User positioning

• US 20040067759A1
• Filed: 08/01/2003
• Published: 04/08/2004
• Est. Priority Date: 02/28/2001
• Status: Active Grant

• Current Assignee: WSOU Investments, LLC (WSOU Holdings, LLC)
• Original Assignee: Nokia Corporation
• Inventors: Spirito, Maurizio, Ruutu, Ville
• Granted Patent: US 7,715,849 B2
• Time in Patent Office: Days
• US Class Current: 455/456.1
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management

Abstract

The invention proposes a method for locating a network element, comprising the steps of obtaining (S1) the coordinates (xS, yS) of a second network element (BTS) to which the first network element (MS) is connected or attached; detecting (S2) a serving area (S), which is served by the second network element (BTS); detecting (S3) a propagation delay of the first network element with respect to the second network element (BTS); determining (S4) a propagation delay depending area (C), which is an area having a distance to the second network element (BTS) based on the propagation delay and a width based on the propagation delay; and forming (S5) an intersection area (I) of the serving area (S) and the propagation delay depending area (C); wherein a location estimate of the first network element (MS) is determined (S6) from the intersection area (I). Thus, an uncertainty area where a first network element is located can be reduced and the location accuracy can be improved.

Claims

1. A method for locating a network element, comprising the steps of

obtaining (Si) the coordinates (x_s, y_s) of a second network element (BTS) to which the first network element (MS) is connected or attached;

detecting (S2) a serving area (S), which is served by the second network element (BTS);

detecting (S3) a propagation delay of the first network element with respect to the second network element (BTS);

determining (S4) a propagation delay depending area (C), which is an area having a distance (R₁) to the second network element (BTS) based on the propagation delay and a width (R₂) based on the propagation delay; and

forming (S5) an intersection area (I) of the serving area (S) and the propagation delay depending area (C);

wherein a location estimate of the first network element (MS) is determined (S6) from the intersection area (I).

2. The method according to claim 1, wherein the step of determining the propagation delay depending area (C) comprises the step of calculating an estimated distance and calculating a confidence interval for the estimated distance, wherein the propagation delay depending area (C) is determined based on the estimated distance and the confidence interval.

3. The method according to claim 2, wherein the estimated distance and the confidence interval is calculated based on statistical data of the propagation delay.

4. The method according to claim 3, wherein the statistical data comprises a propagation delay measurement error.

5. The method according to claim 3, wherein the statistical data comprises the estimation error of the distance between the two network elements as obtained by comparing the true distance and the distance estimated using the propagation delay.

6. The method according to claims 3, 4 or 5, wherein already available location information of the first network element is used to form the statistical data.

7. The method according to claim 6, wherein the already available location information of the first network element is obtained using other, more accurate location methods, such as Enhanced Observed Time Difference (E-OTD), Angle OF Arrival (AOA), GPS, or Assisted-GPS.

8. The method according to claim 1, wherein the propagation delay is indicated by a Timing Advance (TA).

10. The method according to claim 1 or 9, wherein the serving area (S) is a geographical area to which the second network element (BTS) is associated.

11. The method according to claim 1 or 9, wherein the serving area (S) is defined by a geographical map.

12. The method according to claim 1 or 9, wherein the serving area (S) is the geographical region the borders of which are mathematically defined by the coordinates of the origin (x₀,y₀), the orientation of the serving area measured taking (x₀,y₀) as origin of a polar reference φ

_s, the angular width of the serving area Δ

φ

_s, a front radius (R_F) which defines the distance from the origin (x₀,y₀) in the angular region inside the range φ

_s±

φ

_s, and a back radius (R_B) which defines the distance from the origin (x₀,y₀) in the angular region outside the range φ

_s±

φ

_s.

13. The method according to claim 1 or 9, wherein the step of obtaining the coordinates of the second network element (BTS) is performed by checking a Cell Identity (CI) of the cell the second network element is associated to.

14. The method according to claim 1, wherein calculation of location estimates in dependence on the coordinates of the second network element and the propagation delay is performed beforehand.

16. The method according to claim 14, further comprising the step of storing the location estimates calculated beforehand in look-up tables, wherein the location estimates can be retrieved based on the coordinates or identity of the second network element and the propagation delays.

17. The method according to claim 12, further comprising the step of storing the location estimates calculated beforehand in look-up tables, wherein the location estimates can be retrieved based on the identity of the second network element.

