Synchronization Of A Peer-To-Peer Communication Network

• US 20090017851A1
• Filed: 07/09/2007
• Published: 01/15/2009
• Est. Priority Date: 07/09/2007
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Wu, Xinzhou, Li, Junyi, Larola, Rajiv
• Granted Patent: US 7,983,702 B2
• Time in Patent Office: Days
• US Class Current: 455/502
• CPC Class Codes: H04J 3/1605 Fixed allocated frame structures
• CPC Class Codes: H04W 56/002 Mutual synchronization

Abstract

In an ad hoc peer-to-peer communications network, timing synchronization is facilitated between two or more nodes. A node can establish an original symbol timing and receive a first timing synchronization symbol from a peer node. A timing adjustment can be calculated based in part on the first timing synchronization symbol. An adjusted symbol timing can be established by adjusting the first symbol timing by the calculated timing adjustment amount. The adjusted symbol timing can be conveyed to one or more peer nodes, in order to facilitate timing synchronization among the nodes.

Claims

1. A method of operating a first wireless communications terminal, the method comprising:

determining an original symbol timing;

receiving a first timing synchronization signal from at least a second wireless communications terminal;

calculating a timing adjustment based in part on the first timing synchronization signal;

determining an adjusted symbol timing by adjusting the original symbol timing by an amount determined by the calculated timing adjustment; and

transmitting a second timing synchronization signal with the adjusted symbol timing.

2. The method of claim 1, further comprising:

prior to determining the original symbol timing, receiving a timing reference signal from a network broadcast source;

determining the original symbol timing based on the timing reference signal; and

determining, based on the timing reference signal, a sequence of timing synchronization time intervals to be used for receiving timing synchronization signals from other wireless communications terminals; and

wherein the first timing synchronization signal is received in a first one of the timing synchronization time intervals.

3. The method of claim 2, wherein the network broadcast source is at least one of a terrestrial base station transmitter, a terrestrial TV or radio transmitter, or a satellite transmitter, or combinations thereof.

4. The method of claim 1, wherein the first and the second wireless communications terminals are peer devices operated in a peer-to-peer communications system.

5. The method of claim 4, further comprising:

transmitting a traffic signal to a third wireless communications terminal with the adjusted symbol timing, the third wireless communications terminal being different from the second wireless communications terminal and the traffic signal including data traffic intended to be received by the third wireless communications terminal.

6. The method of claim 2, wherein the second timing synchronization signal is transmitted in at least a portion of a second one of the sequence of timing synchronization time intervals.

7. The method of claim 6, further comprising:

listening in at least part of the remaining portion of the second time interval for receiving a timing synchronization signal transmitted by a wireless communications terminal.

8. The method of claim 6, further comprising:

prior to transmitting the second timing synchronization signal in the portion of the second time interval, choosing the portion of the second time interval as a function of at least one of the identifier of the network broadcast source, the identifier of the first terminal, a random number, or a pseudo random number, or combinations thereof.

9. The method of claim 6, further comprising:

transmitting a third signal with the original symbol timing in at least a portion of a third one of the sequence of timing synchronization time intervals, the third one of the sequence of timing synchronization intervals preceding the second one of the sequence of timing synchronization intervals.

10. The method of claim 1, further comprising:

setting the original symbol timing to be equal to the adjusted symbol timing; and

repeating the steps of receiving a timing synchronization signal from at least a wireless communications terminal, calculating a timing adjustment based in part on the timing synchronization signal, determining a new adjusted symbol timing based on the calculated timing adjustment and transmitting a timing synchronization signal with the new adjusted symbol timing.

11. A wireless communications apparatus, comprising:

a memory that retains instructions related to ascertaining a first symbol timing, receiving a first timing synchronization signal, establishing a timing adjustment based in part on the received first timing synchronization signal, adjusting the first symbol timing as a function of the established timing adjustment, and conveying the adjusted symbol timing with a second timing synchronization signal; and

a processor, coupled to the memory, configured to execute the instructions retained in the memory.

