Back to results
US 8,077,013 B2Granted
RFID reader Q-parameter aided by RF power measurement
AssigneeImpinj, Inc.
InventorScott A. Cooper
Life of this patent
Estimating the term…
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.
Claims52
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 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 of 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.
7 more elements
A method for a Radio Frequency Identification (RFID) reader system to inventory a population of RFID tags, comprising:
- 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 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.
7 more elements
A component for a Radio Frequency Identification (RFID) reader system operable to communicate with a plurality of RFID tags, the component operable to:
- 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.
9 more elements
A method for a component of a Radio Frequency Identification (RFID) reader system, comprising:
- 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.
9 more elements
Dependencies are inferred from the claim text.