Multiplicative updating of precoder or postcoder matrices for crosstalk control in a communication system

1. A method of controlling crosstalk between channels of a communication system, comprising:

estimating crosstalk between channels of the system;

generating a compensation matrix based on the crosstalk estimates; and

generating compensated signals based on the compensation matrix;

wherein the compensation matrix is generated using a multiplicative update process in which a previous version of the compensation matrix comprising one or more non-zero off-diagonal elements is updated by at least one of pre-multiplying by a first auxiliary matrix and post-multiplying by a second auxiliary matrix, a given one of the auxiliary matrices also comprising one or more non-zero off-diagonal elements;

wherein pre-multiplying by the first auxiliary matrix comprises performing multiplicative updates of entries of a precoder matrix on a column-by-column basis, at least one multiplicative update performed on entries of the precoder matrix on the column-by-column basis comprising subtracting from a column of the precoder matrix a multiple of at least one other column of the precoder matrix; and

wherein post-multiplying by the second auxiliary matrix comprises performing multiplicative updates of entries of a postcoder matrix on a row-by row basis, at least one multiplicative update performed on entries of the postcoder matrix on the row-by-row basis comprising subtracting from a row of the postcoder matrix a multiple of at least one other row of the postcoder matrix.

2. The method of claim 1 wherein the multiplicative updates performed on entries of the precoder matrix on the column-by-column basis comprise subtracting a multiple of one column of the precoder matrix from another column of the precoder matrix.

3. The method of claim 1 wherein the step of generating compensated signals based on the compensation matrix comprises generating pre-compensated signals using the precoder matrix.

4. The method of claim 3 further comprising the step of transmitting the pre-compensated signals from an access node of system to respective network terminals of the system over respective ones of the channels.

5. The method of claim 1 wherein the multiplicative updates performed on entries of the postcoder matrix on the row-by-row basis comprise subtracting a multiple of one row of the postcoder matrix from another row of the postcoder matrix.

6. The method of claim 1 wherein the step of generating compensated signals based on the compensation matrix comprises generating post-compensated signals using the postcoder matrix.

7. The method of claim 6 further comprising the step of receiving uncompensated signals in an access node of the system from respective network terminals of the system over respective ones of the channels, wherein the post-compensated signals are generated from respective ones of the received uncompensated signals.

8. The method of claim 1 , wherein the at least one multiplicative update performed on entries of the precoder matrix on the column-by-column basis comprises subtracting a multiple of two or more columns of the precoder matrix from another column of the precoder matrix.

9. A non-transitory computer-readable storage medium having embodied therein executable program code that when executed by a processor of an access node of the system causes the access node to perform the steps of the method of claim 1 .

10. An apparatus comprising:

an access node configured to control crosstalk between channels of communication system;

wherein the access node comprises:

a plurality of transceivers; and

vectoring circuitry coupled to the transceivers;

the vectoring circuitry comprising a processor coupled to a memory and being operative to estimate crosstalk between the channels of the system, to generate a compensation matrix based on the crosstalk estimates, and to generate compensated signals based on the compensation matrix;

wherein the compensation matrix is generated using a multiplicative update process in which a previous version of the compensation matrix comprising one or more non-zero off-diagonal elements is updated by at least one of pre-multiplying by a first auxiliary matrix and post-multiplying by a second auxiliary matrix, a given one of the auxiliary matrices also comprising one or more non-zero off-diagonal elements;

wherein pre-multiplying by the first auxiliary matrix comprises performing multiplicative updates of entries of a precoder matrix on a column-by-column basis, at least one multiplicative update performed on entries of the precoder matrix on the column-by-column basis comprising subtracting a multiple of at least one column of the precoder matrix from at least one other column of the precoder matrix; and

wherein post-multiplying by the second auxiliary matrix comprises performing multiplicative updates of entries of a postcoder matrix on a row-by row basis, at least one multiplicative update performed on entries of the postcoder matrix on the row-by-row basis comprising subtracting a multiple of at least one row of the postcoder matrix from at least one other row of the postcoder matrix.

