Research On Rfid-based Indoor Location System

RFID(Radio Frequency Identification)technology is the application of Automatic Equipment Identification in radio. Remarkable advancements in RFID are increasingly accomplished through its non-contact characteristic, anti-interference capability, short-time recognition, high confidentiality and low cost. It is widely used in various fields, such as management of transportation, industrial and business automation. With the development of communication technology and the rapid growing multimedia service, the demand on indoor location is increasing. Especially in the airport hall, hospital, underground parking, mine, dock and other environments, we often need to know the object's location, such as mobile terminals or the holders, the facilities and materials. However, the complex feature of indoor environment makes the indoor location technology have become the key point of research in recent years.This thesis focuses on RFID-based indoor location technology. Main tasks are summarized as follows:1. Summarize the indoor location technology on principles, characteristics and successful application cases, by reading a large number of documents. Then, carry out the topic of this thesis by making a description on RFID technology, such as compositions of system, operating frequency, current development and advantages.2. Analyze the current RFID indoor location technology. Among all the methods, this thesis focuses on PDOA(Phase Difference of Arrival)and proposes a way to measure the phase: Using the IQ demodulation signal. In order to prove this theory correct, we not only use the mathematical formulas, but also build an UHF model (working in 915MHz) on MATLAB platform to estimate the deviation of PDOA.3. Make a description on the hardware of the passive RFID indoor location system based on PDOA. The thesis focuses on the reader's modules, including the RF signal generator, power amplifier, IQ demodulation, small-signal amplification and MCU control module. After that, the process of testing the system's hardware is briefly described.4. Make a description on the software of the location system, including the EPC C1 Gen2 protocol and software modules of MCU control. Then, the thesis gives the test result of the location system and compares it with the actual value and the result of method based on RSSI.5. Discuss the factors which affect the location accuracy, including the label's rotation, multipath and NLOS propagation. Theoretical analysis shows that the result of TOA/TDOA can be easily influenced by multipath and NLOS propagation. Test data indicates that the rotation of Tag can affect the accuracy of PDOA.