Robust secure beamforming for integrated sensing and communication systems with the active RIS.

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 with an active reconfigurable intelligence surface (RIS), where targets are potential eavesdroppers. In particular, we investigate secure communication and sensing in the RIS-aided RSMA ISAC system and provide a robust active beamforming scheme for the case of targets' imperfect channel state information (CSI). Specially, we formulate the maximization problem of radar signal to interference plus noise ratio (SINR) meanwhile satisfying the security outage probability (SOP) constraints for the individual user. To address the intractability of this non-convex problem, we propose a suboptimal iterative algorithm relying on semi-definite relaxation (SDR) and the Taylor expansion to alternately solve two tractable subproblems. Simulation results show the outperformance of alternating optimization (AO) algorithm in guaranteeing secure communication and sensing for the active RIS-aided RSMA ISAC system.