Position computation in a positioning system using synchronization time bias

• US 7,499,712 B2
• Filed: 07/31/2003
• Issued: 03/03/2009
• Est. Priority Date: 09/05/2002
• Status: Active Grant

• Current Assignee: Qualcomm, Inc., Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: Qualcomm, Inc.
• Inventors: Marshall, Grant, Riley, Wyatt T.
• Primary Examiner(s): Nguyen; Tu X
• Application Number:
  US10/632,637
• Publication Number:
  US 20040077311A1
• Time in Patent Office: 2,042 Days
• Field of Search: 455/502, 455/517, 455/456, 455/456.1, 455/561, 455/408, 455/414.2, 455/13.2, 455/440, 455/448, 455/404.2, 455/456.2, 455/456.3, 455/456.4, 455/456.5, 455/456.6, 455/67.11, 342/357.12, 342/357.06, 342/387, 342/357.14, 342/358, 342/357.15, 342/357.16, 342/347.17
• US Class Current: 455/456.1
• CPC Class Codes: G01S 19/20 Integrity monitoring, fault detection or fault isolation of space segment
• CPC Class Codes: G01S 19/48 by combining or switching between position solutions derived from the satellite radio beacon positioning system and position solutions derived from a further system

Abstract

In general, this disclosure is directed to techniques for computing a positioning solution for a mobile unit based on signals received from the satellite navigation system and the wireless communication system. The techniques allow for, and resolve, a synchronization bias that constrains a system time for the satellite navigation system and a system time for the wireless communication system relative to each other. The mobile unit may utilize the defined constraint to compute a position solution in environments where additional independent measurements would otherwise be required. The mobile unit may incorporate Receiver Autonomous Integrity Monitoring (RAIM) functionality to validate the position and time solutions derived from each of received signals. According to the techniques described herein, the mobile unit may be able to utilize the defined synchronization bias to apply RAIM or similar techniques in environments where such techniques would otherwise be indeterminate.

Claims

1. A method comprising:

receiving signals from a satellite navigation system and signals from a terrestrial wireless communication system;

receiving a timing bias from the wireless communication system, wherein the timing bias includes a common system synchronization bias that defines a difference between a system time for the satellite navigation system and a system time for the wireless communication system; and

determining a position solution for a mobile unit based on a hybrid position location technique for an asynchronous environment, and as a function of the received signals, a number of independent measurements based on a position location technique for a synchronous environment, wherein the number of independent measurements is fewer than a minimum number of measurements for an asynchronous position location technique, and using the common system synchronization bias.

2. The method of claim 1, wherein determining the position solution comprises:

computing the system time for the satellite navigation system;

computing the system time for the wireless communication system as a function of the computed system time of the satellite navigation system and the synchronization bias; and

computing a position solution as a function of the received signals and the computed system times.

3. The method of claim 1, wherein the synchronization bias constrains the system time of the wireless communication system within a range of time from the system time of the satellite navigation system.

4. The method of claim 1, wherein the synchronization bias defines an expected time offset between the system time for the satellite navigation system and the system time for the wireless communication system.

5. The method of claim 1, wherein computing a position solution comprises computing a latitude, a longitude and an altitude for the mobile unit.

6. The method of claim 1, wherein the satellite navigation system comprises a Global Positioning System (GPS).

7. The method of claim 1, further comprising receiving data from a component of the wireless communication system that defines the synchronization bias.

8. The method of claim 1, further comprising applying an altitude-aiding technique to determine an extra measurement for use in determining the position solution.

9. The method of claim 1, further comprising:

receiving a total of M signals from the wireless communication system and the satellite navigation network;

generating M distance measurements from the signals; and

detecting the presence of one or more erroneous distance measurements from one or more of the signals based on the M distance measurements and the synchronization bias.

10. The method of claim 9, wherein M≧

4.

11. The method of claim 9, wherein the position solution comprises M variables.

12. The method of claim 9, further comprising:

applying an altitude-aiding technique to determine an extra measurement; and

detecting the presence of the erroneous distance measurements based at least in part on the extra measurement.

