Capacity and outage performance analysis of secure cooperative RF-FSO relaying system in the presence of multiple eavesdroppers

Abstract

This paper presents the performance analysis of the cooperative radio frequency-free space optical (RF-FSO) relaying system in the presence of multiple eavesdroppers. In this work, the RF link is modeled with Hyper-Gamma (HG) distribution and the FSO link is modeled with unified Gamma–Gamma (ΓΓ) distribution. The RF-FSO combined channel is linked together through a decode-and-forward (DF) based relaying scheme. It is assumed that unknown number of eavesdroppers try to wiretap the confidential data sent from the source by using HG fading channels in the physical layer. The key concern of this work is to ensure safe data transmission through the proposed RF-FSO channel by defending them against passive eavesdropping activities. This work offers the mathematical closed-form expressions of the probability of strictly positive secrecy capacity (PSPSC), secure outage probability (SOP), and average secrecy capacity (ASC) in respect of Meijer’s G function. To acquire better insights into the proposed model, the asymptotic expression of SOP is also provided. Moreover, the impacts of receiver detection type, atmospheric turbulence, pointing error, and eavesdropper signal-to-noise ratio (SNR) on the secrecy performances are investigated in the derived outcomes. The demonstration of the supremacy of the proposed model is done based on the generic nature HG fading channel. Finally, all analytical outputs are checked through Monte Carlo simulations for validation purpose.