Wireless-Powered Communications With Non-Orthogonal Multiple Access

Abstract

We study a wireless-powered uplink communication system with non-orthogonal\nmultiple access (NOMA), consisting of one base station and multiple energy\nharvesting users. More specifically, we focus on the individual data rate\noptimization and fairness improvement and we show that the formulated problems\ncan be optimally and efficiently solved by either linear programming or convex\noptimization. In the provided analysis, two types of decoding order strategies\nare considered, namely fixed decoding order and time- sharing. Furthermore, we\npropose an efficient greedy algorithm, which is suitable for the practical\nimplementation of the time-sharing strategy. Simulation results illustrate that\nthe proposed scheme outperforms the baseline orthogonal multiple access scheme.\nMore specifically, it is shown that NOMA offers a considerable improvement in\nthroughput, fairness, and energy efficiency. Also, the dependence among system\nthroughput, minimum individual data rate, and harvested energy is revealed, as\nwell as an interesting trade-off between rates and energy efficiency. Finally,\nthe convergence speed of the proposed greedy algorithm is evaluated, and it is\nshown that the required number of iterations is linear with respect to the\nnumber of users.\n