Efficient tag management in large-scale RFID systems

Abstract

Nowadays, Radio Frequency IDentification (RFID) technology is widely used in many applications including supply chain monitoring, warehouse management, inven-tory control, etc. Unlike the barcode system that has to read the data closely, RFID extends the operation distance from inches to tens of feet (for passive tags) or even hundreds of feet (for active tags). With RFID technology, a system could automat-ically obtain the products information without manual operations. Time-efficiency is one of the most important concern for a modern RFID system. How to efficiently manage and monitor large RFID systems is a practical but challenge research issue.In the thesis, to quickly obtain required information to improve the management efficiency for large RFID systems, we design efficient tag scanning protocols for three important applications, namely unknown tag identification, tag searching and tag stocktaking. To obtain the information of tags/products, the traditional method is to scan tags and collect the tags' IDs in the system, which is usually referred to as tag identification. Since a tag ID is 96-bits long, ID-collection for a large RFID system that contains tens of thousands of tags usually takes too much time. If the system has to identify each tag every time when scanning the system, the scanning time will be obviously unbearable. To shorten the scanning time, we try to avoid tedious ID transmission from tags to readers, which greatly improves the scanning process.The major contributions of the thesis for efficiently management of large RFID systems are threefold. First, we propose efficient protocols to identify all unknown tag in large RFID systems. The existing work identifies unknown tags with a given probability but cannot identify them completely. Our proposed protocol recognizes known tags without ID transmission and deactivates them to prohibit their further replies. After deactivating all the known tags, the remaining active tags must be unknown tags. Then the reader completely identifies unknown tags. By employing two novel techniques slot pairing and multiple reselections to resolve the known tag collision, the enhanced protocols greatly shorten the time to deactivate the known tags. Second, we propose two efficient tag searching protocols to quickly search tags with given IDs (i.e. wanted tags). The existing work uses bloom filter to search wanted tags. However, it performs badly when the number of wanted tags is large. Our protocols employ the novel technique testing slot to iteratively eliminate nontarget tags without ID transmission round by round, and then quickly obtain the searching result. Third, we present efficient tag stocktaking protocols that quickly take stocking of tags and update the inventory accordingly (i.e., deleting absent tags and adding new tags). Compared to existing tag identification protocols, the proposed stocktaking protocols identify only unknown tags and missing tags, which avoid the time waste of ID re-collection. Meanwhile, these protocols require only very slight modification of the standard protocol, making it easy to be implemented with COTS tags. We also exploit the analog network coding technique to further improve the performance of tag stocktaking protocols.