18. The method according to claim 1 or 9, wherein the first network element (MS) is a mobile station.

19. The method according to claim 1 or 9, wherein the second network element (BTS) is a base station.

20. The method according to claim 1, further comprising the steps of

identifying neighbor network elements (NI₁, . . . , NI_N), which can be received by the first network element, and

obtaining hearablity areas (H₁, . . . , H_N) defining areas in which the signal level of neighbor network elements is equal or higher than a predetermined signal level,

wherein the step of forming an intersection area (I) comprises forming an intersection area of the serving area (S), the propagation delay depending area (C) and the hearablity areas of those neighbor network elements identified by the first network element (MS).

24. The method according to claim 20, 21, or 22, wherein the hearability area of each neighbor network element is stored beforehand in a database, and wherein the step of obtaining the hearbility areas is performed by accessing the database.

25. The method according to claim 20, 21, or 22, wherein in the identifying step the strength (RXLEV) of a signal received from a neighbor network element is measured by the first network element on the Broadcast Common Control Channel (BCCH) frequency of the neighbor network element.

26. The method according to claim 20, 21 or 22, wherein in the step of obtaining the hearability areas the hearability areas are ordered in dependence on the received signal strength, and wherein in the step of forming the intersection area the order is considered.

27. The method according to claim 20, 21, or 22, wherein for each neighbor cell a plurality of coverage areas are provided each of which has a different signal level, wherein the step of forming an intersection is performed by using the coverage areas having different signal levels.

29. The method according to claim 1, 9, 20, 21 or 22, comprising the step of using information about a probability density of locations of first network elements.

35. The method according to claim 1, 9, 20, 21 or 22, wherein the location estimate of the first network element is the center point of the intersection area.

37. The method according to claims 1, 20, 21 or 22, wherein the confidence area of the first network element, where the first network element is located with a certain probability, is estimated using the intersection area.

38. The method according to claim 37, where the confidence area estimate is the intersection area.

9. A method for locating a network element, comprising the steps of

obtaining the identity of a second network element (BTS) to which the first network element (MS) is connected or attached;

detecting a serving area (S), which is served by the second network element (BTS);

wherein a location estimate of the first network element (MS) is determined from the serving area (S).

15. The method according to claim 9, wherein calculation of location estimates in dependence on the serving area of the second network, is performed beforehand.

22. The method according to claim 9, further comprising the steps of

identifying neighbor network elements (NI₁, . . . , NI_N), which can be received by the first network element, and

obtaining hearablity areas (H₁, . . . , H_N) defining areas in which the signal level of neighbor network elements is equal or higher than a predetermined signal level,

wherein the step of forming an intersection area (I) comprises forming an intersection area of the serving area (S), and the hearablity areas of those neighbor network elements.

39. The method according to claim 9, wherein the confidence area of the first network, where the first network element is located with a certain probability, is estimated using the serving area.

40. The method according to claim 39, where the confidence area estimate is the serving area.

21. A method for locating a network element, comprising the steps of

identifying neighbor network elements (NI₁, . . . , NI_N), which can be received by the first network element, and

obtaining hearablity areas (H₁, . . . , H_N) defining areas in which the signal level of neighbor network elements is equal or higher than a predetermined signal level, and

forming an intersection area of the hearablity areas of those neighbor network elements identified by the first network element (MS),

wherein a location estimate of the first network element (MS) is determined from the intersection area (I).

23. A method for locating a network element, comprising the steps of

obtaining the coordinates (x_s, y_s) and of a second network element (BTS) to which the first network element (MS) is connected or attached;

detecting a propagation delay of the first network element with respect to the second network element (BTS);

determining a propagation delay depending area (C), which is an area having a distance (R₁) to the second network element (BTS) based on the propagation delay and a width (R₂) based on the propagation delay; and

identifying neighbor network elements (NI₁, . . . , NI_N), which can be received by the first network element, and

obtaining hearablity areas (H₁, . . . , H_N) defining areas in which the signal level of neighbor network elements is equal or higher than a predetermined signal level,

forming an intersection area (I) of the propagation delay depending area (C) and the hearablity areas of those neighbor network elements;

wherein a location estimate of the first network element (MS) is determined from the intersection area (I).

28. A method for locating a network element, comprising the steps of

obtaining the coordinates (x_s, y_s) of a second network element (BTS) to which the first network element (MS) is connected or attached;

and

using information about a probability density of locations of first network elements,

wherein a location estimate of the first network element (MS) is determined from the probability.

