The Reading of Transmission-Only Active RFID Tags

Abstract Radio frequency identification (RFID) enables everyday objects to be identified, tracked, and recorded. Because of expense, size, and lifetime requirements, some simple active RFID tags are designed with only transmitters. Transmission-only tags are unaware of each other and simply blink ID packets periodically over a common channel. The question is what really happens: a false alarm due to consecutive blink collisions or a missed object event? The authors model the access of transmission-only RFID tags as pure ALOHA and develop a mathematical analysis to identify tag blinks without prior knowledge of the number of tags in the interrogation zone. The authors estimate the tag set based on the free channel in an observation window. Simulation results and experiments with Spider tags from RFCODE are presented.