Precoder Design for RIS-Assisted Interference Suppression in Full-Duplex Integrated Satellite-Terrestrial Networks

This article investigates the performance of a reconfigurable intelligent surface (RIS)-assisted full-duplex (FD) integrated satellite-terrestrial network (ISTN). Particularly, the RIS structure is incorporated into the ISTN topology to curb the effects of the undesirable self-interference (SI) resulting from the FD operation, cross-tier interference (CTI), and intracell interference (ICI). To examine this network performance, an optimization problem is formulated to maximize the sum rate of users by jointly optimizing the active beamforming and RIS reflection coefficients. To address the non-convexity of the optimization problem, it is decomposed into two subproblems: one which involves applying the fractional programming (FP) technique to find the optimal solution for the active beamforming variable, while the other subproblem constitutes the use of successive convex approximation (SCA) to optimize the passive beamforming variable. These subproblems are solved alternately until convergence. Numerical results presented herein confirm that the proposed algorithm outperforms the benchmark schemes.