Research On Key Techniques And Simulation Of UHF RFID Air Interface Protocol

Radio Frequency Identification (RFID) is a kind of contactless automatic identification technology. In a RFID system, wireless RF communication techniques are used to achieve the duplex communication between the reader and tags, which are the core components of a RFID system. Air interface protocol is the communication standard of exchanging messages between the reader and tags in a RFID system. UHF RFID system has further identification distance and can be used in fields of internet of things, electronic business affairs, traffic control, military control and other fields of national economy widely, so it is becoming a hot topic of research.The main task of this dissertation is study and simuation of UHF RFID system air interface protocol. The air interface protocol is composed of physical layer and tag-identification layer. Many key techniques are included in both of the two layers.Data coding is one of the key techniques of physical layer in the air interface protocol. Firstly, the principle of data coding of the RFID system which is a special communication system are provided in the dissertation. Then, three kinds of data coding methods of the dominant protocol, which are PIE, FM0, Miller-modulated subcarrier, are studied and simulated separately. On the basis of the prior work, we propose an improved PIE data coding method. Based on theory analyzing and simulation, we can draw the conclusion that the proposed method has the following two advantages compared to the basic method. For one thing, when the two methods work at the same bit rate, the proposed method can provide more energe for tags and has narrower bandwidth than the basic method. For the other thing, when the two methods occupy the same bandwidth, the proposed method has higher bit rate than the basic method. What's more, the energy provided for the tags is not affected when using the proposed method.Tag anti-collision is one of the key techniques in protocol's tag-identification layer. According to the characters of the tag anti-collision methods, it can be devided into two means, which are stochastic ALOHA-based anti-collision algorithm and deterministic binary tree-based anti-collision algorithm. Both of the two means have many improved algorithms, which are mostly studied and simulated in the dissertation. The advantages and disadvantages of all these algorithms are also discussed. On the basis of the prior research, we propose a mixed anti-collision algorithm, and the concrete operation flow of the algorithm is also provided. Based on analysis and simulation, we can draw the conclusion that the proposed algorithm has the following two advantages. Firstly, the reader can identify all the tags within its scope using less query cycles. Secondly, the efficiency of the proposed algorithm can nearly reach 50% and be higher while the number of tags within the reader's scope increasing.In the aspect of simulation of the air interface protocol, using different tools of Matlab, the physical layer and tag-identification layer of the protocol are simulated separately. In the end, we propose a method which can simulate the air interface protocol completely. The flow of the total process of protocol simulation is provided. According to the analysis of simulation result, one can understand the inner relationship between the physical layer and tag-identification layer.