PVT optimization architecture for always-on GPS receivers

• US 7,538,726 B1
• Filed: 04/10/2007
• Issued: 05/26/2009
• Est. Priority Date: 04/10/2007
• Status: Active Grant

• Current Assignee: U-Blox AG (u-blox Holding AG)
• Original Assignee: AIR Semiconductor Ltd.
• Inventors: Tester, David P., Wise, Adrian P.
• Primary Examiner(s): Tarcza; Thomas H
• Assistant Examiner(s): Nguyen; Nga X
• Application Number:
  US11/733,270
• Time in Patent Office: 777 Days
• Field of Search: 34235701-35717
• US Class Current: 342/357.29
• CPC Class Codes: G01S 19/05 providing aiding data
• CPC Class Codes: G01S 19/258 relating to the satellite constellation, e.g. almanac, ephemeris data, lists of satellites in view
• CPC Class Codes: G01S 19/28 Satellite selection
• CPC Class Codes: G01S 19/34 Power consumption
• CPC Class Codes: G01S 19/46 the supplementary measurement being of a radio-wave signal type

Abstract

A method to reduce power consumption in a device is disclosed. The method generally includes the steps of (A) generating a plurality of pseudorange signals by tracking a plurality of position signals received from a plurality of satellites in a positioning system, at least one of the position signals from each one of the satellites respectively, (B) calculating both an initial position and an initial time bias from the pseudorange signals using a processing capability of the device at a normal capacity and (C) calculating both an updated position and an updated time bias using the processing capability reduced to a first capacity, wherein the first capacity (i) consumes less power than the normal capacity and (ii) is suitable to process the updated position and the updated time bias using a limited number comprising less than all of the pseudorange signals.

Claims

1. A method to reduce power consumption in a device, comprising the steps of:

(A) generating in said device a plurality of pseudorange signals by tracking a plurality of position signals received from a plurality of satellites in a positioning system, at least one of said position signals from each one of said satellites respectively;

(B) calculating in said device both an initial position and an initial time bias from said pseudorange signals using a processing capability of said device at a normal capacity; and

(C) calculating in said device both an updated position and an updated time bias using said processing capability reduced to a first capacity, wherein said first capacity (i) consumes less power than said normal capacity and (ii) is suitable to process said updated position and said updated time bias using a limited number comprising less than all of said pseudorange signals being tracked.

2. The method according to claim 1, wherein said limited number comprises at most four of said pseudorange signals.

3. The method according to claim 1, further comprising the step of:

determining that a drift rate of a local time kept by said device is less than a threshold.

4. The method according to claim 3, wherein step (C) comprises the sub-step of:

calculating said updated position using said processing capability reduced to a second capacity if said drift rate is less than said threshold, wherein said second capacity (i) consumes less power than said first capacity and (ii) is suitable to process said updated position using all of (a) said local time and (b) at most three of said pseudorange signals.

5. The method according to claim 4, further comprising the steps of:

determining that said local time is invalid; and

increasing said processing capability to said first capacity if said local time is invalid such that said updated time bias is calculated from at least four of said pseudorange signals.

6. The method according to claim 1, further comprising the step of:

detecting that a change rate of a particular variable of a current position of said device is negligible, said particular variable comprising one of (i) an X position of said device, (ii) a Y position of said device and (iii) a Z position of said device.

7. The method according to claim 6, wherein step (C) comprises the sub-step of:

calculating two other variables within said updated position using said processing capability reduced to a second capacity, wherein said second capacity (i) consumes less power than said first capacity and (ii) is suitable to process said updated time bias and said two other variable using all of (a) said particular variable and (b) at most three of said pseudorange signals.

8. The method according to claim 1, further comprising the steps of:

identifying a subset of said pseudorange signals that produces a best figure of merit; and

limiting said calculation of said updated time bias and said updated position to said pseudorange signals in said subset.

9. The method according to claim 8, wherein said best figure of merit comprises at least one of (i) a smallest dilution of precision and (ii) a strongest received power of said position signals.

10. The method according to claim 8, further comprising the step of:

storing spatial restriction information in said device, said spatial restriction information corresponding to a particular position in said positioning system.

11. The method according to claim 10, further comprising the step of:

determining that at least one of said position signals previously obstructed is currently visible to said device according to said spatial restriction information in response to said updated position approximately matching said particular position.

12. The method according to claim 11, further comprising the step of:

locking on to said at least one position signal before said identification of said subset.

13. The method according to claim 1, further comprising the step of:

reducing said processing capability to a second capacity in response to receiving at most two of said position signals, wherein said second capacity (i) consumes less power than said first capacity and (ii) is suitable for processing two variables of said updated position using all of (a) a local time, (b) a last known value of a third variable of said updated position and (c) said at most two of said pseudorange signals.

14. The method according to claim 1, further comprising the step of:

reducing said processing capability to a second capacity in response to receiving at most one of said position signals, wherein said second capacity (i) consumes less power than said first capacity and (ii) is suitable for processing one among three variables of said updated position and said updated time bias using said at most one of said pseudorange signals.

22. The method according to claim 1, further comprising the step of:

reducing a tracking capability from an initial capacity prior to said calculating of said initial position and said initial time bias to a reduced capacity afterwards, wherein said device tracks at most six of said pseudorange signals while in said reduced capacity.

15. A device comprising:

a tracking engine configured to generate a plurality of pseudorange signals by tracking a plurality of position signals received from a plurality of satellites in a positioning system, at least one of said position signals from each one of said satellites respectively; and

a position calculator configured to (i) calculate both an initial position and an initial time bias from said pseudorange signals using a processing capability of said device at a normal capacity and (ii) calculate both an updated position and an updated time bias using said processing capability reduced to a first capacity, wherein said first capacity (a) consumes less power than said normal capacity and (b) is suitable to process said updated position and said update time bias using a limited number comprising less than all of said pseudorange signals being tracked.

16. The device according to claim 15, wherein said tracking engine is further configured to track a greater number of said position signals than said limited number of said pseudorange signals.

17. The device according to claim 15, wherein said position calculator is further configured to reduce said processing capability to a second capacity, wherein said second capacity (i) consumes less power than said first capacity and (ii) is suitable to process said updated position using at most three of said pseudorange signals.

18. The device according to claim 15, wherein power is removed from at least one hardware module to reduce said processing capability.

19. The device according to claim 15, wherein execution of a first software module is stopped and execution of a second software module is started to reduce said processing capability.

20. The device according to claim 15, further comprising a zone module configured to store spatial restriction information, said spatial restriction information corresponding to a particular position in said positioning system.

23. The device according to claim 15, wherein said tracking engine is further configured to reduce a tracking capability from an initial capacity prior to said calculation of said initial position and said initial time bias to a reduced capacity afterwards, wherein said tracking engine tracks at most six of said pseudorange signals while in said reduced capacity.

21. A device comprising:

means for generating a plurality of pseudorange signals by tracking a plurality of position signals received from a plurality of satellites in a positioning system, at least one of said position signals from each one of said satellites respectively; and

means for (i) calculating both an initial position and an initial time bias from said pseudorange signals using a processing capability of said device at a normal capacity and (ii) calculating both an updated position and an updated time bias using said processing capability reduced to a first capacity, wherein said first capacity (a) consumes less power than said normal capacity and (b) is suitable to process said updated position and said updated time bias using a limited number comprising less than all of said pseudorange signals being tracked.