Forward compatible and expandable high speed communications system and method of operation

• US 6,252,900 B1
• Filed: 06/30/1997
• Issued: 06/26/2001
• Est. Priority Date: 06/30/1997
• Status: Expired due to Term

• Current Assignee: Realtek Semiconductor Corp.
• Original Assignee: Integrated Telecom Express, Inc.
• Inventors: Chen, Steve, Liu, Ming-Kang, Liu, Young Way
• Primary Examiner(s): Chin, Stephen
• Assistant Examiner(s): Fan, Chieh M.
• Application Number:
  US08/884,895
• Time in Patent Office: 1,457 Days
• Field of Search: 375/219, 375/220, 375/222, 375/260, 375/316, 375/354, 364/705.05, 370/94.2, 395/200.63, 455/522
• US Class Current: 375/219
• CPC Class Codes: H04L 27/2601 Multicarrier modulation systems
• CPC Class Codes: H04L 5/1446 of transmission speed
• CPC Class Codes: Y02D 30/50 in wire-line communication networks, e.g. low power modes or reduced link rate

Abstract

A high speed communications system is provided which uses a selectable, desirable portion of the total available bandwidth of a transmission channel. In a preferred embodiment, the invention is an ADSL compatible modem which selects a sub-set of the available downstream DMT sub-channels based on an evaluation of such sub-channels by appropriate signal processing circuitry. An analog front end (AFE) contains sub-band filtering causes an upstream transceiver to use only this selected number of available sub-channels for downstream data transmission. This reduces hardware costs and complexity while still preserving compatibility with applicable ADSL standards and providing a high speed data link. The target data rate of the modem can be further enhanced to the point of achieving full protocol capability by increasing or upgrading the AFEs, and/or the signal processing circuitry in order to increase the number of processable transmitted downstream sub-channels.

Claims

1. A high speed communications system capable of supporting a downstream data transmission from an upstream transceiver using an analog signal consisting of M data carrying signals contained within a bandwidth F, said system comprising:

a channel interface circuit for coupling to and receiving said analog signal; and

a front end receiving circuit for processing the analog signal and converting it to a digital signal;

a processing circuit for performing signal processing operations on N of said M data carrying signals (N<

M) from the digital signal using a first frequency portion f1 of the digital signal (f1<

F) and for extracting selected data from said N data carrying signals; and

wherein said selected data can be varied by varying resources available to said processing circuit, and said processing circuit does not process data carrying signals from the downstream data transmission outside of said first frequency portion f1.

2. The system of claim 1, wherein the N data carrying signals are selected by the processing circuit so as to reduce the amount of processing required to extract the selected data from the digital signal as compared to an amount of processing required to extract the selected data if it were carried by a different set of N data carrying signals.

3. The system of claim 2, wherein the N data carrying signals can be selected during an initialization process setting up a data link to the upstream transceiver.

4. The system of claim 3, wherein M data carrying signals can be sent by the upstream transmitter during an initialization process, and thereafter, only N data carrying signals are sent.

5. The system of claim 1, wherein the front end circuit includes:

(i) a sub-band filter for passing the first frequency bandwidth portion f₁ of said bandwidth F;

(ii) and an analog to digital converter.

6. The system of claim 1, wherein the selected data can be augmented to further include data obtained from an additional second frequency bandwidth portion f2 of said bandwidth F, when resources available to said processing circuit are also augmented so that an additional number of data carrying signals P from the M data carrying signals (N+P<

M) can be processed.

7. The system of claim 6, further including one or more sub-band filters for passing the first frequency bandwidth portion f1 and second frequency bandwidth portion f2 of said bandwidth F and an analog to digital converter.

8. The system of claim 7, wherein a target data rate of the system can be increased by processing an additional number of data carrying signals P from the M data carrying signals, where N+P<

M.

9. The system of claim 1, wherein the selected data to be extracted from the digital signal can be controlled by a user of such system.

10. The system of claim 9, wherein a user of such system can increase a target data rate of the system by modularly augmenting the front end circuit to include additional bandwidth and analog to digital conversion capacity such that an additional number of data carrying signals P from the M data carrying signals (N+P<

M) can be processed.

11. The system of claim 1, further including a front end transmitting circuit for transmitting control information to cause said upstream transceiver to transmit downstream data only using the N data carrying signals.

