On security performance analysis of IRS-aided VLC/RF hybrid system

Abstract

Intelligent reflecting surface (IRS) has been introduced into wireless communication to improve physical layer security (PLS) due to its ability of reconfiguring propagation environments. However, most current research on IRS-aided PLS is for standalone radio frequency (RF) or visible light communication (VLC), and few has focused on IRS-aided VLC/RF hybrid systems combining the wide coverage of RF and high speed of VLC. We study the PLS of an IRS-aided dual-hop VLC/RF hybrid system, where the first VLC link is to transmit optical signal, and the second RF link assisted by IRS is to extend communication region inaccessible to visible light, and the two hops are connected by a relay in decode-and-forward or amplify-and-forward mode. Two eavesdropping scenarios are considered: eavesdropping from IRS and eavesdropping from relay. Then, the closed-form expressions of secrecy outage probability and strictly positive secrecy capacity probability are derived for four combinations of eavesdropping scenarios and relay modes, and corresponding asymptotic solutions are obtained. Finally, simulations are carried out to verify the superiority of the proposed system over a conventional hybrid system without IRS, and the proposed system shows different security performance for various scenarios and relay modes, and IRS has a positive effect on improving PLS.