Dynamic codec speed selection and bandwidth preallocation in a voice packet network method and apparatus

• US 6,754,232 B1
• Filed: 01/12/2000
• Issued: 06/22/2004
• Est. Priority Date: 01/12/2000
• Status: Expired due to Term

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Tasker, Michael E.
• Primary Examiner(s): QURESHI, AFSAR M
• Application Number:
  US09/481,776
• Time in Patent Office: 1,623 Days
• Field of Search: 370/252, 370/253, 370/352-353, 370/355, 370/354, 370/357, 370/395.2, 370/395.21, 370/395.51, 370/395.52, 370/395.6, 370/465, 370/466, 370/467, 370/468, 370/477
• US Class Current: 370/477
• CPC Class Codes: G10L 19/22 Mode decision, i.e. based on audio signal content versus external parameters
• CPC Class Codes: H04L 65/1101 Session protocols
• CPC Class Codes: H04L 65/70 Media network packetisation
• CPC Class Codes: H04M 2207/203 composed of PSTN and data network, e.g. the Internet
• CPC Class Codes: H04M 3/002 Applications of echo suppressors or cancellers in telephonic connections in two-way loud-speaking telephone systems H04M9/08, echo suppressors or cancellers per se H04B3/20
• CPC Class Codes: H04M 7/0072 Speech codec negotiation H04L65/1069 takes precedence

Abstract

Dynamic compressor/decompressor (codec) speed selection includes monitoring a call in a telephone system to determine the type of codec being used thereon and to measure the payload on the codec. The capacity of the codec is determined based upon the determined type of codec being used. Speed selection further includes comparing the determined capacity with the measured payload; and selectively switching the call to a higher operational speed based upon the result of the comparing. Preferably, the monitoring includes detecting a modem answer tone of the telephone call and basing the determination of the type of codec at least partly thereon. The monitoring also preferably includes detecting silence of the telephone call and basing the selective switching at least partly thereon. Echo cancellation and/or suppression is disabled upon such selective switching. In accordance with one embodiment of the invention, the switching includes requesting an up-speed codec. In such case, the method further includes verifying network bandwidth prior to the requesting of the up-speed codec. The network bandwidth is pre-allocated in accordance with the invention after the up-speed codec is requested and prior to the selective switching of the call to a higher operational speed. Finally, the monitoring further includes determining whether the call is silent and upon such determination automatically switching the call back to a lower operational speed.

Claims

1. In a voice packet network, a dynamic codec speed selection method comprising:

monitoring a call in a telephone system to determine the type of codec being used thereon and to measure the payload on the codec;

determining the capacity of the codec based upon the determined type of codec being used;

comparing the determined capacity with the measured payload; and

selectively switching the call to a higher operational speed based upon the result of said comparing.

2. The method of claim 1 which further comprises recording the result of said monitoring.

3. The method of claim 1 wherein said switching is performed by signaling the codec in accordance with a voice over frame relay (VoFR) protocol.

4. The method of claim 3 wherein the VoFR protocol is FRF.11.

5. The method of claim 1 wherein said monitoring includes detecting a modem answer tone of the telephone call and basing the determination of the type of codec at least partly thereon.

6. The method of claim 5 wherein said detecting is of a modem answer tone of the telephone call at either a source or destination telephone number, which further comprises signaling whether the modem answer tone is detected at the source or the destination telephone number.

7. The method of claim 1 wherein said monitoring includes detecting silence of the telephone call and basing said selective switching at least partly thereon.

8. The method of claim 1 which further comprises disabling echo cancellation upon said selective switching.

9. The method of claim 1 which further comprises disabling echo suppression upon said selective switching.

10. The method of claim 1 wherein said switching includes requesting an up-speed codec.

11. The method of claim 10 which further comprises verifying network bandwidth prior to said requesting of the up-speed codec.

12. The method of claim 11 which further comprises pre-allocating network bandwidth after said requesting of the up-speed codec and prior to said switching.

13. The method of claim 1 wherein said monitoring further includes determining whether the call is silent and upon such determination automatically switching the call to a lower operational speed.

14. The method of claim 13 wherein said determining is of silence of a defined duration.

15. The method of claim 14 wherein said defined duration is programmable to support a modem pass-through mode of operation and a fax pass-through mode of operation.

16. The method of claim 13 which further comprises re-enabling echo cancellation upon said automatic switching to a lower operational speed.

17. The method of claim 13 which further comprises re-enabling echo suppression upon said automatic switching to a lower operational speed.

18. The method of claim 13 wherein said automatic switching to a lower operational speed includes requesting a down-speed codec.

19. The method of claim 1 which further comprises signaling a destination telephone number upon said selective switching to disable echo cancellation and suppression.

20. The method of claim 19 wherein said signaling is performed over the telephone line bearing the detected modem traffic.