12. The system of claim 11, wherein the control information transmitted to the upstream transceiver includes feedback information indicating that only N of the M data carrying signals are desirable for downstream data transmission, even during times when said channel is capable of supporting more than N data carrying signals.

13. The system of claim 1, further including a front end transmitting circuit for transmitting an upstream data signal using a second frequency bandwidth F2 different from F, and L data carrying signals, and where L<

M.

14. A high speed communications system capable of supporting a downstream data transmission from an upstream transceiver using an analog signal consisting of M data carrying signals contained within a bandwidth F, said system comprising:

a channel interface circuit for coupling to and receiving said analog signal; and

a front end receiving circuit for processing the analog signal and converting it to a digital signal;

a processing circuit for extracting N data carrying signals (N<

M) from the digital signal using a first frequency portion f1 of the digital signal (f1<

F); and

a front end transmitting circuit for transmitting control information to cause said upstream transceiver to transmit downstream data only using the N data carrying signals; and

wherein the control information transmitted to the upstream transceiver includes feedback information indicating that only N of the M data carrying signals are desirable for downstream data transmission, even during times when said channel is capable of supporting more than N data carrying signals and

further wherein the control information transmitted to the upstream transceiver further includes feedback information indicating that;

(i) the system can support any data protocols used by said upstream transceiver; and

(ii) that they are connected through a channel with substantial signal attenuation characteristics for data signals other than the N data carrying signals.

15. A scalable high speed communications system capable of supporting an upstream transceiver which can transmit M modulated sub-channels using an analog signal through a channel to said system, said system comprising:

a channel interface circuit for coupling to and receiving said analog signal from the channel;

an analog front end circuit for processing the analog signal and converting it to a digital signal, the front end circuit including a sub-band filter and an analog to digital converter;

a processing circuit for extracting data from the digital signal, the digital signal including data from a first number N of said sub-channels, where N<

M/k where k is a scaling factor, and said processing circuit can accommodate any integer value for k>

=1, and;

wherein said N sub-channels can be varied based on resources available to said processing circuit, and said processing circuit extracts data only from said N sub-channels, regardless of whether additional ones of said M sub-channels can be used for transmitting data between the system and said upstream transceiver; and

further wherein the N sub-channels are selected so as to reduce the amount of processing required to extract the selected data from the digital signal, as compared to an amount of processing required to extract the selected data if it were carried by a different set of N sub-channels.

16. The system of claim 15, wherein the front end circuit includes:

(i) a sub-band filter for passing only the N sub-channels;

(ii) and an analog to digital converter.

17. The system of claim 15, wherein the selected data further includes data obtained from an additional second number of sub-channels P, so that an additional number of sub-channels (N+P<

M) can be processed.

18. The system of claim 17, further including one or more sub-band filters for passing the first number N and second number P of said sub-channels and an analog to digital converter.

19. The system of claim 18, wherein a target data rate of the system can be increased by processing an additional number of sub-channels P from the M sub-channels, and where N+P<

M.

20. The system of claim 15, wherein the selected data to be extracted is taken from bandpassed data passed through said sub-band filter, and which selected data can be controlled by a user of such system.

21. The system of claim 15, wherein the upstream transceiver uses discrete multi-tone (DMI) modulation for generating the M modulated sub-channels, and the channel supports asymmetric digital subscriber loop (ADSL) transmission standards.

22. The system of claim 15, further including a front end transmitting circuit for transmitting an upstream data signal using a second set of sub-channels L separate from M, where L<

M.

23. A scalable high speed communications system capable of supporting an upstream transceiver which can transmit M modulated sub-channels using an analog signal through a channel to said system, said system comprising:

a channel interface circuit for coupling to and receiving said analog signal from the channel;

an analog front end circuit for processing the analog signal and converting it to a digital signal, the front end circuit including a sub-band filter and an analog to digital converter;

a processing circuit for extracting data from the digital signal the digital signal including data from a first number N of said sub-channels, where N≦

M/k, where k is a scaling factor, and said processing circuit can accommodate any integer value for k>

=1, and;

wherein said N sub-channels can be varied based on resources available to said processing circuit, and said processing circuit extracts data only from said N sub-channels, regardless of whether additional ones of said M sub-channels can be used for transmitting data between the system and said upstream transceiver; and

further wherein the N sub-channels are selected so as to reduce the amount of processing required to extract the selected data from the digital signal, as compared to an amount of processing required to extract the selected data if it were carried by a different set of N sub-channels;

further wherein the N sub-channels can be selected by an initialization process to set up a data link to the upstream transceiver.

