Patent ID: 8028910
Filing Date: 2011-10-04
Classification: G06K

Abstract:
1. A method for tag identification of a Radio Frequency Identification (RFID) reader within the identification range of the RFID reader for identifying a plurality of RFID tags which transmit their own IDs to the RFID reader when prefixes of queries received from the RFID reader match front portions of the RFID tags' IDs, comprising: a first step of initializing a queue (Q) field and storing a prefix having 1 to n bits (n=the bit numbers of a tag's ID) of a candidate queue (CQ) field in the queue field, wherein, assuming that a pair of processes, in which the RFID reader transmits a query and one or more RFID tag respond to it, is one round, the RFID reader has a data field including the queue field and the candidate queue field which store prefixes to be transmitted in a subsequent round, wherein the RFID reader re-transmits prefixes one bit longer than prefixes previously transmitted in each successive round and continues to extend prefixes until the ID's of all tags have been identified; a second step of transmitting a query with the prefix stored in the queue field to the RFID tags, and deleting the transmitted prefix from the queue field; a third step of inserting a prefix, in which prefixes 0 and 1 corresponding to one bit are inserted into a rear portion of a prefix of a previously transmitted query, into the queue field if two or more tags respond to the previously transmitted prefix and, therefore, the tags cannot be identified, and inserting the prefix of the previously transmitted query into the candidate queue field and deleting an unnecessary prefix stored in the candidate queue if there is no response or only one tag responds with respect to the previously transmitted prefix; and a fourth step of determining whether a prefix stored in the queue field exists, and returning to the second step if there is a prefix stored in the queue field, wherein the RFID reader identifies a new tag entering identification range of the RFID reader based upon the prefixes of identified nodes stored in the candidate queue field when an ID of the new tag matches one of the prefixes of the identified nodes and identifies the new tag based on the prefixes of no-response nodes stored in the candidate queue field when the ID of the new tag does not match one of the prefixes of the identified nodes.