Methods and systems for RFID tag geographical location using beacon tags and listening tags

• US 8,228,171 B2
• Filed: 09/22/2008
• Issued: 07/24/2012
• Est. Priority Date: 06/20/2008
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Bauchot, Frederic, Clement, Jean-Yves, Marmigere, Gerard, Picon, Joaquin, Rey-Robert, Xavier, Tassy, Vincent
• Primary Examiner(s): Bugg, George
• Assistant Examiner(s): Yacob, Sisay
• Application Number:
  US12/234,772
• Publication Number:
  US 20090315685A1
• Time in Patent Office: 1,401 Days
• Field of Search: 340/10.1, 340/10.41, 340/572.1, 340/5.92, 340/8.1, 342/387, 342463-465, 700/226, 235/385
• US Class Current: 340/10.1
• CPC Class Codes: G01S 13/46 Indirect determination of position data
• CPC Class Codes: G01S 13/758 using a signal generator powered by the interrogation signal
• CPC Class Codes: G01S 13/825 with exchange of information between interrogator and responder
• CPC Class Codes: G01S 2013/466 by Trilateration, i.e. two antennas or two sensors determine separately the distance to a target, whereby with the knowledge of the baseline length, i.e. the distance between the antennas or sensors, the position data of the target is determined
• CPC Class Codes: G01S 5/0289 of multiple transceivers, e.g. in ad hoc networks
• CPC Class Codes: H04Q 2213/13003 Constructional details of switching devices

Abstract

RFID method and system are provided. A reader transmits a reader signal to beacon tags and a listening tag. The beacon tags transmit beacon signals including a beacon identification and a beacon distance to the reader. The listening tag receives the beacon signals. Neighbor distances are calculated for the beacon tags based on when the beacon signals are received, when the listening tag receives the reader signal, and a constant processing time. The neighbor distances are the individual distances from the listening tag to the beacon tags. A list is stored including the beacon identification for the beacon tags, the beacon distance, and the neighbor distances. The listening tag transmits the list and a listening tag identification to the reader. A geographical position of the listening tag is calculated based on the beacon distance, beacon coordinates, and a listening tag distance which is from the reader to the listening tag.

Claims

1. A radio frequency identification method for locating a listening tag using beacon tags comprising:

transmitting a reader signal by a reader;

receiving the reader signal by a plurality of beacon tags;

receiving the reader signal by a listening tag;

transmitting, respectively by the plurality of beacon tags, a plurality of beacon signals, wherein each of the plurality of beacon signals respectively comprises;

a beacon identification, and

a beacon distance to the reader;

in response to the listening tag receiving the plurality of beacon signals, calculating by the listening tag neighbor distances for each of the plurality of beacon tags based on a combination of;

a time at which each of the plurality of beacon signals is received by the listening tag;

a time at which the listening tag receives the reader signal; and

a constant processing time as a constant value for each of the plurality of beacon tags to receive and to process data of the reader signal before respectively transmitting the plurality of beacon signals;

wherein, to compute the neighbor distances, the listening tag computes a delay time between the time at which the listening tag receives the reader signal and the time at which the listening tag respectively receives the plurality beacon signals, in order for the listening tag to subtract the constant processing time;

wherein the neighbor distances are individual distances from the listening tag to each of the plurality of beacon tags;

storing a list by the listening tag, wherein the list comprises;

the beacon identification and beacon distance to the reader for each of the plurality of beacon tags; and

the neighbor distances for each of the plurality of beacon tags as calculated by the listening tag;

transmitting, by the listening tag, to the reader;

the list; and

a listening tag identification;

calculating a geographical position of the listening tag based on;

the beacon distance for each of the plurality of beacon tags;

beacon coordinates for each of the plurality of beacon tags; and

a listening tag distance which is a distance from the reader to the listening tag.

2. The method of claim 1, wherein the reader calculates the geographical position of the listening tag based on trilateration;

and

wherein the listening tag stores the delay time, between the time at which the listening tag receives the reader signal and the time at which the listening tag respectively receives the plurality beacon signals, in the list.

3. The method of claim 1, wherein the listening tag calculates the geographical position of the listening tag based on trilateration.

4. The method of claim 3, wherein the listening tag transmits the geographical position of the listening tag to the reader.

5. The method of claim 1, wherein the reader knows the beacon coordinates for each of the plurality of beacon tags.

6. The method of claim 1, wherein each of the plurality of beacon tags knows its respective beacon coordinates.

7. The method of claim 6, wherein each of the plurality of beacon signals further comprises beacon coordinates, respectively.

8. The method of claim 7, wherein the list further comprises the beacon coordinates for each of the plurality of beacon tags.

