Enhanced Sensing Performance in ISAC Systems With Communication Security Rate Constraints

This paper proposes a novel joint waveform design and precoding strategy leveraging a Reflective Intelligent Surface (RIS) to enhance physical layer security in Integrated Sensing and Communication (ISAC) systems. By using orthogonal communication and sensing subspaces, the system enables simultaneous multi-user communication and detection of suspicious users. Sensors deployed on a Dual-Functional Radar-Communication (DFRC) base station provide critical data, such as user positions, to improve communication channel security. The detection performance is quantified using the Cramer-Rao Bound (CRB), and an optimization approach is introduced to minimize CRB while ensuring the communication security rate and adhering to energy constraints. To solve the non-convex optimization problem, we propose a combination of the Augmented Lagrangian Method (ALM) and Block Coordinate Descent (BCD) algorithms to optimize emission precoding and RIS phase shifts. Simulation results confirm that the proposed approach not only enhances sensing performance under physical layer security constraints but also delivers more accurate results compared to existing methods, significantly advancing ISAC systems for surveillance applications.