The reconfigurable intelligent surface (RIS) has aroused much research attention recently due to its potential benefits in 5G and beyond wireless networks. This paper considers a general multi-hop RIS-aided multi-user communication system and the weighted sum-rate maximization problem is studied by jointly designing the active beamforming matrix at the base station and multiple phase-shift matrices at the RISs (considering both continuous and discrete phase constraints). To tackle the resulting highly nonconvex optimization problem, a problem-tailored low-complexity and globally convergent algorithm based on block minorization-maximization (BMM) is proposed. The effectiveness of the proposed BMM approach and the performance improvement gained with multi-hop RISs are both demonstrated through numerical simulations. The merits of the proposed algorithms are further illustrated by indicating their adaptivity in solving many other RIS-related system designs.

中文翻译：

---

多跳RIS辅助多用户通信的加权和速率最大化：一种最小化最大化方法

可重构智能表面（RIS）由于其在5G和无线网络之外的潜在优势，最近引起了很多研究关注。本文考虑了一个通用的多跳RIS辅助多用户通信系统，并通过共同设计基站的有源波束成形矩阵和RIS​​的多个相移矩阵来研究加权总和速率最大化问题（考虑了连续和连续两个方面）。和离散相位约束）。为了解决由此产生的高度非凸优化问题，提出了一种基于块最小化最大化（BMM）的针对问题的低复杂度全局收敛算法。数值模拟证明了所提出的BMM方法的有效性以及通过多跳RIS获得的性能改进。