Wireless telephone that rapidly reacquires a timing reference from a wireless network after a sleep mode

• US 6,212,398 B1
• Filed: 12/03/1998
• Issued: 04/03/2001
• Est. Priority Date: 12/03/1998
• Status: Expired due to Term

• Current Assignee: Unwired Planet LLC (JP Morgan Chase & Co)
• Original Assignee: Ericsson, Inc. (Telefonaktiebolaget LM Ericsson)
• Inventors: Roberts, Clarence V., Henry, Raymond C. Jr.
• Primary Examiner(s): Eisenzopf, Reinhard J.
• Assistant Examiner(s): Kincaid, Lester G.
• Application Number:
  US09/205,535
• Time in Patent Office: 852 Days
• Field of Search: 455/502, 455/68, 455/69, 455/70, 455/71, 455/67.1, 455/67.6, 455/574, 455/343, 455/38.3, 370/311, 375/354-357
• US Class Current: 455/502
• CPC Class Codes: H04B 1/1615 Switching on; Switching off, e.g. remotely battery saving circuits associated with selective call operation H04W52/00; details of power consumption reduction in a PLL, H03L7/0802, H03L7/14, H03L2207/08, H03L2207/18; muting amplifiers by gain control see H03G3/34
• CPC Class Codes: H04W 52/0229 where the received signal is a wanted signal
• CPC Class Codes: H04W 52/0245 according to signal strength
• CPC Class Codes: H04W 52/0293 having a sub-controller with a low clock frequency switching on and off a main controller with a high clock frequency
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A method for rapidly reacquiring a timing reference after a sleep period in a wireless telephone receiving pilot signals from one or more base stations in a wireless network, wherein the wireless telephone has a master timer (local time reference), a fast, accurate clock source, a slow, less accurate but power efficient clock source and a memory. The method includes the steps of entering the sleep period by storing one or more parameters related to the pilot signals and how the pilot signals are changing over time, calculating a prediction of the parameters of the pilot signals after a sleep period based on the stored parameters, storing the prediction, starting the slow clock, and stopping the master timer (local time reference) and fast clock source. The method further includes the steps of ending the sleep period by generating a wake-up interrupt by the slow clock after the sleep period, restarting the master timer and fast clock source responsive to the wake-up interrupt, and reacquiring pilot signals using the predictions stored previously. A time correction factor can then be computed that closely aligns the received pilot signals on the prediction which is then weighted and the master timer is adjusted by the weighted time correction.

Claims

1. In a wireless telephone receiving pilot signals having a plurality of parameters from one or more base stations in a wireless network, said wireless telephone having a master timer synchronized to a timing reference in the wireless network, a slow clock, a processor and a memory, a method for rapidly reacquiring the timing reference after the master timer emerges from a sleep period, said method comprising:

storing one or more of the pilot signals'"'"' parameters over time;

calculating predicted parameters of the pilot signals after the sleep period based on the stored parameters;

turning off power to the master timer and halting the processor;

generating a wake-up interrupt responsive to the slow clock after the sleep period;

turning power on to the master timer responsive to the wake-up interrupt;

reacquiring the pilot signals having a plurality of parameters from one or more base stations;

computing a time correction that most likely aligns the parameters of the received pilot signals and the predicted parameters; and

adjusting the master timer by the time correction.

2. The method of claim 1 further including the steps of turning on power to the slow clock before turning off power to the master timer and turning off power to the slow clock after turning on power to the master timer.

3. The method of claim 1 wherein the step of computing a time correction includes weighting ones of the time corrections of the received pilot signals in the computation, and wherein the master timer is adjusted by the weighted time correction.

4. The method of claim 1 wherein the slow clock increments a counter and wherein the sleep period ends when the counter reaches a predetermined number.

5. The method of claim 1 wherein one of the parameters of each pilot signal is a time offset, and wherein the step of storing one or more parameters includes storing the time offsets.

6. The method of claim 5 wherein the step of calculating a prediction of the pilot signals'"'"' parameters comprise calculating a prediction of each pilot signals'"'"' time offset after the sleep period.

7. The method of claim 3 wherein one of the pilot signals'"'"' parameters comprises signal strength and wherein said step of weighting the time corrections comprises weighting the time corrections based on the signal strength of the pilot signals.

