Abstract
In this paper, we develop two energy-efficient joint power allocation (PA) and beamforming (BF) design schemes for a two-user downlink millimeter-wave system with non-orthogonal multiple access under imperfect channel state information. The optimization problem is formulated by considering the maximum power and minimum rate constraints. Specifically, by means of block coordinate descent algorithm, the problem is transformed into two sub-problems: PA problem and BF problem. First, we derive a closed-form optimal PA solution for each iteration of concave-convex procedure so as to obtain a suboptimal PA scheme for the fixed BF. With this PA scheme, two suboptimal BF schemes are proposed based on successive convex approximation and one-dimensional search method, respectively. Simulation results validate the rational of two proposed schemes and show that the former scheme can achieve higher energy efficiency while the latter has small performance loss but lower complexity .
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