30. The method according to claim 28 or 29, wherein the probability density information comprises empirical user density studies.

31. The method according to claim 28 or 29, wherein the probability density information comprises geographical information.

32. The method according to claim 28 or 29, wherein the probability density information comprises population density information.

33. The method according to claim 28 or 29, wherein the probability density information comprises traffic information.

34. The method according to claim 28 or 29, wherein the probability density information are stored beforehand in a database for each serving area (S).

36. The method according to claim 28 or 29, wherein the location estimate of the first network element is the weighted center point of the intersection area using probability density of locations of first network elements as weight.

41. A network control device for locating a first network element (MS), comprising

a serving area determining means being adapted to obtain coordinates (x_s, y_s) of a second network element, (BTS) to which the first network element (MS) is connected or attached, and to detect a serving area (S), which is served by the second network element (BTS);

a propagation delay depending area detecting means being adapted to detect a propagation delay of the first network element with respect to the second network element (BTS), and to determine a propagation delay depending area (C), which is an area having a distance (R₁) to the second network element (BTS) based on the propagation delay and a width (R₂) based on the propagation delay; and

a location estimating means being adapted to form an intersection area (I) of the serving area (S) and the Propagation delay depending area (C); and

to determine a location estimate of the first network element (MS) from the intersection area (I).

42. The network control device according to claim 41, wherein the propagation delay depending area detecting means is adapted to calculate an estimated distance and calculate a confidence interval for the estimated distance, wherein the propagation delay depending area (C) is determined based on the estimated distance and the confidence interval.

43. The network control device according to claim 42, wherein the estimated distance and the confidence interval is calculated based on statistical data of the propagation delay.

44. The network control device according to claim 43, wherein the statistical data comprises a propagation delay measurement error.

45. The network control device according to claim 43, wherein the statistical data comprises the estimation error of the distance between the two network elements as obtained by comparing the true distance and the distance estimated using the propagation delay.

46. The network control device according to claims 43, 44 or 45, wherein already available location information of the first network element is used to form the statistical data.

47. The network control device according to claim 46, wherein the already available location information of the first network element is obtained using other, more accurate location methods, such as Enhanced Observed Time Difference (E-OTD), Angle OF Arrival (AOA), GPS, Assisted-GPS etc.

48. The network control device according to claim 41, wherein the propagation delay is indicated by a Timing Advance (TA).

50. The network control device according to claim 41 or 49, wherein the serving area (S) is a geographical area to which the second network element (BTS) is associated.

51. The network control device according to claim 41 or 49, wherein the serving area (S) is defined by a geographical map.

52. The network control device according to claim 41 or 50, wherein the serving area determining means is adapted to determine the serving area (S) as the geographical region the borders of which are mathematically defined by the coordinates of the origin (x₀,y₀), the orientation of the serving area measured taking (x₀,y₀) as origin of a polar reference φ

_s, the angular width of the serving area Δ

φ

_s, a front radius (R_F) which defines the distance from the origin (x₀,y₀) in the angular region inside the range φ

_s±

Δ

φ

_s, and a back radius (R_B) which defines the distance from the origin (x₀,y₀) in the angular region outside the range φ

_s±

Δ

φ

_s.

53. The network control device according to claim 41 or 49, wherein the serving area determining means performs obtaining the coordinates of the second network element (BTS) by checking a Cell Identity (CI) of the cell the second network element is associated to.

54. The network control device according to claim 41, wherein calculation of location estimates in dependence on coordinates of the second network element and propagation delays is performed beforehand.

56. The network control device according to claim 54, further comprising a look-up table retrieving device adapted to access a look-up table storing location estimates which have been calculated beforehand,

wherein the look-up table retrieving device is adapted to retrieve the location estimates based on the coordinates of the second network element and the propagation delay.

58. The network control device according to claim 41 or 49, wherein the first network element (MS) is a mobile station.

59. The network control device according to claim 41, wherein the second network element (BTS) is a base stations.

60. The network control device according to claim 41, further comprising

a hearability determining means being adapted to identify neighbor network elements (NI₁, . . . , NI_N), which can be received by the first network element, and to obtain hearablity areas (H₁, . . . , H_N) defining areas in which the signal level of neighbor network elements is equal or higher than a predetermined signal level,

wherein the location estimating means is adapted to form the intersection area (I) of the serving area (S), the propagation delay depending area (C) and the hearablity areas of those neighbor network elements identified by the first network element (MS).

