Message synchronization over a stochastic network

• US 7,660,366 B2
• Filed: 08/30/2004
• Issued: 02/09/2010
• Est. Priority Date: 08/30/2004
• Status: Active Grant

• Current Assignee: Harmonic Incorporated
• Original Assignee: Harmonic Incorporated
• Inventors: Picco, Martin Raptis, Koren, Noam
• Primary Examiner(s): Odom; Curtis B
• Application Number:
  US10/931,178
• Publication Number:
  US 20060045020A1
• Time in Patent Office: 1,989 Days
• Field of Search: 375/327, 375354-358, 375373-376, 370229-235
• US Class Current: 375/327
• CPC Class Codes: H04J 3/0632 Synchronisation of packets and cells, e.g. transmission of voice via a packet network, circuit emulation service [CES] queuing arrangements in packet switching elements H04L49/90; synchronising systems for the synchronous transmission of a pulse code modulated video signal with one or more other pulse code modulated signals H04N7/56
• CPC Class Codes: H04J 3/0682 by delay compensation, e.g. by compensation of propagation delay or variations thereof, by ranging
• CPC Class Codes: H04L 47/10 Flow control; Congestion control
• CPC Class Codes: H04L 47/263 Rate modification at the source after receiving feedback
• CPC Class Codes: H04L 47/28 in relation to timing considerations
• CPC Class Codes: H04L 47/43 Assembling or disassembling of packets, e.g. segmentation and reassembly [SAR]

Abstract

Methods and apparatus to communicate between a local component and a remote component, where the local component is connected to the remote component using a non-deterministic communication link. A local clock is synchronized with a remote clock to within a maximum offset. A rate message from the remote component is received at the local component, where the rate message includes a first time stamp. A data rate is adjusted using the rate message when the time of the local clock substantially matches a time determined using the first time stamp. A data message is sent to the remote component using the adjusted data rate, where the data message includes a second time stamp for use in processing data in the data message. In some implementations, the time determined using the first time stamp is also determined using information about a communication link delay and/or a clock offset.

Claims

1. A method for communicating between a local component and a remote component, the local component connected to the remote component using a non-deterministic communication link, a local clock of the local component synchronized with a remote clock of the remote component to within a maximum offset, the method comprising:

receiving at a local component a rate message from a remote component, the rate message including a first time stamp;

adjusting a data rate of the local component, using the rate message, when a first time of a local clock substantially matches a time determined using the first time stamp; and

sending a data message at the first time from the local component to the remote component using the adjusted data rate, the data message including a second time stamp for use in processing data in the data message.

2. The method of claim 1, further comprising:

transmitting a complexity message from the local component to the remote component, wherein the rate message is produced using the complexity message.

3. The method of claim 1 wherein adjusting the data rate includes determining the first time of the local clock using a phase-locked loop.

4. The method of claim 1 wherein adjusting the data rate includes statistically estimating the first time of the local clock.

5. The method of claim 1 wherein the time determined using the first time stamp is further determined using at least one of information about a communication link delay and information about an offset between the local clock and a remote clock.

6. The method of claim 5 wherein the information about an offset between the local clock and the remote clock includes information about a maximum offset between the local clock and the remote clock.

7. The method of claim 6 wherein the information about the maximum offset between the local clock and the remote clock includes information about a maximum positive offset and a maximum negative offset.

8. The method of claim 5 wherein the information about a communication link delay includes information about a maximum communication link delay between the local component and the remote component.

9. The method of claim 5 wherein the information about a communication link delay includes information about a communication link delay from the remote component to the local component and information about a communication link delay from the local component to the remote component.

10. The method of claim 5 wherein the first time stamp includes at least one of the information about the communication link delay and the information about the offset between the local clock and the remote clock.

11. The method of claim 1 wherein the second time stamp includes at least one of information about a communication link delay and information about an offset between the local clock and the remote clock.

12. The method of claim 1 wherein adjusting a data rate includes queuing rate information included in the rate message.

13. The method of claim 1, further comprising:

buffering the rate message until the first time of the local clock substantially matches the time determined using the first time stamp.

14. A method for communicating between a local component and a remote component, the local component connected to the remote component using a non-deterministic communication link, a local clock of the local component synchronized with a remote clock of the remote component to within a maximum offset, the method comprising:

sending to a remote component a rate message from a local component, the rate message including a first time stamp for use by the remote component to send a data message to the local component using a data rate included in the rate message when a first time of a remote clock substantially matches a time determined using the first time stamp;

receiving at the local component the data message, the data message including a second time stamp; and

processing data included in the data message using the second time stamp.

15. The method of claim 14, further comprising:

receiving a complexity message from the remote component; and

generating the rate message using the complexity message.

