Multipath assistance for pilot phase measurement processes

• US 6,999,778 B2
• Filed: 07/03/2002
• Issued: 02/14/2006
• Est. Priority Date: 07/03/2002
• Status: Active Grant

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: DiBuduo, Marcus
• Primary Examiner(s): Orgad, Edan
• Assistant Examiner(s): Gantt, Alan T.
• Application Number:
  US10/188,565
• Publication Number:
  US 20040203864A1
• Time in Patent Office: 1,322 Days
• Field of Search: 455/456.1, 455/12.1, 455/456.6, 455/427, 455/67.11, 455/423, 455/424, 455/65, 342/357.06
• US Class Current: 455/456.1
• CPC Class Codes: H04W 48/20 Selecting an access point
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management

Abstract

A method for enhancing the accuracy of Advanced Forward Link Trilateration (AFLT) position location calculations is disclosed. A position determination entity (PDE) constructs a statistical database of pilot phase measurements reported by mobile stations (MSs) located in a geographic region about a reference base station (BS). When a MS'"'"'s location is to be calculated, the MS reports a set of PN phase offsets to the PDE. Using only that set of PN phase offsets, the PDE determines a rough estimate of the MS'"'"'s location using conventional AFLT and also determines the region within which the MS is located. If the PDE determines that the MS did not report one or more earlier arriving PN phase offsets but reported a delayed multipath component, the PDE sends a message to the MS to look for an earlier arriving PN phase offset at a certain time prior to the reported PN phase offset.

Claims

1. In a system comprising a mobile station (MS) and a network of base stations (BSs) communicatively couplable to the MS for establishing connections and maintaining communication channels between them, one or more of the BSs capable of transmitting a unique pilot signal and being used as a reference BS, the MS capable of selecting one of the BSs as the reference BS for use as a timing reference and measuring pseudo-noise (PN) phase offsets for the pilot signals transmitted from non-reference BSs, a method of generating pilot phase measurements (PPMs) for reporting PN phase offsets, comprising:

measuring a first PN phase offset of a pilot signal transmitted from a non-reference BS and received at the MS, and reporting the first PN phase offset in a first PPM;

predicting whether the first PN phase offset is an optimal path PN phase offset; and

if the first PN phase offset is not predicted to be the optimal path PN phase offset, providing the MS with information regarding PN phase offsets for a next measurement, re-measuring the PN phase offset at the MS in accordance with the information, and reporting one or more improved path PN phase offsets in a second PPM.

2. The method as recited in claim 1, further comprising:

for each BS in the network capable of being used as a reference BS, defining one or more regions around and associated with each BS;

for each of the one or more regions,

compiling a statistical database of previously reported PN phase offsets from MSs whose locations are estimated to be within the region and that utilize the BS associated with the region as their reference BS, wherein the compiled statistical database is determined to contain one or more peaks, each peak resulting from a compilation of previously reported and similarly timed PN phase offsets,

identifying one or more groups of peaks from within the compiled statistical database for the region, each identified group of peaks corresponding to the previously reported PN phase offsets of the pilot signals transmitted by a specific non-reference BS, and

for each identified group of peaks, selecting one of the peaks as representing the optimal path PN phase offset for the specific non-reference BS associated with that group of peaks, and selecting one or more of the peaks as representing the one or more improved path PN phase offsets for the specific non-reference BS associated with that group of peaks;

estimating a location of the MS using PN phase offsets previously reported by the MS;

identifying the compiled statistical database corresponding to the region encompassing the estimated location of the MS;

identifying the group of peaks from within the identified compiled statistical database corresponding to the non-reference BS associated with the first PN phase offset; and

predicting whether the first PN phase offset is the optimal path PN phase offset by determining whether the first PN phase offset favorably compares to the peak representing the optimal path PN phase offset from within the identified group of peaks.

3. The method as recited in claim 2, further comprising providing the MS with information for locating the one or more improved path PN phase offsets by:

calculating one or more time differences between the first PN phase offset and the one or more improved path PN phase offsets within the identified group of peaks; and

providing the MS with the one or more time differences to assist the MS in locating and measuring the one or more improved path PN phase offsets.

4. The method as recited in claim 2, further comprising providing the MS with information for locating the one or more improved path PN phase offsets by:

calculating one or more time differences between a reference PN phase offset from the reference BS and the one or more improved path PN phase offsets within the identified group of peaks; and

providing the MS with the one or more time differences to assist the MS in locating and measuring the one or more improved path PN phase offsets.

5. The method as recited in claim 2, wherein if the MS is provided with the information for locating the one or more improved path PN phase offsets, the method further comprises:

locating and measuring a second PN phase offset of a pilot signal received at the MS from a non-reference BS using the information for locating the one or more improved path PN phase offsets; and

reporting the second PN phase offset in a second PPM.

6. The method as recited in claim 5, wherein if the second PN phase offset is reported in the second PPM, the method further comprises predicting whether the second PN phase offset corresponds to one of the improved path PN phase offsets by determining whether the second PN phase offset favorably compares to one of the peaks representing one of the improved path PN phase offsets from within the identified group of peaks.

