A Broad-Typed Multi-Sensing-Range Method for Indoor Position Estimation of Passive RFID Tags

The RFID (Radio Frequency IDentification) system is paid attention as a technology that can realize a ubiquitous environment. Each RFID tag has a unique ID code, and is attached on some object with the infor mation of the objects. A user reads the unique ID code using RFID readers and obtains the information of the object. One of the important applications of RFID technology is the indoor position estimation of RFID tags. It can be applied to a navigation system for people in complex buildings. In this paper, we propose an effective position est imation method named Broad-typed Multi-Sensing-Range (B-MSR ) to improve the conventional methods using sensor mo del on the estimation error. In B-MSR, we introduce a new reader antenna with two flexible antenna elements. For two flexible antenna elements, we can adjust the distance betwee n them. Thus, we can control two kinds of system parameters, the distance between two antenna elements and the transmission power of the RFID reader. In this paper, we settle four sensing ranges. Moreover, B-MSR is adap table to the three dimensional (3D) position estimation with sufficient accuracy. We further propose a 3D positi on estimation algorithm for B-MSR. The performance evaluation shows that B-MSR reduces the initial est imation error, the number of the different sensing points and finally the time to require the estimation than the convent ional methods. Keywords—RFID reader; RFID tag; position estimation ; sensor model; Broad-typed Multi-Sensing-Range metho d