Inventory-cycle-based RFID tag location
Techniques are provided to estimate the location of an RFID tag using tag read information, such as a tag read count or a tag read rate, and an opportunity metric, such as an inventory cycle duration, inventory cycle rate, or inventory cycle count. A tag tracking system determines read information for a tag in a zone and an opportunity metric associated with the tag and the zone. The tag tracking system then computes a success rate based on the tag read information and opportunity metric, and uses the success rate to estimate the location of the tag.
1. A Radio Frequency Identification (RFID) system configured to estimate a location of an RFID tag, the system comprising:
an RFID reader component configured to communicate wirelessly with RFID tags; and
a controller communicatively coupled to the RFID reader component and configured to:
cause the RFID reader component to transmit a first inventorying RF wave to a first zone;
count a first nonzero number of responses from the RFID tag in the first zone;
determine a first success rate based on the first nonzero response count and a first opportunity metric associated with the first zone;
cause the RFID reader component to transmit a second inventorying RF wave to a second zone different from but overlapping with the first zone;
count a second nonzero number of responses from the RFID tag in the second zone;
determine a second success rate based on the second nonzero response count and a second opportunity metric associated with the second zone; and
estimate the tag location within an overlapping portion of the first and second zones based on at least a comparison of the first and second success rates.
2. The system of claim 1 , wherein:
the controller is configured to count the first and second nonzero numbers of responses of the RFID tag by counting over first and second time intervals, respectively; and
the first and second opportunity metrics are based on the first and second time intervals, respectively.
3. The system of claim 1 , wherein the first opportunity metric is based on at least one of:
a number of inventory cycles performed while the RFID reader component transmits the first inventorying RF wave to the first zone; and
a total number of RFID tags inventoried in the first zone.
4. The system of claim 1 , wherein the first opportunity metric is one of an inventory-cycle duration and an inventory-cycle rate.
5. The system of claim 1 , wherein the controller is configured to use at least one of a weighted-averaging method and a centroid-averaging method to estimate the tag location.
6. The system of claim 1 , wherein the controller is configured to estimate the tag location based on the comparison and at least one of:
a received signal strength indicator (RSSI) associated with a response from the RFID tag,
an angle-of-arrival of the response,
a phase of the response,
a Doppler parameter of the response,
a timing of the response, and
data included in the response.
7. The system of claim 1 , wherein the RFID reader component is a synthesized-beam reader (SBR) configured to direct an SBR beam to the first zone.
8. A Radio Frequency Identification (RFID) system configured to estimate a location of an RFID tag, the system comprising:
a synthesized-beam reader (SBR) component configured to generate RF beams; and
a controller communicatively coupled to the SBR component and configured to:
cause the SBR component to direct a first RF beam to a first zone;
count a first nonzero number of responses from the RFID tag using the first RF beam;
determine a first success rate based on the first response count and a first opportunity metric associated with the first RF beam;
cause the SBR component to direct a second RF beam, different from the first beam, to a second zone;
count a second nonzero number of responses from the RFID tag using the second RF beam;
determine a second success rate based on the second response count and a second opportunity metric associated with the second RF beam; and
estimate the tag location with respect to at least one of the first and second zones based on at least a comparison between the first and second success rates.
9. The system of claim 8 , wherein at least one of:
the first zone only constitutes a portion of the first RF beam; and
the second zone only constitutes a portion of the second RF beam.
10. The system of claim 8 , wherein the controller is configured to count the first and second nonzero numbers of responses of the RFID tag by counting over first and second time intervals, respectively; and
the first and second opportunity metrics are based on the first and second time intervals, respectively.
11. The system of claim 8 , wherein the first opportunity metric is based on at least one of:
a number of completed inventory cycles associated with the first RF beam; and
a total number of RFID tags inventoried using the first RF beam.
12. The system of claim 8 , wherein the first opportunity metric is one of an inventory-cycle duration and an inventory-cycle rate.
13. The system of claim 8 , wherein the controller is configured to use at least one of a weighted-averaging method and a centroid-averaging method to estimate the tag location.
14. The system of claim 8 , wherein the controller is further configured to estimate the tag location based on at least one of:
a received signal strength indicator (RSSI) associated with a response from the RFID tag,
an angle-of-arrival of the response,
a phase of the response,
a Doppler parameter of the response,
a timing of the response, and
data included in the response.
15. A Radio Frequency Identification (RFID) system configured to estimate a location of an RFID tag, the system comprising:
an RFID reader component configured to communicate wirelessly with RFID tags; and
a controller communicatively coupled to the RFID reader component and configured to:
cause the RFID reader component to transmit an inventorying RF wave on a beam directed at a target location;
count a nonzero number of responses from the RFID tag on the beam;
determine a current success rate based on the nonzero response count and an opportunity metric associated with the beam;
determine an expected success rate associated with the RFID tag; and
estimate the tag location with respect to the target location based on the current success rate and the expected success rate.
16. The system of claim 15 , wherein the opportunity metric is based on a number of completed inventory cycles.
17. The system of claim 15 , wherein the opportunity metric is one of an inventory-cycle duration and an inventory-cycle rate.
18. The system of claim 15 , wherein the controller is configured to determine the expected success rate based on at least one of a prior success rate and a calculated success rate.
19. The system of claim 15 , wherein the controller is configured to determine the expected success rate based on at least one of a prior location of the RFID tag, an identifier associated with the RFID tag, data previously received from the RFID tag, a noise characteristic associated with the target location, and a physical characteristic associated with the target location.
20. The system of claim 15 , wherein the controller is configured to estimate the tag location based on the current success rate, the expected success rate, and at least one of:
a received signal strength indicator (RSSI) associated with a response from the RFID tag,
an angle-of-arrival of the response,
a phase of the response,
a Doppler parameter of the response,
a timing of the response, and
data included in the response.
21. The system of claim 15 , wherein the beam is a synthesized-beam reader (SBR) beam.