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 introduce the 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. Additionally, RAPB extends to active and passive beamforming (APB) with perfect channel estimation. Simulation results demonstrate the UL/DL rate improvements achieved considering various levels of imperfect CSI. The proposed RAPB/APB schemes validate their effectiveness across different RIS deployment and RIS/BS configurations. Benefited from robust beamforming, RAPB outperforms existing methods in terms of non-robustness, deployment without RIS, conventional successive convex approximation, and half-duplex systems.

翻译：第六代（6G）无线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的潜力。全双工（FD）系统实现了基站（BS）的并发收发，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的能力可以缓解这一问题。此外，准确获取RIS的信道状态信息（CSI）构成关键挑战。我们的目标是在反射信道非理想CSI条件下，最大化下行（DL）用户数据速率，同时保证上行（UL）用户的服务质量（QoS）。为此，我们针对RIS-FD引入了鲁棒主动BS和被动RIS波束赋形（RAPB）方案，同时考虑SI和非理想CSI。RAPB融合了分布鲁棒设计、条件风险价值（CVaR）和惩罚凸凹规划（PCCP）技术。此外，RAPB还扩展至完美信道估计下的主动与被动波束赋形（APB）。仿真结果展示了考虑不同非理想CSI程度下UL/DL速率的提升。所提出的RAPB/APB方案在不同RIS部署和RIS/BS配置下验证了其有效性。得益于鲁棒波束赋形，RAPB在非鲁棒性、无RIS部署、传统逐次凸近似及半双工系统等现有方法中表现出更优性能。