Cooperating Receiver Selection for UMTS Wireless Location

• US 20110159891A1
• Filed: 12/29/2009
• Published: 06/30/2011
• Est. Priority Date: 12/29/2009
• Status: Active Grant

• Current Assignee: Skyhook Holding, Inc. (Liberty Broadband Corp.)
• Original Assignee: TruePosition Incorporated
• Inventors: Segall, Edward Joseph, Issakov, Simon, Mia, Rashidus S.
• Granted Patent: US 8,442,538 B2
• Time in Patent Office: Days
• US Class Current: 455/456.3
• CPC Class Codes: H04W 36/18 for allowing seamless reselection, e.g. soft reselection
• CPC Class Codes: H04W 4/02 Services making use of location information
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management

Abstract

For Wireless Communications Networks (WCNs) that support soft handover, cooperator receiver selection for a TDOA, AOA, TDOA/AOA, or hybrid network-based or network-overlay Wireless Location System (WLS) must contend with one or more network base stations as a serving cell. When the active set contains more than one member, two techniques for determining a set of cooperating and demodulating receivers to use in the signal collection for location estimation is disclosed. In one embodiment, the active set members are constructively reduced to a single member that is used as a proxy serving cell. In another embodiment, the information contained in the active set membership is retained and a new set of demodulating and cooperator receivers are generated based on the entire membership of the active set.

Claims

1. A method of identifying a set of cooperator and demodulator signal collection receivers for use in locating a mobile device in a Code Division Multiple Access (CDMA)-based wireless communications network (WCN), comprising:

obtaining data identifying an active set of base stations through which active communication is established between the mobile device and the WCN;

based on the active set, identifying at least one cooperator receiver and at least one demodulator receiver;

employing the at least one cooperator receiver and the at least one demodulator receiver to collect signal data from the mobile device; and

employing the signal data to locate the mobile device.

2. A method as recited in claim 1, wherein demodulator receivers are identified based on a pre-computed static list of cooperator and demodulator receivers for sectors corresponding to the base stations.

3. A method as recited in claim 2, further comprising generating the pre-computed static list based on a radio propagation model for a service area.

4. A method as recited in claim 1, wherein the method is used in a mixed mode system (such as GSM/UMTS) in which multi-mode location measurement units (LMUs) are deployed for locating both TDMA/FDMA and CDMA mobile devices.

5. A method as recited in claim 1, further comprising detecting a triggering event to initiate location of the mobile device, and communicating triggering information and tasking information to a wireless location system (WLS), wherein the tasking information includes active set membership information.

6. A method as recited in claim 1, wherein said identifying further comprises:

for each base station, determining a geographic area associated with the base station and dividing the geographic area into radial segments; and

selecting, for each of the radial segments, cooperator receivers such that the selected cooperator receivers are substantially equally distributed among the base stations and a range of relative azimuths about each base station.

7. A method as recited in claim 6, wherein said selecting further comprises:

selecting cooperators based on a pre-computed static list of cooperator receivers for a sector corresponding to the base stations in the active set.

8. A method as recited in claim 6, wherein the radial segments are centered on a geographic centroid of each base station.

9. A method as recited in claim 7, wherein the number of radial segments is eight.

10. A method as recited in claim 7, wherein said selecting comprises stepping through the radial segments using a spatially symmetric pattern and adding cooperator receivers to the cooperator receiver list based on an associated quality metric for the radial segment.

11. A method as recited in claim 10, wherein said selecting further comprises cycling through the base stations in the active set in conjunction with said stepping through the radial segments.

12. A method as recited in claim 11, further comprising continuing the selection of cooperator receivers until a predetermined number of cooperator receivers is reached or all radial segments for the base stations in the active set have been analyzed.

13. A method as recited in claim 12, further comprising:

for each added cooperator receiver, determining an average path loss for the added cooperator receiver and adding cooperator receivers within a predetermined proximity and a predetermined average path loss.

14. A method as recited in claim 6, wherein the WCN comprises a distributed antenna system (DAS) and at least one base station of the active set comprises DAS antennas, further comprising using the DAS antennas as at least part of the active set.

15. A method as recited in claim 6, wherein the WCN comprises a distributed antenna system (DAS) and at least one base station of the active set comprises DAS antennas, further comprising using as the active set the union of active set members without DAS antennas and DAS antennas of the remaining active set members.

16. A method as recited in claim 13, wherein the at least one demodulator receiver is identified as a cooperator receiver within a predetermined proximity.

