Intelligent Reflecting Surface Aided Robust Secure Integrated Sensing and Communication Systems

This paper investigates the intelligent reflecting surface (IRS)-aided robust secure communication where in an integrated sensing and communication (ISAC) system, a multi-antenna dual-functional radar and communication base station serves a single-antenna communication user and detects a malicious eavesdropping target simultaneously. An IRS equipped with lots of reflecting elements is deployed to assist the secure communication. By considering the scenario where the eavesdropper's instantaneous channel state information (CSI) is not perfectly known, a robust secure communication design is proposed which aims to maximize the secrecy rate by jointly optimizing the transmit beamforming and the IRS reflecting coefficients while satisfying the sensing constraints. A bounded uncertainty model is adopted to capture the angle error and fading channel error of the eavesdropper, and a tractable bound for their joint uncertainty is derived via some mathematical manipulations. Moreover, a block coordinate descent-based algorithm is utilized to tackle the formulated non-convex problem. Simulation results show that the proposed algorithm can achieve secure communication effectively even with the eavesdropper's imperfect CSI.