Joint Energy-Efficient Power Allocation and Beamforming for Uplink mmWave-NOMA System

In this paper, we study the joint power allocation (PA) and beamforming (BF) design problem to maximize the energy efficiency (EE) for an uplink millimeter-wave (mmWave) system with non-orthogonal multiple access (NOMA). To track this non-convex optimization problem, we decompose it into the PA problem and BF design problem. For any feasible fixed BF, the condition of the optimal decoding order is firstly presented to reduce the decoding complexity, and then the optimal and suboptimal PA solutions with closed-form expressions are derived, respectively. On this basis, two suboptimal joint design schemes of PA and BF are proposed based on the one-dimensional search method. Furthermore, the extensions of the proposed schemes to mmWave-NOMA system with imperfect channel information and more users are also presented. Simulation results verify the effectiveness of the proposed two joint schemes, and they can achieve superior EE performance over the existing schemes and the conventional time division multiple access scheme.