Reduced Memory Vectored DSL Sub-band Tone Sampling
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Solution Overview
Problem
Vectored DSL systems face significant challenges in managing the large amounts of data required for FEXT channel estimates and cancellation coefficients, leading to bandwidth and memory storage bottlenecks, particularly in upstream communication and storage.
Innovation Solution
The approach involves dividing DSL frequency bands into sub-bands, using approximation and differential/incremental value methods to reduce the data needed for FEXT channel estimates and cancellation coefficients, allowing for reduced memory storage and bandwidth usage by transmitting and storing only subset data, and employing techniques like linear and polynomial approximations, and incremental value representations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If full-precision FEXT data for all tones is transmitted and stored, then crosstalk cancellation accuracy is improved, but bandwidth usage and memory requirements increase significantly
Solution Approach 1:
The frequency spectrum is divided into multiple sub-bands, and within each sub-band, only a subset of tones (e.g., every fourth tone) is used to measure and transmit FEXT data. This segmentation reduces the quantity of data while maintaining coverage across the entire frequency range through interpolation.
Solution Approach 2:
Measured FEXT data from the subset of tones is used to create approximate copies of the FEXT characteristics for the remaining tones in each sub-band. This copying approach allows the system to reconstruct full-precision FEXT cancellation coefficients for all tones using data from only a fraction of the total tones.
2Reliability
If FEXT data for all tones is collected and processed, then vectoring performance is improved, but upstream bandwidth consumption increases
Solution Approach 1:
The invention extracts only the essential FEXT measurement data from a subset of tones in each sub-band, removing the redundant data from the remaining tones. This extraction process reduces upstream bandwidth consumption while retaining the critical information needed for effective vectoring through the use of approximation and interpolation techniques.
3Quantity of substance
If approximation methods are used for FEXT cancellation coefficients, then memory storage requirements are reduced, but processing complexity increases
Solution Approach 1:
The system performs preliminary approximation of FEXT cancellation coefficients using measured data from subset tones before actual vectoring operations. By pre-calculating approximate coefficients and storing only these reduced data sets, the system reduces memory requirements while the additional processing is performed in advance rather than during real-time operation.
Data Source
AI summary
A reduced-memory vectored DSL system includes methods and apparatus for reducing the bandwidth and memory storage demands on a vectored DSL system in which FEXT data is transmitted and stored. An upstream-end device such as a DSLAM communicates with a plurality of downstream-end devices such as CPE modems. When test signal data, such as training and/or tracking data, is sent to determine FEXT characteristics of the DSL system, error signals are available for all or substantially all of the upstream and/or downstream frequency band DSL tones used in the system. Dividing a frequency band into sub-bands, only a subset of tones in each sub-band is used for deriving FEXT data, such as a FEXT channel response, FEXT channel coefficients and/or FEXT cancellation coefficients. For tones in the sub-band subsets, full-precision FEXT data values can be derived. For other tones, approximations of the FEXT data can be derived.