Location determination method and system for asset tracking devices

• US 20060125694A1
• Filed: 07/30/2005
• Published: 06/15/2006
• Est. Priority Date: 07/30/2004
• Status: Active Grant

• Current Assignee: G2 Microsystems Pty Limited
• Original Assignee: G2 Microsystems Pty Limited
• Inventors: Ryan, Philip J., Smith, Geoffrey J., Gloekler, John S., O'Sullivan, John, Dejanovic, Thomas
• Granted Patent: US 7,315,281 B2
• Time in Patent Office: Days
• US Class Current: 342/463
• CPC Class Codes: C07D 263/58 with hetero atoms or with carbon atoms having three bonds to hetero atoms with at the most one bond to halogen, e.g. ester or nitrile radicals, directly attached in position 2
• CPC Class Codes: C07D 265/36 condensed with one six-membered ring
• CPC Class Codes: C07D 413/04 directly linked by a ring-member-to-ring-member bond
• CPC Class Codes: C07D 413/06 linked by a carbon chain containing only aliphatic carbon atoms
• CPC Class Codes: C07D 413/10 linked by a carbon chain containing aromatic rings
• CPC Class Codes: C07D 413/14 containing three or more hetero rings
• CPC Class Codes: C07D 417/04 directly linked by a ring-member-to-ring-member bond
• CPC Class Codes: C07D 417/14 containing three or more hetero rings
• CPC Class Codes: G01S 5/0263 by combining or switching between positions derived from two or more separate positioning systems

Abstract

A method of determining a geographical location of an asset tracking device, includes searching, by the asset tracking device, for available location determination schemes at the geographical location, selecting one of the available location determination schemes, and determining coordinates of the geographical location using the selected location determination scheme. Some embodiments also include making a decision based, at least in part, upon the geographical location coordinates determined by using the selected location determination scheme. Some embodiments include transmitting a location message, the location message including the coordinates of the geographical location and an indication as to the selected location determination scheme.

Claims

1. A method of determining a position of an asset tracking device within a geographical location, comprising:

searching, by the asset tracking device, for available location determination schemes at the geographical location;

selecting one of the available location determination schemes; and

determining coordinates of the position of the asset tracking device using the selected location determination scheme.

2. The method of claim 1, further comprising making a decision based, at least in part, upon the coordinates determined by using the selected location determination scheme.

3. The method of claim 1, further comprising transmitting a location message, the location message including the coordinates of the location of the asset tracking device.

4. The method of claim 3, wherein the location message includes an identification of the selected location determination scheme.

5. The method of claim 3, wherein the location message is addressed to a tracking entity.

6. The method of claim 1, further comprising:

receiving, at the asset tracking device, a request for a location message.

7. The method of claim 1, wherein the selected location determination scheme is a time of arrival scheme.

8. The method of claim 1, wherein the selected location determination scheme is a time difference of arrival scheme.

9. The method of claim 1, wherein the selected location determination scheme is a received signal strength indicator scheme.

10. The method of claim 1, wherein determining coordinates of the position of the asset tracking device comprises:

listening, by the asset tracking device, for beacon packets transmitted by one or more reference tags, to determine which reference tags are within range;

wherein each beacon packet includes the coordinates of the position of the transmitting reference tag.

11. The method of claim 10, further comprising:

transmitting, from the asset tracking device, an RTS packet;

receiving, at the asset tracking device, a CTS packet;

transmitting, from the asset tracking device, a first PRN sequence;

receiving, at the asset tracking device, a second PRN sequence; and

determining, subsequent to receiving the second PRN sequence, the time or arrival of the second PRN sequence;

wherein the first PRN sequence and the second PRN sequence are identical, and wherein transmissions are in an 802.11 protocol, and the first and second PRN sequences are transmitted in place of an 802.11 payload.

12. The method of claim 11, further comprising:

receiving, at the asset tracking device, timing information from the reference tag; and

determining the position coordinates of the asset tracking device.

13. The method of claim 1, wherein searching, by the asset tracking device, for available location determination schemes at the geographical location, is performed subsequent to a determination that the asset tracking device is unable to determine its position coordinates based upon GPS signals.

14. The method of claim 13, wherein the asset tracking device is unable to determine its position coordinates because the GPS signals are obstructed.

15. The method of claim 13, wherein the asset tracking device is unable to determine its position coordinates because the GPS signals have a signal strength that is below a predetermined threshold.

16. The method of claim 1, further comprising the asset tracking device transitioning from a sleep state to a wake state at predetermined time intervals.

17. The method of claim 1, wherein the asset tracking device is an RFID tag.

18. The method of claim 17, wherein the asset tracking device is attached to an item to be tracked.

19. The method of claim 5, wherein the tracking entity is communicatively coupled to the asset tracking device through the Internet.

20. A system, comprising:

at least one asset tracking device, the asset tracking device including a communications module, a processing and storage module coupled to the communications module, and a location module coupled to the processing and storage module;

a network access point, wirelessly coupled to the at least one asset tracking device; and

a local positioning system comprising a plurality of reference tags, each of the reference tags having its known position coordinates stored therein, the reference tags wirelessly coupled to receive signals transmitted from the at least one asset tracking device, and to transmit signals to the at least one asset tracking device;

wherein the at least one asset tracking device is operable to determine that its location module is unable to determine position coordinates from GPS signals, is further operable to search for one or more reference tags of the local positioning system, to communicate with the local positioning system so as gather the information necessary to compute it position coordinates; and

wherein the at least one asset tracking device is an RFID tag attached to an item to be tracked.