Multi-Stage Echo Cancellation for Coaxial Cable Plants
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Solution Overview
Problem
Current echo cancellers in coaxial cable plants are ineffective in canceling high echo noise floors, especially at higher frequencies, and struggle to accurately monitor and locate echoes, leading to interference with upstream signals.
Innovation Solution
A multi-stage echo canceller system that includes analog and digital cancellers to estimate echo channel coefficients, transform them between frequency and time domains, and use inverse Fourier transforms to generate impulse responses, allowing for precise location and strength analysis of partial echoes and effective cancellation of downstream echo signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If current echo cancellers are used in coaxial cable plants, then basic echo cancellation is provided, but high echo noise floors especially at higher frequencies cannot be canceled
Solution Approach 1:
The echo canceller is divided into multiple stages: a first echo canceller that processes the entire bandwidth, and a second echo canceller that specifically targets high-frequency portions. This segmentation allows each stage to specialize in different frequency ranges, enabling effective cancellation of high echo noise floors that a single-stage canceller cannot handle.
Solution Approach 2:
The patent introduces a frequency dimension by separating the echo cancellation process into different frequency bands. The second echo canceller operates specifically on high-frequency components, adding a dimensional approach to the traditional single-stage cancellation method and enabling targeted suppression of high-frequency echo noise.
2Reliability
If current echo cancellers are used, then downstream echo signals are partially canceled, but accurate location and strength analysis of echoes is not achieved
Solution Approach 1:
An intermediary signal processing path is introduced that extracts echo components from the upstream signal, transforms them to the frequency domain, and analyzes their characteristics. This intermediary analysis path enables precise measurement of echo location and strength without interfering with the primary cancellation function.
Solution Approach 2:
The system uses feedback by continuously monitoring the upstream signal for echo components, analyzing their characteristics, and using this information to refine the cancellation process. The echo channel estimates derived from feedback enable accurate determination of echo location and strength.
3Object-affected harmful factors
If multi-stage echo canceller with analog and digital processing is implemented, then high frequency echo noise is canceled, but system complexity increases
Solution Approach 1:
The patent merges analog and digital processing within the multi-stage architecture. The first echo canceller handles broad-band cancellation, while the second echo canceller focuses on high-frequency digital processing. This merging of processing types and stages achieves superior echo noise cancellation while managing system complexity through functional integration.
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 system can capture and cancel at least 25 dB of noise floor, significantly improving upstream signal quality compared to current echo cancellers which can only capture 0–5 dB, and effectively removes both signal and noise parts of echoes at higher frequencies.
Implementation Method 1
transform the EC estimate coefficients from frequency domain to time domain to generate the impulse response using an Inverse Fast Fourier Transform (IFFT)
Data Source
AI summary
Disclosed herein is a multi-stage echo cancellation scheme. The disclosed embodiments include an apparatus and method for monitoring and canceling echoes greater than 25 dB in a coaxial cable plant. The method includes obtaining echo channel estimate coefficients from a cable node. The method determines a location and strength of each partial echo in an impulse response using the echo channel estimate coefficients. Optionally, the method determines a frequency response of each partial echo in the impulse response.