Systems and methods for approximating the location of an RFID tag

• US 7,423,516 B2
• Filed: 05/04/2006
• Issued: 09/09/2008
• Est. Priority Date: 05/04/2006
• Status: Active Grant

• Current Assignee: ABL IP Holding LLC (Acuity Brands, Inc.)
• Original Assignee: GOLIATH Solutions LLC (Osa Acquisition, LLC)
• Inventors: Overhultz, Gary L.
• Primary Examiner(s): Bugg, George A
• Assistant Examiner(s): Hunnings, Travis R
• Application Number:
  US11/418,319
• Publication Number:
  US 20070257795A1
• Time in Patent Office: 859 Days
• Field of Search: 340/505, 340/572.1, 340/10.1, 340/539.21
• US Class Current: 340/10.5
• CPC Class Codes: G01S 5/0295 Proximity-based methods, e.g. position inferred from reception of particular signals

Abstract

In accordance with the teachings described herein, systems and methods are provided for approximating the location of an RFID tag in an RFID system. The RFID system may include a plurality of receivers that receive RF signals from the RFID tag. Tag read count data for two or more of the plurality of receivers may be used to identify a number of times that each of the two or more receivers has received an RF signal from the RFID tag over a period of time. Signal strength data may be used to identify the strength of the RF signals received from the RFID tag. A combination metric for each of the two or more receivers may be determined as a function of the tag read count data and the signal strength data. The combination metrics may be compared to identify one of the receivers that is closest in proximity to the RFID tag.

Claims

1. A computer-implemented method of approximating a location of a radio frequency identification (RFID) tag in an RFID system, the RFID system including a plurality of receivers that receive RF signals from the RFID tag, the method comprising:

receiving tag read count data for two or more of the plurality of receivers, the tag read count data identifying a number of times that each of the two or more receivers has received an RF signal from the RFID tag over a period of time;

receiving signal strength data relating to the RF signals received from the RFID tag by the two or more receivers;

determining a combination metric for each of the two or more receivers, the combination metric being determined as a function of the tag read count data and the signal strength data; and

comparing the combination metrics to identify one of the receivers that is closest in proximity to the RFID tag.

2. The method of claim 1, wherein the signal strength data includes received signal strength indicator (RSSI) values.

3. The method of claim 1, wherein the signal strength data identifies maximum RSSI values received by each of the two or more receivers.

4. The method of claim 3, wherein the combination metrics are calculated by multiplying the maximum RSSI values by the read count data.

5. The method of claim 1, further comprising:

normalizing the combination metrics with respect to one of the combination metrics having a highest value;

wherein the normalized combination metrics are compared to identify the one receiver that is closest in proximity to the RFID tag.

6. The method of claim 5, further comprising:

comparing the normalized combination metrics with a threshold value; and

if two or more receivers have normalized combination metrics above the threshold value, then applying additional criteria to identify the one receiver that is closest in proximity to the RFID tag from the two or more receivers having normalized combination metrics above the threshold value.

7. The method of claim 6, wherein the additional criteria includes whether the two or more receivers having normalized combination metrics above the threshold value are located adjacent to each other in the RFID system.

8. The method of claim 6, wherein the threshold value is 0.75.

9. The method of claim 7, wherein if the two or more receivers having normalized combination metrics above the threshold value are located adjacent to each other in the RFID system, then selecting a receiver having a highest normalized combination metric as the one receiver that is closest in proximity to the RFID.

10. The method of claim 6, wherein the RFID system further includes a plurality of transmitters, the RFID tag modulating signals received from the plurality of transmitters to generate the RF signals.

11. The method of claim 10, wherein the additional criteria includes a transmitter combination metric for each of the two or more receivers having normalized combination metrics above the threshold value, the transmitter combination metrics being determined as a function of the tag read count data and the signal strength data for each unique combination of the plurality of transmitters and the two or more receivers having normalized combination metrics above the threshold value.

12. The method of claim 11, wherein a receiver having a highest transmitter combination metric is selected as the one receiver that is closest in proximity to the RFID.

13. An RFID system, comprising:

a radio frequency identification (RFID) tag;

a plurality of receivers that receive RFID signals from the RFID tag;

one or more processors that receive tag read count data for two or more of the plurality of receivers, the tag read count data identifying a number of times that each of the two or more receivers has received an RF signal from the RFID tag over a period of time;

the one or more processors receiving signal strength data relating to the RF signals received from the RFID tag by the two or more receivers;

the one or more processors determining a combination metric for each of the two or more receivers, the combination metric being determined as a function of the tag read count data and the signal strength data; and

the one or more processors comparing the combination metrics to identify one of the receivers that is closest in proximity to the RFID tag.

