Secure Wireless Communication via Intelligent Reflecting Surface

TL;DR

This paper explores how an intelligent reflecting surface (IRS) can enhance secure wireless communication by jointly optimizing beamforming to maximize secrecy rate, especially in challenging scenarios with strong, correlated eavesdropper channels.

Contribution

It introduces an IRS-assisted secure communication framework and proposes an efficient algorithm for joint beamforming optimization under complex channel conditions.

Findings

Significant secrecy rate improvement with IRS compared to no IRS

Proposed algorithm outperforms heuristic schemes

Effective in scenarios with strong, correlated eavesdropper channels

Abstract

An intelligent reflecting surface (IRS) can adaptively adjust the phase shifts of its reflecting units to strengthen the desired signal and/or suppress the undesired signal. In this letter, we investigate an IRS-aided secure wireless communication system where a multi-antenna access point (AP) sends confidential messages to a single-antenna user in the presence of a single-antenna eavesdropper. In particular, we consider the challenging scenario where the eavesdropping channel is stronger than the legitimate communication channel and they are also highly correlated in space. We maximize the secrecy rate of the legitimate communication link by jointly designing the AP's transmit beamforming and the IRS's reflect beamforming. While the resultant optimization problem is difficult to solve, we propose an efficient algorithm to obtain high-quality suboptimal solution for it by applying the alternating optimization and semidefinite relaxation methods. Simulation results show that the proposed design significantly improves the secrecy communication rate for the considered setup over the case without using the IRS, and outperforms a heuristic scheme.