16. The method of claim 14 wherein processing data included in the data message includes processing data included in the data message when a second time of a local clock substantially matches a time determined using the second time stamp.

17. The method of claim 16 wherein the time determined using the second time stamp is further determined using at least one of information about a communication link delay and information about an offset between the local clock and the remote clock.

18. The method of claim 17 wherein the information about an offset between the local clock and the remote clock includes information about a maximum offset between the local clock and the remote clock.

19. The method of claim 18 wherein the information about the maximum offset between the local clock and the remote clock includes information about a maximum positive offset and a maximum negative offset.

20. The method of claim 17 wherein the information about a communication link delay includes information about a maximum communication link delay between the local component and the remote component.

21. The method of claim 17 wherein the information about a communication link delay includes information about a communication link delay from the remote component to the local component and information about a communication link delay from the local component to the remote component.

22. The method of claim 17 wherein the second time stamp includes at least one of the information about the communication link delay and the information about the offset between the local clock and the remote clock.

23. The method of claim 14 wherein the first time stamp includes at least one of information about a communication link delay and information about an offset between a local clock and the remote clock.

24. The method of claim 14 wherein processing data included in the data message includes buffering the data message until a second time of a local clock substantially matches a time determined using the second time stamp.

25. A method for communicating between a local component and a remote component, the method comprising:

providing a non-deterministic communication link connecting a local component to a remote component;

synchronizing to within a maximum offset a local clock of the local component with a remote clock of the remote component;

sending a rate message from the remote component to the local component, the rate message including a first time stamp;

adjusting a data rate of the local component using the rate message, when a first time of the local clock substantially matches a time determined using the first time stamp, information about a communication link delay, and information about the maximum offset;

sending a data message, at the first time, from the local component to the remote component using the adjusted data rate, the data message including a second time stamp; and

processing data included in the data message when a second time of the remote clock substantially matches a time determined using the second time stamp, information about the communication link delay, and information about the maximum offset.

26. The method of claim 25 wherein the local component is an encoder and the remote component is a multiplexer.

27. The method of claim 25, further comprising:

transmitting a complexity message from the local component to the remote component, wherein the rate message is produced using the complexity message.

28. A local component, the local component connected to a remote component using a non-deterministic communication link, the local component comprising:

means for synchronizing to within a maximum offset a local clock of a local component to a remote clock of a remote component;

means for adjusting a data rate of the local component using a rate message from the remote component, the rate message including a first time stamp, the means adjusting a data rate of the local component using the rate message when a time of a local clock substantially matches a time determined using the first time stamp; and

means for sending a data message from the local component to the remote component using the adjusted date rate that arrives at the remote component in time to be processed by the remote component.

29. The local component of claim 28 wherein the means for synchronizing include a phase-locked loop.

30. The local component of claim 28 wherein the means for synchronizing include statistical estimation.

31. The local component of claim 28 wherein the means for adjusting include a rate adjustment unit.

32. The local component of claim 28 wherein the means for sending include a time-stamping component.

33. A multiplexer comprising:

an output assembly unit operable to assemble data into an output stream;

an input unit operable to receive a data message including data and a time stamp and to provide the data to an output assembly unit when a time of a local clock substantially matches a time determined using the time stamp; and

a rate control unit operable to send a time-stamped rate message to a remote component, the rate message including information about a data rate of a future data message.

34. The multiplexer of claim 33 wherein the rate control unit generates the rate message using information about a complexity of the future data message.

35. The multiplexer of claim 33 wherein the rate control unit timestamps the rate message using information about the time of the local clock.

36. The multiplexer of claim 33 wherein the input unit provides the data to the output assembly unit using at least one of information about a communication link delay and information about an offset between the local clock and a remote clock.

42. The multiplexer of claim 33, where the data rate of the future data message is an adjusted data rate determined based on a data rate of the received data message.

37. An encoder comprising:

a synchronization unit operable to synchronize an encoder clock with a remote clock to within a maximum offset;

a transmitter operable to time stamp and transmit a data message at a data rate; and

a rate adjustment unit operable to adjust the data rate responsive to a corresponding rate message when a time of the encoder clock substantially matches a time determined using a time stamp in the corresponding rate message.

38. The encoder of claim 37 wherein the synchronization unit includes a phase-locked loop.

39. The encoder of claim 37 wherein the transmitter time stamps the data message using information about the time of the encoder clock.

40. The encoder of claim 37 wherein the rate adjustment unit adjusts the data rate using at least one of information about a communication link delay and information about the maximum offset.

41. The encoder of claim 37 wherein the transmitter transmits a timestamped complexity message that is used to generate the corresponding rate message.