Joint User Ordering, Beamforming and Power Allocation for Downlink MIMO-NOMA Systems

Abstract

This paper investigates the power minimization problem for the downlink of multi-input multi-output non-orthogonal multiple access (MIMO-NOMA) systems. The problem aims to minimize the total transmission power while satisfies some signal-to-interference-plus-noise power ratio (SINR) requirements of the users. Specially, three aspects, namely the user ordering, power allocation and receive beamforming design, are jointly considered. We first discuss the optimality of each aspect respectively, given that the other two aspects are fixed. Then we use the results to devise an iterative algorithm, in which the three aspects are updated alternatively. The convergence and optimality of the proposed algorithm are discussed. Simulation results show that optimizing user ordering can significantly improve system performance.