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：精细尺度的RFID定位系统备受关注。现有的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）来在其无线电范围内定位RFID标签。然而，在零售商店、仓库或制造工厂等场景中，用户手持便携式移动设备在区域内行走时，仍需一种紧凑、便携、可移动的精细RFID定位解决方案。本文介绍了POLAR系统的设计、实现与评估，这是一种用于精细RFID定位的手持式便携系统。我们的设计引入两项关键创新，实现了鲁棒、准确且实时的RFID标签定位。第一项创新是复杂控制极化（CCP）机制，通过软件控制两个线性极化天线的极化方向，实现全方向RFID标签的定位。第二项创新是联合标签发现与定位（JTDL）方法，可在零开销的情况下同时定位和读取标签，且不受标签朝向影响。基于这两项技术，我们开发了一套端到端的手持系统，解决了自干扰、高效库存盘点及自定位等实际挑战。评估表明，在实际室内环境中，POLAR在x/y/z各维度的中位精度可达厘米级。