9. The method of claim 1, wherein the reader calculates the listening tag distance.

10. The method of claim 1, wherein the listening tag calculates the listening tag distance.

11. A radio frequency identification system for locating a listening tag using beacon tags, the system comprising:

a reader configured to transmit and receive, wherein the reader transmits a reader signal;

a plurality of beacon tags configured to transmit and receive, wherein the plurality of beacon tags receive the reader signal and the plurality of beacon tags respectively transmit a plurality of beacon signals;

wherein each of the plurality of beacon signals respectively comprises;

a beacon identification, and

a beacon distance to the reader;

a listening tag configured to transmit and receive, wherein the listening tag receives the reader signal and the listening tag receives the plurality of beacon signals, respectively;

wherein in response to the listening tag receiving the plurality of beacon signals, the listening tag calculates neighbor distances for each of the plurality of beacon tags based on a combination of;

a time at which each of the plurality of beacon signals is received by the listening tag;

a time at which the listening tag receives the reader signal; and

a constant processing time as a constant value for each of the plurality of beacon tags to receive and to process data of the reader signal before respectively transmitting the plurality;

wherein, to compute the neighbor distances, the listening tag computes a delay time between the time at which the listening tag receives the reader signal and the time at which the listening tag respectively receives the plurality beacon signals, in order for the listening tag to subtract the constant processing time;

wherein the neighbor distances are individual distances from the listening tag to each of the plurality of beacon tags;

wherein the listening tag stores a list, the list comprising;

the beacon identification and beacon distance to the reader for each of the plurality of beacon tags; and

the neighbor distances for each of the plurality of beacon tags as calculated by the listening tag;

wherein the listening tag transmits the list and a listening tag identification to the reader;

wherein a geographical position of the listening tag is calculated based on;

the beacon distance for each of the plurality of beacon tags;

beacon coordinates for each of the plurality of beacon tags; and

a listening tag distance which is a distance from the reader to the listening tag.

12. The system of claim 11, wherein the reader is configured to calculate the geographical position of the listening tag based on trilateration.

13. The system of claim 11, wherein the listening tag is configured to calculate the geographical position of the listening tag based on trilateration.

14. The system of claim 13, wherein the listening tag transmits the geographical position of the listening tag to the reader.

15. The system of claim 11, wherein the reader knows the beacon coordinates for each of the plurality of beacon tags, and the beacon coordinates are stored in memory of the reader.

16. The system of claim 11, wherein each of the plurality of beacon tags knows its respective beacon coordinates, stored in a respective memory of the plurality of beacon tags.

17. The system of claim 16, wherein each of the plurality of beacon signals further comprises beacon coordinates, respectively.

18. A computer program product, tangibly embodied on a non-transitory computer readable medium, for utilizing radio frequency identification to locate a listening tag using beacon tags, the computer program product including instructions for causing a computer to execute a method, comprising:

transmitting a reader signal by a reader;

receiving the reader signal by a plurality of beacon tags;

receiving the reader signal by a listening tag;

transmitting, respectively by the plurality of beacon tags, a plurality of beacon signals, wherein each of the plurality of beacon signals respectively comprises;

a beacon identification, and

a beacon distance to the reader;

in response to the listening tag receiving the plurality of beacon signals, calculating neighbor distances for each of the plurality of beacon tags based on a combination of;

a time at which each of the plurality of beacon signals is received by the listening tag;

a time at which the listening tag receives the reader signal; and

a constant processing time as a constant value for each of the plurality of beacon tags to receive and to process data of the reader signal before respectively transmitting the plurality of beacon signals;

wherein, to compute the neighbor distances, the listening tag computes a delay time between the time at which the listening tag receives the reader signal and the time at which the listening tag respectively receives the plurality beacon signals, in order for the listening tag to subtract the constant processing time

wherein the neighbor distances are individual distances from the listening tag to each of the plurality of beacon tags;

storing a list by the listening tag, wherein the list comprises;

the beacon identification and beacon distance to the reader for each of the plurality of beacon tags; and

the neighbor distances for each of the plurality of beacon tags as calculated by the listening tag;

transmitting, by the listening tag, to the reader;

the list; and

a listening tag identification;

calculating a geographical position of the listening tag based on;

the beacon distance for each of the plurality of beacon tags;

beacon coordinates for each of the plurality of beacon tags; and

a listening tag distance which is a distance from the reader to the listening tag.

19. The computer program product of claim 18, wherein the reader calculates the geographical position of the listening tag based on trilateration.

20. The computer program product of claim 18, wherein the listening tag calculates the geographical position of the listening tag based on trilateration.