12. The wireless communications apparatus of claim 11, the memory further retains instructions related to changing the first symbol timing to the adjusted symbol timing and repeating the steps of receiving a second timing synchronization signal, establishing a timing adjustment based in part on the second received timing synchronization signal, adjusting the symbol timing as a function of the established timing adjustment;

and conveying the adjusted symbol timing with a subsequent timing synchronization signal.

13. The wireless communications apparatus of claim 11, the memory further retains instructions related to conveying a traffic signal with the adjusted symbol timing that includes data traffic intended to be received by another device.

14. The wireless communications apparatus of claim 11, the memory further retains instructions related to receiving a timing reference signal, and determining the first symbol timing and a sequence of timing synchronization time intervals based on the received timing reference signal.

15. The wireless communications apparatus of claim 14, the memory further retains instructions related to transmitting the second timing synchronization signal in at least a portion of a first one of the sequence of timing synchronization time intervals and listening in at least a portion of a remaining portion of the first one of the sequence of timing synchronization for signals.

16. The wireless communications apparatus of claim 14, the memory further retains instructions related to choosing a portion of the second time interval as a function of at least one of an identifier of a network broadcast source, an identifier of a first terminal, a random number, or a pseudo random number, or combinations thereof and transmitting the second timing synchronization signal in at least a portion of a first one of the sequence of timing synchronization time intervals.

17. A wireless communications apparatus that facilitates synchronization in a peer-to-peer communications network, comprising:

means for establishing an original signal timing from a received timing reference signal;

means for receiving a first timing synchronization signal from a peer;

means for calculating a timing adjustment based on at least the first timing synchronization signal;

means for adjusting the original signal timing by a determined adjustment amount; and

means for transmitting the adjusted signal timing in a second timing synchronization signal.

18. The wireless communications apparatus of claim 17, further comprising:

means for receiving a timing reference signal;

means for determining the original signal timing and a sequence of timing synchronization time intervals based on the received timing reference signal, the sequence of timing synchronization time intervals are used from receiving timing synchronization signals.

19. The wireless communications apparatus of claim 17, further comprising:

means for changing the original symbol timing to the adjusted symbol timing;

means for receiving a next timing synchronization signal;

means for calculating a timing adjustment based on at least the next timing synchronization signal;

means for adjusting the changed original signal timing by a determined adjustment amount; and

means for transmitting the adjusted signal timing in a next timing synchronization signal.

20. A machine-readable medium having stored thereon machine-executable instructions for:

establishing at a first device a first symbol timing;

receiving a first timing synchronization symbol from a second device;

calculating a timing adjustment based in part on the first timing synchronization symbol;

determining an adjusted symbol timing by adjusting the first symbol timing by an amount determined by the calculated timing adjustment; and

conveying a second timing synchronization symbol that includes the adjusted symbol timing.

21. The machine-readable medium of claim 20, the machine-executable instructions further comprises

prior to establishing at a first device a first symbol timing, receiving a timing reference signal from a network broadcast source, wherein the network broadcast source is at least one of a terrestrial base station transmitter, a terrestrial television or radio transmitter, or a satellite transmitter, or combinations thereof;

determining the first symbol timing based on the timing reference signal; and

determining, based on the timing reference signal, a series of timing synchronization signals to be used for receiving timing synchronization signals from other devices, wherein the first timing synchronization signal is received in a first one of the timing synchronization time intervals.

22. In a wireless communication system, an apparatus comprising:

a processor configured to;

determine an original symbol timing based in part on a timing reference signal received from a network broadcast source;

receive a first timing synchronization signal from at least a second wireless communications terminal;

calculate a timing adjustment based in part on the first timing synchronization signal;

determine an adjusted symbol timing by adjusting the original symbol timing by an amount determined by the calculated timing adjustment; and

transmit a second timing synchronization signal with the adjusted symbol timing.