Timing synchronization methods and apparatus

• US 8,565,169 B2
• Filed: 01/12/2010
• Issued: 10/22/2013
• Est. Priority Date: 01/12/2010
• Status: Expired due to Fees

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Tavildar, Saurabh, Sampath, Ashwin, Li, Junyi
• Primary Examiner(s): Pham, Chi
• Assistant Examiner(s): HYUN, SOON D
• Application Number:
  US12/686,062
• Publication Number:
  US 20110170465A1
• Time in Patent Office: 1,379 Days
• Field of Search: None
• US Class Current: 370/329
• CPC Class Codes: H04W 56/0015 one node acting as a reference for the others
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

Various methods and apparatus are directed to achieving timing synchronization and propagating timing information pertaining to an external, e.g., non Wi-Fi, timing signal source. In some embodiments, a mobile communications device receives and processes a timing signal, e.g., a first Wi-Fi beacon, which is propagating timing information about an external timing signal from a device which directly received the external timing signal. Thus, a mobile wireless communications device achieves timing synchronization with respect to an external timing signal which it is unable to receive directly. In various embodiments, the mobile communications device may, and sometimes does, further propagate the timing information about the external timing signal, e.g., via a second Wi-Fi beacon signal which it generates and transmits. Synchronization with respect to an external signal source facilitates longer sleep states and decreased power consumption.

Claims

1. A method of operating a first mobile communications device operating in an unlicensed frequency band, the method comprising:

while operating in a first mode of operation, receiving a timing signal of a first type from a second mobile communications device, said first type of timing signal being synchronized to an external timing signal from an external timing signal source;

determining if said second mobile communications device has been synchronized with said external timing signal based on direct receipt of said external timing signal or based on a signal from another communications device which received said external timing signal;

synchronizing an internal clock based on the received timing signal from the second mobile communications device; and

after synchronizing the internal clock, switching to a second mode of operation wherein sleep state intervals in said second mode of operation are longer in duration than sleep state intervals in said first mode of operation.

2. The method of claim 1, wherein said timing signal from the second mobile communications device communicates timing information which is transmitted by the second communications device after having achieved synchronization with said external timing signal.

3. The method of claim 2, wherein said external timing signal is one of a global positioning signal, eLoran signal, LORAN-C signal, CDMA 2000 signal, WWVB signal, DTV signal and LTE signal.

4. The method of claim 1, wherein determining if said second mobile communications device has been synchronized with said external timing signal based on direct receipt of said external timing signal or based on a signal from another communications device which received said external timing signal includes:

recovering information from the received timing signal indicating whether said second mobile communications device is synchronized with said external timing signal based on direct receipt of said external timing signal or based on a signal from another communications device which received said external timing signal.

5. The method of claim 1, further comprising, when it is determined that said second mobile communications device is synchronized with the external timing signal based on direct receipt of said external timing signal:

deciding whether or not to periodically transmit a timing synchronization signal during said second mode of operation.

6. The method of claim 5, wherein said timing signal from the second mobile communications device is received in a beacon signal;

and

wherein said decision whether or not to periodically transmit a timing synchronization signal is a function of;

a number of first type timing signals being received on a periodic basis from other communications devices which are synchronized with said external signal based on receipt of said external timing signal.

7. A first mobile communications device comprising:

means for receiving a timing signal of a first type from a second mobile communications device while operating in a first mode of operation, said first type of timing signal being synchronized to an external timing signal from an external timing signal source;

means for determining if said second mobile communications device has been synchronized with said external timing signal based on direct receipt of said external timing signal or based on a signal from another communications device which received said external timing signal;

means for synchronizing an internal clock based on the received timing signal from the second mobile communications device; and

means for switching to a second mode of operation, wherein sleep state intervals in said second mode of operation are longer in duration than sleep state intervals in said first mode of operation, after synchronizing the internal clock.

8. The first mobile communications device of claim 7, wherein said timing signal from the second mobile communications device communicates timing information which is transmitted by the second communications device after having achieved synchronization with said external timing signal.

9. The first mobile communications device of claim 8, wherein said external timing signal is one of a global positioning signal, eLoran signal, LORAN-C signal, CDMA 2000 signal, WWVB signal, DTV signal and LTE signal.

10. The first mobile communications device of claim 7, wherein said means for determining includes:

means for recovering information from the received timing signal indicating whether said second mobile communications device is synchronized with said external timing signal based on direct receipt of said external timing signal or based on a signal from another communications device which received said external timing signal.

11. The first mobile communications device of claim 7, further comprising:

means for deciding whether or not to periodically transmit a timing synchronization signal during said second mode of operation when it is determined that said second mobile communications device is synchronized with the external timing signal based on direct receipt of said external timing signal.

12. The first mobile communications device of claim 8, wherein said timing signal from the second mobile communications device is received in a beacon signal.

13. A computer program product for use in a first mobile communications device, the computer program product comprising:

a non-transitory computer readable medium comprising;

code for causing at least one computer to receive a timing signal of a first type from a second mobile communications device while operating in a first mode of operation, said first type of timing signal being synchronized to an external timing signal from an external timing signal source;

code for causing said at least one computer to determine if said second mobile communications device has been synchronized with said external timing signal based on direct receipt of said external timing signal or based on a signal from another communications device which received said external timing signal;

code for causing said at least one computer to synchronize an internal clock based on the received timing signal from the second mobile communications device; and

code for causing said at least one computer to switch to a second mode of operation wherein sleep state intervals in said second mode of operation are longer in duration than sleep state intervals in said first mode of operation, after synchronizing the internal clock.

14. The computer program product of claim 13, wherein said code for causing said at least one computer to determine includes:

code for causing said at least one computer to recover information from the received timing signal indicating whether said second mobile communications device is synchronized with said external timing signal based on direct receipt of said external timing signal or based on a signal from another communications device which received said external timing signal.

15. The computer program product of claim 14, wherein said external timing signal is one of a global positioning signal, eLoran signal, LORAN-C signal, CDMA 2000 signal, WWVB signal, DTV signal and LTE signal.

16. A first mobile communications device comprising:

at least one processor configured to;

receive a timing signal of a first type from a second mobile communications device while operating in a first mode of operation, said first type of timing signal being synchronized to an external timing signal from an external timing signal source;

recover information from the received timing signal indicating whether said second mobile communications device is synchronized with said external timing signal based on direct receipt of said external timing signal or based on a signal from another communications device which received said external timing signal;

synchronize an internal clock based on the received timing signal from the second mobile communications device; and

switch to a second mode of operation wherein sleep state intervals in said second mode of operation are longer in duration than sleep state intervals in said first mode of operation, after synchronizing the internal clock; and

memory coupled to said at least one processor.

17. The first mobile communications device of claim 16, wherein said timing signal from the second mobile communications device communicates timing information which is transmitted by the second communications device after having achieved synchronization with said external timing signal.

18. The first mobile communications device of claim 17, wherein said external timing signal is one of a global positioning signal, eLoran signal, LORAN-C signal, CDMA 2000 signal, WWVB signal, DTV signal and LTE signal.

19. The first mobile communications device of claim 17, wherein said at least one processor is further configured to:

decide whether or not to periodically transmit a timing synchronization signal during said second mode of operation when it is determined that said second mobile communications device is synchronized with the external timing signal based on direct receipt of said external timing signal.