Method, apparatus and system for estimating user position with a satellite positioning system in poor signal conditions

• US 6,473,694 B1
• Filed: 04/06/2001
• Issued: 10/29/2002
• Est. Priority Date: 04/06/2001
• Status: Active Grant

• Current Assignee: Nokia Technologies Oy (Nokia Corporation)
• Original Assignee: Nokia Corporation
• Inventors: Syrjarinne, Jari, Akopian, David
• Primary Examiner(s): Cuchlinski, Jr., William A.
• Assistant Examiner(s): NGUYEN, THU V
• Application Number:
  US09/828,594
• Time in Patent Office: 571 Days
• Field of Search: 701/200, 701/207, 701/213-215, 342/352-353, 342/357-1-3, 342/357-6-3, 342/357.12, 342/357-5-3, 342/358, 455/427, 455/432, 455/130, 455/132, 455/152.1
• US Class Current: 701/213
• CPC Class Codes: G01S 19/252 Employing an initial estimate of location in generating assistance data
• CPC Class Codes: G01S 19/258 relating to the satellite constellation, e.g. almanac, ephemeris data, lists of satellites in view
• CPC Class Codes: G01S 19/42 Determining position

Abstract

A method and corresponding apparatus and system for solving for the position of a satellite positioning system receiver having a receiver clock with a receiver clock offset and responsive to ranging codes from some number of satellites, the ranging code from each satellite including a navigation component conveying information about the satellite and having a time of flight from the satellite, the method of use in signal conditions where the ranging codes can be baseband processed so that at least a repeating part of the pseudorange for each satellite can be determined. The method includes the system time at arrival, i.e. for example the time or arrival according to GPS time, as an independent variable of the pseudorange function for each of the ranging codes, an independent variable in addition to the receiver position, and solves simultaneously for the receiver position and the system time at arrival.

Claims

1. A method for solving for the position of a satellite positioning system receiver, the receiver having a receiver clock with a receiver clock offset and responsive to ranging codes from at least one satellite, the ranging code from the at least one satellite including a navigation component conveying information about the satellite and having a time of flight from the satellite, the method of use in signal conditions where the ranging codes can be baseband processed so that at least a repeating part of the pseudorange for the at least one satellite can be determined, the method comprising the steps of:

a) including the system time at arrival as an independent and additional variable of the pseudorange function for each of the ranging codes, a variable in addition to the receiver position;

b) providing estimates of the times of flight of the ranging codes and of the repeating part of the pseudoranges for each of the ranging codes;

c) receiving information about the at least one satellite sufficient to determine the orbit of the at least one satellite, although not necessarily the position of the at least one satellite; and

d) solving simultaneously for the receiver position and the system time at arrival.

2. The method of claim 1, further comprising the step of including the receiver clock offset as an independent and additional variable.

3. The method of claim 2, further comprising the step of performing a Taylor-series expansion of the pseudorange function about an initial guess or estimate of each of the independent variables for as many of the satellites as there are independent variables thereby providing a system of pseudorange equations.

4. The method of claim 3, further comprising the step of solving the system of pseudorange equations using a determinate single-point solution that is either an iterative least squares solution or an exact algebraic solution, depending on the number of pseudorange equations.

5. The method of claim 3, further comprising the step of solving the system of pseudorange equations using a Kalman filter.

6. The method of claim 1, wherein the information about the at least one satellite includes the orbit parameters for the at least one satellite.

7. The method of claim 1, wherein the satellite positioning system is the global satellite positioning system (GPS) and the system time at arrival is the GPS time at arrival.

8. The method of claim 1, wherein the repeating part of the pseudorange is the submillisecond part of the pseudorange.

9. The method of claim 1, wherein the method is of use in signal conditions where the ranging codes can be baseband processed providing at least the submillisecond part of the pseudorange.

10. A receiver for a satellite positioning system, the satellite positioning system including at least one satellite providing satellite ranging codes, the receiver having a receiver clock with an unknown receiver clock offset, the receiver able to solve for its position in signal conditions such that even if some of the navigation component of satellite ranging codes accessible to the receiver cannot be demodulated, the ranging codes can be baseband processed so that at least a repeating part of the pseudorange for the at least one satellite can be determined, the receiver comprising:

i) a non-volatile memory, for storing a program for solving for the receiver position;

ii) a processor for executing the stored program;

iii) an antenna responsive to the satellite ranging codes;

iv) an antenna responsive to information about the at least one satellite and about the location of a nearby reference point;

wherein the program solves for position according to the procedure including the steps of;

a) including the system time at arrival as an independent and additional variable of the pseudorange function for each of the ranging codes, a variable in addition to the receiver position;

b) providing estimates of the times of flight of the ranging codes and of the repeating part of the pseudoranges for the ranging codes for each of the at least one satellite;

c) receiving information about the at least one satellite sufficient to determine the orbit of the at least one satellite, although not necessarily the position of the at least one satellite; and

d) solving simultaneously for the receiver position and the system time at arrival.

