Resource Allocation for Energy Harvesting-Powered D2D Communications Underlaying NOMA-Based Networks

This paper investigates the resource allocation problem in device-to-device (D2D) communications underlaying a non-orthogonal multiple access (NOMA)-based cellular network with energy harvesting, where the energy harvesting-powered D2D communications share the downlink resources of the cellular network. To fully exploit the high-data-rate D2D links in this system, a two-phase framework is proposed for D2D users. In particular, the D2D users harvest energy from the base station (BS) in the first phase and then transmit their own information using the harvested energy in the second one. Meanwhile, the D2D communications could cause severe interference to cellular users (CUs) and hence probably ruin the SIC decoding order of the CUs. To deal with this issue, joint power allocation and time scheduling scheme is proposed to maximize the throughput of the D2D links while guaranteeing the quality of service (QoS) for each CU. Through rigorous derivation, the optimal power control and time scheduling parameters are analyzed to simplify the optimization problem formulation. The closed-form optimal solution is derived in some cases. In other cases, a gradient-based algorithm is employed to find an appropriate sub-optimal solution. The simulation results are demonstrated to validate the superiority of the proposed scheme over the conventional orthogonal multiple access (OMA) scheme.