Reconfigurable intelligent surfaces (RISs), also known as intelligent reflecting surfaces (IRSs), or large intelligent surfaces (LISs),1 have received significant attention for their potential to enhance the capacity and coverage of wireless networks by smartly reconfiguring the wireless propagation environment. Therefore, RISs are considered a promising technology for the sixth-generation (6G) of communication networks. In this context, we provide a comprehensive overview of the state-of-the-art on RISs, with focus on their operating principles, performance evaluation, beamforming design and resource management, applications of machine learning to RIS-enhanced wireless networks, as well as the integration of RISs with other emerging technologies. We describe the basic principles of RISs both from physics and communications perspectives, based on which we present performance evaluation of multiantenna assisted RIS systems. In addition, we systematically survey existing designs for RIS-enhanced wireless networks encompassing performance analysis, information theory, and performance optimization perspectives. Furthermore, we survey existing research contributions that apply machine learning for tackling challenges in dynamic scenarios, such as random fluctuations of wireless channels and user mobility in RIS-enhanced wireless networks. Last but not least, we identify major issues and research opportunities associated with the integration of RISs and other emerging technologies for applications to next-generation networks.1Without loss of generality, we use the name of RIS in the remainder of this paper.

中文翻译：

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可重构智能表面：原理和机遇


可重构智能表面 (RIS)，也称为智能反射表面 (IRS) 或大型智能表面 (LIS)1，因其通过智能地重新配置无线传播环境来增强无线网络容量和覆盖范围的潜力而受到广泛关注。因此，RIS被认为是第六代（6G）通信网络的一项有前途的技术。在此背景下，我们全面概述了 RIS 的最新技术，重点关注其工作原理、性能评估、波束成形设计和资源管理、机器学习在 RIS 增强型无线网络中的应用，以及RIS 与其他新兴技术的集成。我们从物理和通信的角度描述了 RIS 的基本原理，在此基础上我们提出了多天线辅助 RIS 系统的性能评估。此外，我们系统地调查了 RIS 增强型无线网络的现有设计，包括性能分析、信息论和性能优化观点。此外，我们还调查了应用机器学习来应对动态场景中挑战的现有研究贡献，例如无线信道的随机波动和 RIS 增强型无线网络中的用户移动性。最后但并非最不重要的一点是，我们确定了与 RIS 和其他新兴技术集成以应用于下一代网络相关的主要问题和研究机会。1在不失一般性的情况下，我们在本文的其余部分使用 RIS 的名称。