Method, System, and Computer-Readable Medium for Calculating an Echo Path Delay

• US 20080080702A1
• Filed: 10/03/2006
• Published: 04/03/2008
• Est. Priority Date: 10/03/2006
• Status: Abandoned Application

• Current Assignee: Genband US LLC (Ribbon Communications, Inc.)
• Original Assignee: Santera Systems LLC
• Inventors: TONG, Allen Y., SHU, Kuang-I, PERRY, Sam O., ZHANG, Naigang
• Application Number:
  US11/538,384
• Publication Number:
  US 20080080702A1
• Time in Patent Office: Days
• US Class Current: 379/406.08
• CPC Class Codes: H04B 3/23 using a replica of transmitted signal in the time domain, e.g. echo cancellers

Abstract

A method, system, and computer-readable medium for calculating a minimum echo path delay are provided. An accurate calculation of a minimum echo path delay is made based on characteristics of the echo path. The minimum echo path delay calculation may be periodically repeated thus providing for dynamic calculation of the minimum echo path delay in a manner that accounts for variations in echo path characteristics. The minimum echo path delay may be calculated based on discrete processing latencies identified in the echo path, by a network round trip delay, or by modeling an acoustic echo of an in-band audio signal, performing a frequency analysis thereon to calculate a spectrum signature of the modeled acoustic echo, and monitoring a send path for a match with the modeled acoustic echo after applying an instance of the in-band audio signal into the echo path.

Claims

1. A method of determining an echo path delay in a communication network, comprising:

receiving a signal on a send path transmitted to a communication terminal;

determining characteristics of an echo path between a media gateway and the communication terminal; and

calculating a minimum echo path delay between the media gateway and the communication terminal based on the characteristics, wherein the characteristics include a processing latency associated with one or more processing entities in the echo path and a path delay of the echo path.

2. The method of claim 1, further comprising completing a media path setup with the communication terminal including configuration of a receive path from the media gateway to the communication terminal, and a send path from the communication terminal to the media gateway.

3. The method of claim 1, wherein determining characteristics further comprises identifying the one or more processing entities in the echo path each having a respective processing delay associated therewith, and wherein calculating a minimum echo path delay further comprises calculating a sum of each respective processing delay, wherein the minimum echo path delay is set to the sum.

4. The method of claim 3, wherein the one or more processing entities includes at least one of an encoder, jitter buffer, and a decoder, and wherein the respective processing delay comprises an encoder processing delay, a jitter buffer delay, and a decoder processing delay.

5. The method of claim 3, wherein determining characteristics further comprises identifying a round-trip transmission delay between the communication terminal and the media gateway.

6. The method of claim 5, wherein identifying a round-trip transmission delay further comprising measuring the round-trip transmission delay using a real-time control protocol function.

7. The method of claim 1, wherein determining characteristics further comprises determining a packet network round trip delay between the media gateway and the communication terminal, and wherein calculating a minimum echo path delay further comprises setting the minimum echo path delay to the round trip delay.

8. The method of claim 7, wherein determining a packet network round trip delay further comprises:

recording a receipt time of a real time control protocol receiver report at the media gateway;

calculating a first difference between a real time control protocol last sender report timestamp and the receipt time; and

calculating a second difference between the first difference and a real time control protocol delay since last sender report, wherein the minimum echo path delay is set to the second difference.

9. The method of claim 1, wherein determining characteristics of the echo path further comprises performing a spectrum analysis of the echo path.

10. The method of claim 9, wherein performing a spectrum analysis further comprises:

modeling transmission of an audio signal through the echo path;

obtaining a spectrum signature of the audio signal;

evaluating a signal on a send path from the communication terminal to the media gateway; and

calculating a spectrum signature of the signal.

11. The method of claim 10, wherein evaluating a signal on the send path comprises applying an instance of the audio signal in-band on the echo path, the method further comprising recording a time at which the audio signal is applied to the echo path.

12. The method of claim 11, further comprising:

comparing the spectrum signature of the signal with the spectrum signature of the audio signal;

determining whether the spectrum signature of the signal matches the spectrum signature of the audio signal; and

responsive to determining the spectrum signature of the signal matches the spectrum signature of the audio signal, setting the minimum echo path delay to a difference between a time at which the signal is evaluated on the send path and the time at which the test signal is applied to the echo path.

13. The method of claim 10, wherein modeling transmission of an audio signal comprises:

encoding the audio signal with an instance of an encoder including in the echo path;

decoding the encoded audio signal;

attenuating the decoded audio signal to produce an attenuated audio signal;

encoding the attenuated audio signal; and

decoding the encoded and attenuated audio signal.

14. A computer-readable medium having computer-executable instructions for execution by a processing system, the computer-executable instructions for calculating an echo path delay, comprising:

instructions that receive a signal on a send path transmitted to a communication terminal;

instructions that determine characteristics of an echo path between a media gateway and the communication terminal; and

instructions that calculate a minimum echo path delay between the media gateway and the communication terminal based on the characteristics, wherein the characteristics include a processing latency associated with one or more processing entities in the echo path and a path delay of the echo path.

15. The computer-readable medium of claim 14, further comprising instructions that complete a media path setup with the communication terminal including completing configuration of a receive path from the media gateway to the communication terminal and a send path from the communication terminal to the media gateway.

16. The computer-readable medium of claim 14, wherein the instructions that determine characteristics further comprises instructions that identify the one or more processing entities in the echo path each having a respective processing delay associated therewith, and wherein the instructions that calculate a minimum echo path delay further calculate a sum of each respective processing delay, wherein the minimum echo path delay is set to the sum.

