Research on Physical Layer Security Performance of Multi-user Mixed RF/FSO Communication System in FSO Eavesdropping Environment

This paper presents a mixed RF/FSO communication system in the environment of FSO eavesdropping, and studies the optimization of physical layer security (PLS) of the system. In this system model, the RF link experiences Rayleigh fading, and the FSO link follows the Fischer-Snedecor F distribution. An eavesdropper with an optical receiving device is located near the destination node in the FSO link. The optical eavesdropping device near the destination node captures and eaveson the optical signal transmitted by the relay. Based on the above system model, we derive closed-form expressions for the mixed RF/FSO communication system’ s Secrecy Outage Probability (SOP) and Strictly Positive Secrecy Capacity (SPSC). Monte Carlo simulations are performed to verify the accuracy of these expressions. The effects of various key factors on the system security performance are analyzed by simulation. The results show that the increase of the optimal user transmission signal-to-noise (SNR) ratio, the decrease of the eavesdropping SNR and the improvement of weather conditions have obvious effects on the system security performance, which provides a good theoretical basis for the physical layer security application of mixed RF/FSO system in the environment of FSO eavesdropping.