Access terminal-assisted time and/or frequency tracking

Patent metadata

Field	Value
Publication number	US-9642105-B2
Application number	US-94702210-A
Country	US
Kind code	B2
Filing date	Nov 16, 2010
Priority date	Nov 17, 2009
Publication date	May 2, 2017
Grant date	May 2, 2017

Abstract

An access point (e.g., a femto cell) that is connected in an active call with an access terminal may cooperate with that access terminal or another access terminal to derive timing information from one or more neighboring access points (e.g., macro access points). In addition, an access point may cooperate with an idle access terminal to derive timing information from one or more neighboring access points. For example, an access terminal may determine the difference between pilot transmission timing or frame transmission timing of a femto cell and a macro cell, and report this timing difference to the femto cell. Based on this timing difference, the femto cell may adjust the timing and/or frequency of its transmissions so that these transmissions are synchronized in time and/or frequency as per network operation requirements.

First claim

What is claimed is:

1. A method of communication, comprising:
determining, at a femto cell access point, that the femto cell access point is communicating with an access terminal via an active call over a dedicated channel between the femto cell access point and the access terminal;
acquiring, at the femto cell access point, timing information from the access terminal during the communication as a result of the determining that the femto cell access point is communicating over the dedicated channel; and
adjusting, at the femto cell access point, a clock that controls transmissions by the femto cell access point, wherein the adjusting of the clock is based on the acquired timing information.

2. The method of claim 1 , wherein the timing information is indicative of a difference between timing associated with the femto cell access point and timing associated with at least one other cell.

3. The method of claim 1 , wherein the adjusting of the clock comprises adjusting a phase of a signal transmitted by the femto cell access point so that the adjusted phase is synchronized with a phase of transmission of at least one other access point or with a phase of a timing source.

4. The method of claim 1 , wherein the adjusting of the clock comprises adjusting a frequency of a signal transmitted by the femto cell access point so that the adjusted frequency is synchronized with a transmit frequency of at least one other access point or is matched to a frequency specified by network operation requirements.

5. The method of claim 1 , wherein:
the timing information is indicative of timing of another access point or a timing source, which drives timing of an event at the access terminal; and
the adjusting of the clock comprises adjusting timing of a signal transmission by the femto cell access point so that the adjusted timing is synchronized with the timing of the event.

6. The method of claim 1 , wherein the timing information is indicative of a phase difference between a first pilot signal received by the access terminal from the femto cell access point and a second pilot signal received by the access terminal from another access point.

7. The method of claim 1 , wherein the acquiring of the timing information comprises receiving a pilot strength measurement message from the access terminal, receiving a candidate frequency search report from the access terminal, receiving a measurement report message from the access terminal, or receiving a route update message from the access terminal.

8. The method of claim 1 , wherein the timing information is indicative of a timing difference between a time at which a frame from the femto cell access point is received by the access terminal and a time at which a frame from another access point is received by the access terminal.

9. The method of claim 8 , wherein the acquiring of the timing information comprises receiving an observed time difference report from the access terminal.

10. The method of claim 1 , wherein the acquiring of the timing information comprises sending a request to the access terminal for the timing information as a result of the determining that the femto cell access point is communicating over the dedicated channel.

11. The method of claim 10 , wherein the acquiring of the timing information further comprises receiving a message including the timing information from the access terminal.

12. The method of claim 10 , wherein the request for the timing information includes a list that is indicative of at least one pilot signal for which the access terminal is to search to provide the timing information.

13. The method of claim 10 , wherein the request for the timing information comprises a request for the access terminal to repeatedly provide timing information reports.

14. The method of claim 13 , wherein:
the timing information reports are indicative of a plurality of timing differences between the femto cell access point and another access point over a period of time;
the adjusting of the clock comprises determining a rate of change of the timing differences;
the adjusting of the clock further comprises determining a frequency adjustment based on the rate of change of the timing differences; and
the adjusting of the clock further comprises adjusting a frequency of the clock based on the frequency adjustment.

15. The method of claim 10 , further comprising:
estimating a reliability of the clock; and
determining a rate at which the timing information should be provided by the access terminal based on the estimated reliability,
wherein the request for the timing information comprises a request for the access terminal to provide the timing information at the determined rate.

16. The method of claim 10 , wherein the request for the timing information comprises a request for the access terminal to search for signals on at least one specified carrier frequency.

17. The method of claim 10 , wherein the request for the timing information comprises a request for the access terminal to search for signals from a plurality of other access points.

18. The method of claim 17 , wherein:
the timing information is indicative of a plurality of timing differences between the femto cell access point and at least a portion of the other access points; and
the adjusting of the clock is based on the plurality of timing differences.

19. The method of claim 10 , further comprising acquiring other timing information from at least one other access terminal, wherein the adjusting of the clock is further based on the other timing information.

20. The method of claim 19 , wherein the timing information acquired from the access terminal is associated with a type of radio technology and the other timing information acquired from the at least one other access terminal is associated with at least one other type of radio technology.

21. The method of claim 19 , further comprising sending at least one request to the at least one other access terminal to provide the other timing information.

22. The method of claim 1 , wherein the timing information is indicative of a timing difference between the femto cell access point and another access point, the method further comprising:
determining that the other access point has sufficiently accurate timing; and
electing to use the timing information received from the access terminal for the adjusting of the clock as a result of the determining that the other access point has sufficiently accurate timing.

23. The method of claim 1 , wherein the timing information acquired from the access terminal is associated with a first timing source, the method further comprising:
acquiring timing information associated with at least one other timing source;
for each timing source, determining a reliability of the timing source; and
for each timing source, weighting the timing information associated with the timing source based on the determined reliability of the timing source,
wherein the adjusting of the clock is based on the weighted timing information.

24. The method of claim 1 , further comprising determining that the access terminal is in idle mode, wherein the timing information is acquired from the access terminal as a result of the determining that the access terminal is in idle mode.

25. The method of claim 24 , wherein the determining that the access terminal is in idle mode comprises requesting the access terminal to register with the femto ce

Assignees

• Patel Chirag Sureshbhai
• Yavuz Mehmet
• Makh Vansh Pal Singh
• Blessent Luca
• Meshkati Farhad
• Qualcomm Inc

Inventors

• Patel Chirag Sureshbhai
• Yavuz Mehmet
• Makh Vansh Pal Singh
• Blessent Luca
• Meshkati Farhad

Classifications

• H04W56/0015 Primary

  one node acting as a reference for the others · CPC title

• H04W56/00 Primary

  Synchronisation arrangements · CPC title