21. The method of claim 20 wherein said signaling is performed by passing through the voice bearer channel path a prescribed end-to-end control message instructing the destination telephone number to disable echo cancellation and suppression.

22. Apparatus for use in a dynamic codec switching system for modem signals carried via a voice over frame relay (VoFR) protocol over a voice frame network, the apparatus comprising:

a codec mechanism coupled with one or more network nodes;

a modem answer tone detector for signaling when a modem is detected at a call-originating or call-terminating network node defining a channel therebetween; and

a switch coupled with said codec mechanism and responsive to the modem detection signaling for automatically up-speeding the codec mechanism.

23. The apparatus of claim 22 which further comprises a silence detector for signaling when the detected modem is idle, wherein said switch responsive to the silence detection signaling automatically down-speeds the codec mechanism.

24. The apparatus of claim 22 wherein said codec mechanism includes plural discrete codecs of different speed capacity and wherein such switch performs such up-speeding by selecting a higher-speed one of said plural discrete codecs.

25. The apparatus of claim 22 wherein said codec mechanism includes one or more codecs of selectable speed and wherein said switch performs such up-speeding by selecting a higher operational speed of the one or more codecs.

26. The apparatus of claim 22 which further comprises a line monitor for confirming such up-speeding of the codec mechanism after such signaling.

27. The apparatus of claim 26 wherein said line monitor confirms such up-speeding by measuring up-speed bandwidth in both the transmit and receive directions of the channel.

28. The apparatus of claim 26 which further comprises a silent-out mechanism responsive to said line monitor in the event that up-speeding is not confirmed thereby within a predefined period of time, said silent-out mechanism signaling said switch to down-speed the codec mechanism.

29. The apparatus of claim 28 wherein said silent-out mechanism performs said signaling of said switch by discarding packets for a predefined period of time after a failure of said line monitor to confirm such up-speeding.

30. The apparatus of claim 22 which further comprises a bandwidth monitor responsive to said switch for over-riding said switch to deny such up-speeding of the codec mechanism upon detection of insufficient bandwidth in the network.

31. A computer-readable medium containing a program for selecting the speed of a codec for use in a voice packet network, the program comprising:

instructions for monitoring a call in a telephone system to determine the type of codec being used;

instructions for determining the capacity of the codec based upon the determined type of codec being used;

instructions for comparing the determined capacity with the measured payload; and

instructions for selectively switching the call to a higher operational speed based upon the result of said comparing.

32. The computer-readable medium in accordance with claim 31 wherein the program further comprises:

instructions for recording the result of such monitoring.

33. The computer-readable medium in accordance with claim 31 wherein the program further comprises:

instructions for disabling echo cancellation upon such selective switching.

34. The computer-readable medium in accordance with claim 31, wherein such switching includes requesting an up-speed codec, and wherein the program further comprises:

instructions for verifying network bandwidth prior to such requesting of the up-speed codec.

35. The computer-readable medium in accordance with claim 34 wherein the program further comprises:

pre-allocating network bandwidth after such requesting of the up-speed codec and prior to such switching.

36. The computer-readable medium in accordance with claim 31 wherein said instructions for switching include instructions for signaling the codec in accordance with a voice over frame relay (VoFR) protocol.

37. The computer-readable medium in accordance with claim 31 wherein said instructions for monitoring include instructions for determining whether the call is silent and upon such determination automatically switching the call to a lower operational speed.

38. The computer-readable medium in accordance with claim 37 wherein such determining is of silence of a defined duration.

39. The computer-readable medium in accordance with claim 38 wherein such defined duration is programmable to support a modem pass-through mode of operation and a fax pass-through mode of operation.

40. The computer-readable medium in accordance with claim 37 wherein the

instructions for re-enabling echo cancellation upon such automatic switching to a lower operational speed.

41. The computer-readable medium in accordance with claim 37 wherein the program further comprises:

instructions for re-enabling echo suppression upon such automatic switching to a lower operational speed.

42. The computer-readable medium in accordance with claim 31 wherein the program further comprises:

instructions for signaling a destination telephone number upon such selective switching to disable echo cancellation and suppression.

43. The computer-readable medium in accordance with claim 42 wherein such signaling is performed over the telephone line bearing the detected modem traffic.

44. The computer-readable medium in accordance with claim 43 wherein said instructions for signaling include instructions for passing through the voice bearer channel path a prescribed end-to-end control message instructing the destination telephone number to disable echo cancellation and suppression.

45. A computer-readable medium containing a program for selecting the speed of a codec for use in a voice packet network, the program comprising:

codec mechanism software coupled with one or more network nodes;

modem answer tone detector software for signaling when a modem is detected at a call-originating or call-terminating network node defining a channel therebetween; and

switch software coupled with said codec mechanism software and responsive to the modem detection signaling for automatically up-speeding the codec mechanism software.