DSL Crosstalk Cancellation via Joint Signal Sequences
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Solution Overview
Problem
Existing DSL systems face significant performance degradation due to crosstalk, particularly near-end crosstalk (NEXT) and far-end crosstalk (FEXT), which current vectoring technologies cannot fully address, especially in overlapped spectrum duplex (OSD) systems, limiting the expansion of frequency spectrum and increasing processing delays.
Innovation Solution
A method and system that simultaneously cancel NEXT and FEXT signals in DSL systems by forming upstream and downstream signal sequences, using FEXT and NEXT cancellation coefficients to process these signals, thereby improving processing speed and reducing delays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If frequency division multiplexing technology is used to enable xDSL and POTS to coexist, then spectrum utilization is improved, but crosstalk interference increases
Solution Approach 1:
The patent converts the harmful crosstalk signals into useful information by having interfering lines transmit pilot signals that carry crosstalk characteristics. These pilot signals are then used to calculate cancellation coefficients that eliminate the harmful NEXT and FEXT interference, transforming the harmful electromagnetic coupling into a beneficial source of cancellation data.
Solution Approach 2:
The patent introduces pilot signals as intermediary elements that mediate between the interfering lines and the affected lines. These pilot signals serve as carriers of crosstalk information, enabling the system to measure and characterize the interference without disrupting normal data transmission, thus facilitating the cancellation process.
2Reliability
If vectoring technology is used to cancel FEXT, then FEXT cancellation is improved, but NEXT interference remains uncanceled
Solution Approach 1:
The patent merges the FEXT cancellation function with a new NEXT cancellation function into a unified joint cancellation system. By combining the cancellation of both far-end and near-end crosstalk in a single coordinated process using joint cancellation coefficients, the system achieves comprehensive interference elimination that addresses both FEXT and NEXT simultaneously.
Solution Approach 2:
The patent extends the vectoring technology to perform multiple functions: it maintains the existing FEXT cancellation capability while adding NEXT cancellation capability. The joint cancellation coefficients serve both purposes, making the system universally applicable to both types of crosstalk interference rather than being limited to FEXT only.
3Reliability
If separate FEXT and NEXT cancellation processing is performed, then cancellation completeness is improved, but processing delay increases
Solution Approach 1:
The patent merges separate FEXT and NEXT cancellation operations into a single joint processing step. Instead of performing FEXT cancellation and then NEXT cancellation in sequence, the system calculates joint cancellation coefficients that handle both interference types simultaneously, reducing the number of processing steps and minimizing delay.
Solution Approach 2:
The patent performs preliminary calculation of joint cancellation coefficients that incorporate both FEXT and NEXT characteristics in advance. By pre-computing the combined cancellation parameters based on pilot signals before actual data transmission, the system avoids real-time sequential processing and reduces latency during normal operation.
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
This approach effectively cancels both NEXT and FEXT signals in DSL systems, enhancing processing speed and reducing delays, thereby improving overall system performance and enabling more efficient use of limited frequency spectrum.
Implementation Method 1
Because of the principle of electromagnetic induction, multiple signals received by the DSLAM interfere with each other, which is referred to as crosstalk.
Data Source
AI summary
A method for canceling crosstalk between lines in a DSL system is presented. The method includes obtaining an upstream signal that is sent by corresponding customer premises equipment (CPE) and that is received by each central office (CO), forming an upstream signal sequence including upstream signals of all COs, obtaining a downstream signal that is sent by each CO to the CPE corresponding to each CO, and forming a downstream signal sequence including downstream signals of all the COs; performing FEXT cancellation processing on the upstream signal sequence to obtain a first signal sequence, and processing the downstream signal sequence to determine NEXT signals in the upstream signals of all the COs; and performing NEXT cancellation processing on the first signal sequence using the determined NEXT signals, to obtain a second signal sequence, and sending upstream signals in the second signal sequence to all the COs.