Performance analysis and optimization for UAV-based FSO communication systems

Recently, with the increasingly mature development of unmanned aerial vehicle (UAV) technology, free-space optical (FSO) communication with the UAV relay has gradually attracted extensive attention from scholars at home and abroad. In this paper, a hovering UAV-based FSO dual-hop decode-andforward system with multiple sources is investigated. In the system, channel attenuation coefficient is affected by atmospheric loss, atmospheric turbulence, pointing error and angle-of-arrival fluctuation. By analyzing the probability density functions (PDF) of these four factors, we derive a tractable expression for the PDF of the total channel gain. Then, closed-form expression of the end-to-end outage probability and asymptotic outage performance bounds are derived to evaluate the influence of different factors on the system performance. Based on the derived theoretical expressions, the location of UAV and the number of source nodes are jointly optimized to improve the overall system performance and reduce the system cost. Numerical results show that the derived theoretical expressions are accurate to evaluate the outage performance of the system. Moreover, the proposed optimization algorithm significantly improves the system performance and can provide the optimal parameter selection for UAV system design.