Method for simultaneous detection of a plurality of RFID tags using multiuser detection
First Claim
1. A method for distinguishing responses received by an RFID detector from a plurality of simultaneously queried RFID tags, the method comprising:
- querying the plurality of RFID tags;
receiving an aggregated RF response from the plurality of RFID tags;
characterizing the aggregated RF response according to a plurality of characteristics, the plurality of characteristics including at least RF amplitude and RF phase;
according to the characterization of the aggregated RF response, estimating at least one parameter, the at least one parameter including a number of RFID tag responses included in the aggregated RF response; and
applying multiuser detection including jointly demodulating a plurality of colliding RFID tag responses included in the aggregated RF response according to the at least one estimated parameter so as to distinguish each of the RFID tag responses included in the aggregated RF response.
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Accused Products
Abstract
A method and apparatus are disclosed that apply multiuser detection (MUD) analysis to an aggregated RF response from a plurality of simultaneously queried RFID tags, so as to distinguish the individual tag responses. The claimed method thereby significantly reduces RFID detection latency when multiple tags are simultaneously queried. Some embodiments transmit carrier waves at more than one frequency, such as a plurality of equally-spaced frequencies, so as to enhance the MUD analysis by incorporating a multi-frequency dimension. Other embodiments incorporate additional spatial dimensions by deploying multiple RF detection antennae at separated locations. The number of colliding tag responses must be estimated before MUD analysis can be applied. In some embodiments other signal parameters must be estimated, such as signal bias and an impulse function for each responding tag that characterizes alterations of the RF signal while in transit due to propagation distance, passage through intervening objects, and reflections.
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Citations
22 Claims
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1. A method for distinguishing responses received by an RFID detector from a plurality of simultaneously queried RFID tags, the method comprising:
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querying the plurality of RFID tags; receiving an aggregated RF response from the plurality of RFID tags; characterizing the aggregated RF response according to a plurality of characteristics, the plurality of characteristics including at least RF amplitude and RF phase; according to the characterization of the aggregated RF response, estimating at least one parameter, the at least one parameter including a number of RFID tag responses included in the aggregated RF response; and applying multiuser detection including jointly demodulating a plurality of colliding RFID tag responses included in the aggregated RF response according to the at least one estimated parameter so as to distinguish each of the RFID tag responses included in the aggregated RF response. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. An apparatus for distinguishing responses received from a plurality of simultaneously queried RFID tags, the apparatus comprising:
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an RF transmitter configured to transmit a querying RF signal to the plurality of RFID tags; an RF receiver configured to receive an aggregated RF response from the plurality of RFID tags; an RF characterizer configured to characterize the aggregated RF response according to a plurality of characteristics, the plurality of characteristics including at least RF amplitude and RF phase; and a computer controlled by software configured to direct the computer to estimate at least one parameter pertaining to the characterized aggregated RF response, the at least one parameter including a number of RFID tag responses included in the aggregated RF response, the software being further configured to direct the computer to apply multiuser detection including jointly demodulating a plurality of colliding RFID tag responses included in the aggregated RF response according to the at least one estimated parameter, so as to distinguish each of the RFID tag responses included in the aggregated RF response. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21, 22)
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Specification