Ultramassive multiple-input, multiple-output (MIMO) is one of the key enablers in the forthcoming 6G networks to provide high-speed data services by exploiting spatial diversity. In this article, we consider a new paradigm, termed holographic radio for ultramassive MIMO, where numerous tiny and inexpensive antenna elements are integrated to realize high directive gain with low hardware cost. We propose a practical way to enable holographic radio by a novel metasurface-based antenna, i.e., reconfigurable holographic surface (RHS). Specifically, RHSs incorporating densely packed tunable metamaterial elements are capable of holographic beamforming. Based on the working principle and hardware design of RHSs, we conducted full-wave analyses of RHSs and built an RHS-aided point-to-point communication platform supporting real-time data transmission. Both simulated and experimental results show that the RHS has great potential to achieve high directive gain with a limited size, thereby substantiating the feasibility of RHS-enabled holographic radio. Moreover, future research directions for RHS-enabled holographic radio are also discussed.

中文翻译：

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可重构全息表面：实现全息无线电的新范式


超大规模多输入多输出 (MIMO) 是即将推出的 6G 网络通过利用空间分集提供高速数据服务的关键推动因素之一。在本文中，我们考虑了一种新的范例，称为超大规模 MIMO 全息无线电，其中集成了许多微小且廉价的天线元件，以较低的硬件成本实现高定向增益。我们提出了一种通过新型超表面天线（即可重构全息表面（RHS））实现全息无线电的实用方法。具体来说，包含密集封装可调谐超材料元件的 RHS 能够进行全息波束形成。基于RHS的工作原理和硬件设计，我们对RHS进行了全波分析，构建了RHS辅助的支持实时数据传输的点对点通信平台。仿真和实验结果均表明，RHS具有在有限尺寸下实现高定向增益的巨大潜力，从而证实了RHS全息无线电的可行性。此外，还讨论了支持 RHS 的全息无线电的未来研究方向。