Joint Height Optimization and Channel Allocation for NOMA Enhanced UAV Relay Networks

In this paper, we investigate how to apply the nonorthogonal multiple access (NOMA) technique into the UAVassisted relay networks, and how to optimize system parameters to further improve the network performance. Specifically, we incorporate NOMA with the decode-and-forward (DF) relay protocol, where the destinations can receive the signals of the source and the relay simultaneously via NOMA. Theoretical analysis demonstrates that the proposed NOMA-DF-relay protocol is superior to the traditional orthogonal multiple access (OMA) based DF-relay protocol in terms of data rate. To fully exploit the advantages of the proposed protocol, we formulate a joint UAV height optimization and channel allocation problem with the objective to maximize the total data rate under the constraints of the rate requirement of each user. Based on the golden section method and the matching theory, we propose an efficient algorithm to solve the formulated problem optimally. Simulation results indicate that the NOMA-DF-relay protocol is superior to the OMA-DF-relay protocol, and the proposed algorithm can further improve the total data rate in comparison with the other schemes.