System and method for asset location in wireless networks

• US 7,174,172 B2
• Filed: 02/25/2005
• Issued: 02/06/2007
• Est. Priority Date: 02/25/2005
• Status: Active Grant

• Current Assignee: Symbol Technologies, LLC (Zebra Technologies Corporation)
• Original Assignee: Symbol Technologies, Inc. (Zebra Technologies Corporation)
• Inventors: Katz, Joseph, Sharony, Jacob
• Primary Examiner(s): Eng; George
• Assistant Examiner(s): Miller; Brandon J.
• Application Number:
  US11/067,127
• Publication Number:
  US 20060194587A1
• Time in Patent Office: 711 Days
• Field of Search: 455/456.2, 455/456.3, 455/456.4, 455/456.5, 455/456.6, 455/115.1, 340/539.13
• US Class Current: 455/456.1
• CPC Class Codes: G01S 5/02521 using a radio-map
• CPC Class Codes: G01S 5/06 Position of source determined by co-ordinating a plurality of position lines defined by path-difference measurements G01S5/12 takes precedence
• CPC Class Codes: H04W 4/029 Location-based management or tracking services
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management

Abstract

Described is a system and method for tracking an asset. The system may include a plurality of wireless access points and a computing arrangement communicating with the access points. The arrangement determines a location area of the device as a function of first data and a location of each of at least three access points of the plurality of the access points. The first data includes at least one of first signal strength data and second signal strength data. The first signal strength data is indicative of a strength of a first signal transmitted by the device and received by the at least three access points. The second signal strength data is indicative of a strength of a second signal transmitted by the at least three access points and received by the device. The location area is an area within a predetermined reception range of the at least three local access points. The arrangement determines the location of the device within the location area as a function of second data and a further location of each of the at least three further access points of the plurality of access points. The second data is indicative of a travel time of a third signal from the device to each of the at least three further access points.

Claims

1. A computing arrangement for determining a location of a wireless communications device, comprising:

a processor;

a memory arrangement storing a location of each of at least three access points; and

a communication arrangement receiving first data, the first data including at least one of first signal strength data and second signal strength data, the first signal strength data being indicative of a strength of a first signal transmitted by the device and received by the at least three access points, the second signal strength data being indicative of a strength of a second signal transmitted by the at least three access points and received by the device,

wherein the processor determines a location area of the device as a function of the first data and the location, the location area being an area within a predetermined reception range of the at least three access points, and

wherein the processor determines a location of the device within the location area as a function of second data and a further location of each of at least three further access points, the second data being indicative of a travel time of a third signal from the device to each of the at least three further access points.

2. The computing arrangement according to claim 1, wherein the processor determines the at least three further access points which are located one of (i) within the location area and (ii) in close proximity to the location area.

3. The computing arrangement according to claim 1, wherein the at least three access points include the at least three further access points.

4. The computing arrangement according to claim 1, wherein at least one of the at least three further access points includes a smart antenna for directing a focused signal beam towards the location area.

5. The computing arrangement according to claim 1, wherein the location area is a coarse location of the device.

6. The computing arrangement according to claim 1, wherein the device includes at least one of a cell phone, a radio frequency tag, a laptop, a wireless transducer, a barcode scanner and a handheld computer.

7. The computing arrangement according to claim 1, wherein the first data includes a received signal strength indicator (“

RSSI”

) data.

8. The computing arrangement according to claim 1, wherein the second data includes a time difference of arrival (“

TDoA”

) data.

9. A method for determining a location of a wireless communication device, comprising:

(a) determining a location area of the device as a function of first data and a location of each of at least three access points, the first data including at least one of first signal strength data and second signal strength data, the first signal strength data being indicative of a strength of a first signal transmitted by the device and received by the at least three access points, the second signal strength data being indicative of a strength of a second signal transmitted by the at least three access points and received by the device, the location area is an area within a predetermined reception range of the at least three local access points; and

(b) after the step (a), determining the location of the device within the location area as a function of second data and a further location of each of at least three further access points, the second data being indicative of a travel time of a third signal from the device to each of the at least three further access points.

10. The method according to claim 9, further comprising:

before the step (a), determining the at least three further access points which are located one of (i) within the location area and (ii) in close proximity to the location area.

11. The method according to claim 9, wherein the at least three access points include the at least three further access points.

12. The method according to claim 9, wherein at least one of the at least three further access points includes a smart antenna for directing a focused signal beam towards the location area.

13. The method according to claim 9, wherein the location area is a coarse location of the device.

14. The method according to claim 9, wherein the device includes at least one of a cell phone, a radio frequency tag, a laptop, a wireless transducer, a barcode scanner and a handheld computer.

15. The method according to claim 9, wherein the first data includes a received signal strength indicator (“

RSSI”

) data.

16. The method according to claim 9, wherein the second data includes a time difference of arrival (“

TDoA”

) data.

17. A system for determining a location of a wireless communications device, comprising:

a plurality of wireless access points; and

a computing arrangement communicating with the access points, the arrangement determining a location area of the device as a function of first data and a location of each of at least three access points of the plurality of access points, the first data including at least one of first signal strength data and second signal strength data, the first signal strength data being indicative of a strength of a first signal transmitted by the device and received by the at least three access points, the second signal strength data being indicative of a strength of a second signal transmitted by the at least three access points and received by the device, the location area being an area within a predetermined reception range of the at least three local access points, and wherein the arrangement determines the location of the device within the location area as a function of second data and a further location of each of at least three further access points of the plurality of access points, the second data being indicative of a travel time of a third signal from the device to each of the at least three further access points.

18. The system according to claim 17, wherein the device includes at least one of a cell phone, a radio frequency tab, a laptop, a wireless transducer, a barcode scanner and a handheld computer.

19. The system according to claim 17, wherein at least one of the at least three further access points includes a smart antenna for directing a focused signal beam towards the location area.

20. The system according to claim 17, wherein the at least three access points include the at least three further access points.