7. The method as recited in claim 2, wherein if the first PN phase offset is predicted to be the optimal path PN phase offset, the method further comprises utilizing the first PN phase offset in Advanced Forward Link Trilateration (AFLT) position location calculations to assist in determining the location of the MS.

8. The method as recited in claim 6, wherein if the second PN phase offset is predicted to be one of the improved path PN phase offsets, the method further comprises utilizing the second PN phase offset in Advanced Forward Link Trilateration (AFLT) position location calculations to assist in determining a location of the MS.

9. The method as recited in claim 2, wherein for each identified group of peaks in each of the one or more regions, the method further comprises identifying an earliest arriving peak as representing the optimal path PN phase offset for the specific non-reference BS associated with that group of peaks.

10. The method as recited in claim 2, wherein for each identified group of peaks in each of the one or more regions, the method further comprises identifying an earliest arriving peak having an amplitude above a predetermined threshold as representing the optimal path PN phase offset for the specific non-reference BS associated with that group of peaks.

11. The method as recited in claim 2, wherein for each identified group of peaks in each of the one or more regions, the method further comprises identifying those peaks having an earlier arrival time than the first PN phase offset as representing the one or more improved path PN phase offsets for the specific non-reference BS associated with that group of peaks.

12. The method as recited in claim 11, further comprising providing the MS with information for locating the one or more improved path PN phase offsets by:

calculating one or more time differences between the first PN phase offset and the one or more improved path PN phase offsets within the identified group of peaks; and

providing the MS with a prioritized sequence of the one or more time differences to assist the MS in locating and measuring the one or more improved path PN phase offsets.

13. The method as recited in claim 2, further comprising:

including an amplitude value in the compiled statistical database for each of the one or more peaks in each of the one or more regions; and

identifying those peaks having an earlier arrival time than the first PN phase offset and having an amplitude value above a predetermined threshold as representing the one or more improved path PN phase offsets for the specific non-reference BS associated with that group of peaks.

14. The method as recited in claim 13, each amplitude value representing a frequency of occurrence of the PN phase offsets associated with each peak.

15. The method as recited in claim 13, each amplitude value representing an average pilot energy of the PN phase offsets associated with each peak.

16. The method as recited in claim 13, each amplitude value representing an combination of a frequency of occurrence and an average pilot energy of the PN phase offsets associated with each peak.

17. The method as recited in claim 13, further comprising providing the MS with information for locating the one or more improved path PN phase offsets by:

calculating one or more time differences between the first PN phase offset and the one or more improved path PN phase offsets;

creating a prioritized sequence of the one or more time differences for the one or more improved path PN phase offsets in descending order according to the amplitude value of the peak associated with each improved path PN phase offset; and

providing the MS with the prioritized sequence of the one or more time differences to assist the MS in locating and measuring the one or more improved path PN phase offsets.

18. The method as recited in claim 2, further comprising defining the one or more regions around each BS such that any MSs within the same region that utilize the BS associated with the region as their reference BS will report similar PN phase offsets, while any two MSs in different regions that utilize the BS associated with the region as their reference BS will report different PN phase offsets.

19. The method as recited in claim 2, wherein the statistical database is compiled using a predetermined number of most recently reported PN phase measurements.

20. In a system comprising a mobile station (MS) and a network of base stations (BSs) communicatively couplable to the MS for establishing connections and maintaining communication channels between them, one or more of the BSs capable of transmitting a unique pilot signal and being used as a reference BS, the MS capable of selecting one of the BSs as the reference BS for use as a timing reference and measuring pseudo-noise (PN) phase offsets for the pilot signals transmitted from non-reference BSs, a position determination entity (PDE) for assisting in MS generation of pilot phase measurements (PPMs) for reporting PN phase offsets, comprising:

a PDE processor programmed for

receiving a first PN phase offset of a pilot signal transmitted from a non-refrence BS and received at the MS in a first PPM,

predicting whether the first PN phase offset is an optimal path PN phase offset, and

if the first PN phase offset is not predicted to be the optimal path PN phase offset, providing the MS with information regarding PN phase offsets for a next measurement so that MS can re-measure the PN phase offset in accordance with the information, and reporting one or more improved path PN phase offsets in a second PPM.

21. The PDE as recited in claim 20, the PDE processor further programmed for:

defining one or more regions around and associated with each BS in the network capable of being used as a reference BS;

for each of the one or more regions,

compiling a statistical database of previously reported PN phase offsets from MSs whose locations are estimated to be within the region and that utilize the BS associated with the region as their reference BS, wherein the compiled statistical database is determined to contain one or more peaks, each peak resulting from a compilation of previously reported and similarly timed PN phase offsets,

identifying one or more groups of peaks from within the compiled statistical database for the region, each identified group of peaks corresponding to the previously reported PN phase offsets of the pilot signals transmitted by a specific non-reference BS, and

for each identified group of peaks, selecting one of the peaks as representing the optimal path PN phase offset for the specific non-reference BS associated with that group of peaks, and selecting one or more of the peaks as representing the one or more improved path PN phase offsets for the specific non-reference BS associated with that group of peaks;

estimating a location of the MS using PN phase offsets previously reported by the MS;

identifying the compiled statistical database corresponding to the region encompassing the estimated location of the MS;

identifying the group of peaks from within the identified compiled statistical database corresponding to the non-reference BS associated with the first PN phase offset; and

predicting whether the first PN phase offset is the optimal path PN phase offset by determining whether the first PN phase offset favorably compares to the peak representing the optimal path PN phase offset from within the identified group of peaks.