17. A method as recited in claim 1, wherein said identifying further comprises:

determining a representative point based on geographic information for the active set and determining a geographic area associated with the representative point; and

dividing the geographic area into radial segments and identifying at least one cooperator receiver and at least one demodulator receiver based on the radial segments.

18. A method as recited in claim 17, wherein the representative point is a geographic centroid.

19. A method as recited in claim 18, wherein the geographic centroid is determined by averaging the geographic coordinates of the base stations in the active set.

20. A method as recited in claim 18, wherein the geographic centroid is determined as a function of signal power levels received from the base stations.

21. A method as recited in claim 18, wherein the geographic centroid is determined as a function of signal quality metrics associated with the base stations.

22. A method as recited in claim 17, wherein the number of radial segments is eight.

23. A method as recited in claim 17, wherein said selecting comprises stepping through the radial segments using a spatially symmetric pattern and adding cooperator receivers to the cooperator receiver list based on an associated quality metric for the radial segment.

24. A method as recited in claim 23, wherein said selecting further comprises cycling through the base stations in the active set in conjunction with said stepping through the radial segments.

25. A method as recited in claim 24, further comprising continuing the selection of cooperator receivers until a predetermined number of cooperator receivers is reached or all radial segments for the base stations in the active set have been analyzed.

26. A method as recited in claim 25, further comprising:

for each added cooperator receiver, determining an average path loss for the added cooperator receiver and adding cooperator receivers within a predetermined proximity and a predetermined average path loss.

27. A method as recited in claim 26, wherein the at least one demodulator receiver is identified as a cooperator receiver within a predetermined proximity.

28. A method as recited in claim 1, wherein said identifying further comprises:

determining a common coverage area for the active set and a geographic centroid for the common coverage area;

dividing the common coverage area into radial segments centered around the geographic centroid and identifying at least one cooperator receiver and at least one demodulator receiver based on the radial segments.

29. A method as recited in claim 28, wherein said identifying further comprises selecting cooperators based on a pre-computed static list of cooperator receivers for a sector corresponding to the base stations in the active set.

30. A method as recited in claim 29, further comprising generating the pre-computed static list based on a radio propagation model for a service area.

31. A method as recited in claim 28, wherein said determining a common coverage area further comprises employing a bounding polygon to approximate a geographic coverage area for each base station and determining an area of overlap as the common coverage area.

32. A method as recited in claim 30, further comprising determining geographically distributed marker points within the common coverage area and, for each of the marker points, using the radio propagation model to determine a quality metric to sectors within a predetermined range of the common coverage area.

33. A method as recited in claim 32, further comprising averaging the quality metrics from each marker point to determine a quality metric for each sector.

34. A method as recited in claim 33, wherein the number of radial segments is eight.

35. A method as recited in claim 33, wherein said selecting comprises stepping through the radial segments using a spatially symmetric pattern and adding cooperator receivers to the cooperator receiver list based on an associated quality metric for the radial segment.

36. A method as recited in claim 35, further comprising repeating the selection of cooperator receivers until a predetermined number of cooperator receivers is reached or all radial segments have been analyzed.

37. A method as recited in claim 36, further comprising:

for each added cooperator receiver, determining an average path loss for the added cooperator receiver and adding cooperator receivers within a predetermined proximity and a predetermined average path loss.

38. A method as recited in claim 37, wherein the at least one demodulator receiver is identified as a cooperator receiver within a predetermined proximity.

66. The system of claim 35, wherein said identifying further comprises:

determining a common coverage area for the active set and a geographic centroid for the common coverage area;

dividing the common coverage area into radial segments centered around the geographic centroid and identifying at least one cooperator receiver and at least one demodulator receiver based on the radial segments.

67. The system of claim 66, wherein said identifying further comprises selecting cooperators based on a pre-computed static list of cooperator receivers for a sector corresponding to the base stations in the active set.

68. The system of claim 67, further comprising instructions for instructing the processor in causing the step of generating the pre-computed static list based on a radio propagation model for a service area.

69. The system of claim 66, wherein said determining a common coverage area further comprises employing a bounding polygon to approximate a geographic coverage area for each base station and determining an area of overlap as the common coverage area.

70. The system of claim 68, further comprising instructions for instructing the processor in causing the steps of determining geographically distributed marker points within the common coverage area and, for each of the marker points, using the radio propagation model to determine a quality metric to sectors within a predetermined range of the common coverage area.

