Outage Probability and Capacity Analysis of Active RIS-Assisted UAV RSMA Communications

Unmanned aerial vehicle (UAV) and active reconfigurable intelligent surface (ARIS) can enhance wireless communications channels through flexible location deployment and intelligent signal reflection. On the other hand, rate-splitting multiple access (RSMA) is an efficient framework for non-orthogonal transmission and multiple access. In this paper, we explore the synergistic advantages of integrating these technologies within a unified UAV-mounted ARIS-assisted communications system employing RSMA. Specifically, we analyze the system outage probability and sum capacity considering independent and non-identically distributed Nakagami-m channels, circularly uniformly distributed random RIS phase shifts, and imperfect successive interference cancellation. We first derive the exact cumulative distribution and probability density functions of the sum single and double Nakagami-m vectors via multivariate Fox’s H-function. These allow us to derive the closed-form expressions for the outage probability, asymptotic outage probability, and sum ergodic capacity of the system. The analytical findings are then verified via extensive numerical simulations, which highlight the superior performance of UAV-ARIS RSMA compared to conventional UAV-based systems.