RIS-Empowered Secure and Reliable Satellite Communications With RSMA

This paper explores the utilization of reconfigurable intelligent surfaces (RIS) in rate-splitting multiple access (RSMA)-based satellite downlink communication systems to enhance secure performance against eavesdropper collusion. Particularly, we propose a novel security framework that leverages RSMA’s message-splitting capability alongside RISassisted transmission to effectively combat security vulnerabilities in satellite communication. By considering user fairness, the minimum secrecy rate among all legitimate users is maximized with the constraints of quality of service (QoS), phase shift matrix of RIS, and transmission power. To address the resulting nonconvex optimization problem, a penalty dual decomposition (PDD) algorithm is further employed, which is supported by a successive convex approximation (SCA) approach for iterative optimization. Numerical results validate that the proposed RISempowered RSMA design significantly outperforms benchmark schemes.