71. The system of claim 70, further comprising instructions for instructing the processor in causing the step of averaging the quality metrics from each marker point to determine a quality metric for each sector.

72. The system of claim 71, wherein the number of radial segments is eight.

73. The system of claim 71, wherein said selecting comprises stepping through the radial segments using a spatially symmetric pattern and adding cooperator receivers to the cooperator receiver list based on an associated quality metric for the radial segment.

74. The system of claim 73, further comprising instructions for instructing the processor in causing the step of repeating the selection of cooperator receivers until a predetermined number of cooperator receivers is reached or all radial segments have been analyzed.

75. The system of claim 74, further comprising instructions for instructing the processor in causing the step of:

for each added cooperator receiver, determining an average path loss for the added cooperator receiver and adding cooperator receivers within a predetermined proximity and a predetermined average path loss.

76. The system of claim 75, wherein the at least one demodulator receiver is identified as a cooperator receiver within a predetermined proximity.

39. A system configured to identify a set of cooperator and demodulator signal collection receivers for use in locating a mobile device in a Code Division Multiple Access (CDMA)-based wireless communications network (WCN), the system comprising at least one processor and at least one storage medium communicatively coupled to said at least one processor, the storage medium having stored therein computer-executable instructions for instructing the processor in causing the following steps:

obtaining data identifying an active set of base stations through which active communication is established between the mobile device and the WCN;

based on the active set, identifying at least one cooperator receiver and at least one demodulator receiver;

employing the at least one cooperator receiver and the at least one demodulator receiver to collect signal data from the mobile device; and

employing the signal data to locate the mobile device.

40. The system of claim 39, wherein demodulator receivers are identified based on a pre-computed static list of cooperator and demodulator receivers for sectors corresponding to the base stations.

41. The system of claim 40, further comprising instructions for instructing the processor in causing the step of generating the pre-computed static list based on a radio propagation model for a service area.

42. The system of claim 39, wherein the set of cooperator and demodulator signal collection receivers is identified in a mixed mode system (such as GSM/UMTS) in which multi-mode location measurement units (LMUs) are deployed for locating both TDMA/FDMA and CDMA mobile devices.

43. The system of claim 39, further comprising instructions for instructing the processor in causing the steps of detecting a triggering event to initiate location of the mobile device, and communicating triggering information and tasking information to a wireless location system (WLS), wherein the tasking information includes active set membership information.

44. The system of claim 39, wherein said identifying further comprises instructions for instructing the processor in causing the steps of:

for each base station, determining a geographic area associated with the base station and dividing the geographic area into radial segments; and

selecting, for each of the radial segments, cooperator receivers such that the selected cooperator receivers are substantially equally distributed among the base stations and a range of relative azimuths about each base station.

45. The system of claim 44, wherein said selecting further comprises:

selecting cooperators based on a pre-computed static list of cooperator receivers for a sector corresponding to the base stations in the active set.

46. The system of claim 44, wherein the radial segments are centered on a geographic centroid of each base station.

47. The system of claim 45, wherein the number of radial segments is eight.

48. The system of claim 45, wherein said selecting comprises stepping through the radial segments using a spatially symmetric pattern and adding cooperator receivers to the cooperator receiver list based on an associated quality metric for the radial segment.

49. The system of claim 48, wherein said selecting further comprises cycling through the base stations in the active set in conjunction with said stepping through the radial segments.

50. The system of claim 49, further comprising instructions for instructing the processor in causing the step of continuing the selection of cooperator receivers until a predetermined number of cooperator receivers is reached or all radial segments for the base stations in the active set have been analyzed.

51. The system of claim 50, further comprising instructions for instructing the processor in causing the step of:

for each added cooperator receiver, determining an average path loss for the added cooperator receiver and adding cooperator receivers within a predetermined proximity and a predetermined average path loss.

52. The system of claim 44, wherein the WCN comprises a distributed antenna system (DAS) and at least one base station of the active set comprises DAS antennas, further comprising using the DAS antennas as at least part of the active set.

53. The system of claim 44, wherein the WCN comprises a distributed antenna system (DAS) and at least one base station of the active set comprises DAS antennas, further comprising using as the active set the union of active set members without DAS antennas and DAS antennas of the remaining active set members.

54. The system of claim 51, wherein the at least one demodulator receiver is identified as a cooperator receiver within a predetermined proximity.

