Patent ID: 8410906
Filing Date: 2013-04-02
Classification: G06K,H04Q

Abstract:
1. A method for communicating between an RFID reader and a plurality of RFID tags, the method comprising: the RFID reader transmitting at a first carrier power level in a forward link that communicates information from the RFID reader to a first set of RFID tags and a second set of RFID tags within the plurality of RFID tags; and the RFID reader compensating for reverse link propagation behavior by transmitting at a second carrier power level supporting reverse link backscatter communications from the first set of RFID tags and the second set of RFID tags to the RFID reader, the second carrier power level being higher than the first carrier power level, wherein a lower subcarrier frequency for the reverse link communications is used for communication between the RFID reader and the first set of RFID tags within the plurality of RFID tags and a second higher subcarrier frequency is used for communication between the RFID reader and the second set of RFID tags within the plurality of RFID tags, the first set of RFID tags being proximately closer to the RFID reader than the second set of RFID tags, wherein at least one additional forward link power level is used by the RFID reader, a first forward power level being used to communicate with the first set of RFID tags within the plurality of RFID tags and a second forward power level being used to communicate with the second set of RFID tags within the plurality of RFID tags, and the first forward power level being smaller than the second forward power level, wherein a first higher data rate is used for the communication between the RFID reader and the first set of RFID tags within the plurality of RFID tags and a second lower data rate is used for the communication between the RFID reader and the second set of RFID tags within the plurality of RFID tags, wherein the RFID reader sends instructions to the first set of RFID tags within the plurality of RFID tags for causing the first set of RFID tags to adjust their transmit power, wherein the RFID tags in the first set that have been accessed are placed into a non-responsive state for a predetermined period of time by the RFID reader after having been accessed for preventing the tags in the first set that are in the non-responsive state from responding to the RFID reader when the RFID reader is communicating with the second set of RFID tags.