BLER and Throughput Analysis of Power Beacon-Based Energy Harvesting UAV-Assisted NOMA Relay Systems for Short-Packet Communications

In this paper, we analyze an unmanned aerial vehicle (UAV) that harvests energy from a power beacon to support the transmissions of finite blocklength packets from a source to two destinations using non-orthogonal multiple access (NOMA) scheme. The impacts of line-of-sight (LoS) and non-LoS communications on the block error rate (BLER) and throughput of the system are presented via the Rician factor. For the evaluation of system performance, we derive the closed-form and approximate expressions of the BLERs of each hop and the end-to-end communication path between source and destination. Based on these derived BLER expressions, we calculate the throughput of the considered UAV-NOMA-short packet communication (SPC) system. Analytical results are verified by Monte-Carlo simulations. Numerical results show that the best system performance can be achieved by selecting a reasonable time switching duration for energy harvesting, blocklength, and the number of training bits. The minimal BLERs can be obtained by controlling the trajectory of the UAV, i.e., its altitude and location on the horizontal plane. The BLER performance of the UAV-NOMA-SPC system is compared with that of the UAV-orthogonal multiple access (OMA)-SPC system, showing that the UAV-NOMA-SPC gives a lower average BLERs than the UAV-OMA-SPC system.