Crosstalk Estimation for FTTC Vectoring Systems
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Solution Overview
Problem
In vector DSL systems, far-end crosstalk (FEXT) between lines of different profiles, such as 17a and 30a, causes interference that affects the stability and performance of fiber-to-the-customer (FTTC) acceleration, as existing techniques can only cancel in-band crosstalk and not out-of-band crosstalk.
Innovation Solution
A method involving a transceiver that generates and sends pilot training signals based on allocated pilot sequences, allowing a vectoring control entity to determine crosstalk channel coefficients from one line into another, enabling precoding processing to eliminate both in-band and out-of-band FEXT interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If frequency division multiplexing is used to enable xDSL and POTS to coexist on the same twisted pair, then spectrum utilization is improved, but crosstalk interference between lines increases
Solution Approach 1:
The patent segments the frequency spectrum into multiple bands and applies different processing techniques to different segments. Specifically, it separates in-band and out-of-band crosstalk components and applies targeted cancellation methods to each segment, thereby managing crosstalk while maintaining spectrum utilization.
Solution Approach 2:
The patent converts the harmful crosstalk signals into useful information by estimating crosstalk channel coefficients from received pilot sequences. These estimated coefficients are then used to construct cancellation signals that eliminate the harmful effects of crosstalk, transforming the interference problem into a solution.
2Reliability
If vectoring technology is introduced to enable joint transmission and reception at CO to cancel FEXT crosstalk, then transmission performance is improved, but device complexity increases
Solution Approach 1:
The patent implements partial vectoring by focusing on estimating and canceling specific crosstalk components (in-band and out-of-band FEXT) rather than implementing complete multi-dimensional vectoring. This partial approach achieves significant performance improvement while avoiding the full complexity of comprehensive vectoring systems.
Solution Approach 2:
The patent performs preliminary crosstalk estimation using pilot sequences before actual data transmission. By pre-calculating crosstalk channel coefficients and preparing cancellation signals in advance, the system reduces the computational complexity during data transmission while maintaining high transmission performance.
3Adaptability or versatility
If 17a line and 30a line coexist with overlapping spectral ranges, then system versatility is improved, but out-of-band crosstalk interference increases
Solution Approach 1:
The patent applies local quality by treating different frequency bands differently. It specifically targets out-of-band crosstalk components that fall within the in-band spectrum of other lines and applies targeted cancellation only to these problematic frequencies, while leaving other frequency regions unaffected. This allows coexistence of different line profiles with overlapping spectra.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively reduces the impact of inter-line crosstalk on line rates and improves the stability and effectiveness of FTTC acceleration by accounting for crosstalk across different spectral ranges.
Implementation Method 1
As a result of electromagnetic induction, multiple signals connected by a DSLAM cause interference to each other, which is referred to as crosstalk (Crosstalk).
Data Source
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AI summary
The present invention provides a crosstalk estimation method, an apparatus, and a system. According to the crosstalk processing method, the apparatus, and the system provided in embodiments of the present invention, a transceiver of a line generates, respectively according to pilot sequences allocated by a vectoring control entity, pilot training signals that are within different spectral ranges and that satisfy a preset relationship with a pilot training signal of another line, so that a receiver of the line can determine sample errors respectively according to the different pilot training signals. Then, the vectoring control entity determines crosstalk channel coefficients from the another line into an inband spectrum and an out-of-band spectrum of the line, and performs precoding processing on a to-be-sent data signal of the line, so as to eliminate impact of crosstalk from the another line to the inband and out-of-band spectrums of the line. This reduces impact on a line rate caused by inter-line crosstalk in a system in which lines of different profiles coexist, and further improves effects and stability of FTTC acceleration.