Research On RFID Indoor Location Technology

Radio Frequency Identification (RFID) is a technology which makes use of RF signals to identify the target and acquire its information automatically. Ordinary location technologies can't satisfy the needs of indoor environment and location accuracy. Because RFID technology has the advantages of non-contact and non-line-of-sight, it's very applicable for the location of logistics and targets' management in factories, warehouses, stores and so on. It has already become a research hotspot nowadays.The content of this paper is mainly about the location research which is based on RFID technology under the environment of indoor radio wave propagation. The indoor environment is very complex, and it's greatly influenced by multipath propagation and random noise. So the research on the algorithms of indoor location system is of great challenge.The paper introduced the fundamental principles and key technologies of RFID. And it gave the following researches and simulations on the basis of analyzing current location theories.1. It adopted empirical path loss model based on numerous measurements to obtain the mapping between signal strength and geometric path.2. It adopted LANDMARC (Location Identification based on Dynamic Active RFID Calibration) system. Making use of the reference tags to assist location, two-dimension position's estimation based on nearest neighbor algorithm was deduced by the method of minimized distance difference. Aiming at the disadvantages of LANDMARC system, it improved the related algorithms and proposed an algorithm of Dynamic Range Adjustment Localization (DRAL).This could minish the influences of environmental random factors on the location measurements.3. It did much simulation, verification and comparison on the improved algorithm through different parameter sets. To increase the system's accuracy further, it adopted the method of ray-tracing propagation model to describe indoor radio wave propagation. The details of indoor radio wave propagation were obtained by this method. According to the electronic map of indoor radio wave propagation, it built the path loss database in different positions. The data of empirical path loss could be obtained through searching the database. The positions of undetermined tags could be estimated using the obtained data and the data of practical path loss. This was of some practical value.