Reconfigurable intelligent surface (RIS) has been recognized as an essential enabling technique for the sixth-generation (6G) mobile communication network. Specifically, an RIS is comprised of a large number of small and low-cost reflecting elements whose parameters are dynamically adjustable with a programmable controller. Each of these elements can effectively reflect a phase-shifted version of the incident electromagnetic wave. By adjusting the wave phases in real time, the propagation environment of the reflected signals can be dynamically reconfigured to enhance communication reliability, boost transmission rate, expand cellular coverage, and strengthen communication security. In this paper, we provide an overview on RIS-assisted wireless communications. Specifically, we elaborate on the state-of-the-art enabling techniques of RISs as well as their corresponding substantial benefits from the perspectives of RIS reflection and RIS modulation. With these benefits, we envision the integration of RIS into emerging applications for 6G. In addition, communication security is of unprecedented importance in the 6G network with ubiquitous wireless services in multifarious verticals and areas. We highlight potential contributions of RIS to physical-layer security in terms of secrecy rate and secrecy outage probability, exemplified by a typical case study from both theoretical and numerical aspects. Finally, we discuss challenges and opportunities on the deployment of RISs in practice to motivate future research.
翻译:重新配置的智能表面(RIS)已被公认为是第六代(6G)移动通信网络的基本赋能技术。具体地说,RIS由大量小型和低成本的反映要素组成,这些要素的参数与可编程控制器可动态调整,每个要素都能够有效反映事件电磁波的分阶段变换版本。通过实时调整波级,反映信号的传播环境可以动态重组,以提高通信可靠性、提高传输率、扩大蜂窝覆盖面和加强通信安全。在本文中,我们概述了RIS辅助无线通信。具体地说,我们详细阐述了RIS的先进赋能技术及其从RIS反射和RIS调控角度的相应重大利益。有了这些好处,我们设想将RIS纳入6G的新兴应用中。此外,通信安全在6G网络中具有前所未有的重要性,在多种垂直和地区有着普遍的无线服务。我们强调RIS对实体-级无线通信安全的潜在贡献,具体地阐述了RIS的最新赋能技术及其从RIS反射镜反射镜反射镜研究中产生的重大利益。我们从典型的理论性研究中,最后讨论了数字机密性研究的概率和风险。