55. The system of claim 39, wherein said identifying further comprises:

determining a representative point based on geographic information for the active set and determining a geographic area associated with the representative point; and

dividing the geographic area into radial segments and identifying at least one cooperator receiver and at least one demodulator receiver based on the radial segments.

56. The system of claim 55, wherein the representative point is a geographic centroid.

57. The system of claim 56, wherein the geographic centroid is determined by averaging the geographic coordinates of the base stations in the active set.

58. The system of claim 56, wherein the geographic centroid is determined as a function of signal power levels received from the base stations.

59. The system of claim 56, wherein the geographic centroid is determined as a function of signal quality metrics associated with the base stations.

60. The system of claim 55, wherein the number of radial segments is eight.

61. The system of claim 55, wherein said selecting comprises stepping through the radial segments using a spatially symmetric pattern and adding cooperator receivers to the cooperator receiver list based on an associated quality metric for the radial segment.

62. The system of claim 61, wherein said selecting further comprises cycling through the base stations in the active set in conjunction with said stepping through the radial segments.

63. The system of claim 62, further comprising instructions for instructing the processor in causing the step of continuing the selection of cooperator receivers until a predetermined number of cooperator receivers is reached or all radial segments for the base stations in the active set have been analyzed.

64. The system of claim 63, further comprising instructions for instructing the processor in causing the step of:

for each added cooperator receiver, determining an average path loss for the added cooperator receiver and adding cooperator receivers within a predetermined proximity and a predetermined average path loss.

65. The system of claim 64, wherein the at least one demodulator receiver is identified as a cooperator receiver within a predetermined proximity.

77. A computer readable storage medium storing thereon computer executable instructions for identifying a set of cooperator and demodulator signal collection receivers for use in locating a mobile device in a Code Division Multiple Access (CDMA)-based wireless communications network (WCN), said computer executable instructions for:

obtaining data identifying an active set of base stations through which active communication is established between the mobile device and the WCN;

based on the active set, identifying at least one cooperator receiver and at least one demodulator receiver;

employing the at least one cooperator receiver and the at least one demodulator receiver to collect signal data from the mobile device; and

employing the signal data to locate the mobile device.

78. The computer readable storage medium of claim 77, wherein demodulator receivers are identified based on a pre-computed static list of cooperator and demodulator receivers for sectors corresponding to the base stations.

79. The computer readable storage medium of claim 78, further comprising instructions for generating the pre-computed static list based on a radio propagation model for a service area.

80. The computer readable storage medium of claim 77, wherein the method is used in a mixed mode system (such as GSM/UMTS) in which multi-mode location measurement units (LMUs) are deployed for locating both TDMA/FDMA and CDMA mobile devices.

81. The computer readable storage medium of claim 77, further comprising instructions for detecting a triggering event to initiate location of the mobile device, and communicating triggering information and tasking information to a wireless location system (WLS), wherein the tasking information includes active set membership information.

82. The computer readable storage medium of claim 77, wherein said identifying further comprises:

for each base station, determining a geographic area associated with the base station and dividing the geographic area into radial segments; and

selecting, for each of the radial segments, cooperator receivers such that the selected cooperator receivers are substantially equally distributed among the base stations and a range of relative azimuths about each base station.

83. The computer readable storage medium of claim 82, wherein said selecting further comprises:

selecting cooperators based on a pre-computed static list of cooperator receivers for a sector corresponding to the base stations in the active set.

84. The computer readable storage medium of claim 82, wherein the radial segments are centered on a geographic centroid of each base station.

85. The computer readable storage medium of claim 83, wherein the number of radial segments is eight.

86. The computer readable storage medium of claim 83, wherein said selecting comprises stepping through the radial segments using a spatially symmetric pattern and adding cooperator receivers to the cooperator receiver list based on an associated quality metric for the radial segment.

87. The computer readable storage medium of claim 86, wherein said selecting further comprises cycling through the base stations in the active set in conjunction with said stepping through the radial segments.

88. The computer readable storage medium of claim 87, further comprising instructions for continuing the selection of cooperator receivers until a predetermined number of cooperator receivers is reached or all radial segments for the base stations in the active set have been analyzed.

89. The computer readable storage medium of claim 88, further comprising instructions for:

for each added cooperator receiver, determining an average path loss for the added cooperator receiver and adding cooperator receivers within a predetermined proximity and a predetermined average path loss.

