Performance Analysis of RSMA-Aided UAV-to-Ground Communications

This paper investigates the performance of downlink rate-splitting multiple access (RSMA)-aided unmanned aerial vehicle (UAV) communication systems, wherein a multi-antenna UAV exploits RSMA to serve multiple ground users. Considering nonline-of-sight environments, double-shadowed scattering channel modeling is adopted to generically characterize the impacts of mobility and shadowing on UAV-to-ground communications, assuming imperfect successive interference cancellation (SIC). Besides, a unified precoder design is proposed to fully capture the benefits of multi-antenna paradigms. Closed-form expressions for the users' outage probability (OP) and ergodic capacity are derived. In addition, asymptotic analysis is carried out to get further insights into the system design, such as the diversity gain and ergodic slope. Numerical results are presented, and it is shown that: 1) the effects of double-shadowed scattering on the system outage performance can be significantly reduced by increasing the number of antennas installed at the UAV; 2) the imperfect SIC error can be minimized by properly optimizing the power allocation of the common stream; and 3) RSMA provides superior users' ergodic capacity compared to its orthogonal and non-orthogonal multiple access counterparts.