Adaptive FEXT Canceller Filtering for In-Service Noise Isolation
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Solution Overview
Problem
Current methods for estimating and compensating far-end crosstalk (FEXT) noise in gigabit Ethernet and DSL systems are inefficient, requiring system shutdown and complex measurement procedures, which disrupt normal operations and are inaccurate due to mixed noise sources.
Innovation Solution
An adaptive FEXT canceller filter is used to detect, estimate, and correct FEXT impairments in real-time within the communication system, employing techniques like linear forward equalization and decision feedback equalization, allowing for simultaneous estimation of all filter tap coefficients without affecting system performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If FEXT noise measurement is performed using energy calculation during regular operation, then the measurement can be performed continuously without system shutdown, but the measurement precision is poor because the measured noise comprises a combination of multiple noise sources (thermal noise, NEXT noise, FEXT noise)
Solution Approach 1:
The patent segments the total measured noise into distinct components (thermal noise, NEXT noise, FEXT noise) by separately measuring and calculating each component. The FEXT noise is isolated by subtracting the calculated thermal and NEXT noise components from the total measured noise, enabling precise FEXT measurement during regular system operation without contamination from other noise sources.
Solution Approach 2:
The patent uses feedback by continuously monitoring the total noise and using previously calibrated noise component models to calculate and subtract the contributions of thermal and NEXT noise. This feedback mechanism allows the system to dynamically isolate FEXT noise in real-time, maintaining measurement precision while operating continuously.
2Measurement precision
If FEXT noise measurement is performed by stopping normal operation and transmitting on adjacent interfering cables only, then the measurement precision is improved by isolating FEXT noise, but the productivity decreases because the system must be stopped from regular communication tasks
Solution Approach 1:
The patent enables continuous FEXT noise measurement during regular system operation by using signal processing techniques to isolate FEXT components from the total noise spectrum. This eliminates the need to stop communication tasks for measurement, as the system continuously processes signals and extracts FEXT noise information alongside normal data transmission and reception activities.
Solution Approach 2:
The patent introduces signal processing algorithms as intermediaries that act on the total received signal to extract and isolate FEXT noise components. These intermediary processing steps allow the system to obtain precise FEXT measurements without physically isolating the interfering cables or stopping transmission, as the isolation is achieved through computational separation of noise sources.
3Measurement precision
If complex measurement procedures are used to isolate FEXT noise, then the measurement precision is improved, but the device complexity increases requiring well-trained technicians for monitoring and processing
Solution Approach 1:
The patent implements self-service by automatically performing FEXT noise isolation and measurement through integrated signal processing algorithms. The system autonomously calculates and subtracts thermal and NEXT noise components from the total measured noise to isolate FEXT noise, eliminating the need for manual intervention by well-trained technicians. The complex processing is handled automatically by the transceiver's built-in processing capabilities.
4Reliability
If traditional FEXT cancellation methods are used, then the FEXT impairment can be corrected, but the hardware requirements and cost increase
Solution Approach 1:
The patent replaces complex hardware-based FEXT cancellation mechanisms with signal processing algorithms implemented in software or firmware. Instead of using additional physical components or specialized hardware circuits to cancel FEXT, the system uses computational methods to estimate and subtract FEXT noise from received signals, reducing hardware requirements while maintaining effective FEXT impairment correction.
Data Source
AI summary
A novel and useful mechanism for the detection, estimation and correction of far-end cross talk (FEXT) caused by transmissions over adjacent wire pairs or cables. The detection, estimation and correction technique of the invention can be used to identify and compensate for FEXT impairments in Ethernet and DSL systems. The detection, estimation and correction is performed utilizing one of several techniques including linear forward filtering, backward decision feedback based filtering and a combination thereof. Results of simulations are presented illustrating the performance improvements provided by the present invention.