Research On Tag Identification Technology In Mobile RFID Systems

Radio frequency identification (RFID) is a kind of information input technology similar to the bar code technology. The technology can input information of tags quickly, remotely and contactlessly. It has the advantages of high safety, no direction, crossing obstacles and wide adaptive ability to environment, etc. RFID is increasingly applied to the logistics, retail, transportation and industrial production and other fields.At present, there exist still many technical problems in RFID technology, including rapid identification problem, RFID system security problem and RFID large data analysis problem. The thesis mainly studies tag fast identification technologies based on two kinds of special but very widespread scenarios.An RFID system usually consists of a reader and a lot of tags. Tags in reader coverage area (reader interrogation region) communicate with the reader through the shared wireless channel. In order to reduce the production cost of tags, their hardware design is usually very simple. This causes that any tag cannot communicate with other tags. In the tag identification process, the phenomenon of simultaneous response of multiple tags to the reader will appear. This results in a tag collision. When the number of tags in the reader coverage area is very large, the collision problem is very serious. It greatly reduces the efficiency of tag identification. Tag anti-collision protocols are an important research content in tag identification technology.So far, a great many of tag identification protocols (also known as anti-collision algorithm) are developed. Most of these protocols are assumed that the reader and all tags are stationary in the process of tag identification, and the tags are in the reader coverage area. The scenario is called normal RFID systems (NRS).Tag identification protocols under this kind of scenario have been very mature. They can achieve very high system efficiency. In real life there still are two very common tag identification scenarios. One scenario is that the reader identifies tags moving along a fixed path. This scenario is called tag movement RFID systems (TMRS) in the thesis. Another scenario is that a single moving reader identifies tags existed in tag identification of small and medium areas. This scenario is called single reader movement RFID systems (SRMRS) in the thesis. The thesis mainly studies the two types of mobile RFID system.TMR systems occur mainly in import and export of the logistics, warehouse, transportation, etc. These places are usually equipped with a reader to quickly read information of tags attached to objects. If existing anti-collision protocols are used in TMRS, tag loss rate (TLR) will be high. This is because there is a random later identification (RLI) phenomenon in TMRS. The phenomenon severely degrades the system performance. This thesis describes the RLI phenomenon in detail. Then, the first come first served (FCFS) mechanism is used to solve the RLI phenomenon. The mechanism includes a tag sequencing method and related storage structure. And two representative and existing tag identification algorithms are improved to let improved ones possess FCFS function and overcome RLI phenomenon.SRMRS systems are mainly used in tag identification of small and medium areas, such as small and medium warehouse, retail stores and so on. In these scenarios, the reader coverage area can not cover all tags. Usually, the tag identification of the scenario adopts mechanism of multiple readers, as leads to increased costs, the complicated algorithm of tag identification and so on. In this thesis, all tags in small and medium areas are identified by moving a single reader. This approach has many advantages. (1) Cost savings. This is because a single reader cost is significantly less than that of multiple readers. (2) Tag identification algorithm design based on a single reader is simple and efficient. This is because the method of a single reader does not consider the problem of multiple reader interference and that of hidden terminal. (3) Good adaptability. This is because the increase of adjacent storage location of tags does not need to increase new readers and only needs let the reader move to new that of tags. However, in order to save tag production costs, many tags have no static storage equipment. So, the type of tags is memoryless. For the existing tag identification protocols, the memoryless tags cause the phenomenon of multiple identification of tag (MIOT) when the moving reader identifies tags in small and medium area. This leads to a substantial decline in terms of the tag identification efficiency. The mechanism of suffix control to MIOT is proposed in the thesis. The mechanism is called MSCMIOT mechanism for simplicity and can control multiple identification of tag effectively. Then, a protocol with MSCMIOT mechanism is developed. The protocol can effectively improve the efficiency of tag identification in the single reader movement RFID systems.