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1. (WO2004036771) METHOD FOR THE EFFICIENT READING OF A POPULATION OF RADIO FREQUENCY IDENTIFICATION TAGS WITH UNIQUE IDENTIFICATION NUMBERS OVER A NOISY AIR CHANNEL

Pub. No.:    WO/2004/036771    International Application No.:    PCT/US2003/033043
Publication Date: Apr 29, 2004 International Filing Date: Oct 20, 2003
IPC: G06K 7/00
Applicants: SYMBOL TECHNOLOGIES, INC.
Inventors: SHANKS, Wayne, E.
ARNOLD, Jens
Title: METHOD FOR THE EFFICIENT READING OF A POPULATION OF RADIO FREQUENCY IDENTIFICATION TAGS WITH UNIQUE IDENTIFICATION NUMBERS OVER A NOISY AIR CHANNEL
Abstract:
A method for reading and tracking radio frequency identification (RFID) tags (112) in the presence of a noisy air channel is provided. In accordance with the method, a binary tree data structure is used to characterize a plurality of RFID tags (102a-102g), each of which is associated with a unique identification (ID) number. During communication between a tag reader (104) and one or more RFID tags (102a-102g), the tag reader (104) traverses the binary tree (3), eliminating tags from communication until one tag with a unique ID number is isolated and verified. As the binary tree is traversed, counters (260 and 265)associated with each node in the tree are incremented based on tag matches, such that, over time, counters associated with nodes in tag-populated branches will tend to have a high value and counters associated with nodes in unpopulated tree branches will tend to have low values. Where the read process is subject to noise and the tag reader is forced to make a decision at a branching node, the tag reader makes a branch prediction based on the current value of the node counters associated with each of the possible alternative branches.