Patent ID: 8693455

Claim:
A method of determining tag positions based on a double difference calculation of measured tag signals in a distributed tag processing system comprising a set of tag readers, the method comprising: at each of a plurality of tag readers in the set of tag readers, receiving tag signals comprising tag data from a same plurality of tags residing in an overlapping coverage area of the plurality of tag readers; at each particular tag reader in the plurality of tag readers, determining an initial position of each tag in the plurality of tags based on a first difference calculation between measurements of the signals received at the particular tag reader from all tags in the plurality of tags; transmitting said initial position of each tag and said measurements of the received signals from each tag reader to an access point; and at said access point, revising the position of each tag in the plurality of tags based on a second difference calculation between measurements of signals of each tag received at different tag readers in the plurality of tag readers.