Cyclical NOMA Based UAV-Enabled Wireless Network

In order to achieve high spectral efficiency and low access delay, this paper introduces cyclical non-orthogonal multiple access (NOMA) into unmanned aerial vehicle (UAV)-enabled wireless network. It allows the UAV to communicate with multiple ground users in the same time-frequency resources, cyclically. The minimum throughput over all ground users is maximized by jointly optimizing multiuser communication scheduling with cyclical NOMA and UAV trajectory. It turns out that the maximization of minimum throughput is a mixed integer non-linear non-convex optimization problem. In this paper, this problem is decoupled into two blocks, i.e., the optimization of multiuser communication scheduling with cyclical NOMA and the optimization of UAV trajectory. Then, a joint optimization algorithm is proposed based on the block coordinate descent method. The simulation results demonstrate that the proposed joint optimization method can double the minimum throughput, compared with cyclical TDMA. In addition, it reduces users' average access delay and UAV's flying range under the same minimum throughput.