Resource Allocation in Wireless Powered Communication Networks With Non-Orthogonal Multiple Access

In this letter, we propose a non-orthogonal multiple access (NOMA) scheme for the uplink of wireless powered communication networks (WPCNs). In order to tackle the doubly near- far effect in WPCNs, the decoding order of the compound information signal received at the base station (BS) is set to be an inverse of the distances between the energy harvesting users (EHU) and the BS. For the proposed scheme, we derive jointly optimal allocations of the BS transmit power and the durations of the energy harvesting and information transmission phases, such that the rate region is maximized. Compared to NOMA schemes with fixed BS transmit power, the proposed scheme achieves notably higher rates, while maintaining high level of system fairness. Compared to time-division multiple access schemes, our scheme leads to significant rate enhancement of cell-edge EHUs, thus improving system fairness.