Backscatter Communication (BackCom) nodes harvest energy from and modulate information over external carriers. Reconfigurable Intelligent Surface (RIS) adapts phase shift response to alter channel strength in specific directions. In this paper, we unify those two seemingly different technologies (and their derivatives) into one architecture called RIScatter. RIScatter is a batteryless cognitive radio that recycles ambient signal in an adaptive and customizable manner, where dispersed or co-located scatter nodes partially modulate their information and partially engineer the wireless channel. The key is to render the probability distribution of reflection states as a joint function of the information source, Channel State Information (CSI), and relative priority of coexisting links. This enables RIScatter to softly bridge BackCom and RIS; reduce to either in special cases; or evolve in a mixed form for heterogeneous traffic control and universal hardware design. We also propose a low-complexity Successive Interference Cancellation (SIC)-free receiver that exploits the properties of RIScatter. For a single-user multi-node network, we characterize the achievable primary-(total-)backscatter rate region by optimizing the input distribution at scatter nodes, the active beamforming at the Access Point (AP), and the energy decision regions at the user. Simulations demonstrate RIScatter nodes can shift between backscatter modulation and passive beamforming.

中文翻译：

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RIScatter：统一反向散射通信和可重构智能表面


反向散射通信 (BackCom) 节点从外部载波收集能量并通过外部载波调制信息。可重构智能表面 (RIS) 采用相移响应来改变特定方向的通道强度。在本文中，我们将这两种看似不同的技术（及其衍生物）统一到一个名为 RIScatter 的架构中。 RIScatter 是一种无电池认知无线电，以自适应和可定制的方式回收环境信号，其中分散或共处一地的分散节点部分调制其信息并部分设计无线信道。关键是将反射状态的概率分布呈现为信息源、信道状态信息（CSI）和共存链路的相对优先级的联合函数。这使得 RIScatter 能够软桥接 BackCom 和 RIS；特殊情况减少为其中之一；或者以混合形式发展以实现异构流量控制和通用硬件设计。我们还提出了一种低复杂度的无连续干扰消除 (SIC) 接收器，它利用了 RIScatter 的特性。对于单用户多节点网络，我们通过优化散射节点处的输入分布、接入点 (AP) 处的主动波束成形以及接入点 (AP) 处的能量决策区域来表征可实现的主（总）反向散射率区域。用户。仿真表明 RIScatter 节点可以在反向散射调制和无源波束形成之间切换。