Multiple tags identification for short id rfid networks

Utilization of radio frequency identification (RFID) tags to localize objects in real time requires the collection of the identities (IDs) of the tags within a short time. This paper presents a novel orthogonal group identification (Ogrid) method that addresses the above requirement. When queried, multiple tags with mutually orthogonal IDs respond, such that these tag IDs can be separated at the reader without using spread spectrum technique. Ogrid yields a small and fixed identification delays for any given tag ID size B. Ogrid is especially suitable for dense networks where the tag ID sizes are relatively short. In the case of B = 16 bits, which supports at most 65536 tags, Ogrid incurs a fixed identification delay of about 4 seconds regardless of the number of tags present, whereas several existing protocols incur average delays of 20 and 100 seconds to identify 10,000 and 50,000 tags, respectively. Results for a dynamic system with tag arrivals and departures further demonstrate the consistently low identification delay of Ogrid.