Joint User Scheduling and Beamforming for RIS-Aided Full-Duplex Integrated Satellite-Terrestrial Networks

While full-duplex (FD) operation boosts spectral efficiency and lowers latency, it is severely limited by self-interference (SI). Recently, the reconfigurable intelligent surface (RIS) technology has been perceived as one of the candidate solutions for alleviating SI. This article proposes a RIS-aided SI-cancellation framework for an FD-based integrated satellite-terrestrial network (FD-ISTN). In particular, we formulate an optimization problem to maximize the sum data rate of users via joint user scheduling and beamforming. The optimization problem is decomposed into two subproblems: one to account for user scheduling and active beamforming, and the second to handle passive beamforming. Furthermore, we propose the generalized power iteration (GPI) approach to address the former subproblem and the successive convex approximation (SCA) technique to manage the latter subproblem. The GPI and SCA-based algorithms are solved alternately to find the solution to the optimization problem. Simulation results demonstrate that the proposed framework significantly improves the spectral and energy efficiency compared with representative baseline schemes, while effectively mitigating SI in FD-ISTNs