Real-time network node location system and method

• US 8,311,558 B2
• Filed: 03/22/2010
• Issued: 11/13/2012
• Est. Priority Date: 03/20/2009
• Status: Expired due to Fees

• Current Assignee: Buzby Networks, LLC
• Original Assignee: Buzby Networks, LLC
• Inventors: Davidson, Erik J., Bilén, Sven G., Weiss, Daniel R., Platt, Nicholas E., Weir, Erik D.
• Primary Examiner(s): Patel, Ajit
• Application Number:
  US12/728,966
• Publication Number:
  US 20100238862A1
• Time in Patent Office: 967 Days
• Field of Search: 455/403, 455/404.1, 455/404.2, 455/422.1, 4554561-4566, 370/310, 370/332, 370/333, 370/338
• US Class Current: 455/456.1
• 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 5/0268 by deriving positions from different combinations of signals or of estimated positions in a single positioning system
• CPC Class Codes: G01S 5/12 by co-ordinating position lines of different shape, e.g. hyperbolic, circular, elliptical or radial
• CPC Class Codes: G01S 5/14 Determining absolute distances from a plurality of spaced points of known location
• CPC Class Codes: H04W 4/029 Location-based management or tracking services

Abstract

A real-time location system and method for a wireless network includes, in one embodiment: (a) obtaining received signal-strength indicator measurements between stationary routers and mobile devices; (b) determining the relative angles of mobile devices from stationary routers using directional antenna systems; and (c) using signal strength and angle information to calculate the location of mobile devices.

Claims

1. A real-time network node location system, comprising:

a tag to broadcast a plurality of signals;

a plurality of routers each comprising at least one omni-directional antenna to receive at least a first part of the plurality of signals and at least one directional antenna to receive at least a second part of the plurality of signals, the plurality of routers to transmit information identifying signal strengths of the at least the first part and the at least the second part of the plurality of signals; and

a location engine to;

process at least the information identifying the signal strengths of the at least the first part of the plurality of signals to determine a position of location of the tag; and

process at least the information identifying the signal strengths of the at least the second part of the plurality of signals to determine an area of location of the tag.

2. The system of claim 1, wherein the location engine is further to determine if the position of location of the tag is within the area of location of the tag, and if the position of location of the tag is within the area of location of the tag, then to determine the position of location of the tag to be a final position of location of the tag.

3. The system of claim 1, the location engine further to transmit a location request to the tag before the tag is to broadcast the plurality of signals.

4. The system of claim 1, the location engine further to process also the information identifying the signal strengths of the at least the second part of the plurality of signals to determine the position of location of the tag.

5. The system of claim 1, the location engine further to process the information representing the signal strengths of the at least the first part of the plurality of signals to determine the area of location of the tag.

6. The system of claim 1, wherein the information identifying the signal strengths of the at least the first part and the at least the second part of the plurality of signals are in the form of received signal-strength indicators (RSSIs).

7. The system of claim 1, wherein the calculation of the position of location of the tag further comprises optimizing multipath parameters in a radio-frequency (RF) propagation model equation.

8. The system of claim 1, wherein the directional antennas of the plurality of routers have half-power beamwidths that are at least substantially 80°

.

9. The system of claim 1, wherein the directional antennas of the plurality of routers have half-power beamwidths that are substantially 90°

.

10. The system of claim 1, wherein the directional antennas of the plurality of routers have half-power beamwidths oriented in substantially the same direction.

11. The system of claim 1, wherein the at least one omni-directional antenna of each router comprises two or more omni-directional antennas.

12. The system of claim 1, wherein the at least one directional antenna of each router comprises two or more directional antennas.

13. A method for real-time determination of the location of a tag, comprising:

(a) broadcasting, from the tag, a plurality of signals to a plurality of routers, each of the routers comprising one or more omni-directional antennas and one or more directional antennas;

(b) receiving, by the one or more omni-directional antennas of each of the plurality of routers, at least a first part of the plurality of signals;

(c) receiving, by the one or more omni-directional antennas of each of the plurality of routers, at least a second part of the plurality of signals;

(d) transmitting, by each of the plurality of routers, to a location engine, information identifying signal strengths of the first part and the second part of the plurality of signals received;

(e) processing, by the location engine, at least the information representing the signal strengths of the first part of the plurality of signals received by each router to determine a position of location of the tag; and

(f) processing, by the location engine, at least the information representing the signal strengths of the first part of the plurality of signals received by each router to calculate an area of location of the tag.

14. The method of claim 13, further comprising (g) determining, by the location engine, if the position of location of the tag is within the area of location of the tag, and if the position of location of the tag is within the area of location of the tag, then determining the position of location of the tag to be a final position of location of the tag.