13. A method comprising:

receiving a request from a mobile unit operating within an environment having a satellite navigation system and a wireless communication system, wherein the wireless communication system comprises more than one base station;

communicating to the mobile unit, in response to the request, common system synchronization bias data that constrains a system time of the satellite navigation system as a function of a system time of the wireless communication system; and

computing, a position solution for the mobile unit based on a hybrid position location technique for an asynchronous environment, based on independent measurements from more than one base station, and as a function of a number of independent measurements based on a position location technique for a synchronous environment, wherein the number of independent measurements is fewer than a minimum number of measurements for an asynchronous position location technique, and the common system synchronization bias data.

14. The method of claim 13, further comprising retrieving the synchronization bias data from a database.

15. The method of claim 14, wherein retrieving from a database comprises retrieving from a database a synchronization bias specific to the requesting mobile unit.

16. The method of claim 14, wherein retrieving from a database comprises:

identifying a current region of the wireless communication system for the requesting mobile unit; and

retrieving the data from the database based on the identified region.

17. The method of claim 13, further comprising:

receiving data from the mobile unit that describes a computed synchronization bias; and

updating the database based on the received data.

18. The method of claim 17, further comprising:

comparing the computed synchronization bias to a threshold bias; and

determining a functional status of a component within the wireless communication system based on the comparison.

19. The method of claim 18, further comprising issuing a service message when the computed synchronization bias exceeds the threshold bias.

20. The method of claim 18, wherein the component comprises a base station within the wireless communication system.

21. The method of claim 18, wherein the component comprises a mobile unit within the wireless communication system.

22. An apparatus comprising:

one or more antennas to receive signals from a satellite navigation system and a wireless communication system, wherein the wireless communication system comprises more than one base station; and

a processor to compute a position solution for a mobile unit based on a hybrid position location technique for an asynchronous environment as a function of the received signals using a number of independent measurements based on a position location technique for a synchronous environment, wherein the number of independent measurements is fewer than a minimum number of measurements for an asynchronous position location technique, and a common system synchronization bias that defines a difference between a system time for the satellite navigation system and a system time for the wireless communication system.

23. The apparatus of claim 22, wherein the satellite navigation system comprises a Global Positioning System (GPS), and the wireless communication system comprises a Code Division Multiple Access (CDMA) wireless communication system.

24. The apparatus of claim 23, wherein the apparatus comprises a mobile GPS receiver.

25. The apparatus of claim 22, wherein the synchronization bias constrains the system time of the wireless communication system within a range of time from the system time of the satellite navigation system.

26. The apparatus of claim 22, wherein the synchronization bias defines an expected time offset between the system time for the satellite navigation system and the system time for the wireless communication system.

27. The apparatus of claim 22, wherein the processor computes a latitude, a longitude and an altitude for a receiver.

28. The apparatus of claim 22, wherein the processor generates M distance measurements from the signals, and applies Receiver Autonomous Integrity Monitoring (RAIM) to detect the presence of one or more erroneous distance measurement from one or more of the signals based on the M distance measurements and the synchronization bias.

29. The apparatus of claim 28, wherein M>

N, where N is a number of position solution variables.

30. The apparatus of claim 28, wherein N=4.

31. The apparatus of claim 22, wherein the processor receives data from a component of the wireless communication system that defines the synchronization bias.

32. The apparatus of claim 31, wherein the processor computes a new synchronization bias for the wireless communication system and satellite navigation system upon determining a position solution, and communicates the computed synchronization bias to the component.

33. The apparatus of claim 22, wherein the processor comprises a digital signal processor.

34. A system comprising:

a server to store common system synchronization bias data that defines a difference between a system time for a satellite navigation system and a system time for a wireless communication system, wherein the wireless communication system comprises more than one base station; and

a device to receive the common system synchronization bias data from the server, and determine a position solution based on a hybrid position location technique for an asynchronous environment as a function of the common synchronization bias data and signals received from the satellite navigation system and the wireless communication system and a number of independent measurements based on a position location technique for a synchronous environment, wherein the number of independent measurements is fewer than a minimum number of measurements for an asynchronous position location technique.

