Efficient monitoring of dynamic tag populations in RFID systems

As RFID tags become more ubiquitously available, e.g., in a supermarket, it is necessary to monitor larger-scale tag populations in a dynamic environment to get updated tag information. This paper considers the problem of monitoring a dynamic tag population, to identify both the missing tags and new tags. Traditional approach can solve the problem by collecting all tag IDs in the current population, which could be slow because it ignores the knowledge of the tag population in a previous scan. To be more efficient, this paper presents two protocols: (1) a baseline protocol with optimized length of random number bits, (2) an improved one-phase protocol with easy labor to identify only the new and missing tags in ALOHA frames by fully utilizing previous tag population knowledge. Our analysis shows that the one-phase protocol can improve the monitoring accuracy by 25% and improve the time efficiency by 55%, as compared with the two-phase protocol proposed in a recent paper which also identifies population changes.