Visible light communication (VLC)-based indoor localization approaches enjoy many advantages, such as utilizing ubiquitous lighting infrastructure, high location accuracy, and no interruption to RF-based devices. However, existing VLC-based localization methods lack a real-time backward channel from the device to landmarks and necessitate computation at the device, which make them unsuitable for real-time tracking of small IoT devices. In this paper, we propose and prototype RETRO, that establishes an almost zero-delay backward channel by retroreflection. RETRO localizes passive IoT devices without requiring computation and heavy sensing (e.g., camera) at the devices. Multiple photodiodes (i.e., landmarks) are mounted on any single unmodified light source to sense the retroreflected optical signal (i.e., location signature). We derive a closed-form expression, which is validated by experiments and ray tracing simulations, for the reflected optical power relative to the location and the orientation of the retroreflector. The expression is applied to a received signal strength indicator and trilateration based localization algorithm. Extensive experiments demonstrate centimeter-level location accuracy and single-digit angular error. For practicality concern, to mitigate the thickness problem of a single retroreflector, the capabilities of different retroreflector arrays are studied. The range of the localization system is theoretically evaluated for different light emission patterns.

中文翻译：

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通过可见光逆反射实现物联网设备的实时室内跟踪

基于可见光通信 (VLC) 的室内定位方法具有许多优势，例如利用无处不在的照明基础设施、定位精度高以及不会中断基于 RF 的设备。然而，现有的基于 VLC 的定位方法缺乏从设备到地标的实时反向通道，并且需要在设备上进行计算，这使得它们不适合对小型物联网设备进行实时跟踪。在本文中，我们提出并原型化 RETRO，它通过回射建立了一个几乎零延迟的反向通道。RETRO 定位无源物联网设备，而无需在设备上进行计算和繁重的传感（例如，相机）。多个光电二极管（即地标）安装在任何单个未修改的光源上以感测回射光信号（即位置特征）。我们推导出一个封闭形式的表达式，该表达式通过实验和光线追踪模拟得到验证，用于相对于后向反射器的位置和方向的反射光功率。该表达式应用于接收信号强度指标和基于三边测量的定位算法。大量实验证明了厘米级的定位精度和个位数的角度误差。出于实用性考虑，为了减轻单个回射器的厚度问题，研究了不同回射器阵列的能力。定位系统的范围在理论上针对不同的光发射模式进行评估。该表达式应用于接收信号强度指标和基于三边测量的定位算法。大量实验证明了厘米级的定位精度和个位数的角度误差。出于实用性考虑，为了减轻单个回射器的厚度问题，研究了不同回射器阵列的能力。定位系统的范围在理论上针对不同的发光模式进行评估。该表达式应用于接收信号强度指标和基于三边测量的定位算法。大量实验证明了厘米级的定位精度和个位数的角度误差。出于实用性考虑，为了减轻单个回射器的厚度问题，研究了不同回射器阵列的能力。定位系统的范围在理论上针对不同的发光模式进行评估。