Performance analysis of mixed RF/FSO system over multiple dominant specular power fading

The performance of a dual-hop mixed radio frequency (RF) /free-space optical (FSO) system with and without pointing error is evaluated. In mixed RF/FSO, the first hop between the sender and relay is considered to be an RF link, and the second hop between the relay and receiver is taken as an FSO link. The RF link is modelled with Two‑Wave Diffused Power (TWDP) fading, and the FSO link is modelled with Gamma–Gamma (GG) turbulence with and without pointing error. Statistical parameters for the joint distribution are calculated to derive the expression for the average bit error rate for MPSK and MQAM modulation schemes. The analytical results closely match the Monte Carlo simulation. Asymptotes taken at high SNR match the numerical results at high SNR (> 20 dB).