Special Operations Channel Identification in Vectored DSL Systems
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Solution Overview
Problem
In vectored DSL systems, high crosstalk, especially at very high frequencies, leads to inaccurate or false initialization and training due to uncancelled far-end crosstalk, causing interference and increased training time, particularly in emerging technologies like G.fast where FEXT can overpower direct signals.
Innovation Solution
A method using orthogonal sequences and low-correlation scrambling polynomials to identify and distinguish the special operation channel (SOC) signals from each line, allowing receivers to accurately measure SNR and FEQ coefficients, even in the presence of strong crosstalk, by assigning identification polynomials to each line and modulating SOC signals with these polynomials to differentiate them from neighboring signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If vectored transmission is used to increase bit rates, then customer available bit rates can be increased up to 100 Mb/s, but high crosstalk occurs between lines causing inaccurate initialization and training
Solution Approach 1:
The patent introduces a special operations channel (SOC) as an intermediary communication path between the distribution point modem and customer premises modem. This SOC operates independently from the data-bearing lines, allowing initialization and training signals to be transmitted without being affected by crosstalk on the data lines. The SOC acts as a mediator that enables accurate channel estimation and training despite the presence of high crosstalk in the vectored transmission system.
2Reliability
If conventional SOC is used for initialization, then robust communication during training is achieved, but neighboring SOC signals interfere with direct channel estimation and cause ghost initialization
Solution Approach 1:
The patent segments the SOC signals by assigning unique identification polynomials to different lines. Each line's SOC signal is modulated with its specific identification polynomial, creating distinct signal patterns that can be individually identified and processed. This segmentation allows the receiver to distinguish between SOC signals from different lines, preventing neighboring signals from interfering with channel estimation and causing ghost initialization.
Solution Approach 2:
The patent applies local quality by assigning different identification polynomials to different lines, creating locally unique signal characteristics. Each line's SOC signal has distinct properties determined by its identification polynomial, allowing the receiver to selectively process only the relevant line's signal while ignoring others. This local differentiation eliminates interference from neighboring SOC signals during initialization and training.
Data Source
AI summary
Methods and devices are provided wherein a signal sent on a special operation channel is modified by an identification of a line.