17. The computer-readable medium of claim 16, wherein the one or more processing entities include at least one of an encoder, jitter buffer, and a decoder, and wherein the respective processing delay comprises an encoder processing delay, a jitter buffer delay, and a decoder processing delay.

18. The computer-readable medium of claim 16, wherein the instructions that determine characteristics identify a round-trip transmission delay between the communication terminal and the media gateway.

19. The computer-readable medium of claim 18, wherein the instructions that identify a round-trip transmission delay measure the round-trip transmission delay using a real-time transmission control protocol function.

20. The computer-readable medium of claim 14, wherein the instructions that determine characteristics further comprises instructions that determine a packet network round trip delay between the media gateway and the communication terminal, and wherein the instructions that calculate a minimum echo path delay further set the minimum echo path delay to the round trip delay.

21. The computer-readable medium of claim 20, wherein the instructions that identify a packet network round trip delay further comprise:

instructions that record a receipt time of a real time control protocol receiver report at the media gateway;

instructions that calculate a first difference between a real time control protocol last sender report timestamp from the receipt time;

instructions that calculate a second difference between the first difference and a real time control protocol delay since last sender report, wherein the minimum echo path delay is set to the second difference.

22. The computer-readable medium of claim 14, wherein the instructions that determine characteristics of the echo path further comprise instructions that perform a spectrum analysis of the echo path.

23. The computer-readable medium of claim 22, wherein the instructions that perform a spectrum analysis further comprise:

instructions that model transmission of an audio signal through the echo path;

instructions that obtain a spectrum signature of the audio signal;

instructions that evaluate a signal on a send path from the terminal to the media gateway; and

instructions that calculate a spectrum signature of the signal.

24. The computer-readable medium of claim 23, wherein the instructions that evaluate a signal on the send path comprise instructions that apply an instance of the audio signal in-band on the echo path, the computer-readable medium further comprising instructions that record a time at which the audio signal is applied to the echo path.

25. The computer-readable medium of claim 24, further comprising:

instructions that compare the spectrum signature of the signal with the spectrum signature of the audio signal;

instructions that determine whether the spectrum signature of the signal matches the spectrum signature of the audio signal; and

instructions that, responsive to determining the spectrum signature of the signal matches the spectrum signature of the audio signal, set the minimum echo path delay to a difference between a time at which the signal is evaluated on the send path and the time at which the test signal is applied to the echo path.

26. The computer-readable medium of claim 23, wherein the instructions that model transmission of an audio signal comprise:

instructions that encode the audio signal with an instance of an encoder including in the echo path;

instructions that decode the encoded audio signal;

instructions that attenuate the decoded audio signal to produce an attenuated audio signal;

instructions that encode the attenuated audio signal; and

instructions that decode the encoded and attenuated audio signal.

27. A converged network, comprising:

a wireless network adapted to terminate a media path with a terminal; and

a media gateway adapted to interface with the wireless network on the media path and receive a signal on a send path transmitted to the terminal, the media gateway comprising an acoustic echo controller adapted to determine characteristics of an echo path comprising at least a portion of the media path and calculate a minimum echo path delay between the media gateway and the based on the characteristics, wherein the characteristics include a processing latency associated with one or more processing entities in the echo path and a path delay of the echo path.

28. The system of claim 27, wherein the acoustic echo controller determines characteristics by identifying the one or more processing entities in the echo path each having a respective processing delay associated therewith, and wherein the minimum echo path delay is calculated by summing each respective processing delay.

29. The system of claim 28, wherein the one or more processing entities comprise one or more of an encoder, a jitter buffer, and a decoder disposed on the media gateway, and wherein the respective processing delay comprises an encoder processing delay, a jitter buffer delay, and a decoder processing delay.

30. The system of claim 28, wherein the acoustic echo controller identifies a round-trip transmission delay between the terminal and the media gateway.

31. The system of claim 30, wherein the round-trip transmission delay is measured using a real-time control protocol function.

32. The system of claim 27, further comprising a packet network included in the media path, wherein the characteristics are determined by calculating a packet network round trip delay between the media gateway and the terminal, and wherein the minimum echo path delay is set to the round trip delay.

33. The system of claim 32, wherein the packet network round trip delay is calculated by recording a receipt time of a real time control protocol receiver report at the media gateway, calculating a first difference between a real time control protocol last sender report timestamp and the receipt time, calculating a second difference between the first difference and a real time control protocol delay since last sender report, wherein the minimum echo path delay is set to the second difference.

34. The system of claim 27, wherein the characteristics of the echo path are determined by performing a spectrum analysis of the echo path.

35. The system of claim 34, wherein the spectrum analysis is performed by modeling transmission of an audio signal through the echo path, obtaining a spectrum signature of the audio signal, evaluating a signal on a send path from the terminal to the media gateway, and calculating a spectrum signature of the signal.

36. The system of claim 35, wherein evaluating a signal on the send path comprises applying an instance of the audio signal in-band on the echo path, and wherein the acoustic echo controller records a time at which the audio signal is applied to the echo path.

37. The system of claim 36, wherein the acoustic echo controller compares the spectrum signature of the signal with the spectrum signature of the audio signal, determines whether the spectrum signature of the signal matches the spectrum signature of the audio signal, and responsive to determining the spectrum signature of the signal matches the spectrum signature of the audio signal, sets the minimum echo path delay to a difference between a time at which the signal is evaluated on the send path and the time at which the test signal is applied to the echo path.

38. The system of claim 35, wherein the acoustic echo controller models transmission of an audio signal by encoding the audio signal with an instance of an encoder including in the echo path, decoding the encoded audio signal, attenuating the decoded audio signal to produce an attenuated audio signal, encoding the attenuated audio signal, and decoding the encoded and attenuated audio signal.