UPBO for vectored DSL

1. A method for performing upstream power back-off (UPBO) for a first digital subscriber line (DSL) line in a vectored DSL system comprising a vectored group of DSL lines comprising the first DSL line and a plurality of other DSL lines, wherein each vectored group DSL line comprises a customer premises equipment (CPE) modem coupled to a digital subscriber line access multiplexer (DSLAM) via a DSL line, the method comprising:

identifying a partial far-end crosstalk (FEXT) cancellation scheme used in the vectored DSL system, wherein the partial cancellation scheme defines performing partial FEXT cancellation on upstream transmissions of the first DSL line, wherein performing partial FEXT cancellation on upstream transmissions of the first DSL line results in residual crosstalk remaining in received signals after partial cancellation has been performed, wherein the partial FEXT cancellation scheme includes:

selecting a subset consisting of less than one or more of all possible disturbers, tones, channels and lines, and

performing FEXT cancellation for only the selected subset;

determining an effect of the residual crosstalk on the received signals associated with the partial FEXT cancellation scheme;

calculating first DSL line partial cancellation UPBO parameters based on the determined effect of the residual crosstalk and one or more selected performance metrics, wherein the one or more performance metrics relate to transmissions by the first DSL line, wherein each one of the one or more performance metric is one of the following: a measured performance metric, a simulated performance metric, and an estimated performance metric; and

operating the vectored group as a vectored DSL system using the calculated first DSL line partial cancellation UPBO parameters.

2. The method of claim 1 wherein the partial cancellation scheme comprises selecting a subset of dominant disturbers from all FEXT disturbers, wherein each FEXT disturber contributes FEXT to upstream transmissions of the first DSL line.

3. The method of claim 1 wherein the partial cancellation scheme comprises performing imperfect FEXT cancellation that yields residual crosstalk.

4. The method of claim 1 wherein one of the one or more performance metrics is at least one of the following: an upstream target data rate for the first DSL line; an upstream target signal to noise ratio (SNR) for the first DSL line.

5. The method of claim 4 wherein each DSL line in the vectored group operates in accordance with a VDSL standard.

6. The method of claim 5 wherein an upstream-end DSL device calculates the first DSL line partial cancellation UPBO parameters and transmits the calculated first DSL line partial cancellation UPBO parameters to the first DSL line CPE.

7. The method of claim 6 wherein the upstream-end DSL device is one of the following: a DSLAM, a vectoring control entity (VCE), a network management system (NMS).

8. A vectored digital subscriber line (DSL) system configured to perform upstream power back-off (UPBO) for a first DSL line in a vectored group of DSL lines comprising the first DSL line and a plurality of other DSL lines, wherein each vectored group DSL line comprises a customer premises equipment (CPE) modem coupled to a digital subscriber line access multiplexer (DSLAM) via a DSL line, the vectored DSL system comprising:

a vectoring control entity (VCE) coupled to the DSLAM and configured to implement a partial cancellation scheme for performing partial far-end crosstalk (FEXT) cancellation on upstream transmissions of the first DSL line received as data in the DSLAM, wherein performing partial FEXT cancellation on upstream transmissions of the first DSL line results in residual crosstalk remaining in data by the DSLAM after partial cancellation has been performed, wherein the VCE is further configured to, in connection with the implemented partial FEXT cancellation scheme:

select a subset consisting of less than one or more of all possible disturbers, tones, channels and lines, and

perform FEXT cancellation for only the selected subset; and

an upstream-end processor coupled to the DSLAM and configured to:

determine an effect of the residual crosstalk on the received signals associated with the partial FEXT cancellation scheme;

select one or more performance metrics relating to transmissions by the first DSL line, wherein each performance metric is one of the following: a measured performance metric; a simulated performance metric; an estimated performance metric; and

calculate first DSL line partial cancellation UPBO parameters based on the determined effect of the residual crosstalk and the one or more selected performance metrics.

9. The vectored DSL system of claim 8 wherein the upstream-end processor comprises a processor located in at least one of the following: the DSLAM; the VCE, a network management system (NMS).

10. The vectored DSL system of claim 9 wherein the VCE is further configured to, in connection with the implemented partial cancellation scheme, select a subset of dominant disturbers from a set of all disturbers, wherein each disturber contributes FEXT to upstream transmissions of the first DSL line, further wherein each disturber is at least one of the following: a disturber line in the vectored group, a disturber tone used by the vectored group.

11. The vectored DSL system of claim 9 wherein the VCE is further configured to, in connection with the implemented partial cancellation scheme, perform imperfect FEXT partial cancellation that yields residual crosstalk.

12. The vectored DSL system of claim 9 wherein one of the one or more performance metrics comprises at least one of the following: an upstream target data rate for the first DSL line, an upstream target signal to noise ratio (SNR) for the first DSL line.

13. The vectored DSL system of claim 12 wherein each DSL line in the vectored group operates in accordance with a VDSL standard.

14. The vectored DSL system of claim 8 wherein the upstream-end processor transmits the calculated first line partial cancellation UPBO parameters to the CPE of the first DSL line.