Position determination for a wireless terminal in a hybrid position determination system

• US 20040203853A1
• Filed: 04/24/2002
• Published: 10/14/2004
• Est. Priority Date: 04/24/2002
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Sheynblat, Leonid
• Granted Patent: US 7,623,871 B2
• Time in Patent Office: Days
• US Class Current: 455/456.1
• CPC Class Codes: G01S 1/026 of associated receivers
• CPC Class Codes: G01S 19/25 involving aiding data received from a cooperating element, e.g. assisted GPS
• CPC Class Codes: G01S 19/40 Correcting position, velocity or attitude
• CPC Class Codes: G01S 19/46 the supplementary measurement being of a radio-wave signal type
• CPC Class Codes: G01S 5/14 Determining absolute distances from a plurality of spaced points of known location
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management

Abstract

Techniques to determine a position estimate for a wireless terminal. An accurate position estimate for the initially obtained (e.g., based on a first (accurate) position determination sub-system). For each of one or more transmitters (e.g., base stations) in a second (less accurate) position determination sub-system, an “expected” pseudo-range is computed based on the accurate position estimate for the terminal and the base station location, a “measured” pseudo-range is also obtained, and a pseudo-range residual is then determined based on the expected pseudo-range and the measured pseudo-range. Therefore, to determine an updated position estimate for the terminal, measured pseudo-ranges are obtained for a sufficient number of transmitters. The measured pseudo-range for each base station may be corrected based on the associated residual. The updated position estimate is then determined based on the corrected pseudo-ranges for these transmitters.

Claims

1. A method for determining a position estimate for a wireless terminal, comprising:

obtaining a measurement for each of a plurality of transmitters, wherein the plurality of transmitters include at least one transmitter in a first position determination sub-system;

correcting the measurement for each of the at least one transmitter in the first sub-system based on a residual for the transmitter; and

determining a position estimate for the terminal based on a plurality of measurements for the plurality of transmitters, wherein the plurality of measurements include at least one corrected measurement for the at least one transmitter in the first sub-system.

2. The method of claim 1, further comprising:

receiving the residual for each of the at least one transmitter in the first sub-system.

3. The method of claim 1, further comprising:

obtaining an accurate position estimate for the terminal based on a second position determination sub-system; and

determining the residual for each of the at least one transmitter in the first sub-system based in part on the accurate position estimate for the terminal.

4. The method of claim 3, wherein the accurate position estimate for the terminal is obtained by processing a plurality of measurements obtained for a plurality of transmitters in the second sub-system.

5. The method of claim 1, wherein the plurality of measurements include at least one measurement obtained for at least one transmitter in a second position determination sub-system.

6. The method of claim 1, wherein the plurality of measurements include at least one corrected measurement for at least one transmitter in the first sub-system and no measurements for transmitters in the second sub-system.

7. The method of claim 5, wherein the second position determination sub-system is a Satellite Positioning System (SPS) and each transmitter in the second position determination sub-system corresponds to a SPS satellite.

8. The method of claim 1, wherein the first position determination sub-system is a cellular communication system and each transmitter in the first position determination sub-system corresponds to a base station.

9. The method of claim 1, wherein the measurement for each transmitter relates to a pseudo-range between the terminal and the transmitter.

10. The method of claim 9, wherein the residual for each transmitter in the first sub-system is indicative of an error in a measured pseudo-range derived based on a signal received from the transmitter.

11. The method of claim 10, wherein the measured pseudo-range for each transmitter in the first sub-system is obtained based on a pilot phase measurement for the signal received from the transmitter.

12. The method of claim 10, wherein the measured pseudo-range for each transmitter in the first sub-system is obtained based on a signal strength measurement for the signal received from the transmitter.

13. The method of claim 10, wherein the measured pseudo-range for each transmitter in the first sub-system is obtained based on a timing measurement for the signal received from the transmitter.

14. The method of claim 1, further comprising:

obtaining an actual measurement for each of the at least one transmitter in the first sub-system; and

computing an expected measurement for each of the at least one transmitter in the first sub-system based on the accurate position estimate for the terminal and a location for the transmitter, and

wherein the residual for each of the at least one transmitter in the first sub-system is determined from the actual measurement and the expected measurement for the transmitter.

15. The method of claim 1, wherein the residual for each of the at least one transmitter in the first sub-system is determined based on a collection of measurements obtained by a plurality of terminals in close proximity in spatial and temporal domains.

16. The method of claim 5, further comprising:

periodically determining the accurate position estimate for the terminal based on the second sub-system.

