Performance Analysis of IRS-Assisted Hybrid FSO/RF Communication System

Abstract

Free space optics (FSO) communication is seen as a cost-effective way to provide higher bandwidth, higher data rates, better link security, higher immunity to interference, etc., compared to radio frequency (RF) communication over short link distances. Despite these advantages, FSO link is severely affected by pointing errors, atmospheric turbulence, and signal loss due to the obstructions caused by buildings, trees, mountains, etc. In this paper, we propose a hybrid communication system model consisting of a FSO subsystem backed by a reliable RF subsystem with the goal to improve the coverage and system reliability. In addition, both the FSO and RF subsystems are assisted by intelligent reflecting surfaces (IRS). Specifically, we carry out the performance analysis of the IRS-assisted hybrid FSO/RF system by deriving approximate closed-form expressions for outage probability, average bit error rate (BER), and ergodic channel capacity assuming intensity modulation/direct detection (IM/DD) technique. The numerical results are shown along with insightful discussions. It is observed from the numerical results that the system performance improves as the number of elements in IRS increases. Further, the IRS-assisted hybrid FSO/RF system performs better in terms of ergodic capacity and average BER than the existing FSO and hybrid FSO/RF systems. Finally, Monte-Carlo simulations are presented to verify the correctness of the analytical results.