GPS position tracking method with variable updating rate for power conservation

• US 7,702,370 B2
• Filed: 03/17/2005
• Issued: 04/20/2010
• Est. Priority Date: 03/17/2005
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Persico, Charles J.
• Primary Examiner(s): Eng; George
• Assistant Examiner(s): Cho; Un C
• Application Number:
  US11/083,419
• Publication Number:
  US 20060211430A1
• Time in Patent Office: 1,860 Days
• Field of Search: 455/456.1, 455/456.5, 455/456.6, 455/574, 342/357.06, 342/357.01, 342/107, 342/114, 342/357.08, 342/357.1, 342/357.12, 342/104, 342/109, 342/457
• US Class Current: 455/574
• CPC Class Codes: G01S 19/34 Power consumption
• CPC Class Codes: G01S 19/39 the satellite radio beacon positioning system transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
• CPC Class Codes: G01S 19/393 Trajectory determination or predictive tracking, e.g. Kalman filtering
• CPC Class Codes: G01S 19/396 Determining accuracy or reliability of position or pseudorange measurements
• CPC Class Codes: G01S 5/0263 by combining or switching between positions derived from two or more separate positioning systems
• CPC Class Codes: G01S 5/0294 Trajectory determination or predictive filtering, e.g. target tracking or Kalman filtering

Abstract

A system and method in which the position update rate is adaptively modified, based on previous position measurements. By adjusting the update rate based on velocity predictions from two or more position fixes, a lower update rate may be used without exceeding the maximum error. Lowering the update rate reduces power consumption in the UE, providing longer battery operation. The updating method may comprise periodically repeating the velocity prediction and periodically adjusting the update rate responsive thereto. The update rate may be adjusted using additional information such as an acceleration prediction, a minimum update rate, or a preferred error. In some embodiments a model for user movement may be used to provide more accurate predictions, for example, stationary, walking, jogging, city driving, and freeway driving. The updating method may comprise receiving user input regarding the maximum position error.

Claims

1. A method for efficiently updating the position of mobile wireless user equipment (UE) to reduce the rate of energy consumption, comprising:

establishing an update rate for determining position;

selecting a maximum error in position;

making a velocity prediction for said UE;

adjusting said update rate responsive to said velocity prediction and said maximum error in position; and

making a series of position fixes at said adjusted update rate.

2. The method of claim 1 further comprising periodically repeating said velocity prediction and periodically adjusting said update rate responsive thereto.

3. The method of claim 1 further comprising making an acceleration prediction, and adjusting said update rate responsive to said acceleration prediction.

4. The method of claim 1 further comprising establishing a minimum update rate, and adjusting said update rate so that it remains above or equal to said minimum update rate.

5. The method of claim 1 further comprising determining a model for user movement responsive to said series of position fixes, and further adjusting said update rate responsive to said movement model and said velocity prediction.

6. The method of claim 5 wherein said movement model comprises stationary, walking, jogging, city driving, and freeway driving.

7. The method of claim 1 further comprising establishing a preferred error, and adjusting said update rate responsive to said preferred error and said maximum error.

8. The method of claim 1 further comprising receiving user input regarding said maximum position error.

9. The method of claim 1 wherein the step of making the velocity prediction for said UE comprises:

making a series of at least two position fixes at said update rate;

estimating a distance between at least two of said position fixes;

determining a time difference between the two position fixes; and

responsive to said time difference and said estimated distance, calculating said velocity prediction of said UE.

10. The method of claim 1 wherein the step of adjusting said update rate responsive to said velocity prediction comprises reducing said update rate to reduce power consumption without exceeding said maximum error in position.

11. The method of claim 1 wherein the step of adjusting said update rate responsive to said velocity prediction comprises increasing said update rate to follow a faster predicted velocity without exceeding said maximum error in position.

12. A method for efficiently updating the position of mobile wireless user equipment (UE) to reduce energy consumption while still providing accurate position information over time, comprising:

making a velocity prediction for said UE, including;

making a first position fix at a first time;

making a second position fix at a second time;

calculating a time delay between the first and second position fixes;

estimating a travel distance between said first and second position fixes; and

responsive to said calculated time delay and said estimated travel distance, calculating an actual velocity and making a velocity prediction of said UE over a next time period;

adjusting the time delay for a next position fix responsive to said velocity prediction and a maximum error in position; and

making a third position fix responsive to said time delay to update the position of said UE at a third time subsequent to said second time.

13. The method of claim 12 wherein said step of making a velocity prediction comprises sequentially making a plurality of position fixes, and responsive to said plurality of position fixes and time said position fixes were taken, calculating a velocity prediction.

14. The method of claim 12 wherein said step of making a velocity prediction comprises averaging at least three previous position fixes.

15. The method of claim 12 further comprising establishing a minimum time delay between subsequent position fixes, and adjusting the time delay so that it remains above or equal to said minimum time delay.

16. The method of claim 12 further comprising determining a maximum position error, providing a predetermined GPS accuracy, and calculating said time delay responsive to said position error, said velocity prediction and said predetermined GPS accuracy.

17. The method of claim 16 further comprising receiving user input regarding said maximum position error.

18. The method of claim 12 further comprising selecting a user movement model responsive to said velocity prediction, and adjusting said time delay responsive to said selected model.

19. The method of claim 18 wherein said movement model comprises stationary, walking, jogging, city driving, and freeway driving.

20. The method of claim 12 further comprising selecting a maximum error in position.

21. A system for efficiently updating the position of mobile wireless user equipment (UE) to reduce the rate of energy consumption, comprising:

means for establishing an update rate for determining position;

means for selecting a maximum error in position;

means for making a velocity prediction for said UE;

means for adjusting said update rate responsive to said velocity prediction and said maximum error in position; and

means for making a series of position fixes at said adjusted update rate.

22. The system of claim 21 further comprising means for periodically repeating said velocity prediction and means for periodically adjusting said update rate responsive thereto.

23. The system of claim 21 further comprising means for making an acceleration prediction, and means for adjusting said update rate responsive to said acceleration prediction.

24. The system of claim 21 further means for comprising establishing a minimum update rate, and means for adjusting said update rate so that it remains above or equal to said minimum update rate.

25. The system of claim 21 further comprising means for determining a movement model for user movement responsive to said series of position fixes, and means for adjusting said update rate responsive to said movement model and said velocity prediction.

26. The system of claim 25 wherein said movement model comprises stationary, walking, jogging, city driving, and freeway driving.

27. The system of claim 21 further comprising means for establishing a preferred error, and adjusting said update rate responsive to said preferred error and said maximum error.

28. The system of claim 21 further comprising means for receiving user input regarding said maximum position error.

29. The system of claim 21 wherein the means for making the velocity prediction comprises:

means for making a series of at least two position fixes at said update rate;

means for estimating the distance between at least two of said position fixes;

means for determining the time difference between the two position fixes; and

means, responsive to said time difference and said estimated distance, for calculating said velocity prediction of said UE.

30. The system of claim 21 wherein the means for adjusting said update rate responsive to said velocity prediction comprises means for reducing said update rate to reduce power consumption without exceeding said maximum error in position.

31. The system of claim 21 wherein the means for adjusting said update rate responsive to said velocity prediction comprises means for increasing said update rate to follow a faster predicted velocity without exceeding said maximum error in position.