35. The system of claim 34, wherein the server selectively retrieves synchronization bias data from a database based on an identifier for the device.

36. The system of claim 34, wherein the server maintains a database to store data defining a set of synchronization biases arranged in accordance with identifiers for respective regions of the wireless communication system.

37. The system of claim 34, wherein the satellite navigation system comprises a Global Positioning System (GPS), and the wireless communication system comprises a Code Division Multiple Access (CDMA) wireless communication system.

38. The system of claim 37, wherein the device comprises a mobile GPS receiver.

39. The system of claim 34, wherein the synchronization bias data constrains the system time of the wireless communication system within a range of time from the system time of the satellite navigation system.

40. The system of claim 34, wherein the synchronization bias data defines an expected time offset between the system time for the satellite navigation system and the system time for the wireless communication system.

41. The system of claim 34, wherein the device computes a latitude, a longitude and an altitude.

42. The system of claim 34, wherein the device comprises one of a mobile unit, a location server, a Position Determination Entity (PDE), a Location Measuring Unit (LMU), a Serving Mobile Location Centers (SMLC), a Wireless Location Gateway (WLG), and a Mobile Location Center (MLC).

43. A method comprising:

receiving signals from a satellite navigation system having synchronous system times and signals from a terrestrial wireless communication system; and

determining a position solution for the device based on a hybrid position location technique for an asynchronous, environment as a function of the signals, a number of independent measurements based on a position location technique for a synchronous environment, wherein the number of independent measurements is fewer than a minimum number of measurements for an asynchronous position location technique, and a common system synchronization bias that defines a difference between the system times, wherein the systems comprise more than one system element.

44. The method of claim 43, wherein determining the position solution comprises:

computing a time for a first one of the systems;

computing a time for a second one of the systems as a function of the computed time of the first system and the synchronization bias; and

computing a position solution as a function of the signals and the computed times for the first and second systems.

45. The method of claim 43, wherein the synchronization bias constrains the system time of a first one of the systems within a defined range from the system time of a second one of the systems.

46. A computer-readable medium encoded with a computer program comprising instructions to cause a processor to determine a position solution for a mobile unit based on a hybrid position location technique for an asynchronous environment as a function of signals received from a satellite navigation system, signals received from a wireless communication system, a number of independent measurements based on a position location technique for a synchronous environment, wherein the number of independent measurements is fewer than a minimum number of measurements for an asynchronous position location technique, and a common system synchronization bias that defines a difference between system times for the satellite navigation system and the wireless communication system, wherein the wireless communication system comprises more than one base station.

47. The computer-readable medium of claim 46, wherein the synchronization bias defines the system time of the wireless communication system as within a range of time from the system time of the satellite navigation system.

48. The computer-readable medium of claim 46, wherein the synchronization bias defines a time offset between the system time for the satellite navigation system and the system time for the wireless communication system.

49. The computer-readable medium of claim 46, wherein the instructions cause the processor to compute a position solution comprises computing a latitude, a longitude and an altitude for a receiver.

50. The computer-readable medium of claim 46, wherein the satellite navigation system comprises a Global Positioning System (GPS).

51. The computer-readable medium of claim 46, wherein the instructions cause the processor to receive data from a component of the wireless communication system that defines the synchronization bias.

52. A method comprising:

receiving sets of position related measurements for a device from a satellite navigation system and signals from a terrestrial wireless communication system, the measurements of each of the sets having a common bias with respect to the measurements of the other set; and

computing a position solution for the device based on a hybrid position location technique for an asynchronous environment as a function of the measurements, wherein a number of independent measurements is based on a position location technique for a synchronous environment, wherein the number of independent measurements is fewer than a minimum number of measurements for an asynchronous position location technique, and the common bias.

