RSMA-Enhanced Physical Layer Security for ISAC Systems

As a key technology of 6G, integrated sensing and communication (ISAC) has attracted much attention, and its security issues are becoming increasingly severe. In this letter, we enhance the physical layer security (PLS) of ISAC systems using rate-splitting multiple access (RSMA). To ensure specific security requirements, we formulate a joint optimization problem that involves the precoding matrix and the common rate. The goal is to maximize the communication-sensing weighted secure sum rate (SSR), thereby enhancing the overall system performance while maintaining security. To solve the non-convex optimization problem, we adopt the staged algorithm named successive convex approximation with penalty (SCA-P) algorithm. Firstly, the original non-convex problem is transformed into a series of more tractable convex problems. Then, penalty terms are introduced to deal with complex constraints. Finally, we gradually approach the optimal solution of the original problem by iteratively solving these convex problems. Simulation results show that the proposed scheme has better security performance than the state-of-the-art schemes.