Study On The Anti-collision Algorithm In Radio Frequency Identification Technology

RFID (Radio Frequency Identification) system is an automatic identification technology that has been developed since 1980s. It can be widely used in all kinds of fields. Compared with barcode recognition technology, optical character recognition technology, biometric identification technology, integrated circuit card, RFID system has particular contactless, anti-interference and environmental adaptability characters, recognizing multiple items simultaneously, so it becomes one of the most excellent Auto-dentification procedures that are widely applied in many fields.We introduce the basic theory knowledge about RFID system such as operational principle, characteristics, communication protocols and so on. Then, we focus on tag anti-collision and reader anti-collision algorithms, which are key technologies in application.In this thesis, we complete thorough research on existing algorithms for tag anti-collision and reader anti-collision, analyzing their characters and limit. Combining with graph coloring algorithm in graph, we propose a distributed adaptive graph- coloring algorithm based on CSMA protocol to reduce reader collisions in the RFID systems. This algorithm adopts distributed graph-coloring to allocate time-slot for every reader. And periodically broadcasting current time-slot of communicating reader and the total number of time-slot for whole reader network on a separate control channel by the reader, while it is reading the tags. Further more, it can adjust dynamically the number of time-slot bythe statistic of successful communication. So the alogrithm can reduce reader collision, optimizes number of time-slot for communication, improve system efficiency and system reading ratio. And it can be applied in fixed RFID readers as well as mobile RFID readers. It is showed by simulation in OPNET, that using this alogrithm, the efficiency of system is increased by 50%(with 25 readers) as compared to CSMA. So it can resolve reader collisions much better than existing anti-collision mechanism. It can promote RFID applications in more fields.