Optimal Power Allocation Scheme for Non-Orthogonal Multiple Access With $lpha $ -Fairness

摘要

This paper investigates the optimal power allocation scheme for sumthroughput maximization of non-orthogonal multiple access (NOMA) system with$lpha$-fairness. In contrast to the existing fairness NOMA models,$lpha$-fairness can only utilize a single scalar to achieve different userfairness levels. Two different channel state information at the transmitter(CSIT) assumptions are considered, namely, statistical and perfect CSIT. Forstatistical CSIT, fixed target data rates are predefined, and the powerallocation problem is solved for sum throughput maximization with$lpha$-fairness, through characterizing several properties of the optimalpower allocation solution. For perfect CSIT, the optimal power allocation isdetermined to maximize the instantaneous sum rate with $lpha$-fairness, whereuser rates are adapted according to the instantaneous channel state information(CSI). In particular, a simple alternate optimization (AO) algorithm isproposed, which is demonstrated to yield the optimal solution. Numericalresults reveal that, at the same fairness level, NOMA significantly outperformsthe conventional orthogonal multiple access (MA) for both the scenarios withstatistical and perfect CSIT.