Research Of Indoor Positioning Algorithm Based On The RFID Technology

Radio Frequency Identification (RFID), is a generic term for the technology using radio waves to automatically identify individual items and collect associated information. RFID systems with the advantages such as large quantity of data, confidentiality, anti-interference capability, short recognition time and lower cost, are widely used in various industry sectors. With the popularity of mobile computing devices, the development of wireless location technique, especially indoor wireless location technique is getting more and more concern, such as wireless navigation, warehouse management, logistics tracking, personal entertainment, mobile office units, staff management and other areas. However, ordinary location technologies can't satisfy the needs of indoor environment and location accuracy, RFID technology becomes an excellent candidate for indoor location technique because of its advantages of non-contact and non-line-of-sight nature.Because the indoor environment is very complex, and it's greatly influenced by multipath propagation and random noise, the research on the algorithms of indoor location system is of great challenge. The main topic of this dissertation is the systemic research for indoor positioning algorithms based on RFID technology. The principal tasks and improvements are as follows:1. Describe the relative research work on the indoor location technique in detail. Then on the basis of analysis and comparison of the indoor distance measuring technique, and combining the charasteristic of RFID technology, a distance measuring method is chosen for RFID location technique with lower cost.2. Two improvement plans are suggested based on typical RFID positioning algorithms with the ranging method of received signal strength indication(RSSI). Firstly, mainly analyze three RFID positioning algorithms, including a method based on the distance-loss model, the LANDMARC method and the VIRE method. Several experiments vertify their performance and the advantages and disadvantages of them are pointed out. Then on the basic of analysis of model building conditions for the propagation path of indoor signal, the method based on the distance-loss model is improved by use of the ideas of the latter two methods. Experiment tests and simulation results show that the new plans improve performance.3. Based on the principle of virtual tag in the VIRE method, adaptive VIRE(AVIRE) is brought up which makes positioning system better adapt to the complicated and changeable indoor environment. AVIRE can adaptively find out the appropriate RSSI threshold for each tracking object, which can eliminate unlikely positions more accurately. In additon, a new weight expression is designed for postion estimation in order to improve accuracy. Simulation results show that the average accuracy of AVIRE is improved 36.1% than LANDMARC, which exceeds far more than VIRE's improvement; and the average adjusting speed of RSSI threshold of AVIRE is improved 63.5% than VIRE.