Secure Beamforming for Multiple Intelligent Reflecting Surfaces Aided mmWave Systems

TL;DR

This paper proposes a novel secure beamforming approach for mmWave systems aided by multiple IRSs, optimizing IRS control and beamforming to maximize secrecy rate under practical constraints.

Contribution

It introduces an alternating optimization algorithm combining SCA and MO techniques for joint IRS control and beamforming in multi-IRS mmWave systems, enhancing security.

Findings

The proposed algorithm significantly improves secrecy rate.

It outperforms traditional single IRS schemes.

Numerical results validate the effectiveness of the method.

Abstract

In this letter, secure beamforming in a multiple intelligent reflecting surfaces (IRSs)-aided millimeter-wave (mmWave) system is investigated. In this system, the secrecy rate is maximized by controlling the on-off status of each IRS as well as optimizing the phase shift matrix of the IRSs. This problem is posed as a joint optimization problem of transmit beamforming and IRS control, whose goal is to maximize the secrecy rate under the total transmission power and unit-modulus constraints. The problem is difficult to solve optimally due to the nonconvexity of constraint conditions and coupled variables. To deal with this problem, we propose an alternating optimization (AO)-based algorithm based on successive convex approximation (SCA) and manifold optimization (MO) technologies. Numerical simulations show that the proposed AO-based algorithm can effectively improve the secrecy rate and outperforms the traditional single IRS-aided scheme.