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

We investigate how to well utilize Radio Frequency Identification (RFID) techniques for Real-Time Location Systems (RTLS). A new control method, LOCate TRacking tag through rEader power control and Candidate region intersection (LOCTREC), has been proposed to improve the RTLS estimation accuracy by eliminating trivial tag information from the estimation procedure. Multi-readers were deployed and operated with multi-power level to progressively refine the target tag region for accurate location estimation. To enhance the LOCTREC, visual tag interpolation algorithms were adopted to further refine the tag grid to enhance location estimation. Experiments showed that the estimation errors is 70% smaller than its counterpart of LANDMARC and SpotON which deploy regularly spaced reference tags to determine signal strength. For intuitive displaying the result, a video surveillance module was integrated with the RTLS to visually render the located objects, based on which context-aware services can be developed. One example is a smart wheelchair (SWC) with a friendly user-environment control interface that enables SWC users to interact with his living environment like a normal healthy person.