Method and mobile station for determining a code phase

• US 20040125015A1
• Filed: 12/27/2002
• Published: 07/01/2004
• Est. Priority Date: 12/27/2002
• Status: Active Grant

• Current Assignee: CSR Technology Incorporated (Qualcomm, Inc.)
• Original Assignee: SiRF Technology Holdings Incorporated (Qualcomm, Inc.)
• Inventors: King, Thomas M., Geier, George J.
• Granted Patent: US 6,888,497 B2
• Time in Patent Office: Days
• US Class Current: 342/357.06
• CPC Class Codes: G01S 19/30 code related G01S19/246 takes precedence
• CPC Class Codes: G01S 5/0221 Receivers

Abstract

A method (500) and a mobile station (160) for determining a code phase are described herein. The mobile station (160) may generate a first auto correlation function (ACF) associated with correlation samples over a range of code phases corresponding to a line-of-sight signal. The mobile station (160) may generate a second ACF within the mobile station based on measured correlation samples over a range of code phases. The mobile station (160) may compare the first ACF to the second ACF to generate a code phase offset between the first and second ACFs. The mobile station (160) may adjust the first ACF to match the second ACF.

Claims

1. In a wireless communication system, a method for determining a code phase, the method comprising:

generating a first auto correlation function (ACF) within the mobile station, the first ACF being associated with correlation samples over a range of code phases corresponding to a line-of-sight signal;

generating a second ACF within the mobile station based on measured correlation samples over a range of code phases;

comparing the first ACF to the second ACF to generate a code phase offset between the first and second ACFs, the code phase offset having at least one code phase adjustment; and

adjusting the first ACF to match the second ACF.

2. The method of claim 1, wherein the step of generating a first ACF within the mobile station comprises generating an ideal ACF, the ideal ACF being one of an infinite-bandwidth triangular ACF curve, an one-size-fits-all (OSFA) ACF curve based on a bandwidth, and an OSFA ACF curve based on averaged measurements over a period of time.

3. The method of claim 1, wherein the step of adjusting the first ACF so that the at least one code phase adjustment exceeds a minimum threshold to determine the code phase comprises adjusting the first ACF so that the code phase offset exceeds a threshold to determine a code phase associated with one of a pseudo-range measurement and a time-of-arrival measurement.

4. The method of claim 1, wherein the step of adjusting the first ACF to match the second ACF comprises adjusting the first ACF to match the second ACF so that the at least one code phase adjustment exceeds a minimum threshold.

5. The method of claim 1, wherein the step of adjusting the first ACF to match the second ACF comprises adjusting the first ACF for a number of times to match the second ACF.

6. The method of claim 1, wherein the step of adjusting the first ACF to match the second ACF comprises providing at least one code phase adjustment to a first code phase to determine a second code phase, and wherein the first code phase corresponds to a peak magnitude associated with the second ACF.

7. The method of claim 1, wherein the step of adjusting the first ACF to match the second ACF comprises providing at least one magnitude adjustment to an initial peak to determine a code phase, and wherein the initial peak is a peak magnitude associated with the first ACF.

8. The method of claim 1, wherein step of adjusting the first ACF to matche the second ACF comprises:

determining a residual between the first and second ACFs at one of the plurality of measured correlation samples;

comparing the residual to a noise variance to generate a plurality of residual factors, each of the plurality of residual factors being associated with one of the plurality of measured correlation samples;

determining a weight factor from the plurality of residual factors;

deweighting a final code phase in response to the weight factor exceeding a first threshold, the final code phase being associated with a location calculation of the mobile station;

removing the final code phase from use in the location calculation in response to the weight factor exceeding a second threshold, the second threshold being greater than the first threshold; and

determining the code phase based on measured correlation samples over one of an interval less than the code phase interval and a range less than the range of code phases in response to the weight factor being greater than a third threshold.

9. The method of claim 1, wherein the communication system comprises one of a code division multiple access (CDMA) based communication system and a time division multiple access (TDMA) based communication system.

