Vectoring Processor Crosstalk Mitigation for VDSL2 and G.fast
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Solution Overview
Problem
Crosstalk mitigation in mixed deployments of VDSL2 17a and 35b, and G.fast 106a/b and 212a transmit profiles is inefficient due to aliasing interference, leading to lower-than-expected data rates and requiring significant buffering and latency in vectoring processors.
Innovation Solution
A method and processor for jointly processing DMT communication signals using a common tone spacing, where frequency samples are input alternately in groups within and mirrored groups outside the legacy spectrum to a vectoring processor, minimizing buffering and latency while mitigating both nominal and aliased crosstalk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If frequency samples are processed sequentially in traditional order, then the vectoring processor can mitigate crosstalk, but large memory buffers and latency are required
Solution Approach 1:
The frequency spectrum is segmented into two distinct subsets: a first subset (legacy spectrum) and a second subset (extended spectrum). This segmentation allows independent processing strategies for each subset, enabling the system to handle aliasing interference separately and efficiently without requiring large buffers for entire spectrum processing.
Solution Approach 2:
The system applies preliminary filtering to remove aliasing interference from the second subset before vectoring processing. By pre-removing the aliased components that would otherwise require buffering and complex joint processing, the system reduces latency while maintaining crosstalk mitigation effectiveness.
2Productivity
If the transmit spectrum is extended to higher frequencies for higher data rates, then data rate increases, but crosstalk between neighboring transmission lines becomes more pronounced
Solution Approach 1:
The system addresses crosstalk in the frequency domain by introducing a dimensional separation between legacy and extended spectra. By treating these as distinct frequency dimensions with different processing rules, the system can exploit the structure of aliasing interference to mitigate crosstalk while maintaining high-frequency transmission benefits.
Solution Approach 2:
The system converts the harmful aliasing interference, which normally degrades signal quality, into a manageable structure. By recognizing the periodic nature of aliasing and filtering it predictably, the system transforms what would be random interference into a controlled phenomenon that can be compensated for, enabling higher data rates despite extended spectrum usage.
3Device complexity
If traditional vectoring processing is used without aliasing mitigation, then processing is simpler, but aliasing interference degrades performance
Solution Approach 1:
The system performs preliminary filtering to remove aliasing components before the main vectoring processing stage. This preliminary action simplifies the subsequent processing by eliminating the need to handle aliased interference, maintaining signal quality without significantly increasing overall system complexity.
Solution Approach 2:
The processing is segmented into distinct stages: aliasing removal for the second subset, followed by vectoring processing. This segmentation allows each stage to be optimized independently, preventing the need for complex joint processing while maintaining high signal quality through targeted interference mitigation.
Data Source
AI summary
The method includes inputting first groups of frequency samples to be transmitted over, respectively received from, first and second subsets of subscriber lines at respective first tones and following a first group selection order, alternated with mirrored second groups of frequency samples to be transmitted over, respectively received from, the second subset of subscriber lines at respective mirrored second tones of the first tones, and following a mirrored second group selection order of the first group selection order, to a vectoring processor for joint mitigation of first crosstalk present over the first and second subsets of subscriber lines at the respective first tones and second crosstalk present over the second subset of subscriber lines at the respective second tones. The first tones are common to the first and second transmit spectra. Mirroring is with respect to a folding frequency derived from a reference sampling frequency applicable to the first subset of subscriber lines.