Velocity responsive time tracking

• US 7,263,349 B2
• Filed: 03/12/2002
• Issued: 08/28/2007
• Est. Priority Date: 03/12/2002
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Abrishamkar, Farrokh, Rick, Roland, Sih, Gilbert
• Primary Examiner(s): GELIN, JEAN ALLAND
• Application Number:
  US10/097,043
• Publication Number:
  US 20030176201A1
• Time in Patent Office: 1,995 Days
• Field of Search: 455/414.1, 455/434, 455/441, 455/452.2, 455/9, 455/10, 455/502, 455/504, 455/505, 455/506, 455/67.16, 455/136, 455/181.1, 455/213, 455/240.1, 455/266
• US Class Current: 455/414.1
• CPC Class Codes: H04B 1/7085 using a code tracking loop, e.g. a delay-locked loop

Abstract

The velocity of a wireless communications device (WCD) is estimated. In response to this estimated velocity, a tracking speed of a filter is determined that corresponds to the estimated velocity. The filter filters a timing error signal to produce a control signal that controls the timing of a synchronization clock. This synchronization clock may be a finger clock that controls the timing of a pseudonoise (PN) sequence generator configured for despreading a pilot symbol sequence.

Claims

1. A method of providing velocity responsive tracking of a timing reference in a signal received by a wireless communications device (WCD), comprising the steps of:

estimating the velocity of the WCD;

determining a tracking speed of a filter, the tracking speed corresponding to the estimated velocity, wherein determining the tracking speed comprises;

mapping the estimated velocity to a velocity range; and

selecting a speed that corresponds to the velocity range as the tracking speed; and

filtering a timing error signal with the filter to produce a control signal that controls the timing of a synchronization clock.

2. The method of claim 1, wherein said determining step comprises increasing the tracking speed as the estimated velocity increases.

3. The method of claim 2, wherein said increasing step comprises increasing the filter bandwidth.

4. The method of claim 1, wherein said determining step comprises decreasing the tracking speed as the estimated velocity decreases.

5. The method of claim 4, wherein said decreasing step comprises decreasing the bandwidth of the filter bandwidth.

6. The method of claim 1, wherein said determining step comprises the step of:

changing the tracking speed from a first speed to a second speed when the estimated velocity surpasses a velocity threshold, VU.

7. The method of claim 6, wherein the second speed is greater than the first speed.

8. The method of claim 1, wherein said determining step comprises the step of:

changing the tracking speed from a first speed to a second speed when the estimated velocity is less than a velocity threshold, VL.

9. The method of claim 8, wherein the second speed is less than the first speed.

10. The method of claim 1, wherein said estimating step comprises the step of measuring a level crossing rate of a multipath signal.

11. The method of claim 1, wherein the synchronization clock is a finger clock that controls the timing of a pseudonoise (PN) sequence generator configured for despreading a pilot symbol sequence.

12. A system for providing velocity responsive tracking of a timing reference in a signal received by a wireless communications device (WCD), comprising:

a velocity estimator that estimates the velocity of the WCD; and

a filter having a tracking speed that corresponds to the estimated velocity, wherein said filter filters a timing error signal to produce a control signal that controls the timing of a synchronization clock, and wherein said filter maps the estimated velocity to a velocity range, and selects a speed that corresponds to the velocity range as the tracking speed.

13. The system of claim 12, wherein said filter increases the tracking speed as the estimated velocity increases.

14. The system of claim 12, wherein said filter decreases the tracking speed as the estimated velocity decreases.

15. The system of claim 12, wherein said filter changes the tracking speed from a first speed to a second speed when the estimated velocity surpasses a velocity threshold, VU.

16. The system of claim 15, wherein the second speed is greater than the first speed.

17. The system of claim 12, wherein said filter changes the tracking speed from a first speed to a second speed when the estimated velocity is less than a velocity threshold, VL.

18. The system of claim 17, wherein the second speed is less than the first speed.

19. The system of claim 12, wherein said velocity estimator measures a level crossing rate of a multipath signal to produce said velocity estimate.

20. The system of claim 12, wherein the synchronization clock is a finger clock that controls the timing of a pseudonoise (PN) sequence generator configured for despreading a pilot symbol sequence.

21. A system for providing velocity responsive tracking of a timing reference in a signal received by a wireless communications device (WCD), comprising:

means for estimating the velocity of the WCD;

means for determining a tracking speed of a filter, the tracking speed corresponding to the estimated velocity, wherein the means for determining the tracking speed comprises;

means for mapping the estimated velocity to a velocity range; and

means for selecting a speed that corresponds to the velocity range as the tracking speed; and

means for filtering a timing error signal with the filter to produce a control signal that controls the timing of a synchronization clock.

22. The system of claim 21, wherein said determining means comprises means for increasing the tracking speed as the estimated velocity increases.

23. The system of claim 22, wherein said increasing means comprises means for increasing the filter bandwidth.

24. The system of claim 21, wherein said determining means comprises means for decreasing the tracking speed as the estimated velocity decreases.

25. The system of claim 24, wherein said decreasing means comprises means for decreasing the bandwidth of the filter bandwidth.

26. The system of claim 21, wherein said determining means comprises:

means for changing the tracking speed from a first speed to a second speed when the estimated velocity surpasses a velocity threshold, VU.

27. The system of claim 26, wherein the second speed is greater than the first speed.

28. The system of claim 21, wherein said determining means comprises:

means for changing the tracking speed from a first speed to a second speed when the estimated velocity is less than a velocity threshold, VL.

29. The system of claim 28, wherein the second speed is less than the first speed.

30. The system of claim 21, wherein said estimating means comprises means for measuring a level crossing rate of a multipath signal.

31. The system of claim 21, wherein the synchronization clock is a finger clock that controls the timing of a pseudonoise (PN) sequence generator configured for despreading a pilot symbol sequence.