Tagoram: Real-time tracking of mobile RFID tags to high precision using COTS devices

(ACM). In this work, we present an RFID-based system, Tagoram, for object localization and tracking using COTS RFID tags and read- ers. Tracking mobile RFID tags in real time has been a daunting task, especially challenging for achieving high precision. Our sys- tem achieves these three goals by leveraging the phase value of the backscattered signal, provided by the COTS RFID readers, to es- timate the location of the object. In Tagoram, we exploit the tag's mobility to build a virtual antenna array by using readings from a few physical antennas over a time window. To illustrate the basic idea of our system, we firstly focus on a simple scenario where the tag is moving along a fixed track known to the system. We pro- pose Differential Augmented Hologram (DAH) which will facili- tate the instant tracking of the mobile RFID tag to a high precision. We then devise a comprehensive solution to accurately recover the tag's moving trajectories and its locations, relaxing the assumption of knowing tag's track function in advance.We have implemented the Tagoram system using COTS RFID tags and readers. The system has been tested extensively in the lab environment and used for more than a year in real airline ap- plications. For lab environment, we can track the mobile tags in real time with a millimeter accuracy to a median of 5mm and 7.29mm using linear and circular track respectively. In our year- long large scale baggage sortation systems deployed in two air- ports, our results from real deployments show that Tagoram can achieve a centimeter-level accuracy to a median of 6.35cmin these real deployments.In many applications, we have to identify an object and then locate the object to within high precision (centimeter- or millimeter-level). Legacy systems that can provide such accuracy are either expensive or suffering from performance degradation resulting from various impacts, e.g., occlusion for computer vision based approaches.