Robust Secure Hybrid Beamforming for RSMA Integrated Sensing and Communication Systems

Sharing resources in integrated sensing and communication (ISAC) systems poses a serious threat to the security of users information. In this paper, we consider the rate-splitting multiple access (RSMA) ISAC system based on the partially-connected hybrid beamforming architecture, where the target is a potential eavesdropper. To improve the performance of sensing and secure communication, we provide a robust hybrid beamforming scheme. Specially, we derive performance metrics for sensing and secure communication under the target location uncertainty. Then we formulate the sensing performance optimization problem meanwhile satisfying the secure communication, hardware and power constraints. To address the intractability of this non-convex problem, we propose a suboptimal iterative algorithm relying on semidefinite relaxation (SDR) and inner majorization-minimization (iMM) to alternately design digital and analog beamformers. Simulation results show the outperformance of the proposed approach over the existing hybrid beamformer design based on Eucliden distance in guaranteeing secure communication and sensing.