Joint Beamforming and Intelligent Reflecting Surface Optimization for Enhanced Physical Layer Security

Abstract Enhancing physical layer security through the deployment of Intelligent Reflecting Surfaces (IRS) is an emerging and significant research direction in Six-Generation (6G) wireless networks. Existing methods mainly focus on optimizing the transmit beamforming of the Access Point (AP) and the phase shift of the IRS to maximize the secrecy rate, while neglecting the optimization of the IRS amplitude. We propose a joint optimization framework that simultaneously optimizes the IRS amplitude, IRS phase shifts, and AP beamforming to enhance the secrecy rate. Due to the problem’s non-convexity, existing alternating optimization methods face high challenges, particularly for large-scale IRS systems and high-power scenarios. To tackle these issues, we propose a competition mechanism based multi-strategy swarm optimization algorithm, which aims to better balance global exploration and local exploitation capabilities, thereby achieving more optimal IRS configurations. Simulations demonstrate that jointly optimizing IRS amplitude, phase, and AP beamforming significantly improves secrecy rate over phase-only beamforming methods.