Study Of UHF RFID Localization Algorithm In Multi-path Channel

With the rapid development of Internet, Internet of Things, Mobile Communications and Big Data technologies, people are more eager to get the information of localization than ever. UHF RFID indoor localization techniques will be widely used as it is cheap, easily deployed and long range communications. Indoor wireless channels are more complicated when compared to the channels outdoors because there are more obstacles in indoor environment, and it will cause multipath and N LOS propagations. In multipath and N LOS channels, the accuracy of localization will drop a lot.In this dissertation, to improve the UHF RFID localization accuracy in multipath channels, the traditional statistical model would be combined the traditional statistical model with backscatter communications, and the channel model that could be applied to UHF RFID would be derived, and the influence of multipath channel in UHF RFID localization would also be analyzed. Based on these analyses, a Passive UHF RFID localization algorithm based on Multidimensional Scaling(MDS) and use several reference tags(PDOA-MDS) would be proposed. This algorithm extracts the Phase Difference of Arrival(PDOA) information of the tag to be located and the reference tags. With the PDOA information we could construct the distance matrix of the tag to be located and the reference tags, and then the location of the tag using MDS method could be obtained. Compared with Ranging- Multilateral localization algorithms, this method will improve the localization accuracy in multipath channels, and will use less reference tags and reduce the amount of computing when compared to Non-ranging methods.Then the UHF RFID multipath channel in computer simulation environment was built, and the algorithm simulations ran on this platform. The simulation result indicates that in AWGN channels, the PDOA-MDS algorithm could obtain similar localization accuracy compared with Ranging- Multilateral localization algorithms. However, in multipath channels, the PDO A-MDS algorithm could obtain much better localization accuracy than Ranging- Multilateral localization algorithms.