11. The method of claim 1 , wherein the at least one multiplicative update performed on entries of the postcoder matrix on the row-by-row basis comprises subtracting a multiple of two or more columns of the postcoder matrix from another row of the postcoder matrix.

12. A communication system comprising the apparatus of claim 10 .

13. The apparatus of claim 10 wherein the vectoring circuitry comprises:

a vector control entity operative to estimate the crosstalk between the channels of the system and to generate the compensation matrix; and

a vectoring signal processing module operative to generate the compensated signals based on the compensation matrix.

14. The apparatus of claim 10 wherein the processor comprises a vector processor configured to generate the compensated signals.

15. The apparatus of claim 14 wherein the vector processor comprises a column update module coupled to a precoder, and the compensation matrix comprises the precoder matrix utilized by the precoder to generate pre-compensated signals.

16. The apparatus of claim 15 wherein the column update module is configured to perform the multiplicative updates of entries of the precoder matrix on the column-by-column basis using the first auxiliary matrix.

17. The apparatus of claim 14 wherein the vector processor comprises a row update module coupled to a postcoder, and the compensation matrix comprises the postcoder matrix utilized by the postcoder to generate post-compensated signals.

18. The apparatus of claim 17 wherein the row update module is configured to perform the multiplicative updates of entries of the postcoder matrix on the row-by-row basis using the second auxiliary matrix.

19. The apparatus of claim 14 wherein the vector processor is implemented in the form of a single integrated circuit.

20. An integrated circuit comprising:

a vector processor operative to generate compensated signals based on a compensation matrix;

wherein the compensation matrix is generated based on estimates of crosstalk between channels of a communication system;

wherein the compensation matrix is generated using a multiplicative update process in which a previous version of the compensation matrix comprising one or more non-zero off-diagonal elements is updated by at least one of pre-multiplying by a first auxiliary matrix and post-multiplying by a second auxiliary matrix, a given one of the auxiliary matrices also comprising one or more non-zero off-diagonal elements;

wherein pre-multiplying by the first auxiliary matrix comprises performing multiplicative updates of entries of a precoder matrix on a column-by-column basis, at least one multiplicative update performed on entries of the precoder matrix on the column-by-column basis comprising subtracting a multiple of at least one column of the precoder matrix from at least one other column of the precoder matrix; and

wherein post-multiplying by the second auxiliary matrix comprises performing multiplicative updates of entries of a postcoder matrix on a row-by row basis, at least one multiplicative update performed on entries of the postcoder matrix on the row-by-row basis comprising subtracting a multiple of at least one row of the postcoder matrix from at least one other row of the postcoder matrix.

21. A method of controlling crosstalk between channels of a communication system, comprising:

estimating crosstalk between channels of the system;

generating a compensation matrix based on the crosstalk estimates; and

generating compensated signals based on the compensation matrix;

wherein the compensation matrix is generated using a multiplicative update process in which a previous version of the compensation matrix comprising one or more non-zero off-diagonal elements is updated by at least one of pre-multiplying by a first auxiliary matrix and post-multiplying by a second auxiliary matrix, a given one of the auxiliary matrices also comprising one or more non-zero off-diagonal elements; and

wherein the auxiliary matrix comprises an approximate inverse of a resultant channel matrix, the auxiliary matrix being formed by subtracting a matrix based at least in part on a residual channel matrix from an identity matrix.

22. The method of claim 21 , wherein the auxiliary matrix is formed by subtracting a scaled version of the residual channel matrix from an identity matrix.

23. The method of claim 21 , wherein the auxiliary matrix is formed by subtracting a portion of the residual channel matrix from an identity matrix.

24. The method of claim 21 wherein the auxiliary matrix is formed by subtracting the residual channel matrix from an identity matrix.