DSL Pilot Sequence Muting for Crosstalk Reduction
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Solution Overview
Problem
In DSL systems, severe far-end crosstalk (FEXT) reduces channel rates and line availability due to electromagnetic induction, causing signal detection failures during initialization, especially in scenarios with hybrid line lengths where long lines suffer strong crosstalk from short lines.
Innovation Solution
A method involving a vectoring control entity (VCE) that modifies uplink pilot sequences by setting non-zero elements to zero in the subscriber side transceiver's pilot sequence, reducing crosstalk and improving signal-to-noise ratio during DSL initialization, allowing accurate synchronization symbol detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a wider frequency band is used in G. fast to provide higher access rates, then the access rate is improved, but far-end crosstalk (FEXT) energy increases and causes severer impact on transmission performance
Solution Approach 1:
The patent applies preliminary anti-action by having showtime lines proactively send muted pilot sequences (with zeroed elements at positions where joining lines have non-zero elements) before joining lines attempt initialization. This pre-established interference pattern allows the central office transceiver to predict and cancel FEXT from showtime lines, enabling joining lines to initialize successfully even with wider frequency bands in use.
Solution Approach 2:
The patent changes the parameter structure of pilot sequences by selectively setting certain elements to zero based on the joining line's pilot sequence pattern. This parameter modification creates a muted pilot sequence that maintains synchronization functionality while eliminating interference at critical frequency positions, thereby resolving the contradiction between wide bandwidth utilization and FEXT mitigation.
2Reliability
If showtime lines transmit normal pilot sequences, then the lines maintain normal operation, but crosstalk interferes with joining line signal detection during initialization
Solution Approach 1:
The patent applies local quality by modifying only specific elements of the showtime line's pilot sequence (setting elements to zero at positions where the joining line has non-zero elements) while leaving other elements unchanged. This localized modification eliminates interference at critical positions without disrupting the overall operation of showtime lines, thereby enabling both reliable showtime line operation and accurate joining line signal detection.
Solution Approach 2:
The patent segments the pilot sequence into multiple elements and selectively mutes specific segments (elements) based on the joining line's pilot sequence pattern. This segmentation approach allows the system to maintain normal operation on showtime lines while creating interference-free zones for joining line initialization, resolving the contradiction between operational reliability and detection precision.
3Adaptability or versatility
If hybrid line lengths are used in the DSL system, then line flexibility is improved, but long lines suffer strong crosstalk from short lines causing signal detection failure
Solution Approach 1:
The patent introduces a muted pilot sequence as an intermediary mechanism between showtime lines and joining lines. This intermediary signal structure (with selectively zeroed elements) mediates the interaction between lines of different lengths by providing a reference pattern that allows the central office transceiver to cancel crosstalk from short showtime lines, thereby enabling reliable initialization of long joining lines while maintaining line length flexibility.
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
The solution effectively reduces crosstalk, enhances signal detection strength, and increases the signal-to-noise ratio, enabling successful initialization of DSL lines by converting pilot sequences to minimize interference from showtime lines on joining lines.
Implementation Method 1
because of an electromagnetic induction principle, crosstalk is generated between a plurality of signals that access the DSLAM
Data Source
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AI summary
Embodiments of the present invention provide a method and an apparatus for digital subscriber line initialization, where the method is performed by a subscriber side transceiver on a showtime line. The method includes: receiving a first notification message sent by a vectoring control entity VCE, where the first notification message includes first indication information, the first indication information indicates at least one first index, and an element of the at least one first index in a joining uplink pilot sequence is 1 or -1; and converting a first uplink pilot sequence of the showtime line into a second uplink pilot sequence according to the first notification message; and sending the second uplink pilot sequence to a central office transceiver on the showtime line. Therefore, in the embodiments of the present invention, crosstalk suffered when a central office transceiver on a joining line detects an uplink pilot signal is reduced, so that noise can be reduced, a signal-to-noise ratio can be increased, and strength of detecting a synchronization symbol by the central office transceiver on the joining line can be further improved.