Energy-Efficient Power Allocation for Millimeter-Wave System With Non-Orthogonal Multiple Access and Beamforming

In this paper, two power allocation (PA) and beamforming (BF) schemes of a downlink millimeter-wave communication system with non-orthogonal multiple access (mmWave-NOMA) over mmWave fading channels is presented. The proposed scheme is developed based on the maximization of the energy efficiency (EE) of the mmWave-NOMA system. First, with the EE analysis under the simplified channel model, the optimization of the PA and BF design for maximizing EE of the mmWave-NOMA system subject to minimum rate and maximum total power constraints is formulated. Since this optimization problem cannot be solved directly, it is decomposed into sub-problems that can be solved efficiently. An optimal PA scheme for ideal BF is developed, and a suboptimal BF with one dimensional search is derived, which has lower complexity than an existing suboptimal BF scheme. With this suboptimal BF scheme, a closed-form PA procedure is obtained. Second, based on the block coordinate descent method, a suboptimal joint PA and BF scheme is proposed for the system over practical channels. Simulation results verify that the proposed suboptimal schemes are valid, they have almost the same EE performance as the ideal scheme for the simplified channel model and superior performance over the latter for the practical channel model.