22. The PDE as recited in claim 21, the PDE processor further programmed for providing the MS with information for locating the one or more improved path PN phase offsets by:

calculating one or more time differences between the first PN phase offset and the one or more improved path PN phase offsets within the identified group of peaks; and

providing the MS with the one or more time differences to assist the MS in locating and measuring the one or more improved path PN phase offsets.

23. The PDE as recited in claim 21, the PDE processor further programmed for providing the MS with information for locating the one or more improved path PN phase offsets by:

calculating one or more time differences between a reference PN phase offset from the reference BS and the one or more improved path PN phase offsets within the identified group of peaks; and

providing the MS with the one or more time differences to assist the MS in locating and measuring the one or more improved path PN phase offsets.

24. The PDE as recited in claim 21, the PDE processor further programmed for:

receiving a second PN phase offset of a pilot signal received at the MS from a non-refrence BS in a second PPM if the PDE provided the MS with the information for locating the one or more improved path PN phase offsets; and

predicting whether the second PN phase offset corresponds to one of the improved path PN phase offsets by determining whether the second PN phase offset favorably compares to one of the peaks representing one of the improved path PN phase offsets from within the identified group of peaks.

25. The PDE as recited in claim 21, wherein if the first PN phase offset is predicted to be the optimal path PN phase offset, the PDE processor is further programmed for utilizing the first PN phase offset in Advanced Forward Link Trilateration (AFLT) position location calculations to assist in determining the location of the MS.

26. The PDE as recited in claim 24, wherein if the second PN phase offset is predicted to be one of the improved path PN phase offsets, the PDE processor is further programmed for utilizing the second PN phase offset in Advanced Forward Link Trilateration (AFLT) position location calculations to assist in determining a location of the MS.

27. The PDE as recited in claim 21, wherein for each identified group of peaks in each of the one or more regions, the PDE processor is further programmed for identifying an earliest arriving peak as representing the optimal path PN phase offset for the specific non-reference BS associated with that group of peaks.

28. The PDE as recited in claim 21, wherein for each identified group of peaks in each of the one or more regions, the PDE processor is further programmed for identifying an earliest arriving peak having an amplitude above a predetermined threshold as representing the optimal path PN phase offset for the specific non-reference BS associated with that group of peaks.

29. The PDE as recited in claim 21, wherein for each identified group of peaks in each of the one or more regions, the PDE processor is further programmed for identifying those peaks having an earlier arrival time than the first PN phase offset as representing the one or more improved path PN phase offsets for the specific non-reference BS associated with that group of peaks.

30. The PDE as recited in claim 29, the PDE processor further programmed for providing the MS with information for locating the one or more improved path PN phase offsets by:

calculating one or more time differences between the first PN phase offset and the one or more improved path PN phase offsets within the identified group of peaks; and

providing the MS with a prioritized sequence of the one or more time differences to assist the MS in locating and measuring the one or more improved path PN phase offsets.

31. The PDE as recited in claim 21, the PDE processor further programmed for:

including an amplitude value in the compiled statistical database for each of the one or more peaks in each of the one or more regions; and

identifying those peaks having an earlier arrival time than the first PN phase offset and having an amplitude value above a predetermined threshold as representing the one or more improved path PN phase offsets for the specific non-reference BS associated with that group of peaks.

32. The method as recited in claim 31, each amplitude value representing a frequency of occurrence of the PN phase offsets associated with each peak.

33. The method as recited in claim 31, each amplitude value representing an average pilot energy of the PN phase offsets associated with each peak.

34. The method as recited in claim 31, each amplitude value representing an combination of a frequency of occurrence and an average pilot energy of the PN phase offsets associated with each peak.

35. The PDE as recited in claim 31, the PDE processor further programmed for providing the MS with information for locating the one or more improved path PN phase offsets by:

calculating one or more time differences between the first PN phase offset and the one or more improved path PN phase offsets;

creating a prioritized sequence of the one or more time differences for the one or more improved path PN phase offsets in descending order according to the amplitude value of the peak associated with each improved path PN phase offset; and

providing the MS with the prioritized sequence of the one or more time differences to assist the MS in locating and measuring the one or more improved path PN phase offsets.

36. The PDE as recited in claim 21, the PDE processor further programmed for defining the one or more regions around each BS such that any MSs within the same region that utilize the BS associated with the region as their reference BS will report similar PN phase offsets, while any two MSs in different regions that utilize the BS associated with the region as their reference BS will report different PN phase offsets.

37. The PDE as recited in claim 21, wherein the statistical database is compiled using a predetermined number of most recently reported PN phase measurements.