Method and apparatus for pre-distortion of an X-DSL line driver

• US 6,873,653 B1
• Filed: 02/07/2001
• Issued: 03/29/2005
• Est. Priority Date: 12/17/1999
• Status: Expired due to Term

• Current Assignee: Ikanos Communications Incorporated (Qualcomm, Inc.)
• Original Assignee: Ikanos Communications Incorporated (Qualcomm, Inc.)
• Inventors: Zhang, John Zhongxuan, Heidari, Sam, Rezvani, Behrooz, Smith, Dale
• Primary Examiner(s): Tse, Young T.
• Assistant Examiner(s): Ahn, Sam K.
• Application Number:
  US09/779,256
• Time in Patent Office: 1,511 Days
• Field of Search: 375/219, 375/296, 375/285, 375/220, 375/221, 375/222, 375/223, 379/22.02, 379/27.01, 379/28, 379/31, 379/93.26, 379/418
• US Class Current: 375/222
• CPC Class Codes: H04L 27/2601 Multicarrier modulation systems
• CPC Class Codes: H04L 5/16 Half-duplex systems; Simplex/duplex switching; Transmission of break signals non-automatically inverting the direction of transmission

Abstract

An apparatus and method is provided for minimizing in channel distortion in an X-DSL line driver is disclosed. The apparatus may be incorporated in an existing X-DSL architecture without additional circuitry. Out of band monitoring of a channel is implemented to adaptively minimize out of band interference and in band distortion. A unique training sequence, suitable for DMT line codes is set forth. The training sequence allows a full spectral characterization of the downstream signal space with a single upstream monitoring tone. The invention may be used with multi-channel X-DSL line drivers interfacing with any of a number of multi-channel supply architectures. The apparatus may be applied with equal advantage to communication protocols other than X-DSL. The apparatus may be applied with equal advantage in wired and wireless media.

Claims

1. A multi-tone communication device with a transmit path and a receive path configured to couple to a communication medium and with the transmit path and the receive path including transmit components and receive components respectively, the communication device comprising:

a training module for transmitting on the transmit path a training sequence comprising pairs of tones transmitted on the transmit path resulting in an intermodulation which generates a single tone corresponding with a monitor signal on the receive path;

a controller for controlling variations of at least one control parameter of at least a selected one of the transmit components during the transmission of the training sequence by the training module;

a tone detector on the receive path to detect levels of the monitor signal; and

a processor which utilizes the detected levels of the monitor signal to determine which among the variations of the at least one control parameter minimizes leakage between the transmit path and the receive path.

2. The communication device of claim 1, the controller further for controlling the locking of the at least one control parameter at the detected levels determined by the processor to minimize leakage during subsequent operation of the communication device.

3. The communication device of claim 1, wherein the controller controls variations of at least one of, a bias voltage, an input voltage and a temperature of a selected amplification component within the transmit path of the communication device.

4. The communication device of claim 1, further comprising on the receive path:

an analog-to-digital converter (ADC) for digitizing the monitor signal;

the tone detector coupled to the ADC for detecting an amplitude of the monitor signal; and

a memory for storage by the processor of the amplitude of the monitor signal and variations of the at least one control parameter corresponding thereto.

5. The communication device of claim 1, wherein the communication medium comprises one of:

a wired medium and a wireless medium.

6. The communication device of claim 1, wherein the communication device comprises one of:

a physical modem and a logical modem.

7. An X-DSL communication device with a transmit path and a receive path configured to couple to a communication medium and with the transmit path and the receive path including transmit components and receive components respectively, the X-DSL communication device comprising:

a training module for transmitting on the transmit path a training sequence comprising pairs of tones distributed across a downstream set of X-DSL tones resulting in an intermodulation which generates a single tone corresponding with a monitor signal within an upstream set of X-DSL tones;

a controller for controlling variations of at least one control parameter of at least a selected one of the transmit components during the transmission of the training sequence by the training module;

a tone detector on the receive path to detect levels of the monitor signal; and

a processor which utilizes the detected levels of the monitor signal to determine which among the variations of the at least one control parameter minimizes leakage between the transmit path and the receive path.

8. A communication device with a transmit path and a receive path configured to couple to a communication medium and with the transmit path and the receive path including transmit components and receive components respectively, the communication device comprising:

a training module for transmitting on the transmit path a training sequence which generates a monitor signal on the receive path;

a controller for controlling variations of at least one control parameter of at least a selected one of the transmit components during the transmission of the training sequence by the training module;

a tone detector on the receive path to detect levels of the monitor signal;

a processor which utilizes the detected levels of the monitor signal to determine which among the variations of the at least one control parameter minimizes leakage between the transmit path and the receive path; and

an error detector for detecting a difference between an actual level of the monitor signal from an ADC and an estimated level of the monitor signal as estimated by the processor based on a leakage model of the leakage from the transmit path to the receive path together with an initial device model;

the processor both updating the initial device model to offset the difference and subsequently generating an inverse channel model for predistorting signals on the transmit path to linearize the output of the communication device.