11. The apparatus of claim 10, wherein the program further comprises the step of including the receiver clock offset as an independent and additional variable.

12. The apparatus of claim 11, wherein the program further comprises the step of performing a Taylor-series expansion of the pseudorange function about an initial guess or estimate of each of the independent variables for as many of the satellites as there are independent variables thereby providing a system of pseudorange equations.

13. The apparatus of claim 12, wherein the program further comprises the step of solving the system of pseudorange equations using a determinate single-point solution that is either an iterative least squares solution or an exact algebraic solution, depending on the number of pseudorange equations.

14. The apparatus of claim 12, wherein the program further comprises the step of solving the system of pseudorange equations using a Kalman filter.

15. The apparatus of claim 10, wherein the information about the at least one satellite includes the orbit parameters for the at least one satellite.

16. The apparatus of claim 15, wherein the program further comprises the step of including the receiver clock offset as an independent and additional variable.

17. The apparatus of claim 10, wherein the satellite positioning system is the global satellite positioning system (GPS) and the system time at arrival is the GPS time at arrival.

18. The apparatus of claim 10, wherein the repeating part of the pseudorange is the submillisecond part of the pseudorange.

19. The apparatus of claim 10, wherein the apparatus is of use in signal conditions where the ranging codes can be baseband processed providing at least the submillisecond part of the pseudorange.

20. A system for providing navigation solutions, comprising:

A) a receiver for a satellite positioning system, the satellite positioning system including at least one satellite providing satellite ranging codes, the receiver having a receiver clock with an unknown receiver clock offset, the receiver able to solve for its position in signal conditions such that even if some of the navigation component of satellite ranging codes accessible to the receiver cannot be demodulated, the ranging codes can be baseband processed so that at least a repeating part of the pseudorange for each satellite can be determined, the receiver comprising;

i) a non-volatile memory, for storing a program for solving for position;

ii) a processor for executing the stored program;

iii) an antenna responsive to the satellite ranging codes;

iv) an antenna responsive to information about the at least one satellite and about the location of a nearby reference point;

wherein the program solves for position according to the procedure including the steps of;

a) including the system time at arrival as an independent and additional variable of the pseudorange function for each of the ranging codes, a variable in addition to the receiver position;

b) providing estimates of the times of flight of the ranging codes and of the repeating part of the pseudoranges for each of the ranging codes;

c) receiving information about the at least one satellite sufficient to determine the orbit of the at least one satellite, although not necessarily the position of the at least one satellite; and

d) solving simultaneously for the receiver position and the system time at arrival; and

B) a means of providing the information about the at least one satellite.

21. The system of claim 20, wherein the program further comprises the step of including the receiver clock offset as an independent and additional variable.

22. The system of claim 21, wherein the program further comprises the step of performing a Taylor-series expansion of the pseudorange function about an initial guess or estimate of each of the independent variables for as many of the satellites as there are independent variables thereby providing a system of pseudorange equations.

23. The system of claim 22, wherein the program further comprises the step of solving the system of pseudorange equations using a determinate single-point solution that is either an iterative least squares solution or an exact algebraic solution, depending on the number of pseudorange equations.

24. The system of claim 22, wherein the program further comprises the step of solving the system of pseudorange equations using a Kalman filter.

25. The system of claim 20, wherein the information about the at least one satellite includes the orbit parameters for the at least one satellite.

26. The system of claim 25, wherein the program further comprises the step of including the receiver clock offset as an independent and additional vehicle.

27. The system of claim 20, wherein the satellite positioning system is the global satellite positioning system (GPS) and the system time at arrival is the GPS time at arrival.

28. The system of claim 20, wherein the repeating part of the pseudorange is the submillisecond part of the pseudorange.

29. The system of claim 20, wherein the system is of use in signal conditions where the ranging codes can be baseband processed providing at least the submillisecond part of the pseudorange.

30. The system of claim 20, wherein the means of providing the information about the at least one satellite is a cellular base station.

31. The system of claim 20, wherein the means of providing the information about the at least one satellite is the navigation satellite itself.