Cooperative Rate Splitting Secure Transmission With an Untrusted User Relay

Combining rate splitting (RS) with cooperative relay, cooperative RS (CRS) can reduce the interference and improve the sum rate of conventional RS networks. However, since the common message can be decoded by both users, how to prevent the untrusted relay from eavesdropping the other user's private message remains a challenge. In this correspondence, we propose a two-slot CRS scheme to guarantee the security of the far legitimate user from the other untrusted relay. The problem is a non-convex joint optimization of the precoding matrix, slot allocation and rate allocation, which is approximated as a convex one. Then, an iterative algorithm is designed to solve the problem. Simulation results show that the proposed scheme can effectively guarantee the security of the far user towards eavesdropping.