Prioritizing satellite search order based on doppler uncertainty

• US 6,642,886 B2
• Filed: 04/09/2002
• Issued: 11/04/2003
• Est. Priority Date: 02/22/2001
• Status: Expired due to Fees

• Current Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: King, Thomas Michael
• Primary Examiner(s): Issing, Gregory C.
• Application Number:
  US10/119,247
• Publication Number:
  US 20020113732A1
• Time in Patent Office: 574 Days
• Field of Search: 342/357.15, 342/357.06
• US Class Current: 342/357.67
• 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: G01S 19/37 Hardware or software details of the signal processing chain

Abstract

A method and apparatus for determining position in a GPS receiver (FIG. 4) is provided according to the invention. The apparatus includes a first switch (402), the first switch (402) receiving a digital GPS data, a first memory (409), a second memory (410) in parallel with the first memory, with the first memory and the second memory selectable by the first switch (402) for filling with the digital GPS data, and a second switch (416) selectable between the first memory (409) and the second memory (410) in order to extract the digital GPS data therefrom, wherein DSP signal processing (140) extracts digital GPS data from the first memory (409) while the second memory (410) is being filled and extracts digital GPS data from the second memory (410) while the first memory is being filled, and wherein the first memory (409) and the second memory (410) allow the digital GPS data to be processed in real time.

Claims

1. A method in a mobile satellite positioning system receiver, the method comprising:

determining Doppler uncertainty for a plurality of satellites by identifying a range of Doppler frequencies for at least one of the plurality of satellites that is less than a maximum possible range of Doppler frequencies; and

prioritizing satellite search order based upon the Doppler uncertainty for the plurality of satellites.

2. The method of claim 1, determining the Doppler uncertainty for the plurality of satellites based upon at least one of an initial position estimate, an initial position uncertainty, a time estimate, a time uncertainty, an oscillator frequency estimate, and an oscillator frequency uncertainty of the mobile satellite positioning system receiver.

3. The method of claim 1, searching for a second satellite having a Doppler uncertainty that is less than the determined Doppler uncertainty of other satellites not searched.

4. The method of claim 3, determining Doppler uncertainty of the satellites not searched based upon the Doppler frequency of the first and second satellites.

5. The method of claim 3, searching for a third satellite having a third least Doppler uncertainty.

6. The method of claim 1,

acquiring a first satellite of the plurality of satellites, the first satellite of the plurality of satellites having a Doppler uncertainty that is less than the Doppler uncertainty of other satellites of the plurality of satellites;

determining Doppler frequency of the first satellite; and

re-determining Doppler uncertainty of the other satellites of the plurality of satellites based upon the Doppler frequency of the first satellite.

7. The method of claim 6, re-prioritizing satellite search order based upon the re-determined Doppler uncertainty of the other satellites of the plurality of satellites.

8. The method of claim 1, determining the Doppler uncertainty for the plurality of satellites based upon satellite data including at least one of ephemeris and almanac data.

9. The method of claim 8, prioritizing satellite search order based upon the Doppler uncertainty for the plurality of satellites by updating at least one of an initial position estimate, an initial position uncertainty, a time estimate, a time uncertainty, an oscillator frequency estimate, and an oscillator frequency uncertainty of the mobile satellite positioning system receiver.