Selective fusion location estimation (SELFLOC) for wireless access technologies

• US 20040203904A1
• Filed: 12/27/2002
• Published: 10/14/2004
• Est. Priority Date: 12/27/2002
• Status: Active Grant

• Current Assignee: NTT Docomo Incorporated (Nippon Telegraph and Telephone Corporation)
• Original Assignee: DOCOMO Communications Laboratories USA, Inc.
• Inventors: Jain, Ravi Kumar, Kawahara, Toshiro, Gwon, Youngjune Lee
• Granted Patent: US 7,257,411 B2
• Time in Patent Office: Days
• US Class Current: 455/456.1
• 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: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management

Abstract

In an RF environment serviced by 802.11, Bluetooth (TM), or other network transmitters, or combinations, location-estimation methods and systems can advantageously use redundancy to refine an estimated location of an RF receiver. In one embodiment, a method for finding a receiver'"'"'s location includes receiving signals from fixed transmitters, calculating preliminary location estimates, and combining the estimates using predetermined reference information on the RF environment. The reference information preferably includes minimum mean-squared error optimizing coefficients.

Claims

1. A communications unit comprising:

a receiver circuit configured to receive two or more wireless signals from two or more wireless transmitters;

a processing unit coupled to the receiver circuit and configured to generate two or more location estimates in response to the two or more wireless signals;

a digital memory holding reference information on reliabilities of location estimation protocols; and

a combiner circuit coupled to the digital memory and to the processing unit, the combiner circuit configured to generate a refined location estimate in response to the two or more location estimates and the reference information.

2. The communications unit of claim 1, wherein the location estimates are determined in response to received signal strengths of the wireless signals.

3. The communications unit of claim 1, wherein the location estimates are determined in response to propagation delays of the wireless signals.

4. The communications unit of claim 1, wherein the reference information is derived from a minimum mean square error (MMSE) criterion.

5. The communications unit of claim 1, wherein the reference information is predetermined reference information.

6. The communications unit of claim 1, wherein the location estimates include a triangulation-based location estimate.

7. The communications unit of claim 1, wherein the location estimates include a nearest-neighbors-based location estimate.

8. The communications unit of claim 1, wherein the location estimates include a smallest-polygon-based location estimate.

9. The communications unit of claim 1, wherein the location estimates include two or more of:

a triangulation-based location estimate, a nearest-neighbors-based location estimate, or a smallest-polygon location estimate.

10. The communications unit of claim 1, wherein the location estimates include a triangulation-based location estimate and a nearest-neighbors-based location estimate, and the reference information includes data reflecting the comparative reliability of triangulation estimates and nearest-neighbors estimates.

11. The communications unit of claim 1, wherein the location estimates include an 802.11 -based location estimate.

12. The communications unit of claim 1, wherein the location estimates include a Bluetooth (TM)-based location estimate.

13. The communications unit of claim 1, wherein the combiner circuit is implemented in computer-readable program code running on a microprocessor or on a digital signal processor.

14. The communications unit of claim 1, wherein the combiner circuit is a dedicated VLSI circuit.

15. The communications unit of claim 1, wherein the combiner circuit is configured to generate the refined location estimate as a linear combination of the two or more of the location estimates, with relative weights derived from the reference information.

16. The communications unit of claim 1, wherein the location estimates include two or more intermediate location estimates for a triangulation calculation.

17. The communications unit of claim 16, wherein the combiner circuit is configured to generate the refined location estimate as a weighted average of the intermediate location estimates for a triangulation calculation, with relative weights derived from the reference information.

18. The communications unit of claim 1, wherein the location estimates include two or more intermediate location estimates for a nearest-neighbors calculation.

19. The communications unit of claim 18, wherein the combiner circuit is configured to generate the refined location estimate as a weighted average of the intermediate location estimates for the nearest-neighbors calculation, with relative weights derived from the reference information.

20. The communications unit of claim 1, wherein the location estimates include two or more intermediate location estimates for a smallest-polygon calculation.

21. The communications unit of claim 20, wherein the combiner circuit is configured to generate the refined location estimate as a weighted average of the intermediate location estimates for the smallest-polygon calculation, with relative weights derived from the reference information.

22. The communications unit of claim 1,

wherein the processing unit is further configured to generate a preliminary location approximation in response to the wireless signals;

wherein the combiner circuit is further configured to generate the refined location estimate in response to the preliminary location approximation and the reference information.

23. The communications unit of claim 22,

wherein the reference information includes N sets of local reference information corresponding to N local operating regions for the communications unit;

wherein the combiner is configured to select one of the sets of local reference information corresponding to the preliminary location approximation;

wherein the combiner circuit is configured to generate the refined location estimate in response to the selected set of local reference information.

24. The communications unit of claim 23,

wherein the combiner is further configured to iteratively:

(1) make a revised selection of local reference information corresponding to the refined location estimate; and

(2) further refine the refined location estimate in response to the revised selection of local reference information.

