The Performance of Wireless Powered MIMO Relaying Systems with Energy Beamforming

This paper analyzes the performance of energy beamforming in multiple-input multiple-output (MIMO) relaying systems, where the source and destination nodes are equipped with multiple antennas and communicating via a dual-hop amplify-and-forward (AF) single antenna energy-constrained relay, and the destination is subject to co-channel interference (CCI). The wirelessly powered relay scavenge energy from the source information radio-frequency (RF) signal through energy beamforming, using the time-switching receiver, and uses the harvested energy to forward the source message to the destination. To this end, tight lower and upper bound expressions for the outage probability and ergodic capacity of the considered system are presented in closed-form, through which the throughput of the delay-constrained and delay-tolerant transmission is investigated, respectively. Numerical results sustained by Monte Carlo simulations show the tightness of the proposed analytical expressions. The impact of various parameters such as the energy harvesting time, source transmit power and the number of antennas on the system throughput is also considered. It is seen that the system throughput increases as the number of antenna and/or the source transmit power increases. In addition, energy beamforming increases the harvested energy and hence reduces the optimal energy harvesting ratio, as a result, more time is left for information transmission.