RIS Equipped AAV Swarm: Shadowed Aerial-to-Ground Channel Characterization

Unmanned aerial vehicle (UAV) swarm enabled aerial reconfigurable intelligent surface (SARIS) system where multiple UAVs mounted with reconfigurable intelligent surface (RIS) has been proposed as a critical technology to enhance the capacity and coverage of wireless networks. However, the convolved channel nature of distributed RISs system and the high mobility of UAVs pose significant challenges to modeling and statistical characterization of the SARIS system. In this paper, a new analytical framework has been developed for investigating the performance of a SARIS communication system operating in a shadowed double-scattering air-to-ground (AtG) channel. In particular, with the moment matching method, a generalized negative binomial (GNB) distribution is utilized to approximate the probability density function (PDF) and cumulative distribution function (CDF) of the instantaneous signal-to-noise ratio (SNR). Subsequently, we derive the analytical expressions for performance analysis, including coverage probability (CP) and ergodic capacity (EC). Finally, these expressions are validated by Monte Carlo simulations. The performance of the GNB distribution approximation is also compared with that of a Gamma distribution approximation, highlighting the advantages of the proposed GNB distribution approximation in severe composite fading environments.