17. The method of claim 5, further comprising:

determining the accurate position estimate for the terminal based on the second sub-system on per need basis.

18. The method of claim 1, further comprising:

determining error statistics for the residual for each transmitter in the first sub-system.

19. The method of claim 18, further comprising:

updating the error statistics associated with the residual for each transmitter in the first sub-system.

20. A method for determining a position estimate for a wireless terminal, comprising:

determining an accurate position estimate for the terminal based on measured pseudo-ranges to a plurality of satellites in a Global Positioning System (GPS);

computing an expected pseudo-range to each of one or more base stations in a cellular communication system based on the accurate position estimate for the terminal and a location for the base station;

obtaining a measured pseudo-range to each of the one or more base stations;

determining a pseudo-range residual for each of the one or more base stations based on the expected pseudo-range and the measured pseudo-range for the base station;

obtaining a measured pseudo-range for each of a plurality of transmitters, wherein each of the plurality of transmitters is either a GPS satellite or a base station;

correcting the measured pseudo-range for each base station in the plurality of transmitters based on the pseudo-range residual determined for the base station; and

determining an updated position estimate for the terminal based on a plurality of pseudo-ranges for the plurality of transmitters, wherein the plurality of pseudo-ranges include at least one corrected pseudo-range for at least one base station.

21. A method for determining a position estimate for a wireless terminal based on first and second position determination sub-systems, wherein a position estimate based on the first sub-system is typically more accurate than a position estimate based on the second sub-system, the method comprising:

determining the position estimate for the terminal based on the first sub-system if the first sub-system is available;

determining the position estimate for the terminal based on the first and second sub-systems if the first sub-system is partially available, wherein a measurement for each transmitter in the second sub-system used to determine the position estimate is corrected based on a residual, if available, for the transmitter; and

determining the position estimate for the terminal based solely on the second sub-system if the first sub-system is unavailable, wherein the measurement for each of at least one transmitter in the second sub-system used to determine the position estimate is corrected based on the residual for the transmitter.

22. The method of claim 21, further comprising:

selecting one or more transmitter measurements in the second sub-system to be used to determine the position estimate for the terminal.

23. The method of claim 22, wherein the one or more transmitter measurements in the second sub-system are selected based on one or more selection criteria.

24. The method of claim 23, wherein the one or more selection criteria include availability of accurate base station almanac information.

25. The method of claim 23, wherein the one or more selection criteria include presence of repeaters.

26. The method of claim 23, wherein the one or more selection criteria include statistical measures.

27. The method of claim 21, further comprising:

determining an accurate position estimate for the terminal based on the first sub-system, wherein the residual for each of one or more transmitters in the second sub-system is determined based in part on the accurate position estimate for the terminal.

28. The method of claim 21, wherein the first position determination sub-system is a Satellite Positioning System (SPS).

29. The method of claim 21, wherein the second position determination sub-system is a cellular communication system.

30. The method of claim 21, wherein the measurement for each transmitter relates to a pseudo-range between the terminal and the transmitter.

31. The method of claim 21, wherein the position estimate for the terminal is determined based on one or more measurements for the second sub-system only if residuals for transmitters in the second sub-system are deemed to be valid.

32. A memory communicatively coupled to a digital signal processing device (DSPD) capable of interpreting digital information to:

obtaining an accurate position estimate for a wireless terminal based on a first position determination sub-system;

determine a residual for each of one or more transmitters in a second position determination sub-system based in part on the accurate position estimate for the terminal;

obtain a measurement for each of a plurality of transmitters, wherein the plurality of transmitters include at least one transmitter in the second sub-system;

correct the measurement for each of the at least one transmitter in the second sub-system based on the residual for the transmitter; and

determine an updated position estimate for the terminal based on a plurality of measurements for the plurality of transmitters, wherein the plurality of measurements include at least one corrected measurement for the at least one transmitter in the second sub-system.

33. A computer program product for determining a position estimate for a wireless terminal, comprising:

code for obtaining an accurate position estimate for the terminal based on a first position determination sub-system;

code for determining a residual for each of one or more transmitters in a second position determination sub-system based in part on the accurate position estimate for the terminal;

code for obtaining a measurement for each of a plurality of transmitters, wherein the plurality of transmitters include at least one transmitter in the second sub-system;

code for correcting the measurement for each of the at least one transmitter in the second sub-system based on the residual for the transmitter;

code for determining an updated position estimate for the terminal based on a plurality of measurements for the plurality of transmitters, wherein the plurality of measurements include at least one corrected measurement for the at least one transmitter in the second sub-system; and

a computer-usable medium for storing the codes.

