Virtual Noise Configuration for VDSL2 Crosstalk Stability
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Solution Overview
Problem
Crosstalk interference in DSL systems, particularly in mixed deployment scenarios with adjacent twisted-pair phone lines, limits performance due to high frequencies used in VDSL2, leading to unstable connections and frequent re-initializations, and existing methods like upstream power back-off and virtual noise techniques face compatibility issues.
Innovation Solution
Configuring virtual noise in DSL systems based on an upper bound for worst-case FEXT PSD, using a method that determines a 99% worst-case FEXT PSD across subscriber lines, allowing for a single receiver-referred virtual noise PSD to match equalized FEXT PSD, thereby improving compatibility between upstream power back-off and virtual noise techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If upstream power back-off technique is used to reduce crosstalk, then crosstalk levels are reduced, but compatibility issues arise with virtual noise technique
Solution Approach 1:
The patent changes the parameter of virtual noise PSD configuration from line-specific to uniform across all lines. By setting a single receiver-referred virtual noise PSD value that matches the equalized FEXT PSD, the system maintains compatibility between UPBO and virtual noise techniques while continuing to suppress crosstalk interference.
2Stability of the object's composition
If virtual noise is set too low to improve stability, then line stability improves, but data-rate is unnecessarily reduced
Solution Approach 1:
The patent uses feedback by configuring the virtual noise PSD to match the measured or estimated FEXT PSD in the binder. This feedback mechanism ensures that the virtual noise parameter is set optimally - high enough to provide stability protection against actual interference conditions, but not excessively high to unnecessarily limit data-rate.
3Reliability
If virtual noise is set too high to protect against worst-case conditions, then line stability improves, but data-rate is unnecessarily reduced
Solution Approach 1:
The patent applies partial action by configuring virtual noise to match the equalized FEXT PSD rather than using a conservative worst-case upper bound for all lines. This partial matching approach provides sufficient protection against actual interference conditions without the excessive noise floor that would result from universal worst-case configuration, thereby preserving data-rate.
4Productivity
If different virtual noise configurations are used for lines of different lengths, then optimal performance is achieved for each line, but system complexity increases
Solution Approach 1:
The patent applies universality by configuring a single receiver-referred virtual noise PSD value that is applied uniformly across all subscriber lines in the binder, regardless of line length. This universal configuration simplifies system complexity while maintaining effectiveness because the UPBO technique has already equalized the FEXT PSD across different line lengths.
Data Source
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AI summary
An apparatus comprising a transmitter configured to transmit a digital subscriber line (DSL) signal in a line from a plurality of subscriber lines according to a reference virtual noise power spectral density (PSD), wherein the reference virtual noise PSD is based on an upper bound for a worst-case far-end crosstalk (FEXT) PSD in the subscriber lines. Also included is an apparatus comprising at least one processor configured to implement a method comprising obtaining an upper bound for a worst-case FEXT PSD for a plurality of subscriber lines, obtaining a referred virtual noise PSD based on the worst-case FEXT PSD for the lines, and determining a bit-loading for the lines based on the referred virtual noise or a scaled version of the receiver-referred virtual noise.