Patent ID: 7639638
Filing Date: 2009-12-29
Classification: G06K,G06Q,G07B,H04L,H04W

Abstract:
1. A method comprising: sending a first command from an interrogator to a plurality of wireless identification devices to select a first subset of the plurality of wireless identification devices in accordance with an arbitration scheme, the first subset associated with a first branch of a search tree corresponding to a tree search scheme, the first command requesting each of the plurality of wireless identification devices of the first subset to respond approximately simultaneously; sending a second command from the interrogator to the plurality of wireless identification devices to select a second subset of the plurality of wireless identification devices in accordance with the arbitration scheme, the second subset associated with a second branch of the search tree, the second command requesting each of the plurality of wireless identification devices of the second subset to respond in an independently selected one of a plurality of time slots in accordance with an Aloha scheme; detecting a collision between at least two wireless identification devices of the plurality of wireless identification devices; and skipping at least one level of the search tree in response to detecting the collision.