Joint Beamforming and Power Allocation in Downlink NOMA Multiuser MIMO Networks

Abstract

In this paper, a novel joint design of beamforming and power allocation is\nproposed for a multi-cell multiuser multiple-input multiple-output (MIMO)\nnon-orthogonal multiple access (NOMA) network. In this network, base stations\n(BSs) adopt coordinated multipoint (CoMP) for downlink transmission. We study a\nnew scenario where the users are divided into two groups according to their\nquality-of-service (QoS) requirements, rather than their channel qualities as\ninvestigated in the literature. Our proposed joint design aims to maximize the\nsum-rate of the users in one group with the best-effort while guaranteeing the\nminimum required target rates of the users in the other group. The joint design\nis formulated as a non-convex NP-hard problem. To make the problem tractable, a\nseries of transformations are adopted to simplify the design problem. Then, an\niterative suboptimal resource allocation algorithm based on successive convex\napproximation is proposed. In each iteration, a rank-constrained optimization\nproblem is solved optimally via semidefinite program relaxation. Numerical\nresults reveal that the proposed scheme offers significant sum-rate gains\ncompared to the existing schemes and converges fast to a suboptimal solution.\n