Research And Application On RFID Based Indoor Location Methodology

Currently, location awareness demonstrates to be one of the most important characteristics and pursuing goals in ubiquitous computing. As one of the essential technologies of LBS, re-searches on indoor location methodologies and technologies are progressing. However, current indoor location systems still exists some problems, such as high positioning error, unstable per-formance easily influenced by the environment, trifles during system deployment and high cost (?) maintenance. These problems lead researchers to pay more attention on indoor location sys-:em.A comprehensive analysis on location methodologies and typical location systems is made. This thesis technically brings in the concept of virtual reference and constructs environment with a classic radio propagation model in the location area. Based on this methodology of vir-ual reference tag environment, a location algorithm is proposed. Besides, this thesis analyzes he statistical distribution of PRR (Packet Reception Rate), and investigates the relationship between PRR and distance by means of RSSI, which provides a new method and some theo-etical support for the further research on RFID indoor location.At first, this thesis introduces some basic concepts about real-time location system (RTLS), echnical classification and some classic tracking methodologies, for example, TOA, TDOA, AOA and RSSI. Some comparison on characteristics among these methodologies is made. Es-(?)ecially, Log-distance Path Loss Model and the location drawbacks with RSSI are illustrated. Then, this thesis compares some typical indoor location systems, such as RADAR, LocSens, SpotON, LANDAMRC and VIRE, and summarizes existing problems.Furthermore, this thesis technically proposes a methodology named virtual reference based (?)ositioning (VRBP) for the location positioning, which models the RFID positioning systems with virtual reference tags and constructs such information with a classical radio propagation nodel in order to enhance positioning accuracy. Instead of deploying a high density of RFID ags, the notion of VRBP decreases the possibility of signal interference. Furthermore, we pro- pose the VT-LANDMARC, a tracking algorithm which applies the VRBP and manifests a su-perior performance over the original LANDMARC in positioning accuracy. Besides these ad-vantages, with the help of the VRBP, the VT-LANDMARC ameliorates the defect in original LANDMARC that the location error may increase significantly in the margin area. And the VRBP methodology offers a practical solution for the location estimation with a scarce density of reference tags.Then, this thesis compares three metric, LQI, PRR and RSSI respectively, for link quality evaluation. Based on related PRR research, this thesis proposes a method to convert PRR data into RSSI information. After extensive experiments for distinct distances and transmission powers between RFID readers and tags, a PRR database for statistical analysis is established, and the PRR data is converted into RSSI information. Then, some statistical parameters, such as mean value, standard variance, kurtosis and Skewness, are analyzed in order to explore the sta-tistical distribution of PRR and verify the validity of the theoretical derivation. Besides, the thesis also investigates the relationship between PRR and distance by means of RSSI, which provides a new method and some theoretical support for the further research on RFID indoor location.Finally, based on VT-LANDMARC and the proposition of transformation relation between PRR and RSSI, a RFID indoor location system is designed and implemented. This thesis briefly introduces the specification of the utilized RFID devices. And based on the characteristics of RFID devices, this thesis designs a network pattern and proposes a structure model for the loca-tion system. Then, the detail of each module is illustrated respectively. In the end, a perform-ance experiment of this location system is conducted which demonstrates a desirable location accuracy.