On the Ergodic Secrecy Capacity of Reconfigurable Intelligent Surface Aided Wireless Systems Under Mixture Gamma Fading

TL;DR

This paper analyzes the physical layer security of RIS-assisted wireless systems under various fading conditions, deriving a closed-form ergodic secrecy capacity expression that accounts for different RIS sizes and fading models.

Contribution

It provides a novel closed-form expression for ergodic secrecy capacity in RIS-aided systems under mixture Gamma fading, encompassing many common fading models.

Findings

Increasing RIS size boosts legitimate link diversity.

ESC gain diminishes as RIS size grows.

The model covers diverse fading environments.

Abstract

This paper presents a quantified assessment of the physical layer security capabilities of reconfigurable intelligent surface (RIS)-aided wireless systems under eavesdropping. Specifically, we derive a closed-form expression for the ergodic secrecy capacity (ESC) that is adaptable to different types of fading and RIS size. The channels between the transmitter (TX) and RIS, the RIS and legitimate receiver as well as the TX and eavesdropper are assumed to follow independent mixture Gamma (MG) distributions. Note that MG is capable of modeling a large variety of well-known distributions, including Gaussian, Rayleigh, Nakagami-m, Rice, and others. The results reveal that as the RIS size increases, although the legitimate links diversity order increases, the ESC gain decreases.