53. The method of claim 52, wherein receiving sets of position related measurements comprises receiving a first set of position related measurements from a satellite navigation system and a second set of position related measurements from a wireless communication system.

54. The method of claim 53, wherein the common bias represents a difference in system times for the satellite navigation system and the wireless communication system.

55. A method comprising:

receiving sets of position related measurements for a device from a satellite navigation system and signals from a terrestrial wireless communication system;

determining different system times for each of the systems according to a common system bias; and

determining a position solution for the device based on a hybrid position location technique for an asynchronous environment as a function of the measurements and the system times wherein a number of independent measurements is based on a position location technique for a synchronous environment, wherein the number of independent measurements is fewer than a minimum number of measurements for an asynchronous position location technique.

56. The method of claim 55, wherein the measurements of each of the sets having a common bias with respect to the measurements of the other set.

57. The method of claim 55, wherein receiving sets of position related measurements comprises receiving a first set of position related measurements from a satellite navigation system and a second set of position related measurements from a wireless communication system.

58. The method of claim 55, wherein receiving sets of position related measurements comprises receiving a first set of position related measurements from a first ground-based wireless communication system and a second set of position related measurements from a second ground-based wireless communication system.

59. The method of claim 55, wherein the measurements of each of the sets have a common bias with respect to the measurements of the other set, and determining a position solution comprises determining the position solution using a constraint on the system times in accordance with the common bias.

60. The method of claim 59, wherein the common bias represents a difference in the system times for the systems.

61. An apparatus comprising:

one or more antennas to receive signals from a satellite navigation system and a wireless communication system, wherein the wireless communication system comprises more than one base station; and

a processor to compute a position solution for a mobile unit as a function of the received signals using a common system synchronization bias that defines a difference between a system time for the satellite navigation system and a system time for the more than one base station of the wireless communication system,

wherein the synchronization bias constrains the system time of the wireless communication system within a range of time from the system time of the satellite navigation system, and the synchronization bias defines an expected time offset between the system time for the satellite navigation system and the system time for the wireless communication system, and

wherein the processor generates M distance measurements from the signals, wherein the number of independent measurements is fewer than a minimum number of measurements for an asynchronous position location technique, and applies Receiver Autonomous Integrity Monitoring (RAIM) to detect the presence of one or more erroneous distance measurement from one or more of the signals based on the M distance measurements and the synchronization bias.

62. The apparatus of claim 61, wherein the processor computes the position solution by computing the system time for the satellite navigation system, computing the system time for the wireless communication system as a function of the computed system time of the satellite navigation system and the synchronization bias, and computing a position solution as a function of the received signals and the computed system times.

63. The apparatus of claim 61, wherein the processor computes a latitude, a longitude and an altitude for the mobile unit.

64. The apparatus of claim 61, wherein the processor receives, via the one or more antennas, altitude-aiding data for use in computing the position solution.

65. The apparatus of claim 61, wherein M<

N, where N is a number of position solution variables.

66. The apparatus of claim 61, wherein the satellite navigation system comprises a Global Positioning System (GPS), and the wireless communication system comprises a Code Division Multiple Access (CDMA) wireless communication system.

67. The apparatus of claim 61, wherein the processor computes the position solution for the mobile unit based on a hybrid position location technique.

68. A method of determining a position solution for a mobile unit, the method comprising:

receiving signals from a satellite navigation system;

receiving signals from a wireless communication system, wherein a system time of the wireless communication system is asynchronous with a system time of the satellite navigation system;

receiving a timing bias value from the wireless communication system;

constraining a difference between the system time for the satellite navigation system and the system time for the wireless communication system based on the timing bias value to configure the mobile unit to a semi-synchronous mode; and

determining a position solution for the mobile unit based on a hybrid position location technique for an asynchronous environment, and as a function of the received signals, a number of independent measurements based on a position location technique for a synchronous environment, wherein the number of independent measurements for the synchronous environment is fewer than a minimum number of measurements for an asynchronous position location technique.