Partial Echo Cancellation for Non-Co-located Crosstalk
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Solution Overview
Problem
Current communication systems face limitations in achieving full duplex transmission over multi-user twisted pair networks due to the inability to effectively cancel near-end crosstalk (NEXT) between non-co-located customer premises equipment (CPEs), which restricts data rates, especially at high frequencies.
Innovation Solution
The implementation of partial echo cancellation techniques that estimate crosstalk effects in upstream and downstream channels, adjusting transmission times and frequencies to minimize the impact of NEXT, and employing TDD or FDD duplexing to avoid simultaneous transmission in affected frequency bands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If full duplex transmission is implemented using echo cancellation, then data rate increases and latency decreases, but near-end crosstalk between non-co-located CPEs degrades signal quality
Solution Approach 1:
The patent applies partial echo cancellation by selectively cancelling echo in certain frequency bands while using TDD or FDD in other bands. Instead of attempting full echo cancellation across all frequencies (which would be excessive and ineffective against NEXT), the system performs partial cancellation where it works and combines it with duplexing methods where it doesn't, thereby achieving practical full duplex operation in multi-user environments
Solution Approach 2:
The frequency spectrum is segmented into different bands: some bands use full duplex with echo cancellation while other bands use TDD or FDD. This segmentation allows the system to optimize each band independently based on channel conditions and NEXT characteristics, resolving the contradiction by distributing traffic across multiple transmission modes
2Productivity
If echo cancellation is applied to enable simultaneous upstream and downstream transmission, then transmission efficiency improves, but signal-to-noise ratio deteriorates due to uncancelled NEXT
Solution Approach 1:
The patent introduces TDD and FDD as intermediary transmission modes that mediate between the need for simultaneous transmission (full duplex) and the need to maintain SNR (avoid NEXT). By using these intermediary modes in frequency bands where echo cancellation is ineffective, the system maintains reliable transmission while still achieving overall full duplex operation in bands where cancellation works
3Loss of time
If simultaneous upstream and downstream transmission is performed on the same frequency, then latency is reduced, but NEXT interference increases
Solution Approach 1:
The patent applies local quality by making the transmission mode frequency-dependent: full duplex with echo cancellation is used in frequency bands where NEXT is manageable, while TDD or FDD is used in bands where NEXT would be problematic. This localized application of different transmission qualities resolves the contradiction by allowing low-latency simultaneous transmission only where it doesn't generate excessive NEXT interference
Data Source
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AI summary
Methods, circuitries, and systems for transmitting data upstream between a first device and a second device and downstream between the second device and the first device are disclosed. A method includes determining an upstream crosstalk effect for an upstream channel and determining a downstream crosstalk effect for a downstream channel. The crosstalk effect includes near end crosstalk from a third device that is non-co-located with respect to the first device and the second device. A data rate of an upstream transmission or downstream transmission is adjusted based on the upstream crosstalk effect and the downstream crosstalk effect.