Comprehensive Channel Modeling of UAV-Assisted FSO Systems under Fog, AoA Fluctuations, and Pointing Errors

This paper investigates the outage performance of unmanned aerial vehicle (UAV)-assisted free-space optical (FSO) communication systems operating in foggy channels. The analysis jointly accounts for atmospheric turbulence, fog-induced attenuation, generalized Beckmann-distributed pointing errors (PE), and angle-of-arrival (AoA) fluctuations caused by UAV orientation jitter. A comprehensive statistical channel model is developed, from which closed-form expressions for outage probability and an analytical characterization of outage capacity are derived. The effects of receiver field-of-view (FoV) limitations and multi-UAV amplify-and-forward relaying on link reliability are also investigated. Numerical results validate the proposed analysis and reveal that AoA fluctuations impose a fundamental performance limit, resulting in an outage floor, particularly under dense fog and narrow-FoV conditions. These findings provide practical design insights for improving the reliability of UAV-assisted FSO communication systems in adverse weather environments.