Secure Transmission Design for RSMA-ISAC Systems

This paper investigates a secure downlink integrated sensing and communication (ISAC) system assisted by rate-splitting mutiple access (RSMA). To ensure the sensing quality but reduce the leakage of legitimate information, we present to make full use of the common signal and dedicated signal as artificial noise (AN) to degrade the quality of the wiretap channels, under certain conditions. Joint beamforming and rate splitting optimization problem is formulated to maximize the minimum secrecy rate among all users, while meeting the constraints of maximum transmit power, communication rates, and the upper bound of squared beampattern error. The non-convex optimization problem is converted into tractable form through mathematical methods. Then, successive convex approximation (SCA)-based iterative algorithm is proposed to solve the re-formulated problem. Simulation results demonstrate the superiority of the proposed RSMA-aided secure scheme in both improving the security performance and achieving flexible trade-off between the sensing and security performances compared with traditional non-orthogonal multiple access (NOMA) scheme.