NOMA-Aided UAV Communications over Correlated Rician Shadowed Fading Channels

In this paper, non-orthogonal multiple access (NOMA) is investigated as a viable solution to address spectrum scarcity in unmanned aerial vehicle (UAV) communications. Specifically, the performance analysis of a NOMA-aided UAV communication system (UCS) with dual-diversity receivers on UAVs is conducted over bivariate Rician shadowed fading channels. Using newly obtained closed-form expressions for the joint probability density function (PDF) and joint cumulative distribution function (CDF), the outage probability and finite signal-to-noise ratio (SNR) diversity gain of NOMA-aided UCS are investigated within a stochastic geometry framework. A comprehensive analysis reveals that NOMA-aided UCSs can support more UAVs on the same spectrum than OMA-based systems, with similar outage probability. It is also shown that the cross correlation affects the diversity gain of NOMA-aided and OMA-based UCSs only at low SNR regimes. Therefore, NOMA-aided UCSs can be an attractive alternative over OMA-based UCSs in future wireless systems.