Tag quantity estimation for RFID based on probability

Anti-Collision algorithm based on probability can be used to estimate the number of frame slots needed at the next query round in tag identification of RFID. Each tag is equipped with a random counter to save the number that is relevant to whether the tag responds the query of reader or not. For this specific anti-collision algorithm, estimating the number of tags is the most important step in the algorithm. The estimation decides the best number of frame slots that minimises the number of collisions and maximises the tag identification speeds in RFID communication. In this paper, an algorithm for estimating the number of tags in the interrogation zone based on Pigeonhole Principle is presented - when number of collision is more than 50% of frame size in the presented query round, both the identification and idle will therefore occupy less than 50% of frame size. When the idle and identification becomes less than 50% of frame size, the indentifying speed will become slower. The presented algorithm analyses the numbers of collisions, idles, and identifications in the present query round to evaluate the optimal number of time slots for the next query round. The experiment results show that the presented algorithm is efficient for estimating the real number of tags.