The sixth-generation (6G) wireless technology recognizes the potential of reconfigurable intelligent surfaces (RIS) as 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. Moreover, accurately obtaining channel state information (CSI) from RIS poses a critical challenge. Our objective is to maximize downlink (DL) user data rates while ensuring quality-of-service (QoS) for uplink (UL) users under imperfect CSI from reflected channels. To address this, we propose a robust active BS and passive RIS beamforming (RAPB) scheme for RIS-FD, accounting for both SI and imperfect CSI. RAPB incorporates distributionally robust design, conditional value-at-risk (CVaR), and penalty convex-concave programming (PCCP) techniques. Simulation results demonstrate the UL/DL rate improvement are achieved by considering different levels of imperfect CSI. The proposed RAPB schemes validate their effectiveness across different RIS deployments and RIS/BS configurations. Benefited from robust beamforming, RAPB outperforms the existing methods in terms of non-robustness, deployment without RIS, conventional approximation, and half-duplex systems.

翻译：第六代（6G）无线通信技术认识到可重构智能表面（RIS）作为一种通过反射智能操控信道路径以服务目标用户的有效技术潜力。全双工（FD）系统支持基站（BS）同时传输与接收，理论上具有双倍频谱效率的优势。然而，FD系统中强自干扰（SI）的存在会显著降低性能，而利用RIS的能力可缓解这一问题。此外，从RIS精确获取信道状态信息（CSI）是一项关键挑战。我们的目标是在反射信道存在非完美CSI的情况下，最大化下行链路（DL）用户数据速率，同时确保上行链路（UL）用户的服务质量（QoS）。为此，我们提出了一种针对RIS-FD的鲁棒主动BS与被动RIS波束成形方案（RAPB），该方案综合考量了SI与非完美CSI。RAPB结合了分布鲁棒设计、条件风险价值（CVaR）以及惩罚凸凹规划（PCCP）技术。仿真结果表明，通过考虑不同程度的非完美CSI，可实现UL/DL速率提升。所提出的RAPB方案在不同RIS部署及RIS/BS配置下均验证了其有效性。得益于鲁棒波束成形，RAPB在非鲁棒性、无RIS部署、传统近似以及半双工系统等场景下均优于现有方法。