24. A scalable high speed communications system capable of supporting an upstream transceiver which can transmit M modulated sub-channels using an analog signal through a channel to said system, said system comprising:

a channel interface circuit for coupling to and receiving said analog signal from the channel;

an analog front end circuit for processing the analog signal and converting it to a digital signal, the front end circuit including a sub-band filter and an analog to digital converter;

a processing circuit for extracting data from the digital signal, the digital signal including data from a first number N of said sub-channels, where N≦

M/k, where k is a scaling factor, and said processing circuit can accommodate any integer value for k>

=1, and;

wherein said N sub-channels can be varied based on resources available to said processing circuit, and said processing circuit extracts data only from said N sub-channels, regardless of whether additional ones of said M sub-channels can be used for transmitting data between the system and said upstream transceiver; and

further wherein the N sub-channels are selectable by an initialization process to set up a data link with the remote transceiver, and are selected so as to reduce the amount of processing required to extract the selected data from the digital signal, as compared to an amount of processing required to extract the selected data if it were carried by a different set of N sub-channels;

further wherein the M sub-channels can be received from the upstream transmitter during said initialization process, and thereafter, only N sub-channels are received.

25. A scalable high speed communications system capable of supporting an upstream transceiver which can transmit M modulated sub-channels using an analog signal through a channel to said system, said system comprising:

a channel interface circuit for coupling to and receiving said analog signal from the channel;

an analog front end circuit for processing the analog signal and converting it to a digital signal, the front end circuit including a sub-band filter adapted to bandpass said analog signal under control of a user of such system, and an analog to digital converter;

a processing circuit for extracting data from the digital signal, the digital signal including data from a first number N of said sub-channels bandpassed by said sub-band filter under control of said user, where N<

M/k, and where k is a scaling factor and said processing circuit can accommodate any integer value for k>

=1 and;

wherein said N sub-channels can be varied based on resources available to said processing circuit, and said processing circuit extracts data only from said N sub-channels, regardless of whether additional ones of said M sub-channels can be used for transmitting data between the system and said upstream transceiver; and

further wherein said user of such system can increase a target data rate of the system by modularly augmenting the front end circuit to include additional bandwidth and analog to digital conversion capacity such that an additional second number of sub-channels P from the M sub-channels (N+P<

M) can be processed.

26. A scalable high speed communications system capable of supporting an upstream transceiver which can transmit M modulated sub-channels using an analog signal through a channel to said system, said system comprising:

a channel interface circuit for coupling to and receiving said analog signal from the channel,

an analog front end circuit for processing the analog signal and converting it to a digital signal, the front end circuit including a sub-band filter adapted to bandpass said analog signal under control of a user of such system, and an analog to digital converter;

a processing circuit for extracting data from the digital signal, the digital signal including data from a first number N of said sub-channels bandpassed by said sub-band filter under control of said user, where N≦

M/k, and where k is a scaling factor, and said processing circuit can accommodate any integer value for k >

=1, and;

wherein said N sub-channels can be varied based on resources available to said processing circuit, and said processing circuit extracts data only from said N sub-channels regardless of whether additional ones of said M sub-channels can be used for transmitting data between the system and said upstream transceiver; and

further wherein said user of such system can increase a target data rate of the system by modularly augmenting the front end circuit to include additional bandwidth and analog to digital conversion capacity such that an additional second number of sub-channels P from the M sub-channels (N+P<

M) can be processed; and

a front end transmitting circuit for transmitting control information to cause said upstream transceiver to transmit downstream data only using the N sub-channels.

