D-Watch: Embracing “bad” multipaths for device-free localization with COTS RFID devices

• Main Authors: WANG, Ju, XIONG, Jie, JIANG, Hongbo, CHEN, Xiaojiang, FANG, Dingyi
• Format: text
• Language: English
• Published: Institutional Knowledge at Singapore Management University 2017
• Subjects: Antennas; AoA; Calibration; Device-free localization; Estimation; multipath; Multiple signal classification; RFID tags; Target tracking; Intrusion detection; Watches; Commodity off the shelves; Device-free localizations; Localization accuracy; Multipath; Passive localization; RF-ID tags; State-of-the-art system; Radio frequency identification (RFID); Databases and Information Systems; Software Engineering
• Online Access: https://ink.library.smu.edu.sg/sis_research/3840; https://ink.library.smu.edu.sg/context/sis_research/article/4842/viewcontent/08048021.pdf
• Institution: Singapore Management University

Device-free localization, which does not require any device attached to the target, is playing a critical role in many applications, such as intrusion detection, elderly monitoring and so on. This paper introduces D-Watch, a device-free system built on the top of low cost commodity-off-the-shelf RFID hardware. Unlike previous works which consider multipaths detrimental, D-Watch leverages the ''bad'' multipaths to provide a decimeter-level localization accuracy without offline training. D-Watch harnesses the angle-of-arrival information from the RFID tags' backscatter signals. The key intuition is that whenever a target blocks a signal's propagation path, the signal power experiences a drop which can be accurately detected by the proposed novel P-MUSIC algorithm. The proposed wireless phase calibration scheme does not interrupt the ongoing data communication and thus reduces the deployment burden. We implement and evaluate D-Watch with extensive experiments in three different environments. D-Watch achieves a median accuracy of 16.5 cm for library, 25.5 cm for laboratory, and 31.2 cm for hall environment, outperforming the state-of-the-art systems. In a table area of 2 m$x$2 m, D-Watch can track a user's fist at a median accuracy of 5.8 cm. D-Watch is also capable of localizing multiple targets which is well known to be challenging in passive localization.