RFID READER Q-PARAMETER AIDED BY RF POWER MEASUREMENT
First Claim
Patent Images
1. A Radio Frequency Identification (RFID) reader system for communicating with a plurality of RFID tags, the system operable to:
- cause to be transmitted to the RFID tags a first reader command that communicates a first value for a Q parameter, the first reader command thus causing each of the RFID tags to occupy one of a plurality of first slots that are defined by the first value;
then cause a plurality of QueryRep commands to be transmitted sequentially to the RFID tags, each QueryRep command for examining of a respective one of the first slots for its occupancy by causing any of the RFID tags occupying the respective first slot to backscatter a response within a tag response time window of the first slot and be silent at a tag silent period of the first slot that is outside the tag response window of the first slot;
receive an initial reference signal during one of the tag silent periods of one of the first slots;
measure an aspect of the initial reference signal;
set a detection threshold from the measured aspect;
detect second signals during at least some of the tag response time windows of the examined first slots;
determine from the second signals whether the occupancy of the examined first slots is none or at least one of the RFID tags, in which the determination for at least a certain one of the first slots is performed by comparing the detection threshold to a power of a second signal corresponding to the certain slot;
decide according to the determined first slot occupancies and according to a Q-algorithm a second value for the Q parameter; and
then cause to be transmitted to the RFID tags a second reader command that communicates the second value for the Q parameter, the reader second command thus causing each of the RFID tags to occupy one of a plurality of second slots that are defined by the second value.
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Abstract
RFID tag responses are detected by an RFID reader system. The tag response may be detected based on a reference measurement during a tag silent period and another one during the tag response. This helps determine whether a slot is empty or occupied, in a slotted aloha algorithm. The result is reported to the Q-algorithm for a better decision.
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Citations
52 Claims
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1. A Radio Frequency Identification (RFID) reader system for communicating with a plurality of RFID tags, the system operable to:
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cause to be transmitted to the RFID tags a first reader command that communicates a first value for a Q parameter, the first reader command thus causing each of the RFID tags to occupy one of a plurality of first slots that are defined by the first value;
then cause a plurality of QueryRep commands to be transmitted sequentially to the RFID tags, each QueryRep command for examining of a respective one of the first slots for its occupancy by causing any of the RFID tags occupying the respective first slot to backscatter a response within a tag response time window of the first slot and be silent at a tag silent period of the first slot that is outside the tag response window of the first slot;
receive an initial reference signal during one of the tag silent periods of one of the first slots;
measure an aspect of the initial reference signal;
set a detection threshold from the measured aspect;
detect second signals during at least some of the tag response time windows of the examined first slots;
determine from the second signals whether the occupancy of the examined first slots is none or at least one of the RFID tags, in which the determination for at least a certain one of the first slots is performed by comparing the detection threshold to a power of a second signal corresponding to the certain slot;
decide according to the determined first slot occupancies and according to a Q-algorithm a second value for the Q parameter; and
then cause to be transmitted to the RFID tags a second reader command that communicates the second value for the Q parameter, the reader second command thus causing each of the RFID tags to occupy one of a plurality of second slots that are defined by the second value. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A method for a Radio Frequency Identification (RFID) reader system to inventory a population of RFID tags, comprising:
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causing to be transmitted to the RFID tags a first reader command that communicates a first value for a Q parameter, the first reader command thus causing each of the RFID tags to occupy one of a plurality of first slots that are defined by the first value;
then causing a plurality of QueryRep commands to be transmitted sequentially to the RFID tags, each QueryRep command for examining of a respective one of the first slots for its occupancy by causing any of the RFID tags occupying the respective first slot to backscatter a response within a tag response time window of the first slot and be silent at a tag silent period of the first slot that is outside the tag response time window of the first slot;
receiving an initial reference signal during one of the tag silent periods of one of the first slots;
measuring an aspect of the initial reference signal;
setting a detection threshold from the measured aspect;
detecting second signals during at least some of the tag response time windows of the examined first slots;
determining from the second signals whether the occupancy of the examined first slots is none or at least one of the RFID tags, in which the determination for at least a certain one of the first slots is performed by comparing the detection threshold to a power of a second signal corresponding to the certain slot;
deciding according to the determined first slot occupancies and according to a Q-algorithm a second value for the Q parameter; and
then causing to be transmitted to the RFID tags a second reader command that communicates the second value for the Q parameter, the reader second command thus causing each of the RFID tags to occupy one of a plurality of second slots that are defined by the second value. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26)
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27. A component for a Radio Frequency Idenfication (RFID) reader system operable to communicate with a plurality of RFID tags, the component operable to:
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receive a first inventory instruction that includes a first value for a Q parameter;
cause to be transmitted to the RFID tags a first reader command that communicates the first value for the Q parameter, the first reader command thus causing each of the RFID tags to occupy one of a plurality of first slots that are defined by the first value;
then cause a plurality of QueryRep commands to be transmitted sequentially to the RFID tags, each QueryRep command for examining a respective one of the first slots for its occupancy by causing any of the RFID tags occupying the respective first slot to backscatter a response within a tag response time window of the first slot and be silent at a tag silent period of the first slot that is outside the tag response time window of the first slot;
receive an initial reference signal during one of the tag silent periods of one of the first slots;
measure an aspect of the initial reference signal;
set a detection threshold from the measured aspect;
detect second signals during at least some of the tag response time windows of the examined first slots;
determine from the second signals whether the occupancy of the examined first slots is none or at least one of the RFID tags, in which the determination for at least a certain one of the first slots is performed by comparing the detection threshold to a power of a second signal corresponding to the certain slot;
transmit a report informing of the determined occupancy;
receive a second inventory instruction that includes a second value for the Q parameter that has been determined responsive to the report; and
then cause to be transmitted to the RFID tags a second reader command that communicates the second value for the Q parameter, the reader second command thus causing each of the RFID tags to occupy one of a plurality of second slots that are defined by the second value. - View Dependent Claims (28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39)
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40. A method for a component of a Radio Frequency Identification (RFID) reader system, comprising:
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receiving a first inventory instruction that includes a first value for a Q parameter;
causing to be transmitted to the RFID tags a first reader command that communicates the first value for the Q parameter, the first reader command thus causing each of the RFID tags to occupy one of a plurality of first slots that are defined by the first value;
then causing a plurality of QueryRep commands to be transmitted sequentially to the RFID tags, each QueryRep command for examining a respective one of the first slots for its occupancy by causing any of the RFID tags occupying the respective first slot to backscatter a response within a tag response time window of the first slot and be silent at a tag silent period of the first slot that is outside the tag response time window of the first slot;
receiving an initial reference signal during one of the tag silent periods of one of the first slots;
measuring an aspect of the initial reference signal;
setting a detection threshold from the measured aspect;
detecting second signals during at least some of the tag response time windows of the examined first slots;
determining from the second signals whether the occupancy of the examined first slots is none or at least one of the RFID tags, in which the determination for at least a certain one of the first slots is performed by comparing the detection threshold to a power of a second signal corresponding to the certain slot;
transmitting a report informing of the determined occupancy;
receiving a second inventory instruction that includes a second value for the Q parameter that has been determined responsive to the report; and
then causing to be transmitted to the RFID tags a second reader command that communicates the second value for the Q parameter, the reader second command thus causing each of the RFID tags to occupy one of a plurality of second slots that are defined by the second value. - View Dependent Claims (41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52)
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Specification