Performance of dual-hop FSO/RF systems with fixed-gain relaying over Fisher-Snedecor and κ-μ shadowed fading channels.

We investigate the performance of a dual-hop mixed free space optical (FSO) /radio frequency (RF) system with fixed-gain relaying under direct detection and heterodyne detection techniques. The FSO link is modeled by the Fisher-Snedecor distribution, which matches well with the experimental data under weak-to-strong turbulence regimes. The RF link experiences - shadowed fading, which unifies popular RF fading models. The - shadowed distribution is approximated by an - distribution. Capitalizing on this approximation, closed-form approximate expressions for the cumulative distribution function, the average bit error rate of different modulation schemes, and the ergodic capacity are derived in terms of the bivariate Fox's H function. Moreover, asymptotic analysis is carried out at a high signal-to-noise ratio to further illustrate the obtained diversity order and the influence of system and channel parameters. Numerical results and Monte Carlo simulations are presented to validate the derived approximate expressions.