27. A scalable high speed communications system capable of supporting an upstream transceiver which can transmit M modulated sub-channels using an analog signal through a channel to said system, said system comprising:

a channel interface circuit for coupling to and receiving said analog signal from the channel;

an analog front end circuit for processing the analog signal and converting it to a digital signal, the front end circuit including a sub-band filter adapted to bandpass said analog signal under control of a user of such system, and an analog to digital converter;

a processing circuit for extracting data from the digital signal the digital signal including data from a first number N of said sub-channels bandpassed by said sub-band filter under control of said user, where N≦

M/k and where k is a scaling factor, and said processing circuit can accommodate any integer value for k>

=1, and,

a front end transmitting circuit for transmitting control information to cause said upstream transceiver to transmit downstream data only using the N sub-channels; and

wherein said N sub-channels can be varied based on resources available to said processing circuit, and said processing circuit extracts data only from said N sub-channels, regardless of whether additional ones of said M sub-channels can be used for transmitting data between the system and said upstream transceiver; and

further wherein said user of such system can increase a target data rate of the system by modularly augmenting the front end circuit to include additional bandwidth and analog to digital conversion capacity such that an additional second number of sub-channels P from the M sub-channels (N+P<

M) can be processed; and

further wherein said control information transmitted to the upstream transceiver includes feedback information indicating that only N of the M sub-channels are usable for downstream data transmission, even during times when said channel is capable of supporting more than N sub-channels.

28. A high speed communications system capable of supporting an upstream transceiver which can transmit M modulated sub-channels using an analog signal through a channel to said system, said system comprising

a channel interface circuit for coupling to and receiving said analog signal from the channel;

an analog front end circuit for processing the analog signal and converting it to a digital signal, the front end circuit including a sub-band filter and an analog to digital converter;

a processing circuit for extracting data from the digital signal, the digital signal including data from a first number N of said subchannels, where N<

M;

a front end transmitting circuit for transmitting control information to cause said upstream transceiver to transmit downstream data only using the N sub-channels; and

wherein the control information transmitted to the upstream transceiver includes feedback information indicating that only N of the M sub-channels are usable for downstream data transmission, even during times when said channel is capable of supporting more than N sub-channels; and

further wherein the control information transmitted to the upstream transceiver further includes feedback information indicating that;

(i) the system can support any data protocols used by said upstream transceiver; and

(ii) that the system and upstream transceiver are connected through a channel with substantial signal attenuation characteristics for sub-channels other than the N sub-channels.

29. A high speed communications system for processing an analog data signal from a channel capable of supporting a downstream data transmission using a bandwidth F from a remote transciever also capable of using a bandwidth F, said system comprising:

a channel interface circuit for coupling to and receiving said analog data signal from the channel, and

a front end receiving circuit for processing the analog data signal and converting it to a digital signal;

a processing circuit for extracting selected data from the digital signal, the digital signal including data from a first frequency bandwidth portion f1 of said bandwidth and for generating feedback information indicating to the remote transceiver that the bandwidth other than f1 is unsuitable for data transmission even when said channel can support said bandwidth F;

wherein the feedback information contains intentionally altered channel characteristic information.

30. A high speed communications system for processing an analog data signal from a channel capable of supporting a downstream data transmission using a bandwidth F from a remote transciever also capable of using a bandwidth F, said system comprising:

a channel interface circuit for coupling to and receiving said analog data signal from the channel; and

a front end receiving circuit for processing the analog data signal and converting it to a digital signal;

a processing circuit for extracting selected data from the digital signal, the digital signal including data from a first frequency bandwidth portion f1 of said bandwidth and for generating feedback information indicating to the remote transceiver that the bandwidth other than f1 is unsuitable for data transmission even when said channel can support said bandwidth F, said feedback information containing intentionally altered channel characteristic information;

wherein the feedback information, including the size and center of first frequency bandwidth portion f1, can be controlled by a user of such system.

31. A high speed communications system for processing an analog data signal from a channel capable of supporting a downstream data transmission using a bandwidth F from a remote transciever also capable of using a bandwidth F, said system comprising:

a channel interface circuit for coupling to and receiving said analog data signal from the channel; and

a front end receiving circuit for processing the analog data signal and converting it to a digital signal;

a processing circuit for extracting selected data from the digital signal, the digital signal including data from a first frequency bandwidth portion f1 of said bandwidth and for generating feedback information indicating to the remote transceiver that the bandwidth other than f1 is unsuitable for data transmission even when said channel can support said bandwidth F, said feedback information containing intentionally altered channel characteristic information;

wherein the feedback information, including the size and center of first frequency bandwidth portion f1, can be controlled by a user of such system; and

further wherein the ratio of f1 to F is approximately 0.5 or less, and this ratio can be increased through modular additions to the front end receiving circuit.

