Performance and Channel Modeling Optimization for Hovering UAV-Assisted FSO Links

Unmanned Aerial Vehicle (UAV)-assisted free-space optical (FSO) communication has become a promising solution in both civil and military applications. Nevertheless, hovering UAV-assisted FSO links suffer from several losses due to atmospheric turbulence, pointing errors (PEs), angle-of-arrival (AOA) fluctuations, and link attenuation related to various weather conditions. In this paper, we optimize the theoretical channel model for hovering UAV-assisted FSO links considering all the above destructive channel factors. Our optimized theoretical channel model agrees with the Monte-Carlo simulation results much better under the full range of channel coefficients compared to previous published works. Based on our optimized theoretical channel model, theoretical expressions of the link outage probability, ergodic and outage capacity, and bit error rate are derived. The impact of various parameters, such as Rytov variance, root-mean-squares (RMS) of PEs and AOA fluctuations, angle of field-of-view, rain rate, visibility, optical beam divergence angle, and transmitted power on the above performance metrics is analytically studied and corroborated by Monte-Carlo simulations. Simulation results also show that for a given receiving aperture, transmit power, and link length, the performance of the hovering UAV-assisted FSO links can be optimized by carefully designing the ratio of optical beam divergence angle to RMS of PEs.