Physical-Layer Security Analysis of Mixed SIMO SWIPT RF and FSO Fixed-Gain Relaying Systems

This paper studies the physical-layer security problem for mixed single-input multiple-output (SIMO) simultaneous wireless information and power transfer (SWIPT) based radio frequency (RF) and free-space optical (FSO) communication systems. The FSO link experiences Málaga turbulence and each RF link suffers from Nakagami-m fading and path loss. We consider one energy harvesting receiver in our system model that may act as a potential eavesdropper. More precisely, to investigate the secrecy performance of considered mixed SIMO SWIPT based RF and FSO communication system, we derive closed-form expressions for the average secrecy capacity and the lower bound of secrecy outage probability by considering the fixed-gain relaying scheme, the multiple-antenna technique, the energy harvesting, the intensity modulation with direct detection, and the heterodyne detection techniques in the presence of pointing error.