Research On The Anti-collision Of UHF RFID System

Wireless radio frequency identification is one branch of automatic identification technology. It mainly uses the wireless way to verify automatically the identity of the distinctive objects with fast speed, high efficiency and simple operation. These years RFID technology have developed rapidly, and applied in many areas in China, for example, the second generation ID card replacement of the residents, the 2008 Beijing Olympic Games game tickets, as well as at the 2010 Shanghai World Expo, all have a comprehensive application of the technology.The global economic crisis broke out last year, and it has brought to China's RFID industry development a critical challenge, for which following the release of the "White Paper" in 2006, the Chinese Ministry of Science issued a "Blue Book" on November 3,2006 once again, This policy will be able to guide the development of RFID industry in the next few years.This dissertation begins with a complete RFID system, describes concretely the types of each frequency band and application, as well as the RF front-end components of the reader --- transmitter and receiver circuit theory, and also describes communication ways between the tag and the reader, and between the reader with the host computer. Secondly for the current popular UHF RFID system, this paper introduced the ISO18000-6 UHF air interface protocol of three Type A, Type B, Type C, Including coding/decoding mode, modulation mode, transmission rate and anti-collision algorithm, and it also pointed out their differences.Thirdly, on the basis of three types of standards described above, the paper paid attention to the multi-tag identification problems of the UHF RFID system. The commonly used anti-collision algorithm is based on TDMA, and it is divided into random-based ALOHA algorithm and Binary Tree search algorithm. This dessert pointed out these two kinds of algorithms respectively, and their following-up improved algorithms, with their performance simulation according to the performance parements, like throughput, system efficiency, the number of searches and the number of such slots. Finally, this paper improved the slotted ALOHA algorithm, which ISO18000-6 C protocol uses.Through estimating the labels'number of the reader's identification field, then adjust the number of slots in every frame, at last we compared this improved algorithm with the original Q algorithm using Matlab, and the result proved that the first one improved channel utilization and increased throughput.