CSMA Multi-stage Anti-collision Protocol for Active RFID Systems

Current anti-collision protocols for active RFID systems stem from the ISO-18000-7 standard, which selects Frame Slotted Aloha as the underlying Medium Access Control protocol. However, these approaches neglect the possibility of using the Listen-Before-Talk mechanism already available in active RFID tags. In this work, a Carrier Sense Multiple Access mechanism with Multi-Stage, (CSMA/MS), derived from the quasi-optimal Sift distribution, is developed in order to substitute the anti-collision procedure in active tags. The key of CSMA/MS is to concatenate various contention windows, where only winners contend in the next contention windows. We demonstrate that this approach nearly achieves a 100% of identification probability per slot, improving Sift results and outperforming standard procedure.