Security-Ensured Integrated Sensing and Communication (ISAC) Systems Enabled by Phase-Coupled Intelligent Omni-Surfaces (IOS)

In this paper, we propose a security-enhanced integrated sensing and communication (ISAC) system enabled by phase-coupled Intelligent Omni-Surfaces (IOS). The IOS, without the need for additional sensors, divides the entire space into two parts: a communication part and a sensing part. The IOS serves multiple users by providing communication services while also creating a virtual line-of-sight (LOS) link for target sensing. Moreover, the IOS is utilized to ensure physical layer security. Due to the possibility of the sensing target intercepting communication information, it is crucial to limit the information leakage rate. To achieve this, we jointly design the communication beamformers, sensing beamformer, and the IOS's two phase-shift matrices. This joint design maximizes the sensing beam pattern gain towards the target, while meeting the requirements of the minimum signal-to-interference-plus-noise ratio (SINR) for communications and the maximum information leakage to possible malicious targets. To address this problem, we propose two types of alternative algorithms. The first type utilizes an independent phase-controlling model, while the second incorporates a coupled-phase model. Both algorithms aim to optimize the IOS's phase-shift matrices.