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

• US 20050101272A1
• Filed: 12/02/2004
• Published: 05/12/2005
• Est. Priority Date: 10/22/2002
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Patrick, Christopher, Rowitch, Douglas N.
• Granted Patent: US 8,473,205 B2
• Time in Patent Office: Days
• US Class Current: 455/161.200
• 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 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 a first level search as part of a position fix attempt;

deriving one or more measurements from the ensuing search results;

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

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

performing a higher level search beyond the first level if the measurements do not satisfy the one or more selected measurement sufficiency criteria, wherein the higher level search is either a second level or a third level search based on one or more prescribed selection criteria.

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 are discarded at run time in favor of other measurements which better represent an SV.

4. A method of searching for position determination signals using a plurality of progressively more sensitive search modes 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 a first level search as part of a position fix attempt;

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

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

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

a step for performing a higher level search beyond the first level if the measurements do not satisfy the one or more selected measurement sufficiency criteria, wherein the higher level search is either a second level or a third level search based on one or more prescribed selection criteria.

5. The method of claim 4 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.

6. The method of claim 5 wherein the measurements are discarded at run time in favor of other measurements which better represent an SV.

7. A memory embodying executable instructions that enable a processor and correlator in combination to:

determine whether any search window parameters exceed prescribed limits;

perform a first level search if any search window parameters exceed prescribed limits, and refining the search window parameters responsive thereto so they are within the prescribed limits;

perform a second level search 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 the one or more selected measurement sufficiency criteria; and

perform a higher level search beyond the second level if the measurements do not satisfy the one or more selected measurement sufficiency criteria.

8. A memory embodying executable instructions that enable a processor and correlator in combination to:

determine whether any search window parameters exceed prescribed limits;

perform a first level search if any search window parameters exceed prescribed limits, and refining the search window parameters responsive thereto so they are within the prescribed limits;

perform a second level search 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 the one or more selected measurement sufficiency criteria; and

perform a higher level search beyond the second level if the measurements do not satisfy the one or more selected measurement sufficiency criteria, wherein the higher level search is either a third level or a fourth level search based on one or more prescribed selection criteria.

9. In combination, 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:

determine whether any search window parameters exceed prescribed limits;

perform a first level search if any search window parameters exceed prescribed limits, and refining the search window parameters responsive thereto so they are within the prescribed limits;

perform a second level search 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 the one or more selected measurement sufficiency criteria; and

perform a higher level search beyond the second level if the measurements do not satisfy the one or more selected measurement sufficiency criteria.

10. In combination, 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:

determine whether any search window parameters exceed prescribed limits;

perform a first level search if any search window parameters exceed prescribed limits, and refining the search window parameters responsive thereto so they are within the prescribed limits;

perform a second level search 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 the one or more selected measurement sufficiency criteria; and

perform a higher level search beyond the second level if the measurements do not satisfy the one or more selected measurement sufficiency criteria, wherein the higher level search is either a third level or a fourth level search based on one or more prescribed selection criteria.