Item-Level RFID Tag Location Sensing Utilizing Reader Antenna Spatial Diversity

Abstract

A robust estimation procedure for sensing the locations of passive UHF radio frequency identification (RFID) tags is introduced based on spatial deployment of the reader antennas for maximum signal diversity. A signal model is developed for the received signal strength indicator seen by each reader antenna and incorporated into a mean-square error testing function. The error function is minimized at each test point in the interrogation zone to find the point with the minimum mean-square error. The minimization is independent of the tag type and orientation, making the proposed method very robust compared with other methods that are based on reference tags and radio maps. Experimental results are presented for a realistic retail scenario with multiple tagged items achieving an estimation accuracy of 35 cm. The location sensing system uses conventional UHF RFID readers, antennas, and passive tags, providing additional capability to existing item-level RFID systems. This added value will help to offset the high cost of large-scale RFID infrastructure development.

Design and Implementation of a Real-Time Object Location System Based on Passive RFID Tags

“…The GPS is there for outdoor positioning and is hard to be utilized for indoor positioning in that shadowing effect will decrease or eliminate the intensity of satellite signals. Several researches have been conducted in designing wireless location algorithms for indoor positioning systems, such as the wireless sensor network (WSN) [8], wireless local area network (WLAN) [9], and radio frequency identification (RFID) [10]. Indoor positioning systems based on available network infrastructures can provide location accuracy from 1 to 10 m, but requiring high complex deployments.…”

Passive UWB RFID for Tag Localization: Architectures and Design

“…Once the CW signal has ended, the falling of the resulting voltage is used for initiating the backscatter modulation of the UWB signals. In this way the propagation-dependent capacitor charge time 9 does not play a significant role in the synchronization jitter, since the discharge starting event is not affected by the path loss and depends only on the tags' circuitry. Such solutions have been proposed and experimented in [19], [40].…”

“…1. While rough localization precision can be obtained with current RFID technology [7]- [9], sub-meter accuracy requires a technology shift. A possibility is represented by the adoption of ultra-wideband (UWB) signals.…”

Indoor Localization Systems for Passive Uhf Rfid Tag Based on Rssi Radio Map Database

“…The concept behind utilizing the reference tags for localization is as follows, firstly relying on distributing a number of tags at known locations. Tags at the known locations are used to estimate the target tag position by applying different techniques [15,16]. Shao and Burkholder [16] link the reference tag technique and radio map fingerprint to improve localization accuracy.…”

“…Tags at the known locations are used to estimate the target tag position by applying different techniques [15,16]. Shao and Burkholder [16] link the reference tag technique and radio map fingerprint to improve localization accuracy. The RSSI based techniques utilize the attenuation of the transmitted power to estimate the distance between the interrogator and the target tag.…”