9. The communication device of claim 8, wherein the communication medium comprises one of:

a wired medium and a wireless medium.

10. The communication device of claim 8, wherein the communication device comprises one of:

a physical modem and a logical modem.

11. A method for operating a multi-tone communication device with a transmit path and a receive path configured to couple to a communication medium and with the transmit path and receive path including transmit components and receive components respectively;

the method comprising;

transmitting on the transmit path a training sequence comprising selected pairs of tones distributed across a downstream set of tones resulting in an intermodulation which generates a single tone corresponding with a monitor signal on the receive path;

varying a level of at least one control parameter of at least a selected one of the transmit components during said transmitting step;

monitoring during the varying step the monitor signal on the receive path;

determining on the basis of the monitoring of the monitor signal the level of the at least one control parameter which minimizes the leakage of the training sequence onto the receive path; and

utilizing the level of the at least one control parameter determined in said determining step during subsequent transmissions.

12. The method of claim 11, wherein the selected one of the transmit components includes an amplifier and wherein the at least one control parameter varies in said varying step includes at least one of:

a bias voltage, an input voltage, and a temperature.

13. The method of claim 11, wherein the monitoring step further comprises the steps of:

digitizing the monitor signal received on the receive path;

detecting an amplitude of the monitor signal; and

storing the amplitude of the monitor signal detected in the detecting step for each variation of the level of the at least one control parameter during said transmitting step the training sequence.

14. The method of claim 11, wherein the communication medium comprises one of:

a wired medium and a wireless medium.

15. The method of claim 11, wherein the communication device comprises one of:

a physical modem and a logical modem.

16. A method for operating an X-DSL communication device with a transmit path and a receive path configured to couple to a communication medium and with the transmit path and the receive path including transmit components and receive components respectively, the method comprising:

transmitting on the transmission path a training sequence comprising selected pairs of tones distributed across a downstream set of X-DSL tones an intermodulation of which generates a single tone corresponding with a monitor signal within an upstream set of X-DSL tones;

varying a level of at least one control parameter of at least a selected one of the transmit components during said transmitting step;

monitoring during the varying step the monitor signal on the receive path;

determining on the basis of the monitoring of the monitor signal the level of the at least one control parameter which minimizes the leakage of the training sequence onto the receive path; and

utilizing the level of the at least one control parameter determined in said determining step during subsequent transmissions.

17. A method for operating a communication device with a transmit path and a receive path configured to couple to a communication medium and with the transmit path and the receive path including transmit components and receive components respectively, the method comprising:

transmitting on the transmission path a training sequence which generates a monitor signal on the receive path;

varying a level of at least one control parameter of at least a selected one of the transmit components during said transmitting step;

monitoring during the varying step the monitor signal on the receive path;

determining on the basis of the monitoring of the monitor signal the level of the at least one control parameter which minimizes the leakage of the training sequence onto the receive path;

utilizing the level of the at least one control parameter determined in said determining step during subsequent transmissions;

estimating the level of the monitor signal throughout the training sequence using a device model table for the components on the transmit and receive paths;

retransmitting the training sequence;

monitoring during the retransmitting step an actual level of the monitor signal on the receive path;

determining an error between the level of the monitor signal estimated in the estimating step and the actual level monitored in the monitoring step and updating the device model table accordingly;

generating an inverse channel model to linearize an output of the transmit path utilizing the device model table; and

predistorting signals transmitted in the transmit path utilizing the inverse channel model generated in the generating step.

18. The method of claim 17, wherein the communication medium comprises one of:

a wired medium and a wireless medium.

19. The method of claim 17, wherein the communication device comprises one of:

a physical modem and a logical modem.

20. A means for configuring a multi-tone communication device with a transmit path and a receive path configured to couple to a communication medium and with the transmit path and the receive path including transmit components and receive components respectively, the means comprising:

means for transmitting on the transmit path a training sequence which comprises pairs of tones distributed across a downstream set of tones resulting in an intermodulation which generates a single tone corresponding with a monitor signal within an upstream set of tones received on the receive path;

means for varying a level of at least one control parameter of at least a selected one of the transmit components during the training sequence;

means for monitoring in the varying means the monitor signal on the receive path;

means for determining on the basis of the monitoring of the monitor signal the level of the at least one control parameter which minimizes the leakage of training sequence onto the receive path; and

means for utilizing the level of the at least one control parameter determined in said determining means during subsequent transmissions.

21. The means for configuring of claim 20, wherein the pairs of tones are distributed across a downstream set of X-DSL tones and the single tone corresponding with the monitor signal is within an upstream set of X-DSL tones received on the receive path.