Optimizing precoder settings using average SINR reports for groups of tones

1. A method, comprising:

transmitting data to at least a first communication network device via at least a first communication line during a sequence of periods;

for each period of the sequence of periods, receiving a separate value, each value being an average of measurements at the communication network device of measures of crosstalk of a plurality of communication network signal subcarriers, wherein each signal subcarrier of the plurality of signal subcarriers is associated with a corresponding matrix of a plurality of matrices; and

for each individual signal subcarrier of the plurality of signal subcarriers, updating the matrix for the individual signal subcarrier based on the received values, the matrix for the individual signal subcarrier being configured to precode data transmissions to the communication network device over the individual signal subcarrier;

wherein updating the matrix comprises:

for a given one of the plurality of signal subcarriers, selecting one or more matrix elements to be updated in a manner configured to increase the value of the measure of crosstalk that is geometrically averaged over the plurality of signal subcarriers;

for the given signal subcarrier, determining an estimate of the measure of crosstalk based at least in part on the geometrically averaged measure of crosstalk;

for the given signal subcarrier, adjusting the matrix for precoding data transmissions for the selected matrix elements; and

keeping respective matrices for precoding data transmissions for a remainder of the plurality of signal subcarriers other than the given subcarrier fixed.

2. The method of claim 1 , wherein the updated matrix for one of the signal subcarriers of the plurality of signal subcarriers is different than the updated matrix for another one of the signal subcarriers of the plurality of signal subcarriers.

3. The method of claim 1 , wherein the updated matrix for one of the signal subcarriers of the plurality of signal subcarriers is the same as the updated matrix for at least another one of the signal subcarriers of the plurality of signal subcarriers.

4. The method of claim 1 , wherein the plurality of communication network signal subcarriers comprises a plurality of communication network signal subcarriers at proximate frequencies.

5. The method of claim 1 , wherein the communication network is a digital subscriber line (DSL) system.

6. The method of claim 1 , wherein the signal subcarrier is a digital subscriber line (DSL) tone.

7. The method of claim 1 , wherein the measure of crosstalk is a signal-to-interference-plus-noise ratio (SINR).

8. The method of claim 1 , wherein the matrix for one of the signal subcarriers of the plurality of signal subcarriers has a different form in each period of the sequence of periods.

9. The method of claim 8 , wherein the matrix for another one of the signal subcarriers of the plurality of signal subcarriers has a fixed form during each period of the sequence of periods.

10. A method, comprising:

transmitting data to at least a first communication network device via at least a first communication line during a sequence of periods;

for each period of the sequence of periods, receiving a separate value, each value being an average of measurements at the communication network device of measures of crosstalk of a plurality of communication network signal subcarriers, wherein each signal subcarrier of the plurality of signal subcarriers is associated with a corresponding matrix of a plurality of matrices; and

for each individual signal subcarrier of the plurality of signal subcarriers, updating the matrix for the individual signal subcarrier based on the received values, the matrix for the individual signal subcarrier being configured to precode data transmissions to the communication network device over the individual signal subcarrier;

selecting one or more matrix elements to be updated in a manner configured to increase the value of the measure of crosstalk that is averaged over the plurality of signal subcarriers;

wherein the updating comprises setting the matrix for precoding data transmissions over the selected one of the signal subcarriers such that the averaged measure of crosstalk is increased and wherein the updating further comprises setting elements of the matrices for precoding data transmissions over other signal subcarriers of the plurality of signal subcarriers to interpolate between corresponding elements of the matrix for the selected one of the signal subcarriers and an updated matrix for precoding data transmissions over a selected signal subcarrier of a second plurality of signal subcarriers.

11. A method, comprising:

transmitting data to a first communication network device via a first communication line during a sequence of periods;

for each period of the sequence of periods, receiving a separate value, each value being an average of measurements at the first communication network device of measures of crosstalk of a plurality of communication network signal subcarriers;

for each individual signal subcarrier of the plurality of signal subcarriers, updating a matrix based on the received values, the matrix being configured to precode data transmissions to the communication network device over the individual signal subcarrier; and

transmitting data to one or more second communication network devices via one or more second communication lines during the sequence of periods, the one or more second communication lines being configured to produce interference on the communication line used to transmit data to the first device;

wherein the transmitting data to the first device comprises transmitting a noise power to the first communication line over the signal subcarriers of the plurality such that a ratio of the noise powers transmitted to first and second ones of the signal subcarriers is equal to a ratio of the data powers transmitted to one of the second devices over the first and second signal subcarriers.

12. A method, comprising:

receiving a first crosstalk measure that is averaged over a group of at least two subcarriers, each subcarrier of the group of subcarriers being associated with a corresponding precoder matrix of a plurality of precoder matrices;

perturbing one or more precoder matrices for one or more subcarriers in the group;

receiving at least a second crosstalk measure averaged over the group of at least two subcarriers; and

updating one or more precoder matrices for one or more subcarriers in the group based on the received crosstalk measures;

wherein perturbing the one or more precoder matrices comprises:

for a given one of the group of signal subcarriers, selecting one or more matrix elements to be updated in a manner configured to increase the first crosstalk measure that is geometrically averaged over the plurality of signal subcarriers;

for the given signal subcarrier, determining an estimate of the measure of crosstalk based at least in part on the geometrically averaged measure of crosstalk;

for the given signal subcarrier, adjusting the corresponding precoder matrix for the selected matrix elements; and

keeping respective precoder matrices for a remainder of the group of signal subcarriers other than the given subcarrier fixed.

13. The method of claim 12 , wherein the updating step further comprises updating a precoder matrix for one subcarrier only.

14. The method of claim 12 , wherein the updating step further comprises updating precoder matrices for all subcarriers using interpolation.

15. The method of claim 12 , wherein the perturbation step and the updating step further comprise using a common power level for all subcarriers in the group.

16. The method of claim 12 , wherein the perturbation step and the updating step further comprise adding artificial noise to each subcarrier in a group proportional to the signal power transmitted on a disturber line on each subcarrier.

17. The method of claim 12 , wherein, during the perturbation and update steps, precoder matrices for subcarriers in a group are defined by control variables.

18. The method of claim 17 , wherein the number of control variables is smaller than the number of coefficients in the precoder matrices.

19. The method of claim 17 , wherein the control variables are precoder matrix coefficients for a subset of subcarriers in the group, and precoder matrix coefficients for the remaining subcarriers are determined by interpolation.

20. The method of claim 17 , wherein the control variables are updated based on one or more of the received crosstalk measures.

21. A method, comprising:

transmitting data to at least a first communication network device via at least a first communication line during a sequence of periods;

for each period of the sequence of periods, receiving a separate value, each value being an average of measurements at the communication network device of measures of crosstalk of a plurality of communication network signal subcarriers, wherein each signal subcarrier of the plurality of signal subcarriers is associated with a corresponding matrix of a plurality of matrices; and

for each individual signal subcarrier of the plurality of signal subcarriers, updating the matrix for the individual signal subcarrier based on the received values, the matrix for the individual signal subcarrier being configured to precode data transmissions to the communication network device over the individual signal subcarrier;

wherein each value is an average of measurements at respective ones of a plurality of communication network devices.

22. The method of claim 21 , wherein each communication network device of the plurality of communication network devices corresponds to a respective signal subcarrier of the plurality of signal subcarriers such that each measurement at a given communication network device of the plurality of communication network devices is a measurement of a measure of crosstalk of a corresponding signal subcarrier of the plurality of signal subcarriers.