Can Artificial Noise Boost Further the Secrecy of Dual-hop RIS-aided Networks?

TL;DR

This paper investigates how artificial noise, via jamming and RISs, can enhance physical layer security in dual-hop RIS-assisted networks, providing analytical expressions and demonstrating significant secrecy improvements.

Contribution

It introduces a comprehensive analysis of physical layer security in dual-hop RIS networks with artificial noise, deriving approximate secrecy metrics and highlighting the benefits of jamming and RIS parameters.

Findings

Secrecy improves with increased jamming power and number of reflective elements.

An intercept probability of 10^{-4} is achievable with 40 REs and 10 dB jamming power.

Jamming is especially effective in scenarios with strong eavesdroppers.

Abstract

In this paper, we quantify the physical layer security of a dual-hop regenerative relaying-based wireless communication system assisted by reconfigurable intelligent surfaces (RISs). In particular, the setup consists of a source node communicating with a destination node via a regenerative relay. In this setup, a RIS is installed in each hop to increase the source-relay and relay-destination communications reliability, where the RISs' phase shifts are subject to quantization errors. The legitimate transmission is performed under the presence of a malicious eavesdropper attempting to compromise the legitimate transmissions by overhearing the broadcasted signal from the relay. To overcome this problem, we incorporate a jammer to increase the system's secrecy by disrupting the eavesdropper through a broadcasted jamming signal. Leveraging the well-adopted Gamma and Exponential distributions approximations, the system's secrecy level is quantified by deriving approximate and asymptotic expressions of the secrecy intercept probability (IP) metric in terms of the main network parameters. The results show that the secrecy is enhanced significantly by increasing the jamming power and/or the number of reflective elements (REs). In particular, an IP of approximately $10^{-4}$ can be reached with $40$ REs and $10$ dB of jamming power-to-noise ratio even when the legitimate links' average signal-to-noise ratios are $10$-dB less than the eavesdropper's one. We show that cooperative jamming is very helpful in strong eavesdropping scenarios with a fixed number of REs, and the number of quantization bits does not influence the secrecy when exceeding $3$ bits. All the analytical results are endorsed by Monte Carlo simulations.