Two-Stage Non-Linear Precoding for Crosstalk Tracking
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Solution Overview
Problem
Current crosstalk mitigation techniques in MIMO wired communication systems, such as DSL, face challenges with increasing crosstalk power exceeding direct signal power, leading to signal clipping and distortions, especially with the advent of new copper access technologies using broader spectra, and require intensive computational resources for updating non-linear precoders, which also break pilot sequence orthogonality.
Innovation Solution
A network unit with a non-linear precoder comprising a first triangular precoding stage and a second linear precoding stage, where pilot signals are inserted at different locations to measure residual crosstalk for low-complex updates of the second precoding matrix, keeping the first matrix unaltered, and only updating when necessary to reduce computational overhead and maintain orthogonality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If non-linear precoding is used to mitigate crosstalk, then crosstalk mitigation performance is improved, but computational complexity increases significantly
Solution Approach 1:
The non-linear precoder is segmented into two distinct stages: a first non-linear precoding stage using a triangular matrix with modulo function, and a second linear precoding stage using a unitary matrix. This segmentation allows the computationally intensive non-linear operations to be performed only once during initialization, while tracking updates can operate in the simpler linear domain, significantly reducing ongoing computational complexity while maintaining crosstalk mitigation performance.
2Reliability
If non-linear precoding is updated frequently to track channel variations, then crosstalk mitigation performance is improved, but computational overhead increases
Solution Approach 1:
The system implements dynamic update strategies where the first precoding matrix is updated less frequently (e.g., periodically or when channel conditions change significantly) while the second precoding matrix can be updated more frequently with lower computational cost. This dynamic approach adapts the update frequency to actual channel conditions, maintaining performance while optimizing computational resource usage.
3Measurement precision
If non-linear precoding is applied to all pilot signals, then crosstalk tracking accuracy is improved, but pilot sequence orthogonality is broken
Solution Approach 1:
The patent applies different precoding treatments to different signal types: data signals undergo full non-linear precoding for optimal crosstalk mitigation, while pilot signals receive modified treatment to preserve orthogonality. Specifically, pilot signals can be processed only through the second linear precoding stage or through a simplified version of the first stage, maintaining their orthogonal properties necessary for accurate channel estimation while still benefiting from crosstalk mitigation where applicable.
Data Source
AI summary
A network unit includes a non-linear precoder for jointly pre-processing transmit samples to be transmitted over respective communication channels for crosstalk mitigation. The non-linear precoder includes a first non-linear precoding stage configured to operate according to a first triangular precoding matrix and including a modulo function, followed by a second linear precoding stage configured to operate according to a second precoding matrix. The network unit further includes a first pilot signal generator configured to generate first pilot signals for pre-processing by the second precoding stage only to yield partially-precoded pilot signals for further transmission over the respective communication channels, and a controller configured to update the second precoding matrix based on first error measurements performed during the transmission of the partially-precoded pilot signals over the respective communication channels while keeping the first precoding matrix unaltered.