Reader scheduling for tag access in RFID systems

“Reader” and “Tag” type devices are utilized in the Radio-Frequency IDentification technology for identification and tracking of objects. A tag can be “read” by a reader when the tag is within the reader's sensing range. However, when tags are present in the intersection area of the sensing ranges of two or more readers, simultaneous activation of the readers may cause “reader collision”. In order to ensure collision-free reading, a scheduling scheme is needed to read tags in the shortest possible time. We study this scheduling problem in a stationary setting and the reader minimization problem in a mobile setting. We show that the optimal schedule construction problem is NP-complete and provide an approximation algorithm and techniques that we evaluate through simulation.