Secrecy capacity of hybrid FSO-RF communication links

In this paper, we analyze the secrecy capacity of hybrid communication links comprising cascaded free space optical (FSO) and radio frequency (RF) wireless systems. We consider the system in which FSO links are used as the medium of data transmission for the first hop followed by RF links for relaying the data to the destination. We consider Gamma–Gamma distributed channel gain for the FSO links and Nakagami-m fading distribution for the RF communication link. This takes care of both the line of sight (LOS) and non-LOS conditions for the RF link. We derive closed-form expressions for end-to-end secrecy capacity. The closed-form expressions are derived by representing the incomplete gamma function in the form of Meijer’s G-function. Further, closed-form solutions to the integrals involving the product of two Meijer’s G-functions are obtained. The analytical expressions have been validated through results obtained from simulations. A close agreement between the simulation and the analytical results is observed.