15. The method of claim 14, wherein if the location engine determines that the position of the tag is not within the area of the tag, then repeating (a) through (g).

16. The method of claim 14, wherein the determination of the position of location of the tag at (e) further comprises optimizing multipath parameters in a radio-frequency (RF) propagation model equation, and wherein the optimizing of the multipath parameters comprises repeating, for each of the plurality of routers, (a) through (g) but with the tag replaced by that router.

17. The method of claim 13, further comprising, before (a), transmitting a location request from the location engine to the tag.

18. The method of claim 13, further comprising, before (e), determining for each of the plurality of routers, by the location engine, an average of the at least the first part of the plurality of signals received by the omni-directional antennas of that router, wherein the processing, by the location engine, of at least the first signals to calculate a position in which the tag may be located comprises processing of at least the average of the at least the first part of the plurality of signals.

19. The method of claim 13, further comprising, before (f), determining for each of the plurality of routers, by the location engine, an average of the at least the second part of the plurality of signals received by the directional antenna of that router, wherein the processing, by the location engine, of the at least the second part of the plurality of signals to calculate an area in which the tag may be located comprises processing of at least the average of the at least the first part of the plurality of signals.

20. The method of claim 13, wherein the directional antennas of the plurality of routers have half-power beamwidths that are substantially 90°

.

21. The method of claim 13, wherein the directional antennas of the plurality of routers have half-power beamwidths that are at least substantially 80°

.

22. The method of claim 13, wherein the directional antennas of the plurality of routers have half-power beamwidths oriented in substantially the same direction.

23. The method of claim 13, the processing by the location engine at (e) to calculate the position of location of the tag further comprising processing the information representing the signal strengths of the at least the second part of the plurality of signals received by each router.

24. The method of claim 13, the processing by the location engine at (f) to calculate the area of location of the tag further comprising processing the information representing the signal strengths of the at least the first part of the plurality of signals received by each router.

25. The method of claim 13, wherein the information identifying the signal strengths of the at least the first part and the second part of the plurality of signals received by each of the plurality of routers are in the form of received signal-strength indicators (RSSIs).

26. The method of claim 13, wherein the calculation of the position of location of the tag at (e) further comprises optimizing multipath parameters in a radio-frequency (RF) propagation model equation.

27. A system for determining a position of location of a tag, comprising:

a plurality of routers each comprising at least one omni-directional antenna, the plurality of routers comprising at least three routers; and

a location engine to;

(a) determine for at least one router, from at least a part of signals sent by the one router and received by the at least one omni-directional antenna of each of at least one other of the routers, an average path loss of signal strength;

(b) optimize, for at least the one router, multipath parameters in a radio-frequency (RF) signal propagation model equation using the average path loss for each of the at least one other of the routers and known distance between the router and each of the at least one other of the routers; and

(c) determine the position of location of the tag using at least the optimized multipath parameters.

28. The system of claim 27, wherein the determination of the position of location of the tag at (c) comprises determining, from at least a part of signals sent by the tag and received by the at least one omni-directional antenna of each of at least any three of the routers, an average path loss of signal strength.

29. The system of claim 28, wherein the determination of the position of location of the tag at (c) further comprises using the optimized multipath parameters and the average path loss for each of the at least any three of the routers in the radio-frequency (RF) signal propagation model equation to determine distances between the tag and the at least any three of the routers.

30. The system of claim 27, wherein the optimization at (b) further comprises determining a final average error in distance between the one router and the at least one other of the routers, and wherein the determination of the position of location of the tag at (c) comprises using the final error in a probability density function.

31. The system of claim 27, the location engine further to:

(d) determine, from at least a part of signals sent by the tag and received by the at least one omni-directional antenna and further received by the at least one directional antenna of each of the at least any three of the routers, an average signal strength of the received signals by each of the at least one omni-directional antenna and the at least one directional antenna; and

(e) determine an area of location of the tag using the average signal strengths.

32. The system of claim 31, wherein (e) comprises:

determining an area of location associated with each router;

determining a first ranking of the at least any three of the routers by average signal strength of the signals received by their at least one omni-directional antennas;

determining a second ranking of the at least any three of the routers by increasing difference between the average signal strength of the signals received by their at least one omni-directional antennas and the average signal strength of the signals received by their at least one directional antennas;

determining the overall top ranked router combined between the first ranking and the second ranking; and

determining the area of location of the tag as the area of location associated with the overall top ranked router.

33. The system of claim 32, the location engine further to:

(f) determine if the position of location of the tag is within the area of location of the tag, and if the position of location of the tag is within the area of location of the tag, then to determine the position of location of the tag to be a final position of location of the tag.

34. The system of claim 27, wherein the determined position of location of the tag at (c) is determined as a final position of location of the tag.