14. The system of claim 13, wherein the signal strength data includes received signal strength indicator (RSSI) values.

15. The system of claim 13, wherein the signal strength data identifies maximum RSSI values received by each of the two or more receivers.

16. The system of claim 15, wherein the combination metrics are calculated by multiplying the maximum RSSI values by the read count data.

17. The system of claim 13, further comprising:

the one or more processors normalizing the combination metrics with respect to one of the combination metrics having a highest value;

wherein the normalized combination metrics are compared to identify the one receiver that is closest in proximity to the RFID tag.

18. The system of claim 17, further comprising:

the one or more processors comparing the normalized combination metrics with a threshold value; and

if two or more receivers have normalized combination metrics above the threshold value, then the one or more processors applying additional criteria to identify the one receiver that is closest in proximity to the RFID tag from the two or more receivers having normalized combination metrics above the threshold value.

19. The system of claim 18, wherein the additional criteria includes whether the two or more receivers having normalized combination metrics above the threshold value are located adjacent to each other in the RFID system.

20. The system of claim 18, wherein the threshold value is 0.75.

21. The system of claim 19, wherein if the two or more receivers having normalized combination metrics above the threshold value are located adjacent to each other in the RFID system, then the one or more processors selecting a receiver having a highest normalized combination metric as the one receiver that is closest in proximity to the RFID.

22. The system of claim 18, further comprising:

a plurality of transmitters that transmit carrier signals to the RFID tag;

wherein the RFID tag modulates the carrier signals to generate the RF signals.

23. The system of claim 22, wherein the additional criteria includes a transmitter combination metric for each of the two or more receivers having normalized combination metrics above the threshold value, the transmitter combination metrics being determined as a function of the tag read count data and the signal strength data for each unique combination of the plurality of transmitters and the two or more receivers having normalized combination metrics above the threshold value.

24. The system of claim 23, wherein a receiver having a highest transmitter combination metric is selected as the one receiver that is closest in proximity to the RFID.

25. An RFID system, comprising:

a radio frequency identification (RFID) tag;

a plurality of receivers that receive RFID signals from the RFID tag;

means for receiving tag read count data for two or more of the plurality of receivers, the tag read count data identifying a number of times that each of the two or more receivers has received an RF signal from the RFID tag over a period of time;

means for receiving signal strength data relating to the RF signals received from the RFID tag by the two or more receivers;

means for determining a combination metric for each of the two or more receivers, the combination metric being determined as a function of the tag read count data and the signal strength data; and

means for comparing the combination metrics to identify one of the receivers that is closest in proximity to the RFID tag.

26. A method for remotely monitoring compliance with an advertising program without human intervention by determining the presence of a plurality of promotional displays each at a predetermined location at a plurality of facilities, comprising:

associating RF means with a plurality of promotional displays each to be displayed for advertising purposes for wirelessly sending data about the displays from the displays;

locating RF receiving means remotely from the displays for receiving the display data;

determining location data for each of the plurality of promotional displays using a computer-implemented method that includes the steps of;

receiving tag read count data for the RF receiving means, the tag read count data identifying a number of times that each of the RF receiving means has received display data from a particular RF means over a period of time;

receiving signal strength data relating to the display data received from the RF means by the RF receiver means;

determining a combination metric for each of the RF receiver means, the combination metric being determined as a function of the tag read count data and the signal strength data; and

comparing the combination metrics to identify which of the RF receiver means is closest in proximity to each of the RF means;

analyzing the display data and the location data to determine the identity of the displays and whether the displays are timely and properly located at the various facilities and thereby in compliance with the advertising program.

27. An RF system for remotely monitoring, without human intervention, compliance with an advertising program that includes displays to be located at a plurality of different facilities by determining the presence of one or more advertising displays at a plurality of predetermined locations, with at least one display at each facility in the program, comprising:

a tag associated with each advertising display, the display being displayed for advertising purposes, and the tag being adapted for RF communication;

at least one RF reader at each facility for receiving tag data from each tag within range of the reader, the receiving tag data indicating the identity of and presence of the tag and its corresponding display in a particular one of the predetermined locations at a facility in the program;

one or more processors that receive tag read count data for the RF readers, the tag read count data identifying a number of times that each of the RF readers has received an RF signal from a particular tag over a period of time;

the one or more processors receiving signal strength data relating to the RF signals;

the one or more processors determining a combination metric for each of the RF readers, the combination metric being determined as a function of the tag read count data and the signal strength data;

the one or more processors comparing the combination metrics to determine location data that identifies which of the RF readers is closest in proximity to each of the tags;

the one or more processors receiving tag data from each tag at the facility; and

the one or more processors analyzing the tag data and the location data to determine whether each display is timely and properly located in each facility and thereby which advertising displays and facilities are in compliance with the advertising program.