34. A digital signal processor comprising:

means for obtaining an accurate position estimate for the terminal based on a first position determination sub-system;

means for determining a residual for each of one or more transmitters in a second position determination sub-system based in part on the accurate position estimate for the terminal;

means for determining a measurement for each of a plurality of transmitters, wherein the plurality of transmitters include at least one transmitter in the second sub- system;

means for correcting the measurement for each of the at least one transmitter in the second sub-system based on the residual for the transmitter; and

means for determining an updated position estimate for the terminal based on a plurality of measurements for the plurality of transmitters, wherein the plurality of measurements include at least one corrected measurement for the at least one transmitter in the second sub-system.

35. The digital signal processor of claim 34, further comprising:

means for determining an actual measurement for each of the one or more transmitters in the second sub-system; and

means for computing an expected measurement for each of the one or more transmitters based on the accurate position estimate for the terminal and a location for the transmitter, and wherein the residual for each of the one or more transmitters in the second sub-system is determined from the actual measurement and the expected measurement for the transmitter.

36. A receiver unit in a wireless communication system, comprising:

a first receiver operative to receive and process a received signal to provide data for a first position determination sub-system;

a second receiver operative to receive and process the received signal to provide data for a second position determination sub-system; and

a processing unit coupled to the first and second receivers and operative to

obtain an accurate position estimate for the terminal based on the data for the first sub-system,

determine a residual for each of one or more transmitters in the second sub-system based in part on the accurate position estimate for the terminal,

obtain an actual measurement for each of a plurality of transmitters based on the data for the sub-system to which each transmitter belongs, wherein the plurality of transmitters include at least one transmitter in the second sub-system,

correct the actual measurement for each of the at least one transmitter in the second sub-system based on the residual for the transmitter, and

determine an updated position estimate for the terminal based on a plurality of measurements for the plurality of transmitters, wherein the plurality of measurements include at least one corrected measurement for the at least one transmitter in the second sub-system.

37. The receiver unit of claim 36, wherein the first receiver is operative to process signals from GPS satellites.

38. The receiver unit of claim 36, wherein the second receiver is operative to process signals from base stations in a cellular communication system.

39. The receiver unit of claim 38, wherein the second receiver implements a rake receiver that comprises a plurality of finger processors, wherein each finger processor is assignable to process a particular multipath component, and wherein a residual is determined for each finger processor assigned to process a multipath component.

40. The receiver unit of claim 36, wherein the actual measurement for each transmitter relates to a pseudo-range between the terminal and the transmitter.

41. A wireless terminal in a wireless communication system, comprising:

a first receiver operative to receive and process a received signal to provide data for a first position determination sub-system;

a second receiver operative to receive and process the received signal to provide data for a second position determination sub-system; and

a processing unit coupled to the first and second receivers and operative to obtain an accurate position estimate for the terminal based on the data for the first sub-system,

determine a residual for each of one or more transmitters in the second sub-system based in part on the accurate position estimate for the terminal,

obtain an actual measurement for each of a plurality of transmitters based on the data for the sub-system to which each transmitter belongs, wherein the plurality of transmitters include at least one transmitter in the second sub-system,

correct the actual measurement for each of the at least one transmitter in the second sub-system based on the residual for the transmitter, and

determine an updated position estimate for the terminal based on a plurality of measurements for the plurality of transmitters, wherein the plurality of measurements include at least one corrected measurement for the at least one transmitter in the second sub-system.

42. A wireless terminal in a wireless communication system, comprising:

a first receiver operative to receive and process a received signal to provide data for a first position determination sub-system;

a second receiver operative to receive and process the received signal to provide data for a second position determination sub-system; and

a processing unit coupled to the first and second receivers and operative to determine a position estimate for the terminal based on the first sub-system if the first sub-system is available,

determine the position estimate for the terminal based on the first and second sub-systems if the first sub-system is partially available, wherein an actual measurement for each transmitter in the second sub-system used to determine the position estimate is corrected based on a residual, if available, for the transmitter, and

determine the position estimate for the terminal based solely on the second sub-system if the first sub-system is unavailable, wherein the actual measurement for each of at least one transmitter in the second sub-system used to determine the position estimate is corrected based on the residual for the transmitter.

43. The terminal of claim 42, wherein the processing unit is further operative to

obtain an accurate position estimate for the terminal based on the first su-system, wherein the residual for each of one or more transmitters in the second sub-system is determined based in part on the accurate position estimate for the terminal.