Position computation in a positioning system using synchronization time bias

• US 20040077311A1
• Filed: 07/31/2003
• Published: 04/22/2004
• Est. Priority Date: 09/05/2002
• Status: Active Grant

• Current Assignee: Qualcomm, Inc., Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: Qualcomm, Inc.
• Inventors: Riley, Wyatt Thomas
• Granted Patent: US 7,499,712 B2
• Time in Patent Office: Days
• US Class Current: 455/12.1
• 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 wireless communication system; and

determining a position solution for a mobile unit as a function of the received signals using a synchronization bias that defines a difference between a system time for the satellite navigation system and a system time for the wireless communication system.

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, wherein computing a position solution comprises applying hybrid position calculation techniques to compute the position solution as a function of the signals received from the satellite navigation system and the signals received from the wireless communication system.

8. The method of claim 1, wherein computing a position solution comprises applying asynchronous techniques to compute the system times in accordance with the synchronization bias.

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

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

11. 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.

12. The method of claim 11, wherein M≧

4.

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

14. The method of claim 11, 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.

15. A method comprising:

receiving a request from a mobile unit operating within an environment having a satellite navigation system and a wireless communication system; and

communicating to the mobile unit, in response to the request, 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.

16. The method of claim 15, further comprising retrieving the synchronization bias data from a database.

17. The method of claim 16, wherein retrieving from a database comprises retrieving from a database a synchronization bias specific to the requesting mobile unit.

18. The method of claim 16, 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.

19. The method of claim 15, further comprising:

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

updating the database based on the received data.

20. The method of claim 15, 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.

21. The method of claim 20, further comprising issuing a service message when the computed synchronization bias exceeds the threshold bias.

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

23. The method of claim 20, wherein the component comprises a mobile unit within the wireless communication system.

24. An apparatus comprising:

one or more antennas to receive signals from a satellite navigation system and a wireless communication system; and

a processor to determine a position solution for a mobile unit as a function of the received signals using a synchronization bias that defines a difference between a system time for the satellite navigation system and a system time for the wireless communication system.

25. The apparatus of claim 24, 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.

26. The apparatus of claim 25, wherein the apparatus comprises a mobile GPS receiver.

27. The apparatus of claim 24, 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.

28. The apparatus of claim 24, 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.

29. The apparatus of claim 24, wherein the processor computes a latitude, a longitude and an altitude for a receiver.

30. The apparatus of claim 24, wherein the processor applies hybrid position calculation techniques to compute the position solution as a function of the signals received from the navigation satellite system and the signals received from the wireless communication system.

31. The apparatus of claim 24, wherein the processor applies asynchronous techniques to compute the system times in accordance with the synchronization bias.

32. The apparatus of claim 24, 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.

33. The apparatus of claim 32, wherein M>

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

34. The apparatus of claim 32, wherein N=4.

35. The apparatus of claim 24, wherein the processor receives data from a component of the wireless communication system that defines the synchronization bias

36. The apparatus of claim 35, 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.

37. The apparatus of claim 24, wherein the processor comprises a digital signal processor.

38. A system comprising:

a server to store 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; and

a device to receive the synchronization bias data from the server, and determine a position solution as a function of the synchronization bias data and signals received from the satellite navigation system and the wireless communication system.

39. The system of claim 38, wherein the server selectively retrieves synchronization bias data from a database based on an identifier for the device.

40. The system of claim 38, 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.

41. The system of claim 38, 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.

42. The system of claim 41, wherein the device comprises a mobile GPS receiver.

43. The system of claim 38, 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.

44. The system of claim 38, 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.

45. The system of claim 38, wherein the device computes a latitude, a longitude and an altitude.

46. The system of claim 38, 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).

47. A method comprising:

receiving signals at a device from a plurality of systems having synchronous system times; and

determining a position solution for the device as a function of the signals and a synchronization bias that defines a difference between the system times.

48. The method of claim 47, 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.

49. The method of claim 47, 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.

50. A computer-readable medium comprising instructions to cause a processor to determine a position solution for a mobile unit as a function of signals received from a satellite navigation system, signals received from a wireless communication system, and a synchronization bias that defines a difference between system times for the satellite navigation system and the wireless communication system.

51. The computer-readable medium of claim 50, 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.

52. The computer-readable medium of claim 50, 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.

53. The computer-readable medium of claim 50, wherein the instructions cause the processor to compute a position solution comprises computing a latitude, a longitude and an altitude for a receiver.

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

55. The computer-readable medium of claim 50, wherein the instructions cause the processor to apply hybrid position calculation techniques to compute the position solution as a function of the signals received from the satellite navigation system and the signals received from the wireless communication system.

56. The computer-readable medium of claim 50, wherein the instructions cause the processor to apply asynchronous techniques to compute the system times in accordance with the synchronization bias.

57. The computer-readable medium of claim 50, wherein the instructions cause the processor to receive data from a component of the wireless communication system that defines the synchronization bias.

58. A computer-readable medium comprising data structure to store one or more synchronization biases for computing position solutions for one or more mobile units, where each of the synchronization biases defines a difference between a system time for a satellite navigation system and a system time for a wireless communication system.

59. The computer-readable medium of claim 58, wherein data structures arrange the synchronization biases in accordance with identifiers for the mobile units.

60. The computer-readable medium of claim 58, wherein data structures arrange the synchronization biases in accordance with identifiers for respective regions within the wireless communication system.

61. A method comprising:

receiving sets of position related measurements for a device, the measurements of each of the sets having a common bias with respect to the measurements of the other set; and

determining a position solution for the device as a function of the measurements and the common bias.

62. The method of claim 61, 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.

63. The method of claim 62, wherein the common bias represents a difference in system times for the satellite navigation system and the wireless communication system.

64. A method comprising:

receiving sets of position related measurements for a device from a plurality of systems;

determining different system times for each of the systems; and

determining a position solution for the device as a function of the measurements and the system times.

65. The method of claim 64, wherein the measurements of each of the sets having a common bias with respect to the measurements of the other set

66. The method of claim 64, 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.

67. The method of claim 64, 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.

68. The method of claim 64, 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.

69. The method of claim 68, wherein the common bias represents a difference in the system times for the systems.