The RWD And Anti-Collision Arithmetic Of RFID System

In the past years, the technology of RFID developed rapidly, and it had been applied in industry production and electronic consumption. Now RFID becomes an important part of IT industry.The advancement of Anti-Collision has an important effect on the RFID. And the rapidness, stability and precision of Anti-Collision algorithm influence the RFID system directly. At present, there are many new Anti-Collision algorithms based on the binary code searching algorithm.From the research of the Anti-Collision algorithm of RFID system, we know that there are multiple RF terminals in the detect region of RF, and the information sent back by the terminal would accumulate, which make the reader can't identify the information. So we need find a method which arranges these RF terminals orderly based on the command sent by the reader to ensure that the information sent by RF terminals wouldn't accumulate, which called Collision in RFID technology. RFID system can adopt certain policy or algorithm to avoid the Collision, and make the echo information of RF terminals be received by reader through RF channel separately. A quick anti-collision algorithm that deals with the collision of multiple RF terminals is proposed in this paper. This algorithm is based on dynamic binary code searching, and some technologies that are applied in the algorithm, such as CRC check, Hamming coding, Manchester coding and DES arithmetic, are analyzed in detail.The national and international advancement of RFID technology is introduced firstly. The technology came into being in the World War II, but developed slowly. In recent twenty years, the RFID technology develops rapidly, and promotes the development of other industry.Then, the paper describes concretely the principle, framework of RFID system, the functionality of every part, the theory and technology that needed by the design of RFID system such as signal coding and modulation, data coding and decoding, the integrality and security of data transfer, and the generation and resolution of anti-collision.Next is the core part of this paper, some popular anti-collision algorithms, such as binary code searching algorithm, dynamic binary code searching algorithm and improvement of it, are analyzed concretely. Based on the above algorithms, this paper proposes a novel algorithm. The algorithm is that the reader sends the collision bit information to the RF terminals each time, and the is the bits except the last collision bit information, and we can identify all the RF terminals.By the comparison between the velocities of there anti-collision, we find that the anti-collision algorithm proposed in this paper is four times quicker than the wince arithmetic, and two times quicker than the best result of dynamic binary coding algorithm. From above comparison, it can conclude that the rapidness is the great characteristic of this algorithm.But there are two defects of this algorithm, one is that the resolution of collision of some RF terminals is not perfect, and it often needs to be reactivated, and the other defect is that it needs adding a waiting state except shielding state, which increases the cost of the system.The last two parts design the hardware based on MCU89C52 and software of the RFID system. The software includes the encryption algorithm (the generation of secret key, expand permutation,S-core permutation), checking module(Hamming coding,Hamming coding),check module,Manchester coding,Manchester coding.There is some time for the prevalence of RFID system, and the main problem is the price. So the development of RFID system not only guarantees the quickness, stability and precision of identification, but also considers the cost of hardware. And the development of Anti-Collision considers the cost. And we can believe that the RFID technology would popularize in the world, and become the necessary of our lives.