Joint Power Allocation and Beamforming for Non-Orthogonal Multiple Access (NOMA) in 5G Millimeter-Wave Communications

TL;DR

This paper proposes a suboptimal joint power allocation and beamforming solution for 2-user mmWave-NOMA systems, demonstrating near-optimal sum-rate performance and superiority over TDMA through extensive evaluations.

Contribution

It introduces a decomposition-based method for joint beamforming and power allocation in mmWave-NOMA, extending to multi-user scenarios and addressing non-convex challenges.

Findings

Achieves near-bound sum-rate performance

Significantly outperforms TDMA in simulations

Effective extension to multi-user scenarios

Abstract

In this paper we explore non-orthogonal multiple access (NOMA) in millimeter-wave (mmWave) communications (mmWave-NOMA). In particular, we consider a typical problem, i.e., maximization of the sum rate of a 2-user mmWave-NOMA system. In this problem, we need to find the beamforming vector to steer towards the two users simultaneously subject to an analog beamforming structure, while allocating appropriate power to them. As the problem is non-convex and may not be converted to a convex problem with simple manipulations, we propose a suboptimal solution to this problem. The basic idea is to decompose the original joint beamforming and power allocation problem into two sub-problems which are relatively easy to solve: one is a power and beam gain allocation problem, and the other is a beamforming problem under a constant-modulus constraint. Extension of the proposed solution from 2-user mmWave-NOMA to more-user mmWave-NOMA is also discussed. Extensive performance evaluations are conducted to verify the rational of the proposed solution, and the results also show that the proposed sub-optimal solution achieve close-to-bound sum-rate performance, which is significantly better than that of time-division multiple access (TDMA).