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 method for a Radio Frequency Identification (RFID) system to estimate a location of an RFID tag with respect to an inventory zone generated by the RFID system, the method comprising:
transmitting an inventorying RF wave in the inventory zone;
counting a nonzero number of responses from the RFID tag in the inventory zone;
determining a current success rate based on the nonzero response count and an opportunity metric associated with the inventory zone;
determining an expected success rate associated with the RFID tag; and
estimating the tag location with respect to the inventory zone based on the current success rate and the expected success rate.
2. The method of claim 1 , wherein the opportunity metric is based on a number of completed inventory cycles.
3. The method of claim 1 , wherein the opportunity metric is one of an inventory-cycle duration and an inventory-cycle rate.
4. The method of claim 1 , further comprising determining the expected success rate based on at least one of a prior success rate and a calculated success rate.
5. The method of claim 1 , further comprising determining 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 inventory zone, and a physical characteristic associated with the inventory zone.
6. The method of claim 1 , further comprising estimating 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.
7. A method for a Radio Frequency Identification (RFID) system to estimate a location of an RFID tag with respect to a beam generated by the RFID system and directed at a target location, the method comprising:
transmitting an inventorying RF wave on the beam;
counting a nonzero number of responses from the RFID tag on the beam;
determining a current success rate based on the nonzero response count and an opportunity metric associated with the beam;
determining an expected success rate associated with the RFID tag; and
estimating the tag location with respect to the target location based on the current success rate and the expected success rate.
8. The method of claim 7 , wherein the opportunity metric is based on a number of completed inventory cycles.
9. The method of claim 7 , wherein the opportunity metric is one of an inventory-cycle duration and an inventory-cycle rate.
10. The method of claim 7 , further comprising determining the expected success rate based on at least one of a prior success rate and a calculated success rate.
11. The method of claim 7 , further comprising determining 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.
12. The method of claim 7 , further comprising estimating 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.
13. The method of claim 7 , wherein the beam is a synthesized-beam reader (SBR) beam.
14. A Radio Frequency Identification (RFID) system configured to estimate a location of an RFID tag with respect to an inventory zone, the system comprising:
an RFID reader configured to generate a beam directed to the inventory zone; and
a processor coupled to the reader and configured to:
cause the reader to transmit an inventorying RF wave on the beam;
count a nonzero number of responses from the RFID tag in the inventory zone;
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 inventory zone based on the current success rate and the expected success rate.
15. The system of claim 14 , wherein the processor is configured to determine the opportunity metric based on a number of completed inventory cycles.
16. The system of claim 14 , wherein the processor is configured to determine the opportunity metric based on one of an inventory-cycle duration and an inventory-cycle rate.
17. The system of claim 14 , wherein the processor is further configured to determine the expected success rate based on at least one of a prior success rate and a calculated success rate.
18. The system of claim 14 , wherein the processor is further 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 inventory zone, and a physical characteristic associated with the inventory zone.
19. The system of claim 14 , wherein the processor is further 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.
20. The system of claim 14 , wherein the reader is a synthesized-beam reader (SBR) and the beam is an SBR beam.