10. In a wireless communication system, a mobile station for determining a code phase, the mobile station comprising:

a receiving unit configured to measure correlations over a range of code phases;

a controller operatively coupled to the receiving unit, the controller having a memory and a processor operatively coupled to the memory,

the controller being programmed to generate a first auto correlation function (ACF) within the mobile station, the first ACF being associated with correlations over a range of code phases corresponding to a line-of-sight signal;

the controller being programmed to generate a second ACF within the mobile station based on measured correlation samples over a range of code phases;

the controller being programmed to compare the first ACF to the second ACF to generate a code phase offset between the first and second ACFs, the code phase offset having at least one code phase adjustment; and

the controller being programmed to adjust the first ACF to match the second ACF.

11. The mobile station of claim 10, wherein the receiving unit is a global positioning system (GPS) receiver.

12. The mobile station of claim 10, wherein the first ACF is an ideal ACF, the ideal ACF being one of an infinite-bandwidth triangular ACF curve, an one-size-fits-all (OSFA) ACF curve based on a bandwidth, an OSFA ACF curve based on averaged measurements over a period of time.

13. The mobile station of claim 10, wherein the code phase is associated with one of a pseudo-range measurement and a time-of-arrival measurement.

14. The mobile station of claim 10, wherein the controller is programmed to adjust the first ACF to match the second ACF so that the code phase adjustment exceeds a minimum threshold.

15. The mobile station of claim 10, wherein the controller is programmed to adjust the first ACF for a number of times to match the second ACF.

16. The mobile station of claim 10, wherein the controller is programmed to adjust the first ACF by providing one of a magnitude adjustment and a code phase adjustment.

17. The mobile station of claim 10, wherein the controller is programmed to determine a residual between the first and second ACFs at one of the plurality of measured correlation samples,

the controller is programmed to compare the residual to a noise variance to generate a plurality of residual factors associated with one of the plurality of measured correlation samples,

the controller is programmed to determine a weight factor from the plurality of residual factors,

the controller is programmed to deweight a final code phase in response to the weight factor exceeding a first threshold, the final code phase being associated with a location calculation of the mobile station,

the controller is programmed to remove the final code phase from use in the location calculation in response to the weight factor exceeding a second threshold, the second threshold being greater than the first threshold, and

the controller is programmed to determine the code phase based on measured correlation samples over one of an interval less than the code phase interval and a range less than the range of code phases in response to the weight factor being greater than a third threshold.

18. The mobile station of claim 10 is operable in accordance with one of a code division multiple access (CDMA) based communication system and a time division multiple access (TDMA) based communication system.

19. In a wireless communication system, wherein a processor operates in accordance with a computer program embodied on a computer-readable medium for determining a code phase, the computer program comprising:

a first routine that directs the processor to generate a first auto correlation function (ACF) within the mobile station, the first ACF being associated with correlation samples over a range of code phases corresponding to a line-of-sight signal;

a second routine that directs the processor to generate a second ACF within the mobile station based on measured correlation samples over a range of code phases;

a third routine that directs the processor to compare the first ACF to the second ACF to generate a code phase offset between the first and second ACFs, the code phase offset having at least one code phase adjustment; and

a fourth routine that directs the processor to adjust the first ACF to match the second ACF.

20. The computer program of claim 19, wherein the first routine comprises a routine that directs the processor to generate an ideal ACF, the ideal ACF being one of an infinite-bandwidth triangular ACF curve, an one-size-fits-all (OSFA) ACF curve based on a bandwidth, and an OSFA ACF curve based on averaged measurements over a period of time.

21. The computer program of claim 19, wherein the fourth routine comprises a routine that directs the processor to adjust the first ACF to match the second ACF so that the at least one code phase adjustment exceeds a minimum threshold to determine the code phase.

22. The computer program of claim 19, wherein the fourth routine comprises a routine that directs the processor to adjust the first ACF for a number to match the second ACF.

