Performance Analysis of SAG FSO/RF Two-Hop Transmission in the Presence of Co-Channel Interference

Abstract

Free-space optical (FSO) communication is a promising solution for future satellite-to-ground networks because it can achieve extremely high data rates. High-altitude platforms (HAPs) have the potential to provide stable satellite-to-ground connections in this context. In this study, we present a unified performance analysis method for two-hop space-air-ground (SAG) links using HAPs relay technology. This method considers co-channel interference (CCI) in radio frequency (RF) links and pointing errors in FSO links. Specifically, we use the translation and inversion properties of Meijer’s G function and its integral characteristics to derive exact closed-form expressions for the cumulative distribution function (CDF) and probability density function (PDF) of the end-to-end signal-to-noise ratio (SNR) in the SAG transmission system. We convert complex composite functions into single Meijer’s G function representations to circumvent the computational complexity of double integrals of Meijer’s G functions. Furthermore, based on the Mellin transform, we derive generalized integral formulas for multiple Meijer’s G functions. Using this theoretical framework, we analyze various performance metrics of the transmission system and obtain unified, exact, closed-form expressions, including outage probability (OP), the average bit error rate (BER) for binary modulation schemes, and the ergodic capacity (EC). All of these are represented in terms of Meijer’s G function. Numerical and Monte Carlo simulation results verify the proposed method’s accuracy with perfect consistency.