RSMA-Enhanced Secure Cognitive Radio for Non-Terrestrial Networks

This paper addresses the rate-splitting multiple access (RSMA) and beamforming (BF) design challenges in cognitive satellite-terrestrial networks. A joint BF design scheme is proposed, where RSMA is applied in the satellite networks, and the terrestrial networks adopt non-orthogonal multiple access. We assume that the channel state information of all users and eavesdropper is imperfect, the objective is to maximize the minimum achievable secrecy rate for satellite users, while securing secrecy rate constraints for primary users, meeting requirements for secondary users, and adhering to power budgets for both the satellite and base station. To solve the non-convex optimization problem, we transform it into a convex problem using the successive convex approximation (SCA) and semidefinite relaxation. An iterative BF algorithm based on SCA is developed to optimize the BF vectors. Numerical simulations validate the effectiveness and robustness of the proposed scheme.