Method and apparatus for optimizing dynamic range in DMT modems

1. A digital subscriber line ‘XDSL’ communication system for provisioning multi-tone modulated communications over a subscriber line, and the communication system comprising:

a digital subscriber line access multiplexer (DSLAM) for distributing a near end crosstalk (NEXT) model of anticipated disturbance from neighboring disturber subscriber lines; and

at least one modem having shared and discrete components forming a transmit path and a receive path and the at least one modem coupled to the DSLAM and responsive to the distributed NEXT model there from to adjust a dynamic range of an analog portion of the receive path to accommodate the anticipated disturbance modeled in the distributed NEXT model, whereby the adjusted range is large enough to substantially avoid clipping of a received signal and at the same time not so large as to result in significant excess dynamic range.

2. The XDSL communication system of claim 1 , wherein the receive path components of the at least one modem further comprises:

an analog-to-digital converter (ADC) with an output coupled to remaining components of the receive path, and an input, and the ADC digitizing a received analog signal; and

an analog gain control (AGC) with an input coupled to the received signal and an output coupled to the input of the ADC, and a level of the AGC utilized to adjust the dynamic range of the analog portion of the receive path.

3. The XDSL communication system of claim 1 , wherein the at least one modem further comprises:

an analog-to-digital converter (ADC) receive path component with an output coupled to remaining components of the receive path, and an input, and the ADC digitizing a received analog signal;

an analog gain control (AGC) receive path component with an input coupled to the received signal and an output coupled to the input of the ADC, and a level of the AGC utilized to adjust the dynamic range of the analog portion of the receive path; and

a range optimizer component coupled to the receive path, and responsive to the NEXT model to adjust a dynamic range of an analog portion of the receive path by injecting a disturber signal into the receive path during a training phase of operation and by adjusting the AGC to substantially avoid clipping thereof.

4. The XDSL communication system of claim 1 , wherein the at least one modem further comprises:

an analog-to-digital converter (ADC) receive path component with an output coupled to remaining components of the receive path, and an input, and the ADC digitizing a received analog signal;

an analog gain control (AGC) receive path component with an input coupled to the received signal and an output coupled to the input of the ADC, and a level of the AGC utilized to adjust the dynamic range of the analog portion of the receive path; and

a range optimizer component coupled to the receive path, and responsive to the NEXT model to adjust a dynamic range of an analog portion of the receive path by calculating the anticipated disturbance modeled in the distributed NEXT model during a training phase of operation and by adjusting the AGC to substantially avoid clipping thereof.

5. An XDSL modem for provisioning XDSL multi-tone modulated communications over a subscriber line, and the modem comprising:

a plurality of shared and discrete components forming a transmit path and a receive path for modulating and demodulating an XDSL communication channel;

a near end crosstalk (NEXT) model of anticipated disturbance from neighboring disturber subscriber lines;

a range optimizer component coupled to the receive path, and responsive to the NEXT model to adjust a dynamic range of an analog portion of the receive path to accommodate the anticipated disturbance modeled in the distributed NEXT model, whereby the adjusted range is large enough to substantially avoid clipping of a received signal and at the same time not so large as to result in significant excess dynamic range.

6. The XDSL modem of claim 5 , wherein the receive path components of the at least one modem further comprise:

an analog-to-digital converter (ADC) with an output coupled to remaining components of the receive path, and an input, and the ADC digitizing a received analog signal; and

an analog gain control (AGC) with an input coupled to the received signal and an output coupled to the input of the ADC, and a level of the AGC utilized to adjust the dynamic range of the analog portion of the receive path.

7. The XDSL modem of claim 5 , wherein the modem further comprises:

an analog-to-digital converter (ADC) receive path component with an output coupled to remaining components of the receive path, and an input, and the ADC digitizing a received analog signal;

an analog gain control (AGC) receive path component with an input coupled to the received signal and an output coupled to the input of the ADC, and a level of the AGC utilized to adjust the dynamic range of the analog portion of the receive path; and

a range optimizer component coupled to the receive path, and responsive to the NEXT model to adjust a dynamic range of an analog portion of the receive path by injecting a disturber signal into the receive path during a training phase of operation and by adjusting the AGC to substantially avoid clipping thereof.

8. The XDSL modem of claim 5 , wherein the modem further comprises:

an analog-to-digital converter (ADC) receive path component with an output coupled to remaining components of the receive path, and an input, and the ADC digitizing a received analog signal;

an analog gain control (AGC) receive path component with an input coupled to the received signal and an output coupled to the input of the ADC, and a level of the AGC utilized to adjust the dynamic range of the analog portion of the receive path; and

a range optimizer component coupled to the receive path, and responsive to the NEXT model to adjust a dynamic range of an analog portion of the receive path by calculating the anticipated disturbance modeled in the distributed NEXT model during a training phase of operation and by adjusting the AGC to substantially avoid clipping thereof.

9. A method for operating an XDSL modem having shared and discrete components forming a transmit path and a receive path for multi-tone modulated XDSL communications, and the method comprising:

obtaining a near end crosstalk (NEXT) model of anticipated disturbance from neighboring disturber subscriber lines;

adjusting a dynamic range of an analog portion of the receive path to accommodate the anticipated disturbance modeled in the distributed NEXT model, whereby the adjusted range is large enough to substantially avoid clipping of a received signal and at the same time not so large as to result in significant excess dynamic range.

10. The method for XDSL communication of claim 9 , further comprising:

adjusting a gain of the received signal to substantially avoid clipping of the received signal including the anticipated disturbance thereto resulting from neighboring disturber subscriber lines.

11. The method for XDSL communication of claim 9 , further comprising:

injecting a disturber signal into the receive path during a training phase of operation; and

adjusting a gain of the received signal to substantially avoid clipping thereof.

12. The method for XDSL communication of claim 9 , further comprising:

calculating the anticipated disturbance modeled in the distributed NEXT model during a training phase of operation; and

adjusting a gain of the received signal to substantially avoid clipping thereof.

13. A means for operating an XDSL modem having shared and discrete components forming a transmit path and a receive path for multi-tone modulated XDSL communications, and the method comprising:

means for obtaining a near end crosstalk (NEXT) model of anticipated disturbance from neighboring disturber subscriber lines;

means for adjusting a dynamic range of an analog portion of the receive path to accommodate the anticipated disturbance modeled in the distributed NEXT model, whereby the adjusted range is large enough to substantially avoid clipping of a received signal and at the same time not so large as to result in significant excess dynamic range.

14. The means for XDSL communication of claim 13 , further comprising:

means for adjusting a gain of the received signal to substantially avoid clipping of the received signal including the anticipated disturbance thereto resulting from neighboring disturber subscriber lines.

15. The means for XDSL communication of claim 13 , further comprising:

means for injecting a disturber signal into the receive path during a training phase of operation; and

means for adjusting a gain of the received signal to substantially avoid clipping thereof.

16. The means for XDSL communication of claim 13 , further comprising:

means for calculating the anticipated disturbance modeled in the distributed NEXT model during a training phase of operation; and

means for adjusting a gain of the received signal to substantially avoid clipping thereof.