Reliability analysis of optical IRS-enabled FSO system with multiple detectors and PCB under composite turbulence fading channels considering the impact of GML

Abstract

Free space optical (FSO) communication with optical intelligent reflecting surface (IRS) assistance is one promising and evolving technology that can relax the line-of-sight requirement and enable more efficient and reliable link performance in obstacles areas. In this work, an optical IRS-enabled FSO system is proposed with partially coherent beam (PCB) and multiple detectors. Specifically, for an end-to-end (e2e) IRS-assisted FSO link, the statistical model of optical signal fluctuations due to atmospheric turbulence is assumed to follow Fisher–Snedecor F-distribution, and the random movements of IRS, transmitter (Tx), and receiver (Rx) due to building sway is modeled by geometric and misalignment losses. Considering the Gaussian–Schell model and intensity modulation/direct detection, the analytical average bit error rate (ABER) expressions of the studied system are obtained for a single detector and multiple detectors, respectively, with selected combining (SC), equal gain combining (EGC) and maximum ratio combining (MRC) aperture diversity schemes over independent identically distributed composite fading channels. And the correctness of the analytical results is verified through the Monte-Carlo based statistical simulation method. Results show that the ABER and outage probability performance of IRS-assisted FSO link degrades with the increase in the strength of atmospheric turbulence and building sway. And even the position fluctuations variances of Tx, IRS, and Rx are the same, their impacts on the e2e IRS-assisted FSO link are not the same. Interestingly, aperture diversity techniques can significantly mitigate these adverse effects, especially in the case of MRC scheme. Besides, the studied system with PCB can achieve better system performance compared to that using coherent beam, and the performance gap would become more obvious as the spatial coherence radius decreases. This work could serve as a guide for the design and research of IRS-enabled FSO communication systems.