UAV-Assisted Cooperative Downlink NOMA: Deployment and Resource Allocation

Abstract

This paper examines the downlink scenario of an unmanned aerial vehicle (UAV)-assisted non-orthogonal-multiple-access (NOMA), where the UAV acts as a decode-and-forward half-duplex (HD) or full-duplex (FD) relay to assist the transmission from a terrestrial base station (TBS) to ground devices. The main objective is to maximize the achievable sum rate for each relaying mode by jointly optimizing the beamforming at TBS and UAV, and the location of the UAV, subject to the power budget constraints at both the TBS and the UAV, the successive interference cancellation (SIC) constraint and the required quality-of-service at all ground devices. In order to tackle the highly-coupled decision variables, an efficient algorithm is designed by considering the alternating optimization approach which divides the original problem into a beamforming design optimization sub-problem and a UAV positioning optimization sub-problem, which are alternatively solved. The two sub-problems were tackled with the aid of the successive convex approximation (SCA). The simulation results demonstrate the accuracy of our solution approach and show the potential gains in the achievable sum rate brought by integrating the FD/HD aerial relay in NOMA networks.