Self-Synchronizing Probe Sequence for Fast FEQ Training
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Solution Overview
Problem
In DSL systems, especially G.fast, strong FEXT interference hampers effective FEQ training, leading to poor vectoring performance and slow convergence, as traditional methods like LMS are inefficient in high FEXT environments.
Innovation Solution
The introduction of a self-synchronizing probe sequence with zero elements (0-elements) allows for synchronization without requiring the bit-index transmission, enabling fast CDMA-like FEQ training by using 0-elements to mark the start or end of the probe sequence, thereby eliminating the need for initial FEQ training and improving convergence speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If traditional FEQ training methods (LMS, BLMS, averaging) are used in high FEXT environments, then the training can be performed, but convergence speed is slow and effectiveness is reduced
Solution Approach 1:
The system performs preliminary synchronization using a self-synchronizing probe sequence with 0-elements that mark the start or end of the sequence. This preliminary action establishes the bit index alignment before FEQ training begins, eliminating the need for slow iterative convergence in high FEXT environments and enabling direct calculation of FEQ coefficients.
2Ease of operation
If bit-index transmission is used for synchronization, then the upstream probe sequence can be aligned, but overhead increases and complexity increases
Solution Approach 1:
The probe sequence is designed with self-synchronizing 0-elements that enable the receiving end to automatically determine the bit index alignment without requiring separate bit-index transmission. The 0-elements serve as intrinsic markers within the probe sequence itself, allowing the system to self-synchronize and eliminating the need for additional synchronization signaling overhead.
3Manufacturing precision
If initial FEQ training is required before probe sequence processing, then channel equalization can be performed, but training time increases and convergence is slower
Solution Approach 1:
The system performs preliminary synchronization using the self-synchronizing probe sequence with 0-elements before FEQ training. This preliminary bit index alignment enables direct calculation of FEQ coefficients from the synchronized probe sequence, eliminating the need for time-consuming iterative training and allowing immediate channel equalization with high accuracy.
Data Source
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AI summary
A method comprising modulating a plurality of synchronized signals by an orthogonal probe sequence (OPS) to generate a plurality of modulated synchronized signals, wherein the OPS comprises a zero element (0-element) column that indicates a start or an end of the OPS, and concurrently transmitting, using one or more transmitters, the plurality of modulated synchronized signals over a duration of a number of discrete multi-tone (DMT) symbols, wherein each of the plurality of modulated synchronized signals is intended for one of a plurality of receivers that are remotely coupled to the one or more transmitters via a vectored group of subscriber lines, and wherein the 0-element column causes all of the plurality of modulated synchronized signals to have a zero-amplitude during a first or a last of the DMT symbols.