Uplink NOMA Random Access for UAV-Assisted Communications

This correspondence paper investigates uplink non-orthogonal multiple access (NOMA) for unmanned aerial vehicle base stations (UAV-BSs). Users under the service area of a UAV-BS perform NOMA random access (RA) by controlling their transmit power so that the UAV-BS can receive one of two predefined power levels. This facilitates successive interference cancellation (SIC) at the UAV-BS. This correspondence paper shows the maximum stable throughput of uplink NOMA RA in terms of the altitude and beamwidth of the UAV-BS. Further, we propose a stabilizing algorithm, with which a UAV-BS broadcasts the throughput-maximal retransmission probability every slot, while users access the channel based on the retransmission probability. Extensive simulations show that the proposed algorithm can achieve the maximum throughput 0.5869 (packets/slot) and stabilize the system with time-varying traffic.