Method for resolving signals collisions between multiple RFID transponders in a field
First Claim
Patent Images
1. A method for reading RFID transponders in a field, the method comprising:
- transmitting a carrier signal;
detecting the presence of at least one of the transponders in the field;
receiving data from all of the transponders in the field;
determining whether the received data is valid; and
in response to determining that the received data is invalid, informing all transponders in the field that there was an incomplete read, the informing including suppressing the carrier.
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Accused Products
Abstract
Communications between an RFID interrogator and an RFID transponder require that no more than one transponder be present in the reading range of the interrogator and transmitting into motion at any given time. If multiple transponders are in the field, then a collision between the return signals of the transponders occurs, rendering the signals unreadable. A method to resolve the collisions and allow for accurate transmission of each transponder'"'"'s data is given. This method is especially effective over other methods when the transponder is a read-only type of device, whereby there is no communications interrogator on board the read-only transponder.
75 Citations
34 Claims
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1. A method for reading RFID transponders in a field, the method comprising:
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transmitting a carrier signal; detecting the presence of at least one of the transponders in the field; receiving data from all of the transponders in the field; determining whether the received data is valid; and in response to determining that the received data is invalid, informing all transponders in the field that there was an incomplete read, the informing including suppressing the carrier. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A method for reading one or more RFID transponders in a field, the transponders including transponders that are active and capable of communicating, the method comprising:
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providing a carrier signal; detecting the presence of at least one transponder, the detecting including using a demodulator and modifying the carrier signal by suppressing the carrier signal for a predetermined number of clock cycles; receiving data from all active transponders in the field, the receiving including receiving the data in groups of one or more bits and checking the validity of each group of data as the group is received; determining whether a valid data transmission has been received by detecting inability to compute a proper synchronization word, a proper CRC, or a proper word length; in response to determining an invalid data transmission, modifying the carrier signal to inform all active transponders in the field that there was an incomplete read; and transmitting the complete data for each transponder to a computer system for processing. - View Dependent Claims (14, 15, 16, 17)
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18. A method for reading one or more RFID transponders in a field, the method comprising:
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providing a carrier signal; detecting the presence of at least one transponder, the detecting including modifying the carrier signal in a predetermined manner; receiving data from all active transponders in the field, the receiving including receiving the data in groups of one or more bits and checking the validity of each group of data as it is received; determining whether a valid data transmission has been received;
the receiving and the determining being iteratively repeated until complete data for each transponder in the field has been read, the determining that complete data has been read for one of the transponders including determining that the CRC is valid and suppressing the carrier;upon determining an invalid data transmission, modifying the carrier signal to inform all active transponders in the field that there was an incomplete read; and transmitting the complete data for each transponder to a computer system for processing. - View Dependent Claims (19, 20, 21, 22, 23)
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24. A method for reading RFID transponders in a field, the method comprising:
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transmitting a carrier signal; receiving data from transponders in the field; determining whether the received data is valid or invalid; and in response to determining that the received data is invalid, informing all transponders in the field that there was an incomplete read, the informing including suppressing the carrier. - View Dependent Claims (25, 26, 27, 28, 29, 30, 31, 32, 33)
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34. An interrogator for reading RFID transponders in a field, the interrogator comprising:
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a modulator configured to transmit a carrier signal; a receiver configured to receive data from transponders in the field; circuitry coupled to the modulator and receiver configured to determine whether the received data is valid or invalid and, in response to determining that the received data is invalid, to inform all transponders in the field that there was an incomplete read, by suppressing the carrier for an amount of time.
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Specification