63. The network control device according to claim 60, 61 or 62, further comprising a hearability area database in which the hearability area of each neighbor network element is stored beforehand, and wherein the hearability determining means obtain the hearbility areas by accessing the database.

64. The network control device according to claim 60, 61 or 62, wherein the hearability determining means is adapted to measure the strength (RXLEV) of a signal received from a neighbor network element on the Broadcast Common Control Channel (BCCH) frequency of the neighbor network element.

65. The network control device according to claim 60, 61 or 62, wherein the hearability determining means is adapted to order the hearability areas in dependence on the received signal strength, and wherein the order of the hearability areas is considered when forming the intersection area the order.

66. The network control device according to claim 60, 61 or 62, wherein for each neighbor cell a plurality of coverage areas are provided each of which has a different signal level, wherein location estimating means performs forming an intersection by using the coverage areas having different signal levels.

67. The network control device according to claim 43, 49, 60, 61 or 62, wherein the location estimating means is further adapted to use information about a probability density of locations of first network elements.

68. The network control device according to claim 67, wherein the probability density information comprises empirical user density studies.

69. The network control device according to claim 67, wherein the probability density information comprises geographical information.

70. The network control device according to claim 67, wherein the probability density information comprises population density information.

71. The network control device according to claim 67, wherein the probability density information comprises traffic information.

72. The network control device according to claim 67, wherein the probability density information are stored beforehand in a database for each serving area (S).

73. The network control device according to claim 41, 49, 60, 61 or 62, wherein the location estimating means is adapted to determine the location estimate of the first network element as the center point of the intersection area.

75. The network control device according to claim 67, wherein the location estimating means is adapted to determine the location estimate of the first network element as the weighted center point of the intersection area using probability density of locations of first network elements as weight.

76. The network control device according to claims 41, 60, 61 or 62, wherein location estimating means is adapted to estimate the confidence area of the first network element, where the first network element is located with a certain probability, using the intersection area.

77. The network control device according to claim 76, where the confidence area estimate is the intersection area.

80. The network control device according to claim 42, wherein the network control device is a Location Server (LS).

81. A network location system comprising a network control device (LS) according to claim 80, and a network management device (LMT) for preparing the look-up table.

82. The network location system according to claim 81, wherein the network management device is a Location Management Tool (LMT).

49. A network control device for locating a first network element (MS), comprising

a serving area determining means being adapted to obtain coordinates (x_s, y_s) of a second network element, (BTS) to which the first network element (MS) is connected or attached, and to detect a serving area (S), which is served by the second network element (BTS);

and

a location estimating means being adapted to determine a location estimate of the first network element (MS) from the serving area (S).

55. The network control device according to claim 49, wherein calculation of location estimates in dependence on the serving area of the second network is performed beforehand.

57. The network control device according to claim 55, further comprising a look-up table retrieving device adapted to access a look-up table storing location estimates which have been calculated beforehand,

wherein the look-up table retrieving device is adapted to retrieve the location estimates based on the coordinates of the second network element.

62. The network control device according to claim 49, further comprising

a hearability determining means being adapted to identify neighbor network elements (NI₁, . . . , NI_N), which can be received by the first network element, and to obtain hearablity areas (H₁, . . . , H_N) defining areas in which the signal level of neighbor network elements is equal or higher than a predetermined signal level,

wherein the location estimating means is adapted to form the intersection area (I) of the serving area (S) and the hearablity areas of those neighbor network elements identified by the first network element (MS).

74. The network control device according to claim 49, wherein the location estimating means is adapted to determine the location estimate of the first network element as the center point of the serving area.

78. The network control device according to claim 49, wherein location estimating means is adapted to estimate the confidence area of the first network, where the first network element is located with a certain probability, using the serving area.

79. The network control device according to claim 78, where the confidence area estimate is the serving area.

61. A network control device for locating a first network element (MS), comprising

a hearability determining means being adapted to identify neighbor network elements (NI₁, . . . , NI_N), which can be received by the first network element, and to obtain hearablity areas (H₁, . . . , H_N) defining areas in which the signal level of neighbor network elements is equal or higher than a predetermined signal level,

a location estimating means being adapted to form an intersection area (I) the hearablity areas of those neighbor network elements identified by the first network element (MS).