Non-linear Precoder Segmentation for DSL Crosstalk Mitigation
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Solution Overview
Problem
Crosstalk mitigation in wired communication systems, particularly in DSL systems, is challenging due to increasing crosstalk coupling with higher frequency bands, leading to signal distortions and limited vectoring gains when not all interfering lines can be included in the vectoring group, and the coexistence of NLP non-capable and NLP capable Customer Premises Equipment (CPEs complicates the implementation of non-linear precoding.
Innovation Solution
A method involving a non-linear precoder with a first triangular precoding stage and a second linear precoding stage, organizing subscriber lines into two groups: one for NLP non-capable lines where signals are scaled to bypass the modulo operation, and another for NLP capable lines where signals are processed through both stages, ensuring effective crosstalk mitigation and coexistence of different CPE types.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If non-linear precoding is implemented to improve crosstalk mitigation performance, then crosstalk reduction is improved, but device complexity increases due to modulo operation requirements
Solution Approach 1:
The system segments subscriber lines into two distinct groups: NLP-capable lines that undergo full non-linear precoding with modulo operation, and NLP-non-capable lines that use scaled linear precoding. This segmentation allows the complex NLP to be applied only where beneficial while maintaining compatibility with legacy equipment, thus improving crosstalk mitigation for capable lines without universally increasing system complexity.
Solution Approach 2:
Different precoding strategies are applied to different groups of lines based on their capabilities. NLP-capable lines receive the full non-linear precoding treatment with modulo operation for optimal crosstalk cancellation, while NLP-non-capable lines receive a simplified scaled linear precoding approach. This local differentiation optimizes performance for each group without forcing complexity on all lines.
2Object-affected harmful factors
If all subscriber lines are included in the vectoring group to improve crosstalk mitigation, then crosstalk reduction is improved, but the system cannot accommodate NLP non-capable CPEs
Solution Approach 1:
The vectoring group is segmented into NLP-capable and NLP-non-capable subscriber lines. This segmentation enables the system to simultaneously support both types of CPEs within the same vectoring group by applying appropriate precoding strategies to each segment, thus maintaining both comprehensive crosstalk mitigation and broad CPE compatibility.
Solution Approach 2:
The precoder is designed with multi-functionality to handle both NLP-capable and NLP-non-capable lines within the same system. By incorporating both full non-linear precoding paths and scaled linear precoding paths, the system achieves universal compatibility with different CPE types while maintaining effective crosstalk mitigation for all lines in the vectoring group.
3Object-affected harmful factors
If signals for NLP non-capable lines are processed through full non-linear precoding to improve crosstalk mitigation, then crosstalk reduction is improved, but transmit power constraints are violated
Solution Approach 1:
For NLP-non-capable lines, the system applies scaled linear precoding where the precoding matrix is multiplied by a scaling factor to ensure that the transmit power remains within the power mask constraints. This parameter adjustment (scaling) maintains power compliance while still providing crosstalk mitigation, avoiding the need for full non-linear precoding on these lines.
Solution Approach 2:
Instead of applying full non-linear precoding with modulo operation to NLP-non-capable lines, the system applies a partial version using scaled linear precoding. This partial action provides sufficient crosstalk mitigation for these lines without exceeding transmit power constraints, achieving an optimal balance between performance and power limitations.
Data Source
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AI summary
The present invention relates to a method for jointly processing signals (U) to be transmitted over respective ones of a plurality of subscriber lines (L1 to L4) through a non-linear precoder (21). The non-linear precoder comprises a first non-linear precoding stage (301; 301') configured to operate according to a first triangular precoding matrix (L; M; N) and including a modulo unit (Γ; γ), followed by a second linear precoding stage (302; 302') configured to operate according to a second precoding matrix (Q; P). In accordance with an embodiment of the invention, the method comprises organizing the plurality of subscriber lines into a first group of subscriber lines (GA) and a second group of subscriber lines (GB), the first group of subscriber lines at least comprising all the subscriber lines of the plurality of subscriber lines that do not support non-linear precoding operation (L2; L4) and the second group of subscriber lines comprising the remaining subscriber lines of the plurality of subscriber lines (L1; L3), scaling first signals (UA) to be transmitted over respective ones of the first group of subscriber lines to confine respective intermediate transmit power levels at the input of the modulo unit and further to bypass or make ineffective the operation of the modulo unit, and processing the so scaled first signals (UA') and second signals (UB) to be transmitted over respective ones of the second group of subscriber lines through the first and second precoding stages. The present invention also relates to a non-linear precoder (21).