25. A method for determining the location of a wireless receiver during operation of the receiver, the method comprising:

a) receiving a plurality of signals from a plurality of base units;

b) determining a plurality of estimated locations in response to the plurality of signals;

c) calculating a weighted average of the estimated locations with weights derived from predetermined data; and

d) using the weighted average as the location of the wireless receiver.

26. The method of claim 25, wherein said determining the plurality of estimated locations includes determining at least one estimated location from a triangulation estimate.

27. The method of claim 25, wherein said determining the plurality of estimated locations includes determining at least one estimated location from a smallest-polygon estimate.

28. The method of claim 25, wherein said determining the plurality of estimated locations includes determining at least one estimated location from a nearest-neighbors estimate.

29. The method of claim 25, wherein said determining the plurality of estimated locations includes:

b1) using a first locating technique to determine a first estimated location, and

b2) using a second locating technique to determine a second estimated location;

wherein the predetermined data includes data reflecting the relative reliabilities of the first and second locating techniques; and

wherein said calculating a weighted average includes;

c1) determining a first weight w1 indicative of the relative reliability of the first locating technique,

c2) determining a second weight w2 indicative of the relative reliability of the second locating technique, and

c3) calculating the weighted average in response to w1, the first estimated location, w2, and the second estimated location.

30. The method of claim 29, wherein the first and second locating techniques are chosen from:

(i) a triangulation technique,

(ii) a nearest-neighbors technique, and

(iii) a smallest-polygon technique.

31. The method of claim 25,

wherein said receiving a plurality of signals includes:

receiving a first subset of signals from a first subset of base units, and

receiving a second subset of signals from a second subset of base units;

wherein said determining the plurality of estimated locations includes;

determining a first triangulation-estimated location from the first subset of signals.

determining a second triangulation-estimated location from the second subset of signals.

32. The method of claim 31, wherein the predetermined data include information comparing the first and second subsets of base units;

and

wherein said calculating a weighted average includes averaging the first and second triangulation-estimated locations, with relative weights derived from the predetermined data.

33. The method of claim 25,

wherein said determining the plurality of estimated locations includes:

determining a first nearest-neighbors-estimated location in response to the plurality of signals and the predetermined data, and

determining a second nearest-neighbors-estimated location in response to the plurality of signals and the predetermined data.

34. The method of claim 33, wherein said calculating a weighted average includes averaging the first and second nearest-neighbors-estimated locations, with relative weights derived from the predetermined data.

35. The method of claim 25,

wherein said determining the plurality of estimated locations includes:

determining a first smallest-polygon-estimated location in response to the plurality of signals and the predetermined data, and

determining a second smallest-polygon-estimated location in response to the plurality of signals and the predetermined data.

36. The method of claim 35, wherein said calculating a weighted average includes averaging the first and second smallest-polygon-estimated locations, with relative weights derived from the predetermined data.

37. A method for determining the location of a wireless receiver during operation of the receiver, the method comprising:

a) determining a preliminary estimated location in response to signals received from at least one of a plurality of base units;

b) in response to the preliminary estimated location, selecting a set of local data from a library of predetermined reference information;

wherein the set of local data characterizes base units local to the preliminary estimated location;

c) receiving signals from the base units local to the preliminary estimated location;

d) determining a plurality of estimated locations in response to the signals from the base units local to the preliminary estimated location;

e) calculating a weighted average of the estimated locations with weights derived from the set of local data; and

f) using the weighted average as the location of the wireless receiver.

38. The method of claim 37, wherein said determining the estimated locations comprises determining the estimated locations with one of the following:

a triangulation technique, a smallest polygon technique, a nearest neighbors technique.

39. The method of claim 37, further comprising:

e1) revising the preliminary estimated location with the weighted average;

e2) repeating steps (b) through (e1) to iteratively refine the weighted average.

40. The method of claim 37, further comprising:

e1) revising the preliminary estimated location with the weighted average;

e2) repeating steps (b) through (e1) a fixed number of times to iteratively refine the weighted average.

41. The method of claim 37, further comprising:

e1) revising the preliminary estimated location with the weighted average;

e2) repeating steps (b) through (e1) to determine a converging value of the weighted average.

42. The method of claim 37, further comprising, prior to operation of the receiver:

collecting the predetermined data, wherein said collecting predetermined data comprises making measurements at a series of known locations.

43. A method for calculating contribution weights for evaluating location estimates generated by a wireless receiver, the method comprising:

a) at each of a plurality of physical sites, using a first protocol to determine a first estimated location of a test unit;

b) at each of the physical sites, using a second protocol to determine a second estimated location of the test unit;

c) determining a first contribution weight and a second contribution weight in response to the actual locations of the physical sites, the first estimated locations of the test unit, and the second estimated locations of the test unit;

wherein the first and second contribution weights are useable by the wireless receiver to determine how much emphasis should be ascribed to the first and second protocols.

