In a backscatter communication system, the backscatter device (BD) transmits its messages to the backscatter receiver (BR) by reflecting the incident signal from an external radio frequency (RF) emitter, instead of using power-hungry active RF components themselves. Thus, backscatter communication has shown great potential for achieving low-power communication. The double-fading effect associated with the backscatter link, however, is a major limiting factor to achieve efficient backscatter communication. Reconfigurable intelligent surfaces (RISs), a recently developed technology, can be applied at the BD to enhance the backscatter link thanks to the fact that both RIS and backscatter communication share the same reflective principle. Such a design can also allow the backscatter communication system to capture the desired RF signal as a reflective carrier in a complex radio environment. In this article, a comprehensive overview of backscatter communication assisted by RIS is given. We first introduce the basics of backscatter communication, which covers the antenna scattering principle, backscatter modulation, and link budget calculation. Then, the details of RIS are discussed, which include antenna-based RIS and metamaterial-based RIS, followed by the discussion of the roles of RIS in backscatter communication. After that, we provide an overview of three types of backscatter communication systems assisted by RIS, including RIS-assisted unmodulated backscatter communication, RIS-assisted ambient backscatter communication, and RIS-assisted symbiotic radio. Emerging applications of these systems, technical challenges, and future opportunities in this emerging field are also presented.

中文翻译：

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可重构智能表面辅助的反向散射通信


在反向散射通信系统中，反向散射设备 (BD) 通过反射来自外部射频 (RF) 发射器的入射信号将其消息传输到反向散射接收器 (BR)，而不是使用耗电的有源 RF 组件本身。因此，反向散射通信显示出实现低功耗通信的巨大潜力。然而，与反向散射链路相关的双衰落效应是实现高效反向散射通信的主要限制因素。可重构智能表面（RIS）是一项最近开发的技术，由于 RIS 和反向散射通信具有相同的反射原理，因此可以在 BD 中应用以增强反向散射链路。这样的设计还可以允许反向散射通信系统在复杂的无线电环境中捕获所需的射频信号作为反射载波。本文全面概述了 RIS 辅助的反向散射通信。我们首先介绍反向散射通信的基础知识，包括天线散射原理、反向散射调制和链路预算计算。然后，讨论了RIS的细节，包括基于天线的RIS和基于超材料的RIS，随后讨论了RIS在反向散射通信中的作用。之后，我们概述了 RIS 辅助的三种类型的反向散射通信系统，包括 RIS 辅助的未调制反向散射通信、RIS 辅助的环境反向散射通信和 RIS 辅助的共生无线电。还介绍了这些系统的新兴应用、技术挑战以及这一新兴领域的未来机遇。