Recent advances in the fabrication and experimentation of reconfigurable intelligent surfaces (RISs) have motivated the concept of the smart radio environment, according to which the propagation of information-bearing waveforms in the wireless medium is amenable to programmability. Although the vast majority of recent experimental research on RIS-empowered wireless communications gravitates around narrowband beamforming in quasi-free space, RISs are foreseen to revolutionize wideband wireless connectivity in dense urban as well as indoor scenarios, which are usually characterized as strongly reverberant environments exhibiting severe multipath conditions. In this article, capitalizing on recent physics-driven experimental explorations of RIS-empowered wave propagation control in complex scattering cavities, we identify the potential of the spatio-temporal control offered by RISs to boost wireless communications in rich scattering channels via two case studies. First, an RIS is deployed to shape the multipath channel impulse response, which is shown to enable higher achievable communication rates. Second, the RIS-tunable propagation environment is leveraged as an analog multiplexer to localize non-cooperative objects using wave fingerprints, even when they are outside the line of sight. Future research challenges and opportunities in the algorithmic design and experimentation of smart rich scattering wireless environments enabled by RISs for sixth generation wireless communications are discussed.

中文翻译：

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用于丰富散射无线通信的可重构智能表面：最近的实验、挑战和机遇


可重构智能表面（RIS）制造和实验的最新进展激发了智能无线电环境的概念，根据该环境，无线介质中信息承载波形的传播是可编程的。尽管最近关于 RIS 无线通信的绝大多数实验研究都集中在准自由空间中的窄带波束成形，但 RIS 预计将彻底改变密集城市和室内场景中的宽带无线连接，这些场景通常具有强烈混响环境的特征严重的多径条件。在本文中，利用最近对复杂散射腔中 RIS 授权的波传播控制的物理驱动实验探索，我们通过两个案例研究确定了 RIS 提供的时空控制在丰富散射信道中促进无线通信的潜力。首先，部署 RIS 来塑造多径信道脉冲响应，这表明可以实现更高的通信速率。其次，RIS 可调谐传播环境被用作模拟多路复用器，使用波指纹来定位非合作对象，即使它们位于视线之外。讨论了第六代无线通信 RIS 支持的智能富散射无线环境的算法设计和实验方面的未来研究挑战和机遇。