There is much interest in fine-grained RFID localization systems. Existing systems for accurate localization typically require infrastructure, either in the form of extensive reference tags or many antennas (e.g., antenna arrays) to localize RFID tags within their radio range. Yet, there remains a need for fine-grained RFID localization solutions that are in a compact, portable, mobile form, that can be held by users as they walk around areas to map them, such as in retail stores, warehouses, or manufacturing plants. We present the design, implementation, and evaluation of POLAR, a portable handheld system for fine-grained RFID localization. Our design introduces two key innovations that enable robust, accurate, and real-time localization of RFID tags. The first is complex-controlled polarization (CCP), a mechanism for localizing RFIDs at all orientations through software-controlled polarization of two linearly polarized antennas. The second is joint tag discovery and localization (JTDL), a method for simultaneously localizing and reading tags with zero-overhead regardless of tag orientation. Building on these two techniques, we develop an end-to-end handheld system that addresses a number of practical challenges in self-interference, efficient inventorying, and self-localization. Our evaluation demonstrates that POLAR achieves a median accuracy of a few centimeters in each of the x/y/z dimensions in practical indoor environments.

翻译：精细粒度RFID定位系统备受关注。现有高精度定位系统通常需要基础设施支持，例如大量参考标签或多天线（如天线阵列）才能实现射频范围内的标签定位。然而，市场仍需要一种紧凑便携、可手持移动的精细RFID定位方案——用户可在零售商店、仓库或制造工厂等区域行走时进行环境测绘。本文提出POLAR系统，这是一种用于精细RFID定位的便携式手持系统的设计、实现与评估。我们的设计引入两项关键创新，实现了对RFID标签的稳健、精准、实时定位。第一项创新是复极化控制（CCP），该机制通过软件控制两个线极化天线的极化方式，实现对任意朝向RFID标签的定位。第二项创新是联合标签发现与定位（JTDL），该方法可在零开销情况下同时完成标签定位与读取，且不受标签朝向影响。基于这两项技术，我们开发了端到端手持系统，解决了自干扰、高效盘点及自主定位等实际挑战。实验评估表明，在实际室内环境中，POLAR在x/y/z各维度上的中位精度可达数厘米级别。