Performance Analysis of UAV-Based MMW/FSO Relay-Assisted System

This paper examines the backhauling of data collected from wireless sensors in dangerous or radiation-contaminated areas using mobile gateway trucks. To mitigate the risk to humans, unmanned trucks and unmanned aerial vehicles (UAVs) are assumed to be utilized for data collection and signal relaying, respectively. As the data measured by the sensors is crucial, a dependable backhauling link is necessary. Therefore, we propose the use of relay-assisted UAV-based hybrid Millimeter-waves and free-space optical (MMW/FSO) systems to establish a reliable communication link. The multiple-input multiple-output free-space optical (MIMO-FSO) system is used to improve the performance of the FSO link. We consider the impact of atmospheric-induced turbulence fading (gamma-gamma), pointing errors, and weather attenuation, such as fog and rain, on the FSO link. We derive an approximate expression for the composite fading of an FSO single-input single-output (SISO-FSO) link using generalized Gauss-Laguerre quadrature. We utilize the $\alpha-\mu$ distribution and consider the proposed receiver arrangement to derive approximate expressions for the probability density function (PDF), cumulative distribution function (CDF), and outage probability of an equal-gain combining FSOMIMO system. We employ the Nakagami-m distribution to characterize the multipath fading effect on the MMW signal and obtain the outage probability of the MMW system. We derive the source-to-destination outage probability expression and use it to evaluate the outage performance of the MMW/FSO relay-based link.