Sum Rate Maximization for NOMA-Assisted UAV Systems with Individual QoS Constraints

Non-orthogonal multiple access (NOMA) is a promising technology to connect more devices than traditional orthogonal multiple access (OMA) technology. On the other hand, unmanned aerial vehicles (UAVs) are playing a more important role in providing ubiquitous connections as flying base stations (BSs). The combination of UAV and NOMA technology has been a hot topic of current researches. This paper investigates a joint power allocation and UAV location optimization problem in two-user downlink NOMA-assisted UAV systems to maximize the sum rate with individual quality of service (QoS) constraints. To solve this complex problem, we divide the original problem into two subproblems. The first one is power allocation optimization problem and the second one involves UAV location optimization. Closed-form optimal solutions of the power allocation factor and the UAV location are obtained. To make a fair comparison, an OMA-UAV system with the same constraints is also considered. Numerical results validate the accuracy of the proposed NOMA scheme and the superiority of the NOMA scheme to the OMA one.