90. The computer readable storage medium of claim 82, wherein the WCN comprises a distributed antenna system (DAS) and at least one base station of the active set comprises DAS antennas, further comprising instructions for using the DAS antennas as at least part of the active set.

91. The computer readable storage medium of claim 82, wherein the WCN comprises a distributed antenna system (DAS) and at least one base station of the active set comprises DAS antennas, further comprising instructions for using as the active set the union of active set members without DAS antennas and DAS antennas of the remaining active set members.

92. The computer readable storage medium of claim 89, wherein the at least one demodulator receiver is identified as a cooperator receiver within a predetermined proximity.

93. The computer readable storage medium of claim 77, wherein said instructions for identifying further comprises:

instructions for determining a representative point based on geographic information for the active set and determining a geographic area associated with the representative point; and

instructions for dividing the geographic area into radial segments and identifying at least one cooperator receiver and at least one demodulator receiver based on the radial segments.

94. The computer readable storage medium of claim 93, wherein the representative point is a geographic centroid.

95. The computer readable storage medium of claim 94, wherein the geographic centroid is determined by averaging the geographic coordinates of the base stations in the active set.

96. The computer readable storage medium of claim 94, wherein the geographic centroid is determined as a function of signal power levels received from the base stations.

97. The computer readable storage medium of claim 94, wherein the geographic centroid is determined as a function of signal quality metrics associated with the base stations.

98. The computer readable storage medium of claim 93, wherein the number of radial segments is eight.

99. The computer readable storage medium of claim 93, wherein said instructions for selecting comprises instructions for stepping through the radial segments using a spatially symmetric pattern and adding cooperator receivers to the cooperator receiver list based on an associated quality metric for the radial segment.

100. The computer readable storage medium of claim 99, wherein said selecting further comprises cycling through the base stations in the active set in conjunction with said stepping through the radial segments.

101. The computer readable storage medium of claim 100, further comprising instructions for continuing the selection of cooperator receivers until a predetermined number of cooperator receivers is reached or all radial segments for the base stations in the active set have been analyzed.

102. The computer readable storage medium of claim 101, further comprising instructions for:

for each added cooperator receiver, determining an average path loss for the added cooperator receiver and adding cooperator receivers within a predetermined proximity and a predetermined average path loss.

103. The computer readable storage medium of claim 102, wherein the at least one demodulator receiver is identified as a cooperator receiver within a predetermined proximity.

104. The computer readable storage medium of claim 77, wherein said instructions for identifying further comprises:

instructions for determining a common coverage area for the active set and a geographic centroid for the common coverage area;

instructions for dividing the common coverage area into radial segments centered around the geographic centroid and identifying at least one cooperator receiver and at least one demodulator receiver based on the radial segments.

105. The computer readable storage medium of claim 104, wherein said instructions for identifying further comprises instructions for selecting cooperators based on a pre-computed static list of cooperator receivers for a sector corresponding to the base stations in the active set.

106. The computer readable storage medium of claim 105, further comprising instructions for generating the pre-computed static list based on a radio propagation model for a service area.

107. The computer readable storage medium of claim 104, wherein said instructions for determining a common coverage area further comprises instructions for employing a bounding polygon to approximate a geographic coverage area for each base station and determining an area of overlap as the common coverage area.

108. The computer readable storage medium of claim 106, further comprising instructions for determining geographically distributed marker points within the common coverage area and, for each of the marker points, using the radio propagation model to determine a quality metric to sectors within a predetermined range of the common coverage area.

109. The computer readable storage medium of claim 107, further comprising instructions for averaging the quality metrics from each marker point to determine a quality metric for each sector.

110. The computer readable storage medium of claim 108, wherein the number of radial segments is eight.

111. The computer readable storage medium of claim 108, wherein said selecting comprises stepping through the radial segments using a spatially symmetric pattern and adding cooperator receivers to the cooperator receiver list based on an associated quality metric for the radial segment.

112. The computer readable storage medium of claim 111, further comprising instructions for repeating the selection of cooperator receivers until a predetermined number of cooperator receivers is reached or all radial segments have been analyzed.

113. The computer readable storage medium of claim 112, further comprising instructions for:

for each added cooperator receiver, determining an average path loss for the added cooperator receiver and adding cooperator receivers within a predetermined proximity and a predetermined average path loss.

114. The computer readable storage medium of claim 113, wherein the at least one demodulator receiver is identified as a cooperator receiver within a predetermined proximity.