capacity are derived in closed-form, through which the throughput of the delay-constrained and delay-tolerant transmission modes are investigated, respectively. Numerical results sustained by Monte Carlo simulations show the tightness of the proposed analytical expressions. The impact of various parameters such as energy harvesting ratio, source transmit power, number of antennas and spatial fading correlation on the system throughput is also considered.