Procedure for searching for position determination signals using a plurality of search modes

• US 8,473,205 B2
• Filed: 12/02/2004
• Issued: 06/25/2013
• Est. Priority Date: 10/22/2002
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Rowitch, Douglas N., Patrick, Christopher
• Primary Examiner(s): Tran, Khoi
• Assistant Examiner(s): PECHE, JORGE O
• Application Number:
  US11/004,313
• Publication Number:
  US 20050101272A1
• Time in Patent Office: 3,127 Days
• Field of Search: 701/213, 701/207, 701/214, 342/357.12, 342/357.2, 342/357.49, 342/429
• US Class Current: 701/468
• CPC Class Codes: G01S 19/24 Acquisition or tracking or demodulation of signals transmitted by the system synchronisation aspects of direct sequence spread spectrum modulation H04B1/7073
• CPC Class Codes: G01S 19/25 involving aiding data received from a cooperating element, e.g. assisted GPS
• CPC Class Codes: G01S 19/28 Satellite selection
• CPC Class Codes: G01S 19/29 carrier including Doppler, related G01S19/246 takes precedence
• CPC Class Codes: H04B 1/70754 Setting of search window, i.e. range of code offsets to be searched H04B1/70758 takes precedence
• CPC Class Codes: H04B 1/7077 Multi-step acquisition, e.g. multi-dwell, coarse-fine or validation

Abstract

A method of and system for searching for position determination signals using a plurality of progressively more sensitive search modes comprising a first level mode, a second mode, and at least one higher level mode. If any of the search window parameters exceed prescribed limits, a first level search is performed, and the search window parameters are refined responsive to the ensuing search results so they are within the prescribed limits. Then, the second level search is performed, and measurements derived from the ensuing search results. If the measurements satisfy selected measurement sufficiency criteria, additional searching within the position fix attempt is avoided. If the measurements do not satisfy the selected measurement sufficiency criteria, a higher level, more sensitive search is performed.

Claims

1. A method of searching for position determination signals using a plurality of progressively more sensitive search modes with sensitivity levels that are characterized by their respective integration periods and which plurality comprises, in order of increasing sensitivity, a first level mode, a second level mode, and a third level mode, the method comprising:

performing, on a wireless subscriber station, a first level search associated with a first integration period as part of a position fix attempt of the wireless subscriber station;

deriving, on the wireless subscriber station, one or more measurements from the ensuing search results;

determining, on the wireless subscriber station, whether the measurements satisfy one or more selected measurement sufficiency criteria;

avoiding additional searching within the position fix attempt if the wireless subscriber station determines that the measurements satisfy the one or more selected measurement sufficiency criteria; and

performing, on the wireless subscriber station, a higher level search beyond the first level search if the wireless subscriber station determines that the measurements do not satisfy the one or more selected measurement sufficiency criteria, wherein;

the higher level search is a second level search if a number of space vehicles in a first set exceeds a threshold number or an estimated time to perform a third level search on a number of space vehicles in a second set exceeds a maximum time remaining in the position fix attempt,

the higher level search is the third level search if the number of space vehicles in the first set does not exceed the threshold number and the estimated time to perform the third level search on the number of space vehicles in the second set does not exceed the maximum time remaining in the position fix attempt,

the second level search is associated with a second integration period that is longer than the first integration period, and

the third level search is associated with a third integration period that is longer than the second integration period.

2. The method of claim 1 further comprising discarding those measurements from the higher level search which are determined to be cross-correlations of the measurements from the first level search.

3. The method of claim 2 wherein the measurements from the higher level search are discarded at run time in favor of other measurements which better represent a space vehicle.

4. The method of claim 1, wherein performing the higher level search comprises:

comparing the number of space vehicles in the first set to the threshold number if the wireless subscriber station determines that the measurements do not satisfy the one or more selected measurement sufficiency criteria; and

performing the second level search if the number of space vehicles in the first set exceeds the threshold number.

5. The method of claim 4, wherein performing the higher level search further comprises:

comparing the estimated time to perform the third level search on the number of space vehicles in the second set to the maximum time remaining in the position fix attempt if the number of space vehicles in the first set does not exceed the threshold number;

performing the second level search if the estimated time to perform the third level search on the number of space vehicles in the second set exceeds the maximum time remaining in the position fix attempt; and

performing the third level search if the estimated time to perform the third level search on the number of space vehicles in the second set does not exceed the maximum time remaining in the position fix attempt.

6. The method of claim 1, wherein the first set comprises space vehicles used in the first level search that exceed a first noise threshold, the second set comprises space vehicles that are likely visible to the wireless subscriber station and excludes space vehicles used in the first level search that exceed a second noise threshold, and the second noise threshold is stronger than the first noise threshold.