8. The method of claim 3 wherein said step of weighting the time corrections is based on the arrival time of each reacquired pilot signal.

9. The method of claim 8 wherein earlier arriving reacquired pilot signals are assigned more weight than later arriving reacquired pilot signals.

10. The method of claim 3 wherein the master timer increments a counter and the step of adjusting the master timer comprises averaging the weighted time corrections and adjusting the timing increments of the counter based on the average.

11. The method of claim 1 wherein the step of calculating a prediction of the pilot signals after a sleep period uses factors internal to the wireless telephone that affect the accuracy of the predicted parameters.

12. The method of claim 11 wherein the internal factors include the age of the slow clock.

13. The method of claim 11 wherein the internal factors include the current state of the slow clock power supply voltage.

14. The method of claim 11 wherein the internal factors include the temperature of the slow clock.

15. The method of claim 11 wherein the internal factors include previous calibration results at known voltage, temperature and age conditions of the slow clock.

16. The method of claim 1 wherein the step of calculating a prediction of the parameters after a sleep period includes using factors external to the wireless telephone that affect the accuracy of the predicted parameters.

17. The method of claim 16 wherein the external factors include movement of wireless telephone.

18. The method of claim 16 wherein the external factors include the arrival time of reflected pilot signals.

19. The method of claim 16 wherein the external factors include the position and course of the wireless telephone.

20. The method of claim 19 wherein the wireless telephone includes a global positioning system and the position and course of the wireless telephone is calculated by the global positioning system.

21. The method of claim 19 wherein the parameters of the pilot signals include the latitude and longitude of the base station, and the position and course of the wireless telephone is based on the change in time of arrival of the pilot signals from several base stations.

22. The method of claim 1 wherein the master timer measures time in chips and the step of adjusting the master timer comprises advancing or delaying the master timer in one chip increments.

23. A wireless telephone that rapidly reacquires a timing reference after a sleep period, said wireless telephone receiving pilot signals having a plurality of parameters from one or more base stations in a wireless network, said wireless telephone comprising:

a sleep controller configured to time the sleep period and generate a wake up interrupt at the end of the sleep period;

a master timer configured to provide a timing reference for the wireless telephone;

a demodulator configured to demodulate the pilot signals using the timing reference and to determine parameters of the pilot signals; and

a processor configured to;

(a) calculate a prediction of the parameters of the pilot signals after the sleep period based on the parameters determined by the digital signal processor,

(b) start the sleep period,

(c) end the sleep period responsive to the interrupt,

(d) compare parameters of pilot signals to the prediction, and

(e) adjust the master timer to align the timing reference of the master timer to the pilot signals.

24. The wireless telephone of claim 23 further comprising a memory for storing a history of the parameters of pilot signals.

25. The wireless telephone of claim 24 wherein the processor is further configured to calculate a prediction of the parameters of the pilot signals after the sleep period based on the parameters determined by the digital signal processor and the history of parameters.

26. The mobile station of claim 23 wherein the processor is further configured to turn on power to the slow clock prior to the sleep period and turn off power to the slow clock after the sleep period.

27. The mobile station of claim 23 wherein the sleep controller includes a counter, said sleep controller being configured to generate the interrupt responsive to the counter reaching a predetermined number.

28. The mobile station of claim 27 further including a slow clock connected to the sleep controller that increments the counter.

29. The mobile station of claim 28 further comprising a fast timing reference that operates at a multiple of the timing reference, said processor being configured to speed up the master timer by advancing the master timer according to the fast timing reference.

30. The mobile station of claim 28 wherein the processor is configured to adjust the master timer by slowing the master timer.

31. The mobile station of claim 23 further comprising a global positioning system, wherein said processor is configured to determine a position of the mobile station and is further configured to calculate the prediction of the parameters of the pilot signals based on the position.

32. The mobile station of claim 31 wherein said processor is configured to determine a plurality of positions over time and store the plurality of positions and wherein the processor is further configured to calculate the prediction of the parameters of the pilot signals based on the stored plurality of positions.

33. The mobile station of claim 23 wherein the processor is further configured to turn off power to the master timer at the beginning of the sleep period, and to turn on power to the master timer responsive to the interrupt at the end of the sleep period.