Performance analysis of hybrid FSO/RF communication over generalized fading models

Abstract

Hybrid free space optics/radio frequency (FSO/RF) communication has been considered as a promising solution for reliable wireless backhaul connectivity for 5G and beyond wireless communication systems. In this paper, comprehensive performance analysis of the hybrid FSO/RF system has been carried out considering single-threshold-based switching strategy for both terrestrial and satellite communication scenarios. We assume that the channel state of the FSO link follows generalized Malaga distribution with pointing errors and atmospheric attenuation. Further, the RF channel fading has been modeled using generalized α-η-κ-μ distribution, which includes most of the well-known RF fading distributions as special cases. We derive the unified closed-form expressions for outage probability, average symbol error rate (SER) and ergodic capacity of the hybrid FSO/RF system considering two types of detection techniques, i.e. heterodyne detection (HD) and intensity modulation/direct detection (IM/DD). Additionally, we determine the range of optimum switching threshold and optimum beam waist values using a numerical optimization method for achieving optimal performance. We also derive simpler asymptotic expressions in terms of elementary functions to obtain diversity gain and coding gain of the hybrid FSO/RF system. The theoretical results of the hybrid FSO/RF system, which are verified using Monte-Carlo simulations, unveil that under strong turbulence, high pointing errors, and adverse weather conditions, the performance of the hybrid FSO/RF system over FSO system is improved significantly due to RF backup link.