Downlink Rate Maximization With Reconfigurable Intelligent Surface Assisted Full-Duplex Transmissions

Reconfigurable intelligent surfaces (RIS) is an effective technique for intelligently manipulating channel paths through reflection to serve desired users. Full-duplex (FD) systems, enabling simultaneous transmission and reception from a base station (BS), offer the theoretical advantage of doubled spectrum efficiency. However, the presence of strong self-interference (SI) in FD systems significantly degrades performance, which can be mitigated by leveraging the capabilities of RIS. In this work, we consider joint BS and RIS beamforming for maximizing the downlink (DL) transmission rate while guaranteeing uplink (UL) rate requirement. We propose an FD-RIS beamforming (FRIS) scheme by adopting penalty convex-concave programming. Simulation results demonstrate the UL/DL rate of the proposed FRIS scheme across different RIS deployments, RIS/BS configurations and rate requirements. FRIS has achieved the highest rate compared to the other approximation methods, conventional beamforming techniques, half-duplex (HD) systems, and deployment without RIS.