Research On RFID Anti-Collision Algorithm

Radio Frequency Identification (RFID) is a contactless automatic identification technology rose from the 1990s, which applies and develops the automatic identification technology into radio technology. There are many advantages of RFID technology such as high accuracy ,strong ability to adapt to the environment, efficient operation, long service life, long reading distance, encrypted tag data, large data storage capacity, and so on. Along with the developing of RFID technology, RFID has more and more important effect on many areas such as supply chain management, logistics, automation, transportation management and control, retail, et al. RFID will become the mainstream of automatic identification technology and has broad prospects.Data integrity problem of RFID is one of the important factors that hinder the development of RFID. It is directly related to the quality of the performance of the whole system level. Collision problem is an important aspect that affects the integrity of the data. There are two kind of collision. They are reader collision and tag collision. The way to solve the collision called the anti-collision algorithm. Comparing with the tag, the reader is more powerful and resource-rich, and also, the reader can communicate with each other. So the reader collision is relatively easy to solve, and the problem of tag anti-collision is considered to be an important and difficult issue to resolve. When more than one tag in the reader area and send datum to the reader at the same time, the signal of the tags will interferes each other and the tags will not be able to be identified. We call it tag collision. It belongs to the multi-target identification problems. Because RFID is the only one technology that can identifies multi object at the same time, multi-target identification is both the advantages and the challenge of RFID technology.In this thesis, we deeply study the issue of tag anti-collision on the basis of the literature search, collation, analysis and synthesis. Main works as follows: 1. The author deeply studies the stochastic anti-collision solution of RFID tag. An improvement algorithm based on dynamic frame slot ALHOA algorithm combined with multiple factor and grouping method is proposed. The algorithm is easy to realize. By judging the system efficiency and comparing the amount of free slots and collision slots, the improved algorithm decides whether to adjust the frame's length dynamically using multiple factor. When the amount of tag exceeds a certain value, grouping identification is used. A program which combined with Matlab engine is written to simulate the process of identifying tags. The result shows that when the amount of tag increases rapidly, the efficiency of RFID system can be hold above 35% stably. It also decreases the amount of slots and the read cycle.2. Base on the research of jumping dynamic search anti-collision algorithm and ID predict algorithm, an improved algorithm, grouping dynamic ID predict algorithm, is proposed. The characteristic of the algorithm is that when the reader issues a request to the tag, there is the possibility that several tags are identified. It realizes by using tag grouping identification and dynamic datum transmission between the reader and tag. After analyzing of the algorithm principle and summarization of the algorithm step, a simulation program is written to calculate the request number of the reader, the answer number of the tags, the effective service rate and the traffic of system. The simulation result reveals that grouping dynamic ID prediction algorithm greatly enhances the effective service rate, dramatically decreases the volume of traffic of system and shows the excellent performance.