G.fast PSD Mask Selection for Crosstalk Reduction
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Solution Overview
Problem
The increasing use of higher frequency Digital Subscriber Line (DSL) protocols like G.fast causes significant near-end crosstalk (NEXT) interference to neighboring VDSL2 lines, which can be more disruptive than far-end crosstalk (FEXT), leading to reduced data rates and performance issues in DSL networks.
Innovation Solution
A method and apparatus that employ a power spectral density (PSD) mask to control the transmission power of G.fast modems, estimating line lengths and adjusting PSD levels to minimize NEXT interference by constraining power in overlapping frequency ranges, using a combination of upstream and downstream FDD masks to set TDD PSD masks that account for the stronger NEXT coupling compared to FEXT.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If G.fast modems transmit at high power spectral density in overlapping frequency ranges, then data transmission rates are improved, but near-end crosstalk interference to neighboring VDSL2 lines increases
Solution Approach 1:
The patent applies local quality by implementing different power spectral density masks for different frequency ranges. Specifically, the TDD PSD mask constrains power in overlapping frequency ranges (where VDSL2 lines operate) while allowing higher power in non-overlapping ranges, thereby enabling high data rates in safe frequency bands while minimizing NEXT interference to neighboring VDSL2 lines.
Solution Approach 2:
The patent changes the power spectral density parameter dynamically by selecting or generating appropriate TDD PSD masks based on line length estimates. The mask parameters are adjusted to balance G.fast performance with protection of neighboring VDSL2 lines, transforming the fixed power distribution into an adaptive one that optimizes both data rates and interference reduction.
2Object-generated harmful factors
If power spectral density masks are used to constrain transmission power in overlapping frequency ranges, then near-end crosstalk interference is reduced, but data transmission rates are limited
Solution Approach 1:
The patent segments the frequency spectrum into overlapping and non-overlapping ranges relative to VDSL2 lines. By applying PSD constraints only to the overlapping segments while allowing full power in non-overlapping segments, the solution achieves interference reduction without unnecessarily limiting overall data transmission capacity.
Solution Approach 2:
The patent introduces dynamics by making the PSD mask selection adaptive to line length estimates. Different mask configurations are applied based on the specific line characteristics, allowing the system to optimize the balance between interference reduction and data rate maximization for each individual connection rather than using a fixed conservative approach.
Data Source
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AI summary
Adigital subscriber line arrangement 1000, 2100, 2200, 3100, 3200, 4000, 5000, 6000, 7000, 7010 comprises a first downstream Access Node (AN) modem 1100, a first upstream Customer Premises Equipment (CPE) modem 2100, a second AN modem 1200, a second CPE modem 2200 and first 3100 and second 3200 metallic pairs connected between the first and second modems respectively. The first AN modem 1100 includes a length estimation module 1130 and a PSD mask selection module 1140 which together with a PSD mask store 1160 operate to select upstream and downstream PSD masks for use by the first CPE modem 2100 and the first AN modem 110 respectively. Selection of the masks depends upon the estimated line length and the manner in which neighbouring communication link 1200, 3200, 2200 is operating. Additionally, a central controller is operable to perform selection or generation of such masks in a similar manner when centralised control over the PSD mask generation is desired.