Patent attributes
A method of establishing wireless communications between an interrogator and individual ones of multiple wireless identification devices, the method comprising utilizing a tree search method to attempt to identify individual ones of the multiple wireless identification devices so as to be able to perform communications, without collision, between the interrogator and individual ones of the multiple wireless identification devices, a search tree being defined for the tree search method, the tree having multiple nodes respectively representing subgroups of the multiple wireless identification devices, wherein the interrogator transmits a command at a node, requesting that devices within the subgroup represented by the node respond, wherein the interrogator determines if a collision occurs in response to the command and, if not, repeats the command at the same node. An interrogator configured to transmit a command at a node, requesting that devices within the subgroup represented by the node respond, the interrogator further being configured to determine if a collision occurs in response to the command and, if not, to repeat the command at the same node includes: transmitting by an interrogator a first signal including a first set of bits, the interrogator to identify a first subgroup of a group of possible random numbers; communicating by each of one or more RFID devices a first response if the one or more RFID devices has generated a random number that is included in the first subgroup; receiving by the interrogator one or more received responses from respective ones of the one or more RFID devices; and responsive to receiving one of the one or more received responses without a collision, retransmitting by the interrogator at least the first signal.