32. A high speed communications system for transmitting digital information in a channel capable of supporting a transmission bandwidth F, said system comprising:

an upstream data transceiver capable of modulating the digital information to generate an analog data signal data transmission using said transmission bandwidth F; and

a downstream data transceiver channel interface circuit for coupling to and receiving said analog data signal from the upstream data transciever through said channel, the downstream data transceiver including

(i) a front end receiving circuit for processing the analog data signal and converting it to a digital signal; and

(ii) a processing circuit for demodulating the digital signal, the digital signal including data from a first frequency bandwidth portion f1 of said bandwidth and for generating feedback information indicating to the upstream transceiver that the bandwidth other than f1 is unsuitable for data transmission; and

(iii) a front end transmitting circuit for transmitting the feedback information using a second frequency bandwidth portion f2 to cause said upstream transceiver to transmit downstream data only using the first frequency portion fl;

wherein the feedback information contains intentionally altered channel characteristic information.

33. The system of claim 32, wherein the ratio of f1 to F is approximately 0.5 and this ratio can be increased through modular additions and/or changes to thefront end receiving circuit.

34. The system of claim 33, wherein the feedback information, including the size and location of first frequency portion f1, can be controlled by a user of such system.

35. A method of operating a high speed communications system that is coupled to a remote transceiver through a channel capable of supporting an analog data transmission having a bandwidth F, said method comprising:

(a) receiving said analog data signal from the remote transceiver through the channel;

and

(b) generating a digital signal based on sampling a portion of the analog data transmission signal corresponding to a first frequency bandwidth portion fl; and

(c) processing the digital signal to extract data from the digital signal; and

(d) generating feedback information indicating to the remote transceiver that the bandwidth other than f1 should not be used for data transmission, even if an analog data signal with bandwidth>

f1 is supportable in the channel and by the remote transceiver; and

(e) determining an optimal size and location of first frequency bandpass portion f1 so as to minimize the amount of processing required to extract the data from the digital signal, as compared to some other size and location for said first frequency bandpass portion f1.

36. The method of claim 35, further including a step prior to step (a):

receiving a control signal from a user of such system for determining size and location of first frequency bandwidth portion f1.

37. The method of claim 35, wherein the system transmits feedback information containing intentionally altered channel characteristic information.

38. A method of operating a high speed communications system that is coupled to a remote transceiver through a channel capable of supporting an analog data transmission having a bandwidth F, said method comprising:

(a) receiving said analog data signal from the remote transceiver through the channel;

and

(b) generating a digital signal based on sampling a portion of the analog data transmission signal corresponding to a first frequency bandwidth portion f1; and

(c) processing the digital signal to extract data from the digital signal; and

generating feedback information indicating to the remote transceiver that the bandwidth other than f1 should not be used for data transmission, even if an analog data signal with bandwidth >

f1 is supportable in the channel and by the remote transceiver; and

wherein step (a) occurs during an initialization period, and said received analog transmission signal is generated by the remote transceiver to have a bandwidth >

f1; and

after said initialization period the remote transceiver only transmits an analog data signal within first frequency bandwidth portion f1.

39. A method of operating a high speed communications system that is coupled to a remote transceiver through a channel capable of supporting an analog data transmission signal including M modulated sub-channels, said method comprising:

(a) receiving said analog data transmission signal from the remote transceiver through the channel; and

(b) generating a digital signal based on sampling a portion of the analog data transmission signal corresponding to a first frequency bandwidth portion f1; and

(c) processing the digital signal to extract data from N of the sub-channels, where N<

M; and

(d) generating feedback information indicating to the remote transceiver that the sub-channels other than the N sub-channels should not be used for data transmission, even if said channel and/or the remote transceiver is capable of supporting more than N sub-channels; and

(e) determining an optimal set of N sub-channels so as to minimize the amount of processing required to extract the data from the digital signal.

40. The method of claim 39, further including a step prior to step (a):

receiving a control signal from a user of such system for determining the identity of the N sub-channels.

