Performance Analysis for Mixed κ-μ Fading and M-Distribution Dual-Hop Radio Frequency/Free Space Optical Communication Systems

Mixed radio frequency (RF) and free space optical (FSO) communications are a promising alternative technology for backbone networks of next-generation wireless communications, but bottlenecks exist due to atmospheric turbulence. In this paper, the performance of amplified-and-forward dual-hop mixed RF/FSO systems with heterodyne detection and intensity modulation/direct detection techniques, in consideration of pointing errors, is investigated. In particular, an asymmetric fading environment is considered where the RF hop is assumed to follow κ-μ fading, which includes Nakagami-m and Rayleigh fading as special cases, while the FSO link is subjected to unified M-distribution fading, which has proven to be a general statistical distribution that accurately describes the fading model for the optical intensity under weak-to-strong turbulence conditions. More specifically, closed-form expressions for both the cumulative distribution function (CDF) and probability distribution function (PDF) of the end-to-end mixed RF/FSO system are derived in terms of the Meijer's G function. Capitalizing on the derived CDF and PDF expressions, novel closed-form expressions for the outage probability, the average bit error rate (BER), and the ergodic capacity under various modulation schemes are presented. Additionally, we present tight asymptotic formulae for the outage probability and the average BER at the high signal-to-noise ratio (SNR) regime in terms of some elementary functions under various modulation schemes, which offer helpful insights into the influence of the channel parameters and system parameters on the performance of the mixed RF/FSO system. Finally, both Monte-Carlo simulation and numerical results are provided to corroborate our derived expressions.