Patent ID: 8421598
Filing Date: 2013-04-16
Classification: G06K,H04Q

Abstract:
1. A power compensating RFID reader comprising: a reader transmitter that is configured to transmit 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 a plurality of RFID tags; and wherein the reader transmitter is configured to compensate 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 the reader transmitter is configured to use a lower subcarrier frequency for the reverse link communications 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 closer to the RFID reader than the second set of RFID tags, wherein the reader transmitter is configured to use at least one additional forward link power level, 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 to communicate with the second set of RFID tags within the plurality of RFID tags, the first forward power level being smaller than the second forward power level, wherein the reader transmitter is configured to use a first higher data rate for the communication between the RFID reader and the first set of RFID tags and a second lower data rate for the communication between the RFID reader and the second set 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 within the plurality 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.