Multihop radio and optical wireless relaying systems over EGK, DGG, and CU fading channels

Optical wireless communications (OWC) systems provide higher data rates in the unlicensed spectrum bands compared to traditional radio frequency (RF) wireless communications systems. OWC systems are categorized as free space optical (FSO) communications and visible light communications (VLC) for outdoor and indoor environments, respectively. In this paper, we propose a multihop serial RF, FSO, and VLC system and investigate the link performance for five different scenarios with amplify-and-forward and decode-and-forward relaying protocols under different channel conditions. Based on the SNR statistics, we show closed-form expressions for the outage probability for all scenarios and derive their diversity orders. In addition, we examine the accuracy and correctness of the derived expressions by means of Monte Carlo simulations. We further prove that the diversity order is a function of the severity of the RF links and the shaping parameters, the atmospheric turbulence, the pointing error in FSO links, the detection method, and number of links. Finally, the presented results complement and extend several results previously reported in the literature.