Performance Analysis of Space-Air-Ground Integrated Network (SAGIN) Over an Arbitrarily Correlated Multivariate FSO Channel

The space-air-ground integrated network (SAGIN) system interconnect several networks in order to achieve a large network topology that is capable of efficient sharing of global information and resources. Nevertheless, the associated communication facilities between the mobile platforms and air-to-ground links are limited to a low-bit rate radio-based technology. Besides, the huge services to be supported require a high capacity link in order to handle multiple information in parallel and in real-time. The free-space optical (FSO) communication system has inherent features to support the network demands. However, support for drifting in the SAGIN system could be challenging for the FSO line-of-sight links because of the requirement for alignment between the receiver and transmitter modules. Also, the FSO system performance is hindered by the atmospheric turbulence-induced fading. In addition, the unmanned aerial vehicles in the SAGIN system can operate in swarm mode to achieve system diversity in order to alleviate turbulence-induced fading. However, this can lead to channel correlation that can impair the system performance. In this paper, we consider the effect of arbitrarily correlated FSO channel on the system performance. To achieve this, we employ exponential model for modeling the correlations between the apertures. Furthermore, to account for the spatial correlation in the air-to-ground as well as air-to-air communications in the SAGIN system, we consider a multivariate Gamma–Gamma (ΓΓ\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\varGamma \varGamma$$\end{document}) distribution. The results of the study sufficiently quantify the effects of the atmospheric turbulence-induced fading as well as correlation on the system.