A Tree Structure Anti-collision Algorithm Of RFID

As the product of information technology in the new times, the radio frequencyidentification (RFID) demonstrates great value of application. RFID is based on radiowave technology, and it makes use of space electromagnetic coupling to realize thewireless two-way data communication and identify some things automatically. Thedevelopment of RFID technology associates with growing-up of many other technologies,which has something to do with computer, wireless data communication, electromagnetism,cryptology and some other fields. Also it has lots of advantages, such as stronglypenetrability, convenient and efficient data reading, high degree of automation, easyoperation etc. For such unique advantages, RFID technology has been widely applied inindustrial manufacture and our daily life, so as to bring about lots of convenience for us.In recent years, the Internet of Things (IOT) has gained more and more recognition,so research on IOT becomes more and more deeply and widely. In the entire systemstructure of IOT, RFID is one of the key technologies of IOT’s sensing layer. For theapplication of IOT in the future, it will make full use of RFID to collect and transmitinformation. One advantage of RFID is multi-objective recognition, that means to identifylarge number of tags rapidly and accuracy among the reading field. But as the massive dataenvironment of IOT, when a lot of tags contend for the same channel to transmit their data,it will cause the problem of data collision, which have a significant influence on theintegrity and efficiency of data transmission. Then how to solve the problem of datacollision in RFID system reasonably becomes to the focus and hotspots of the research onIOT.Actually, the data collision is multi-access problem in wireless communication, andthe Time Division Multiple Access (TDMA) is generally adopted to solve this problem inRFID systems, it means distributing the channel capacity to lots of users according tochronological order. The main anti-collision algorithms are divided into two types: theprobabilistic algorithms based on ALOHA and the deterministic algorithms based on treestructure. The algorithms based on tree structure are able to identify all tags accuracy, thatavoid the problem of some tags cannot be identified. The deterministic algorithms includethe binary search algorithms and query tree algorithms.A multi-tree can be used to express the entire process of anti-collision algorithmsbased on tree structure. And it is composed of reader’s queries and tags’ responses. Thefirst query that is sent by the reader is the root node, which is the start of the query process.If the query process proceeds among the entire tree, it will cause lots of collision. In this paper, an improved anti-collision algorithm is promoted to conquer this problem. Theimproved algorithm divides the whole tree into some branches, among which to identifytags. As a result, the times of reader’s queries and tags collision will be reduced, and thenthe system efficiency is improved. The specific improved contents are as follows:1．A part is added to make sure of the prefixes that all tags have. Every prefix standsfor a branch of the query tree. Before reading information of tags, the reader sends acommand of prefix query, so all prefixes can be identified, and the prefixes will be pushedinto stack for saving.2．The tags that have the same prefix belong to the same branch, so the entire querytree is divided into some small branches. The identification process of tags starts fromevery prefix, then go through every branch. As a result, the probabilisty of tag collision isreduced.3．For reducing the times of reader’s queries and time delay, the back-track strategyand dynamic search are adopted when querying every branch. As a result, the performanceof the entire system will be improved.Furthermore, this paper also discuses and analyses how to select the prefix length.Then ascertain the standard of prefix length selection to achieve the optimal systemperformance.At last, we verify the effectiveness and superiority of the improved algorithm throughthe simulation platform of Matlab. The times of reader queries, the time delay and thethroughput are observed. As the result shows, when the number of tags is large, theimproved algorithm is able to effectively reduce the number of reader queries and timedelay, the throughput is increased at the same time. That means the improved algorithmhas a well performance, and it has value for application.