RFID anti-collision algorithm in logistics service system

RFID is commonly used in many applications such as supply chain management, object tracking. In RFID system there are two parts, readers and tags. Readers communicate with tags through radio frequency by transmit signal to tags and receive reflected power to obtain information. RFID system can not work correctly because of interference by the signal transmitted from different readers and the tag collision caused by several tags transmit signal to one reader. There are two kinds of reader collision problems, frequency interference and tag interference. As collision exists, readers could not communicate all tags in their respective reading zone, therefore time and frequency should be properly arranged to avoid collision. Nowadays there are mainly three algorithms used in solving the collision problem, Colorwave, HiQ, Pulse. For tag collision problem, a novel ultra high frequency (UHF) RFID system scheme, which is based on combination of Dynamic Framed-Slotted-Aloha (DFSA) and Code Division Multiple Access (CDMA) with Orthogonal Variable Spreading Factor (OVSF) code, was proposed.