7. A method of searching for position determination signals using a plurality of progressively more sensitive search modes with sensitivity levels that are characterized by their respective integration periods and which plurality comprises, in order of increasing sensitivity, a first level mode, a second level mode, and a third level mode, the method comprising:

a step for performing, on a wireless subscriber station, a first level search associated with a first integration period as part of a position fix attempt of the wireless subscriber station;

a step for deriving, on the wireless subscriber station, one or more measurements from the ensuing search results;

a step for determining, on the wireless subscriber station, whether the measurements satisfy one or more selected measurement sufficiency criteria;

a step for avoiding additional searching within the position fix attempt if the wireless subscriber station determines that the measurements satisfy the one or more selected measurement sufficiency criteria; and

a step for performing, on the wireless subscriber station, a higher level search beyond the first level search if the wireless subscriber station determines that the measurements do not satisfy the one or more selected measurement sufficiency criteria, wherein;

the higher level search is a second level search if a number of space vehicles in a first set exceeds a threshold number or an estimated time to perform a third level search on a number of space vehicles in a second set exceeds a maximum time remaining in the position fix attempt,

the higher level search is the third level if the number of space vehicles in the first set does not exceed the threshold number and the estimated time to perform the third level search on the number of space vehicles in the second set does not exceed the maximum time remaining in the position fix attempt,

the second level search is associated with a second integration period that is longer than the first integration period, and

the third level search is associated with a third integration period that is longer than the second integration period.

8. The method of claim 7 further comprising a step for discarding those measurements from the higher level search which are determined to be cross-correlations of the measurements from the first level search.

9. The method of claim 8 wherein the measurements from the higher level search are discarded at run time in favor of other measurements which better represent a space vehicle.

10. The method of claim 7, wherein the step for performing the higher level search comprises:

a step for comparing the number of space vehicles in the first set to the threshold number if the wireless subscriber station determines that the measurements do not satisfy the one or more selected measurement sufficiency criteria; and

a step for performing the second level search if the number of space vehicles in the first set exceeds the threshold number.

11. The method of claim 10, wherein the step for performing the higher level search comprises:

a step for comparing the estimated time to perform the third level search on the number of space vehicles in the second set to the maximum time remaining in the position fix attempt if the number of space vehicles in the first set does not exceed the threshold number;

a step for performing the second level search if the estimated time to perform the third level search on the number of space vehicles in the second set exceeds the maximum time remaining in the position fix attempt; and

a step for performing the third level search if the estimated time to perform the third level search on the number of space vehicles in the second set does not exceed the maximum time remaining in the position fix attempt.

12. The method of claim 7, wherein the first set comprises space vehicles used in the first level search that exceed a first noise threshold, the second set comprises space vehicles that are likely visible to the wireless subscriber station and excludes space vehicles used in the first level search that exceed a second noise threshold, and the second noise threshold is stronger than the first noise threshold.

13. A non-transitory memory embodying executable instructions that enable a processor and correlator to:

perform a first level search associated with a first integration period as part of a position fix attempt;

derive one or more measurements from the ensuing search results;

determine whether the measurements satisfy one or more selected measurement sufficiency criteria;

avoid additional searching within the position fix attempt if the measurements satisfy one or more selected measurement sufficiency criteria; and

perform a higher level search beyond the first level search if the measurements do not satisfy the one or more selected measurement sufficiency criteria, wherein;

the higher level search is a second level search if a number of space vehicles in a first set exceeds a threshold number or an estimated time to perform a third level search on a number of space vehicles in a second set exceeds a maximum time remaining in the position fix attempt,

the higher level search is the third level search if the number of space vehicles in the first set does not exceed the threshold number and the estimated time to perform the third level search on the number of space vehicles in the second set does not exceed the maximum time remaining in the position fix attempt,

the second level search is associated with a second integration period that is longer than the first integration period,

the third level search is associated with a third integration period that is longer than the second integration period, and

the first, second and third integration periods function to provide each of the first, second and third level searches, respectively, with different levels of search sensitivity.

14. The memory of claim 13, wherein the executable instructions that enable the processor and the correlator to perform the higher level search further enable the processor and the correlator to:

compare the number of space vehicles in the first set to the threshold number if the wireless subscriber station determines that the measurements do not satisfy the one or more selected measurement sufficiency criteria; and

perform the second level search if the number of space vehicles in the first set exceeds the threshold number.

15. The memory of claim 14, wherein the executable instructions that enable the processor and the correlator to perform the higher level search further enable the processor and the correlator to:

compare the estimated time to perform the third level search on the number of space vehicles in the second set to the maximum time remaining in the position fix attempt if the number of space vehicles in the first set does not exceed the threshold number;

perform the second level search if the estimated time to perform the third level search on the number of space vehicles in the second set exceeds the maximum time remaining in the position fix attempt; and

perform the third level search if the estimated time to perform the third level search on the number of space vehicles in the second set does not exceed the maximum time remaining in the position fix attempt.

16. The memory of claim 13, wherein the first set comprises space vehicles used in the first level search that exceed a first noise threshold, the second set comprises space vehicles that are likely visible to the wireless subscriber station and excludes space vehicles used in the first level search that exceed a second noise threshold, and the second noise threshold is stronger than the first noise threshold.

