Current discussions on the sixth Generation (6G) of wireless communications are envisioning future networks as a unified communication, sensing, and computing platform that intelligently enables diverse services, ranging from immersive to mission critical applications. The recently conceived concept of the smart radio environment, enabled by Reconfigurable Intelligent Surfaces (RISs), contributes towards this intelligent networking trend, offering programmable propagation of information-bearing signals, which can be jointly optimized with transceiver operations. Typical RIS implementations include metasurfaces with nearly passive meta-atoms, allowing to solely reflect the incident wave in an externally controllable way. However, this purely reflective nature induces significant challenges in the RIS orchestration from the wireless network. For example, channel estimation, which is essential for coherent communications in RIS-empowered wireless networks, is quite challenging with the available RIS designs. This article introduces the concept of Hybrid reflecting and sensing RISs (HRISs), which enables metasurfaces to reflect the impinging signal in a controllable manner, while simultaneously sense a portion of it. The sensing capability of HRISs facilitates various network management functionalities, including channel estimation and localization. We discuss a hardware design for HRISs and detail a full-wave proof-of-concept. We highlight their distinctive properties in comparison to reflective RISs and active relays, and present a simulation study evaluating the HRIS capability for performing channel estimation. Future research challenges and opportunities arising from the concept of HRISs are presented.

翻译：目前关于第六代(6G)无线通信的讨论正在设想未来的网络,作为一个统一的通信、感测和计算平台,能够明智地提供各种服务,从浸透到任务的关键应用。最近构想的智能无线电环境概念,由重新配置智能表面(RIS)促成,有助于形成这种智能的联网趋势,提供可编程的含有信息的信号的传播,可以通过收发机操作共同优化。典型的RIS实施包括近乎被动元解剖的元表面,只允许以外部可控制的方式反映事件波。然而,这种纯粹的反射性质在无线网络的RIS调弦化中带来重大挑战。例如,频道估计对于在RIS动力无线网络中进行连贯通信至关重要,对于现有的IRS设计相当具有挑战性。 文章介绍了反映和感测RIS(HRIS)的混合概念,使元表层能够以可控制的方式反映干扰性信号,同时能以外部可控的方式反映事件波波波浪。 HRIS的感测能力使得各种网络管理功能的精确性分析,包括进行我们目前对服务器的精确性变变变动的变变变变变变的变变变变变变的变的变的变的变的内压和变式研究。