On the performance of exploiting a full-duplex multi-antenna relay powered by wireless energy transfer and self-energy recycling with interference alignment

Abstract

In this paper, the full-duplex (FD) relay transmission with simultaneous wireless information and power transfer in the presence of interference signals is investigated. A multiple-input multiple-output (MIMO) transmission in a small cell is considered, in which a half-duplex (HD) base station (BS) transmits data to the HD cell-edge user over an FD wireless powered relay. At the same time, BS transmits data to its near users. This concurrent data transmission to all nodes by BS causes signal interference at near users and relay. Relay harvests power from its received signals, including interference signals and the self-interference (SI) signal induced by the FD transmission, to forward the cell-edge user’s data. Power splitting (PS) and interference alignment (IA) techniques are used at the relay to jointly enable wireless energy transfer and interference management. The method introduced here is called the FD PS IA scheme. This method aims to find the PS ratio and beamforming matrices to maximize the cell-edge user and near users’ transmission rate. With this purpose, a closed-form expression for relay optimal PS ratio is derived. Furthermore, a method for choosing the proper precoding and decoding matrix at the relay and edge user, respectively, is proposed. Also, the IA matrices of BS, relay, and near users are optimized based on minimizing the mean square error iterative algorithm. Finally, numerical results demonstrate the rate gain from the combination of IA and PS at FD relay. Besides that, the performance improvement of information processing and energy harvesting by applying multiple antennas is presented. The significant benefits of harvesting the interference and SI signal power at the FD relay are exposed through analysis and simulations.