Pointing error influence on the performance of dual-hop radio frequency/wireless optical communication system over Nakagami-m/Fisher-Snedecor turbulence channels

Radio-frequency/Wireless Optical Communication (RF/WOC) systems are used for long-distance transmission where the optical signals are severely impacted by atmospheric turbulence. This article provides the performance analysis of a dual-hop RF/WOC system where RF and wireless optical channels undergo Nakagami-m and Fisher-Snedecor (F\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mathcal{F}$$\end{document}) distributions with approximate Beckmann distribution respectively. This system can operate with either coherent heterodyne detection (HD) or non-coherent intensity modulation with direct detection (IM/DD) scheme. The mathematical formulation of the cumulative distribution function (CDF) is derived for instantaneous overall received signal-to-noise ratio (SNR) using the fixed gain amplify and forward (AF) relaying technique. Its CDF is being utilized to create new analytical formulas for outage probability (OP), average bit error rate (ABER), and ergodic capacity (EC). Moreover, asymptotic analysis for the performance metrics is performed to get more insights. Additionally, a single WOC system that was previously studied and modeled by F\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mathcal{F}$$\end{document} fading distribution with pointing errors is compared with the proposed system. The analytical findings demonstrate that the performance of the system is exacerbated by essential factors, including atmospheric turbulence and pointing errors and the HD scheme is preferable to a IM/DD scheme. Moreover, ABER with CBPSK modulation is found better than other binary modulation schemes. Additionally, results reveal that the considered system has remarkable performance improvement over a single WOC system.