44. The method of claim 43, wherein the first and second protocols are selected from:

a triangulation locating technique, a nearest-neighbors locating technique, and a smallest-polygon locating technique.

45. The method of claim 43, wherein said determining the first and second contribution weights comprises determining the first and second contribution weights according to a minimum mean square error (MMSE) criterion.

46. The method of claim 43, wherein the first protocol generates a first intermediate location for a triangulation calculation, and the second protocol generates a second intermediate location for a triangulation calculation.

47. The method of claim 43, wherein the first protocol generates a first intermediate location for a nearest-neighbors calculation, and the second protocol generates a second intermediate location for a nearest-neighbors calculation.

48. The method of claim 43, wherein the first protocol generates a first intermediate location for a smallest-polygon calculation, and the second protocol generates a first intermediate location for a smallest-polygon calculation.

49. A method for calculating contribution weights, the method comprising:

a) at each of a plurality of N physical sites, wherein the coordinates of the N physical sites are (d_X(i), d_Y(i), d_Z(i)), with i=1 . . . N,

using a first protocol to measure a first estimated x-axis coordinate X_A(i) of the physical site, and

using a second protocol to measure a second estimated x-axis coordinate X_B(i) of the physical site; and

b) calculating the contribution weights WA and WB according to the following formula;

$\left[\begin{array}{c}{w}_A\\ w_B\end{array}\right];<br><br>={\left[\begin{array}{cc}E<br><br>\left(X_A\times <br><br>X_A\right)& E<br><br>\left(X_A\times <br><br>X_B\right)\\ E<br><br>\left(X_A\times <br><br>X_B\right)& E<br><br>\left(X_B\times <br><br>X_B\right)\end{array}\right]}^{-1}<br><br>\left[\begin{array}{c}E<br><br>\left(X_A\times <br><br>d_X\right)\\ E<br><br>\left(X_B\times <br><br>d_X\right)\end{array}\right],<br><br>\mathrm{wherein}<br><br>\text{\hspace{1em}<br><br>}<br><br>E<br><br>\left(X_1\times <br><br>X_2\right);<br><br>=\underset{i=1}{\overset{N}{\sum <br><br>}}<br><br>X_1<br><br>\left(i\right)\times <br><br>X_2<br><br>\left(i\right);<br><br>$

and

wherein the contribution weights are useable by a wireless receiver to determine how much emphasis should be ascribed to the first and second protocols.

50. The method of claim 49, further comprising:

calculating a position of a wireless receiver in response to the contribution weights and displaying an output in response to the calculated position.

51. The method of claim 49, wherein the x-axis is one of:

a vertical axis, a horizontal axis, a longitudinal axis, a latitudinal axis;

or a diagonal axis.

52. The method of claim 49, further comprising:

using the contribution weights in a mobile receiver to calculate a refined run-time location estimate {circumflex over (X)}_RT in response to (1) a first run-time location estimate X_RT-A, measured using the first protocol, and (2) a second run-time location estimate X_RT-B. measured using the second protocol, according to the following formula;

{circumflex over (X)}_RT;

=w_A×

X_RT-A+w_B×

X_RT-B.

53. A computer-readable storage medium storing a set of instructions for causing a processing unit in a portable receiver to perform the steps of:

a) receiving a plurality of signals from a plurality of base units;

b) determining a plurality of estimated locations in response to the plurality of signals; and

c) calculating a weighted average of the estimated locations with weights derived from predetermined data.

54. The computer-readable medium of claim 53, wherein said determining the plurality of estimated locations includes determining at least one estimated location from a triangulation estimate.

55. The computer-readable medium of claim 53, wherein said determining the plurality of estimated locations includes determining at least one estimated location from a smallest-polygon estimate.

56. The computer-readable medium of claim 53, wherein said determining the plurality of estimated locations includes determining at least one estimated location from a nearest-neighbors estimate.

57. The computer-readable medium of claim 53, wherein said determining the plurality of estimated locations includes:

b1) using a first locating technique to determine a first estimated location, and

b2) using a second locating technique to determine a second estimated location;

wherein the predetermined data includes data reflecting the relative reliabilities of the first and second locating techniques; and

wherein said calculating a weighted average includes;

c1) determining a first weight wI indicative of the relative reliability of the first locating technique,

c2) determining a second weight w2 indicative of the relative reliability of the second locating technique, and

c3) calculating the weighted average in response to w1, the first estimated location, w2, and the second estimated location.

58. The computer-readable medium of claim 57, wherein the first and second locating techniques are chosen from:

(i) a triangulation technique,

(ii) a nearest-neighbors technique, and

(iii) a smallest-polygon technique.

59. The computer-readable medium of claim 53,

wherein said receiving a plurality of signals includes:

receiving a first subset of signals from a first subset of base units, and

receiving a second subset of signals from a second subset of base units;

wherein said determining the plurality of estimated locations includes;

determining a first triangulation-estimated location from the first subset of signals.

determining a second triangulation-estimated location from the second subset of signals.