An enhanced query tree protocol for RFID tag collision resolution with progressive population estimation

Rapid and reliable resolution of the collisions caused by multiple RFID tags during identification is a key factor for the proliferation application of RFID system. In this paper, an enhanced query tree protocol for memoryless passive RFID tags is proposed, in which the binary identifiers stored in the RFID tags and the binary query strings broadcasted by the RFID reader are mapped to real numbers in the interval [0, 1). During identification, according to the amount of RFID tags already identified and the value which the binary query string adopted by the protocol in the last frame maps to, the overall tag population is estimated, and an optimal binary query string for the protocol to adopt and the reader to broadcast in the next frame is calculated. Evaluation verifies that this protocol outperforms other query tree protocols regarding to the metrics of throughput and time delay.