Method and systems for reducing crosstalk

1. A method of reducing crosstalk in a system, the method comprising:

obtaining a plurality of groups of lines based on crosstalk characteristics of the system, lines in a same group of lines being permitted to be active during a same time slot;

identifying a first set of lines associated with data to send and a second set of lines associated with no data to send, the first set of lines being designated for transmission during a selected time slot;

modifying the first set of lines in accordance with the plurality of groups of lines; and

transmitting symbols during the selected time slot using the modified first set of lines.

2. The method of claim 1 , further comprising:

storing sets of precoder coefficients, a number of the plurality of groups of lines being greater than a number of the stored sets of precoder coefficients; and

determining precoder coefficients for the modified first set of lines based on at least one of the stored sets of precoder coefficients, wherein the transmitting is based on the determined precoder coefficients for the modified first set of lines.

3. The method of claim 2 , wherein the sets of precoder coefficients correspond to clusters of lines, each of the plurality of groups of lines including at least one of the clusters of lines.

4. The method of claim 3 , wherein the plurality of groups of lines includes all possible combinations of the clusters of lines.

5. The method of claim 1 , wherein the modifying includes,

activating lines that are part of both the second set and the modified first set.

6. The method of claim 5 , wherein the transmitting includes,

transmitting idle symbols in the lines that are part of both the second set and the modified first set.

7. The method of claim 1 , wherein the modifying includes,

deactivating lines that are part of the first set and not the modified first set.

8. The method of claim 1 , wherein the obtaining includes,

obtaining at least one quad pair; and

generating the plurality of groups of lines based on the at least one quad pair.

9. The method of claim 1 , further comprising:

estimating a precoding matrix based on the modified first set.

10. The method of claim 9 , wherein the estimating includes estimating a portion of the precoding matrix as:

( P DD ) −1 ≈M DD =( B DD ) −1 (2 I×P DD ( B DD ) −1 )

where D is a set of inactive lines, M DD is a precoder component matrix and B DD is a sparse matrix associated with interactions of one of the plurality of groups.

11. The method of claim 1 , wherein the plurality of groups of lines includes all possible combinations of a plurality of clusters of the lines, the method further comprising:

storing block inverse matrices for the clusters, respectively, a number of the plurality of groups of lines being greater than a number of the stored block inverse matrices; and

determining precoder coefficients for the modified first set of lines based on the stored block inverse matrices.

12. An access node comprising:

a processor configured to,

obtain a plurality of groups of lines based on crosstalk characteristics of the system, lines in a same group of lines being permitted to be active during a same time slot,

identify a first set of lines associated with data to send and a second set of lines associated with no data to send, the first set of lines being designated for transmission during a selected time slot, and

modify the first set of lines in accordance with the plurality of groups of lines; and

a transmitter configured to transmit symbols during the selected time slot using the modified first set of lines.

13. The access node of claim 12 , further comprising:

a memory configured to store sets of precoder coefficients, a number of the plurality of groups of lines being greater than a number of the stored sets of precoder coefficients, wherein

the processor is configured to determine precoder coefficients for the modified first set of lines based on at least one of the stored sets of precoder coefficients, and

the transmitter is configured to transmit the symbols based on the determined precoder coefficients for the modified first set of lines.

14. The access node of claim 13 , wherein the sets of precoder coefficients correspond to clusters of lines, each of the plurality of groups of lines including at least one of the clusters of lines.

15. The access node of claim 14 , wherein the plurality of groups of lines includes all possible combinations of the clusters of lines.

16. The access node of claim 12 , wherein the processor is configured to activate lines that are part of both the second set and the modified first set.

17. The access node of claim 16 , wherein the transmitter is configured to transmit idle symbols in the lines that are part of both the second set and the modified first set.

18. The access node of claim 12 , wherein the processor is configured to deactivate lines that are part of the first set and not the modified first set.

19. The access node of claim 12 , wherein the processor is configured to obtain at least one quad pair and generate the plurality of groups of lines based on the at least one quad pair.

20. The access node of claim 12 , wherein the processor is configured to estimate a precoding matrix based on the modified first set.

21. The access node of claim 20 , wherein the processor is configured to estimate a portion of the precoding matrix as:

( P DD ) −1 ≈M DD =( B DD ) −1 (2 I−P DD ( B DD ) −1 )

where D is a set of inactive lines, M DD is a precoder component matrix and B DD is a sparse matrix associated with interactions of one of the plurality of groups.

22. The access node of claim 12 , wherein the plurality of groups of lines includes all possible combinations of a plurality of clusters of the lines, and the access node further comprises:

a memory configured to store block inverse matrices for the clusters, respectively, a number of the plurality of groups of lines being greater than a number of the stored block inverse matrices, and

the processor is configured to determine precoder coefficients for the modified first set of lines based on the stored block inverse matrices.