Design Of RFID Reader/Write Device And Research On Anti-collision Algorithm

Radio Frequency Identification (RFID) is a kind of automatic identification technology by wire-less telecommunication. RFID technology can promote the level of social informationization greatly. This paper presents the process of designing a Read/Write device based on MF RC500, and gives an improved sloted ALOHA anti-collision algorithm.Read/Write device consists of control system, high frequency circuit and antenna. In this design , the hardware of Read/Write device is comprised of C8051F340 SCM, MF RC500 chip designed by Philips and antenna which is made from the PCB, and the software of Read/Write device involves the program of SCM, which includes the program of communicating with PC machine and the program of controlling MF RC500 to operate the tags, etc.Sloted ALOHA anti-collision algorithm is one of important anti-collision algorithms, the main problem of which is that the collision probability will increase rapidly when the number of tags overnumbers the number of slots, so that the identification efficiency will drop rapidly Improved sloted ALOHA anti-collision algorithm can solve this problem in a certain extent. The strategy of improved sloted ALOHA anti-collision algorithm is that the tags are required to answer as soon as possible by working out the best answer probability of tags in each slot. In detail, the probability that only one tag answers in the first slot must be largest, and once Read/Write device fails in the first slot, the probability that only one tag answers in the second slot must be largest, and so on. This strategy helps to shorten the answer time of tags. The identification efficiency of improved sloted ALOHA anti-collision algorithm can still keep about 36.8%, while the number of tags increases. The upper limit of the tags lies on the largest random number which the circuit of tag can produces.