Research On Reader Anti-collision Protocol In RFID Systems

Radio Frequency Identification(RFID) is a kind of untouchable automatic identification technology, is the key of the Things sensing technology. With its unique advantages, RFID has been widely used in many fields. With the development of RFID technology and the increasing of the requirements, its application area is also expanding. More and more readers and tags are deployed in the systems, so the dense environments informs.In the dense RFID systems, for example the warehouses and supermarkets, there are deploying a large number of readers and tags. In order to ensure that the internal system does not signal blind, all the tags can be detected successfully by the readers, RFID systems will deploy the readers closely. This deployment will cause many readers' read range overlaps. If some readers work simultaneously, the signal collisions occur. There are two kinds of the signal collisions. One is the tag-tag collisions. The other is the reader-reader collision. When the collision occurred, easily lead to leakage of the label is read, it brings recognition accuracy and reading inefficiencies and other issues. Not only the static network constituted by a fixed reader, the signal collision is severe. But also the dynamic network which the mobile reader participated, the collisions will be worse. The collision problem would become worse as the number of readers rises, or the increase of the tags' number. The economic losses which caused by the signal collisions is immeasurable. So the problem of the signal collision must be handled in RFID systems.Currently the tag anti-collision technology has matured. Providing an effective reader anti-collision algorithm is the focus of this paper. In order to solve the problems above, this paper analyzes the principle of the reader signal collision and the solution ideas and solutions way of the reader anti-collision technology. So the main contents of the paper are introduced as follows:Firstly, in order to avoid the reader collisions, a distributed coordination strategy is applied. The application of the dual-channel coordination mechanism and the setting of the appropriate scope of coordination, it handled the problem of the hidden node and the exposed node in the wireless network. Allowing the effective communication between the readers, it improved the recognition accuracy and enhanced the reading speed as purpose.Secondly, proposed an adaptive power control strategies. Wherein, the power control algorithm will adjustment the reader transmit power in real- time according to the channel fading characteristics. which reduced the collisions between adjacent reader, al owing multiple readers work simultaneously to improve the throughput of the system.Thirdly, provide a backoff strategy which helped the power control strategy work. With the increase in numbers of backoff, the backoff time reduced. It avoid the "hunger" phenomenon appear in the last time, reflecting the fairness of the algorithm and the elastic of the system.Finally, designing a state machine, with the three strategies above, we proposed a new reader anti-collision protocol which is named APC-EDica. And then, we compared the new protocol with three kinds of classic anti-collision algorithm, such as APAA, PPC and EDica, at the minimum signal-to- noise ratio standard deviation, throughput and accuracy of identification in the simulate systems.The simulation results show that, whether the stationary or the mobile networks is, APC_EDica protocol has a high recognition accuracy and throughput in intensive RFID systems; and it has the common advantages of dual-channel coordinated algorithm: almost no collisions.