Twins:Device-free Object Tracking using Passive Tags

TL;DR

This paper introduces Twins, a device-free object tracking system using passive RFID tags that exploits a novel interference phenomenon for effective motion detection and localization.

Contribution

It presents a new interference model for passive RFID tags and a practical intrusion detection scheme with a real prototype demonstrating low location error.

Findings

Average location error of 0.75 meters

Effective detection of moving objects

Validated interference model through extensive experiments

Abstract

Without requiring objects to carry any transceiver, device-free based object tracking provides a promising solution for many localization and tracking systems to monitor non-cooperative objects such as intruders. However, existing device-free solutions mainly use sensors and active RFID tags, which are much more expensive compared to passive tags. In this paper, we propose a novel motion detection and tracking method using passive RFID tags, named Twins. The method leverages a newly observed phenomenon called critical state caused by interference among passive tags. We contribute to both theory and practice of such phenomenon by presenting a new interference model that perfectly explains this phenomenon and using extensive experiments to validate it. We design a practical Twins based intrusion detection scheme and implement a real prototype with commercial off-the-shelf reader and tags. The results show that Twins is effective in detecting the moving object, with low location error of 0.75m in average.