23. The computer program of claim 19, wherein the fourth routine comprises a routine that directs the processor to adjust the first ACF so that the code phase offset exceeds a threshold to determine the code phase associated with one of a pseudo-range measurement and a time-of-arrival measurement.

24. The computer program of claim 19, wherein the fourth routine comprises a routine that directs the processor to provide at least one code phase adjustment to a first code phase to determine a second code phase, and wherein the first code phase corresponds to a peak magnitude associated with the second ACF.

25. The computer program of claim 19, wherein the fourth routine comprises a routine that directs the processor to provide at least one magnitude adjustment to an initial peak to determine a code phase, and wherein the initial peak is the peak magnitude associated with the first ACF.

26. The computer program of claim 19, wherein the fourth routine comprises:

a routine that directs the processor to determine a residual between the first and second ACFs at one of the plurality of measured correlation samples,

a routine that directs the processor to compare the residual to a noise variance to generate a plurality of residual factors associated with one of the plurality of measured correlation samples,

a routine that directs the processor to determine a weight factor from the plurality of residual factors,

a routine that directs the processor to deweight a final code phase in response to the weight factor exceeding a first threshold, the final code phase being associated with a location calculation of the mobile station,

a routine that directs the processor to remove the final code phase from use in the location calculation in response to the weight factor exceeding a second threshold, the second threshold being greater than the first threshold, and

a routine that directs the processor to determine the code phase based on measured correlation samples over one of an interval less than the code phase interval and a range less than the range of code phases in response to the weight factor being greater than a third threshold.

27. The computer program of claim 19 is operable in accordance with one of a code division multiple access (CDMA) based communication protocol and a time division multiple access (TDMA) based communication protocol.

28. The computer program of claim 19, wherein the medium is one of paper, a programmable gate array, application specific integrated circuit, erasable programmable read only memory, read only memory, random access memory, magnetic media, and optical media.

29. In a wireless communication system, a device for determining a code phase, the device comprising:

a means for generating a first auto correlation function (ACF) within the mobile station, the first ACF being associated with correlation samples over a range of code phases corresponding to a line-of-sight signal;

a means for generating a second ACF within the mobile station based on measured correlation samples over a range of code phases;

a means for comparing the first ACF to the second ACF to generate a code phase offset between the first and second ACFs, the code phase offset having at least one code phase adjustment; and

a means for adjusting the first ACF to match the second ACF.

30. The device of claim 29, wherein the means for adjusting the first ACF to match the second ACF so that the at least one code phase adjustment exceeds a minimum threshold to determine the code phase.

31. The device of claim 29, wherein the means for adjusting the first ACF for a number of times to match the second ACF.

32. The device of claim 29, wherein the means for adjusting the first ACF to match the second ACF comprises a means for providing at least one code phase adjustment to a first code phase to determine a second code phase, and wherein the first code phase corresponds to a peak magnitude associated with the second ACF.

33. The device of claim 29, wherein the means for adjusting the first ACF to match the second ACF comprises a means for providing at least one magnitude adjustment to an initial peak to determine a code phase, and wherein the initial peak is a peak magnitude associated with the first ACF.

34. The device of claim 29, wherein the means for adjusting the first ACF to match the second ACF comprises:

a means for determining a residual between the first and second ACFs at one of the plurality of measured correlation samples;

a means for comparing the residual to a noise variance to generate a plurality of residual factors, each of the plurality of residual factors being associated with one of the plurality of measured correlation samples;

a means for determining a weight factor from the plurality of residual factors;

a means for deweighting a final code phase in response to the weight factor exceeding a first threshold, the final code phase being associated with a location calculation of the mobile station;

a means for removing the final code phase from use in the location calculation in response to the weight factor exceeding a second threshold, the second threshold being greater than the first threshold; and

a means for determining the code phase based on measured correlation samples over one of an interval less than the code phase interval and a range less than the range of code phases in response to the weight factor being greater than a third threshold.