Efficient Protocols for Identifying the Missing Tags in a Large RFID System

Compared to the classical barcode system, radio frequency identification (RFID) extends the operational distance from inches to a number of feet (passive RFID tags) or even hundreds of feet (active RFID tags). Their wireless transmission, processing, and storage capabilities enable them to support full automation of many inventory management functions in industry. This paper studies the practically important problem of monitoring a large set of active RFID tags and identifying the missing ones-the objects that the missing tags are associated with are likely to be missing as well. This monitoring function may need to be executed frequently and therefore should be made efficient in terms of execution time in order to avoid disruption of normal inventory operations. Based on probabilistic methods, we design a series of missing-tag identification protocols that employ novel techniques to reduce the execution time. Our best protocol reduces the time for detecting the missing tags by an order of magnitude when compared to existing protocols.