Wireless Power Transfer-Based Multi-Pair Two-Way Relaying With Massive Antennas

In this paper, we study a multi-pair two-way relay network consisting of two groups of user equipments (UEs), who want to exchange information through a common relay equipped with massive antennas. In the multiple access phase, the UEs transmit information to the relay using the energy harvested in the last time block, and the relay decodes information using zero-forcing (ZF) or maximal ratio combining (MRC) technique. In the broadcasting phase, the relay performs simultaneous wireless information and power transfer (SWIPT), and each UE receives energy and information using the power-splitting scheme. Due to the channel hardening effect of the large-scale antenna array, the harvested energy of each UE in each time block is asymptotically constant. Based on the derived achievable rates of UEs, a multi-objective optimization problem (MOOP) is formulated to maximize the achievable rates of all the pairs. Through solving the MOOP, the power-splitting ratios of UEs can be determined in closed-form for the ZF-based relaying. For the MRC-based relaying, a two-stage iterative Pareto improvement algorithm is proposed to achieve the Pareto optimality. Simulation results are presented to validate our theoretical analysis and verify the efficiency of our proposed algorithm in improving the system rate.