17. A device including, a processor, a correlator, and a memory, wherein the processor is configured to access software instructions stored in the memory, the processor and correlator in combination for performing the software instructions, the memory embodying executable instructions to:

perform a first level search associated with a first integration period as part of a position fix attempt;

derive one or more measurements from the ensuing search results;

determine whether the measurements satisfy one or more selected measurement sufficiency criteria;

avoid additional searching within the position fix attempt if the measurements satisfy one or more selected measurement sufficiency criteria; and

perform a higher level search beyond the first level search if the measurements do not satisfy the one or more selected measurement sufficiency criteria, wherein;

the higher level search is a second level search if a number of space vehicles in a first set exceeds a threshold number or an estimated time to perform a third level search on a number of space vehicles in a second set exceeds a maximum time remaining in the position fix attempt,

the higher level search is the third level search if the number of space vehicles in the first set does not exceed the threshold number and the estimated time to perform the third level search on the number of space vehicles in the second set does not exceed the maximum time remaining in the position fix attempt,

the second level search is associated with a second integration period that is longer than the first integration period,

the third level search is associated with a third integration period that is longer than the second integration period, and

the first, second and third integration periods function to provide each of the first, second and third level searches, respectively, with different levels of search sensitivity.

18. The device of claim 17, wherein the executable instructions to perform the higher level search comprises executable instructions to:

compare the number of space vehicles in the first set to the threshold number if the wireless subscriber station determines that the measurements do not satisfy the one or more selected measurement sufficiency criteria; and

perform the second level search if the number of space vehicles in the first set exceeds the threshold number.

19. The device of claim 18, wherein the executable instructions to perform the higher level search further comprises executable instructions to:

compare the estimated time to perform the third level search on the number of space vehicles in the second set to the maximum time remaining in the position fix attempt if the number of space vehicles in the first set does not exceed the threshold number;

perform the second level search if the estimated time to perform the third level search on the number of space vehicles in the second set exceeds the maximum time remaining in the position fix attempt; and

perform the third level search if the estimated time to perform the third level search on the number of space vehicles in the second set does not exceed the maximum time remaining in the position fix attempt.

20. The device of claim 17, wherein the first set comprises space vehicles used in the first level search that exceed a first noise threshold, the second set comprises space vehicles that are likely visible to the wireless subscriber station and excludes space vehicles used in the first level search that exceed a second noise threshold, and the second noise threshold is stronger than the first noise threshold.

21. A non-transitory device including memory embodying executable instructions that enable a processor and correlator to search for position determination signals using a plurality of progressively more sensitive search modes with sensitivity levels that are characterized by their respective integration periods and which plurality comprises, in order of increasing sensitivity, a first level mode, a second level mode, and a third level mode, comprising:

means for performing a first level search associated with a first integration period as part of a position fix attempt;

means for deriving one or more measurements from the ensuing search results;

means for determining whether the measurements satisfy one or more selected measurement sufficiency criteria;

means for avoiding additional searching within the position fix attempt if the measurements satisfy the one or more selected measurement sufficiency criteria; and

means for performing a higher level search beyond the first level search if the measurements do not satisfy the one or more selected measurement sufficiency criteria, wherein;

the higher level search is a second level search if a number of space vehicles in a first set exceeds a threshold number or an estimated time to perform a third level search on a number of space vehicles in a second set exceeds a maximum time remaining in the position fix attempt,

the higher level search is the third level search if the number of space vehicles in the first set does not exceed the threshold number and the estimated time to perform the third level search on the number of space vehicles in the second set does not exceed the maximum time remaining in the position fix attempt,

the second level search is associated with a second integration period that is longer than the first integration period, and

the third level search is associated with a third integration period that is longer than the second integration period.

22. The device of claim 21 further comprising:

means for discarding those measurements from the higher level search which are determined to be cross-correlations of the measurements from the first level search.

23. The device of claim 22 wherein the means for discarding discards the measurements from the higher level search at run time in favor of other measurements which better represent a space vehicle.

24. The device of claim 21, wherein the means for performing the higher level search comprises:

means for comparing the number of space vehicles in the first set to the threshold number if the wireless subscriber station determines that the measurements do not satisfy the one or more selected measurement sufficiency criteria; and

means for performing the second level search if the number of space vehicles in the first set exceeds the threshold number.

25. The device of claim 24, wherein the means for performing the higher level search further comprises:

means for comparing the estimated time to perform the third level search on the number of space vehicles in the second set to the maximum time remaining in the position fix attempt if the number of space vehicles in the first set does not exceed the threshold number;

means for performing the second level search if the estimated time to perform the third level search on the number of space vehicles in the second set exceeds the maximum time remaining in the position fix attempt; and

means for performing the third level search if the estimated time to perform the third level search on the number of space vehicles in the second set does not exceed the maximum time remaining in the position fix attempt.

26. The device of claim 21, wherein the first set comprises space vehicles used in the first level search that exceed a first noise threshold, the second set comprises space vehicles that are likely visible to the wireless subscriber station and excludes space vehicles used in the first level search that exceed a second noise threshold, and the second noise threshold is stronger than the first noise threshold.