41. A method of operating a high speed communications system that is coupled to a remote transceiver through a channel capable of supporting an analog data transmission signal including M modulated sub-channels, said method comprising:

(a) receiving said analog data transmission signal from the remote transceiver through the channel; and

(b) generating a digital signal based on sampling a portion of the analog data transmission signal corresponding to a first frequency bandwidth portion f1; and

(c) processing the digital signal to extract data from N of the sub-channels, where N<

M; and

(d) generating feedback information indicating to the remote transceiver that the sub-channels other than the N sub-channels should not be used for data transmission, even if said channel and/or the remote transceiver is capable of supporting more than N sub-channels; and

wherein;

step (a) occurs during an initialization period, and said received analog transmission signal can be generated by said remote transceiver to include data for M sub-channels; and

after step (d) the remote transceiver only transmits an analog data signal using the N sub-channels.

42. A method of operating a high speed communications system that is coupled to a remote transceiver through a channel capable of supporting an analog data transmission signal including M modulated sub-channels, said method comprising:

(a) receiving said analog data transmission signal from the remote transceiver through the channel, and

(b) generating a digital signal based on sampling a portion of the analog data transmission signal corresponding to a first frequency bandwidth portion f1; and

(c) processing the digital signal to extract data from N of the sub-channels where N<

M; and

(d) generating feedback information indicating to the remote transceiver that the sub-channels other than the N sub-channels should not be used for data transmission even if said channel and/or the remote transceiver is capable of supporting more than N sub-channels; and

wherein the system transmits feedback information containing intentionally altered channel characteristic information.

43. A method of operating a high speed communications system that is coupled through a channel to a remote transceiver operating at a maximum data rate Y using a bandwidth F, said method comprising:

(a) receiving an analog initialization signal from the remote transceiver through the channel; and

(b) generating a digital signal based on sampling a portion of the analog data transmission signal corresponding to a first frequency bandwidth portion fl, where f1<

F; and

(c) processing the digital signal to extract data from the digital signal such that an effective receiving rate X (where X<

Y) is achieved by the system;

(d) generating feedback information pertaining to the channel transmission characteristics indicating to the remote transceiver that data rates higher than X should not be used;

(e) thereafter receiving an analog data signal transmitted by the remote transceiver to have a bandwidth fl;

(f) repeating steps (b) and (c);

(g) determining an optimal location and size of bandwidth portion f1 so as to minimize the amount of processing required to extract the data from the digital signal at the receiving rate X, as compared to an amount of processing required to extract the data from the digital signal at the receiving rate X from a different bandwidth portion f1.

44. The method of claim 43, further including a step prior to step (a):

receiving a control signal from a user of such system for determining the effective receiving rate X.

45. A high speed communications data receiver for communicating through a channel with a remote transmitter that is capable of transmitting a data signal with a particular frame rate T and data rate Y, the receiver comprising:

a channel interface circuit for coupling to and receiving said data signal; and

an analog front end circuit for sampling the data signal and converting it to a digital signal; and

a processing circuit that;

(i) is configurable for processing the digital signal at a data rate<

=X and using said frame rate T, where X is determined for such processing circuit prior to initialization of a data transmission and X<

Y/2;

(ii) generates a transmission control signal for causing said remote transmitter to transmit at a data rate no greater than X during a data transmission;

(iii) is configurable to support said data transmission at least in part with assistance from resources from a host processing device;

wherein signal processing requirements for the processing circuit are reduced from that otherwise required to support data rate Y because processing resources sufficient to support a fractional rate of the available data rate Y are used to support said data rate X; and

further wherein X is determined by evaluating signal processing capabilities available to said processing circuit prior to said data transmission, including resources of said host processing device.

46. The system of claim 45, further including a front end transmitting circuit for transmitting the transmission control signal from the processing circuit to cause said remote transceiver to transmit downstream data only at said data rate X.

47. The system of claim 45, wherein the control information transmitted to the remote transceiver includes feedback information indicating that the maximum downstream data transmission data rate is X, even during times when said channel is capable of supporting more than said data rate X.

48. The system of claim 45, wherein the feedback information including the data rate X can be controlled by a user of such system.

