Method and Arrangement in a DSL Vectoring System

A method, performed by a Vectoring Control Entity (VCE), for handling Disorderly Leaving Event (DLE) causing Sudden Termination Change (STC) in a Digital Subscriber Line (DSL) system, the method comprising:

• when a DLE occurs on a line m in a vectored group of DSL lines, and the transmission on line m is at least partly continued:
• obtaining at least one error sample from Customer Premises Equipments (CPEs) connected to other lines in the vectored group of DSL lines;
• calculating an estimate of the channel coefficients (H′) changed due to the DLE based on the at least one error sample, thereby providing a channel estimate;
• and
• modifying a downstream precoder, based on the channel estimate, such that retraining of the other lines in the vectored group due to the DLE is avoided;
• wherein the estimate of the channel coefficients is calculated based on the model H′=H+CΛH, where:
• C is a near-end crosstalk coupling matrix for the CPE end of the vectored group;
• Λ is a diagonal matrix with reflection coefficients, after the DLE, of the CPE-end of cables associated with the vectored group;
• H is a matrix with the channel coefficients before the DLE;
• and
• H′ is a matrix with the estimated channel coefficients after the DLE.

A Vectoring Control Entity (VCE) for handling Disorderly Leaving Event (DLE) causing Sudden Termination Change (STC) in a Digital Subscriber Line (DSL) system, the VCE comprising:

• processing circuitry;
• memory containing instructions executable by the processing circuitry whereby the VCE is operative to, when a DLE occurs on a line m in a vectored group of DSL lines, and the transmission on line m is at least partly continued:
• obtain at least one error sample from Customer Premises Equipments (CPEs) connected to other lines in the vectored group of DSL lines;
• calculate an estimate of the channel coefficients (H′) changed due to the DLE, based on the at least one error sample, thereby providing a channel estimate;
• modify a downstream precoder, based on the channel estimate, such that retraining of the other lines in the vectored group due to the DLE is avoided;
• and
• calculate the estimate of the channel coefficients based on the model H′=H+CΛH, where:
• C is a near-end crosstalk coupling matrix for the CPE end of the vectored group;
• Λ is a diagonal matrix with reflection coefficients, after the DLE, of the CPE-end of cables associated with the vectored group;
• H is a matrix with the channel coefficients before the DLE;
• and
• H′ is a matrix with the estimated channel coefficients after the DLE.

A Digital Subscriber Line Access Multiplexer (DSLAM), comprising:

• a Vectoring Control Entity (VCE) for handling Disorderly Leaving Event (DLE) causing Sudden Termination Change (STC) in a Digital Subscriber Line (DSL) system, the VCE comprising processing circuitry and memory;
• the memory containing instructions executable by the processing circuitry whereby the VCE is operative to, when a DLE occurs on a line m in a vectored group of DSL lines, and the transmission on line m is at least partly continued:
• obtain at least one error sample from Customer Premises Equipments (CPEs) connected to other lines in the vectored group of DSL lines;
• calculate an estimate of the channel coefficients (H′) changed due to the DLE, based on the at least one error sample, thereby providing a channel estimate;
• modify a downstream precoder, based on the channel estimate, such that retraining of the other lines in the vectored group due to the DLE is avoided;
• and
• calculate the estimate of the channel coefficients based on the model H′=H+CΛH, where
• C is a near-end crosstalk coupling matrix for the CPE end of the vectored group;
• Λ is a diagonal matrix with reflection coefficients, after the DLE, of the CPE-end of cables associated with the vectored group;
• H is a matrix with the channel coefficients before the DLE;
• and
• H′ is a matrix with the estimated channel coefficients after the DLE.