A blocking collision tracking tree algorithm in mobile RFID systems

In some RFID applications, the reader needs to identify the staying tags within its interrogation zone repeatedly. Meanwhile, there are some arriving tags continually moving into the interrogation zone of the reader. For these scenes, the adaptive query splitting (AQS) algorithm, the semi-blocking AQS (SBA), and the slot allocated blocking anti-collision (SABA) algorithm are proposed. However, these algorithms all use query tree algorithm to identify arriving tags, which leads to lower identification efficiency. Therefore, the blocking collision tracking tree (BCTT) algorithm is proposed in this paper. BCTT allocates a unique slot number for each identified tag. The identification process of BCTT is divided into two phases. The staying tags are identified in the first phase according to the slot number, which reduce the bits transmitted by tags. In the second phase, the staying tags are blocked to respond the reader's query, so the collision between staying tags and arriving tags are thoroughly avoid. The arriving tags are identified by adopting collision tracking tree algorithm. The query prefix is generated according to the first collided bit, so BCTT can completely eliminate the idle slots, and also significantly reduce the number of collision slots. Especially, if there is only one collided bit in the response, BCTT can identify two tags in a slot. The simulation results indicate that the identification efficiency, identification speed, and communication load of BCTT are obviously superior to other similar algorithms such as SABA.