49. The system of claim 45, wherein the ratio of X to Y is approximately 0.2 or less.

50. A high speed communications data receiver for communicating through a channel at a controllable data rate X with a remote transceiver capable of transmitting a data signal at a frame rate T, and a data rate Y, where X/Y<

½

, the receiver comprising;

a channel interface circuit for coupling to and receiving an analog data signal from the remote transceiver; and

an analog front end circuit for data sampling the analog signal and converting it to a digital signal; and

a processing circuit for determining said rate X based on processing capabilities available for extracting data from the digital signal, and for generating a transmission control signal for causing said remote transceiver to transmit using said frame rate T, and a data rate substantially equal to said data rate X during a data transmission, and said processing circuit being implemented at least in part by signal processing software executed by a host processing device coupled to the data receiver.

51. The receiver of claim 50, wherein said rate X is determined during a calibration routine.

52. The receiver of claim 51, wherein said calibration routine is executed by said processing device to determine the capabilities of such processing circuit.

53. The receiver of claim 50, wherein said rate X is configurable by a user of such receiver based on controlling resources to be made available to said host processing device.

54. The receiver of claim 50, wherein X/Y is approximately 0.2 or less.

55. A method for communicating through a channel with a remote transceiver that is capable of transmitting a data signal at a frame rate T, and a data rate Y, the method comprising the steps of:

receiving said data signal at a local transceiver; and

sampling the data signal and converting it to a digital signal at said local transceiver; and

processing the digital signal at a data rate<

=X and using said frame rate T at said local transceiver, where X is determined for said local transceiver prior to initialization of a data transmission and X<

Y/2; and

generating a transmission control signal for causing said remote transceiver to transmit at a data rate no greater than X during a data transmission; and

transmitting data in the channel at a data rate that is intentionally reduced from that supportable by said remote transceiver and by the channel, so that said local transceiver can;

(1) support such data transmission with data signal sampling resources and digital signal processing resources that are reduced from that required to support data rate Y;

(2) adjust said data rate in response to changes in said data signal sampling resources and digital signal processing resources.

56. The method of claim 55, wherein said transmission control signal, including the data rate X can be controlled by a user of such system.

57. The method of claim 55, wherein the ratio of X to Y is approximately 0.2 or less.

58. A method for communicating through a channel at a controllable data rate X with an upstream transmitter capable of transmitting a data signal at a frame rate T, and a data rate Y, where X/Y <

½

, the method comprising the steps of;

receiving said data signal; and

sampling the data signal and converting it to a digital signal; and

determining said rate X based on processing capabilities available f or extracting data from the digital signal; and

generating a transmission control signal for causing said upstream transmitter to transmit at said frame rate T and a data rate substantially equal to said data rate X during a data transmission

transmitting data in the channel at a data rate that is intentionally reduced from that supportable by the channel, such that said said data transmission can be supported with data signal sampling resources and digital signal processing resources that are reduced from that required to support data rate Y, and said data rate is adjustable in response to changes in said data signal sampling resources and digital signal processing resources.

59. The method of claim 58, wherein said rate X is determined during a calibration routine.

60. The method of claim 59, wherein said calibration routine is executed by a host data processor to determine the capabilities of such processor.

61. The method of claim 58, wherein said rate X is configurable by a user of such receiver based on performance characteristics of a host processor comprising a portion of the processing circuit.

62. The method of claim 58, wherein X/Y is approximately 0.2 or less.

63. A method for communicating through a channel between a local and a remote transceiver, which remote transceiver supports up to a first maximum number M modulated sub-channels, the method comprising the steps of:

(a) determining a second maximum number N of modulated sub-channels supportable by signal processing resources at the local transceiver; and

(b) transmitting data transmission control signals for causing the remote transceiver to transmit using at most said N modulated sub-channels, where N<

=M;

(c) transmitting data between the local and remote transceiver during a data transmission using at most said N modulated sub-channels; and

(d) dynamically adjusting a number of, or a data loading for, said N modulated sub-channels in response to changes in said signal processing resources.

64. The method of claim 63, wherein said signal processing resources are based on a software signal processing routine executed by a microprocessor coupled to the local transceiver.

65. The method of claim 63, wherein said data transmission control signals include T1.413 initialization protocol signals.

66. The method of claim 63, wherein the local and remote transceivers can be configured to support either a full data rate transmission in the channel using said first maximum number M modulated sub-channels, or a reduced data rate transmission using said second maximum number N modulated sub-channels.

67. The method of claim 63, further including a step (d):

adjusting said second maximum number N of modulated sub-channels in response to changes in said signal processing resources.