Backscatter is a key technology for battery-free sensing in industrial IoT applications. To fully cover numerous tags in the deployment area, one often needs to deploy multiple readers, each of which communicates with tags within its communication range. However, the actual backscattered signals from a tag are likely to reach a reader outside its communication range and cause interference. Conventional TDMA or CSMA based approaches for interference avoidance separate readers' media access in time, leading to limited network throughput. In this paper, we propose TRIDENT, a novel backscatter design that enables interference avoidance via frequency-space division. By incorporating a tunable bandpass filter and multiple terminal loads, a TRIDENT tag can detect its channel condition and adaptively adjust the frequency and the power of its backscattered signals. We further propose a frequency assignment algorithm for the readers. With these designs, all the readers in the network can operate concurrently without being interfered. We implement TRIDENT and evaluate its performance under various settings. The results demonstrate that TRIDENT enhances the network throughput by 3.18x, compared to the TDMA-based scheme.

翻译：反向散射是工业物联网应用中无电池传感的关键技术。为充分覆盖部署区域内的众多标签，通常需要部署多个阅读器，每个阅读器与其通信范围内的标签进行通信。然而，标签实际反射的信号可能到达其通信范围外的阅读器并造成干扰。传统基于时分多址或载波侦听多路访问的干扰规避方法在时间维度上分离阅读器的媒体访问，导致网络吞吐量受限。本文提出TRIDENT——一种通过频空分集实现干扰规避的新型反向散射设计。通过集成可调带通滤波器和多个终端负载，TRIDENT标签能够检测其信道状态并自适应调整反射信号的频率与功率。我们进一步提出面向阅读器的频率分配算法。基于这些设计，网络中所有阅读器可无干扰地并发工作。我们实现了TRIDENT系统并在多种设置下评估其性能。实验结果表明，与基于时分多址的方案相比，TRIDENT将网络吞吐量提升了3.18倍。