Mixed RIS-Based RF-FSO Systems over DGG Turbulence and EGK Fading Channels

We investigate the performance of reconfigurable intelligent surface (RIS)-assisted mixed transmission systems of radio frequency (RF) and free space optics (FSO) over extended generalized-K (EGK) fading for the RF links and double generalized gamma (DGG) turbulence with misalignment errors for the FSO link. We have derived closed-form expressions for the most important performance metrics of outage probability and bit error rate for both fixed-gain and channel state information (CSI)-assisted amplify-and-forward (AF) relaying. Moreover, an asymptotic analysis at high signal-to-noise-ratios (SNRs) is done and the diversity order of both relaying methods is derived which provide physical insights. Monte-Carlo simulations confirm the accuracy and validity of the derived expressions.