Transmission Rate Optimization of Full-Duplex Relay Systems Powered by Wireless Energy Transfer

We consider a system where a source node communicates with a destination node with the assistance of a wireless energy-powered full-duplex relay node. The relay node splits its received signal into two components for energy harvesting and information decoding, respectively, and forwards the decoded information using a portion of the harvested energy. To maximize the end-to-end transmission rate, the power splitting factor and energy consumption proportion are jointly optimized for the relay with a single transmit antenna in the presence of self-interference. Furthermore, for the relay with multiple transmit antennas, a suboptimal relay beamformer is first designed and the power splitting factor and energy consumption proportion are then jointly optimized. Finally, the asymptotic transmission rate is analyzed with a large number of transmit antennas. Simulation results are provided to demonstrate that the proposed schemes offer significant rate gain compared with some typical reference schemes, irrespective of the residual self-interference level. Especially, by employing a large number of source or relay transmit antennas, the wireless energy-powered relay system is capable of cutting its energy consumption significantly.