Echo Cancellation Using Dynamic Adaptation Coefficient
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Solution Overview
Problem
Existing echo cancellation systems in two-way communications face challenges in effectively suppressing residual echoes, especially in the presence of background noise, during double talk, and when the echo path changes, while maintaining full-duplex communications.
Innovation Solution
The proposed system includes an echo approximator, a subtractor, and an adaptation coefficient generator that uses an adaptive linear filter with an adaptation coefficient calculated based on the ratio of averages to optimize echo cancellation, along with non-linear processing units in the frequency sub-bands to further suppress echoes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional echo cancellation systems are used, then basic echo removal is achieved, but residual echoes remain especially in presence of background noise, during double talk, and when echo path changes
Solution Approach 1:
The patent implements dynamic adaptation by continuously updating the adaptation coefficient based on real-time signal conditions. The system adjusts the adaptation coefficient μ(n) using the ratio of averages method, which dynamically responds to changing echo paths, background noise levels, and double-talk conditions, allowing the echo canceller to adapt its filtering characteristics in real-time to maintain optimal performance
Solution Approach 2:
The patent changes the key parameter of the adaptation coefficient from fixed or简单地 normalized values to a dynamically calculated value based on the ratio of averages. The adaptation coefficient μ(n) is computed as a function of signal powers and cross-correlations, allowing the system to adjust its convergence rate and stability characteristics according to actual operating conditions, thereby reducing residual echo across varying scenarios
2Measurement precision
If adaptive filter order L is increased to improve echo cancellation accuracy, then better echo approximation is achieved, but computational complexity and processing time increase
Solution Approach 1:
The patent applies partial action by using a moderate filter order L-1 that provides sufficient echo cancellation for most practical scenarios. Rather than always using the maximum possible filter order, the system employs an adaptive coefficient that optimizes performance within a reasonable computational budget, achieving acceptable echo suppression without excessive complexity
Solution Approach 2:
The patent dynamically adjusts the effective adaptation rate through the adaptation coefficient μ(n), which acts as a scaling factor on the filter updates. This allows the system to achieve better convergence behavior and effective precision without necessarily increasing the filter order L, thereby balancing accuracy and computational complexity
3Speed
If adaptation coefficient μ is increased to speed up convergence, then faster adaptation to echo path changes is achieved, but system becomes less stable and more sensitive to noise
Solution Approach 1:
The patent implements dynamic adjustment of the adaptation coefficient μ(n) that automatically scales with signal conditions. During periods of high signal power or double-talk, the adaptation coefficient is reduced to maintain stability. During periods of low noise and clear echo paths, the coefficient increases to accelerate convergence, thus dynamically balancing speed and stability
Solution Approach 2:
The system uses feedback from the residual error signal and signal power estimates to continuously adjust the adaptation coefficient. The ratio of averages method incorporates feedback about current signal conditions into the coefficient calculation, creating a self-regulating mechanism that responds to stability requirements and noise levels in real-time
4Reliability
If non-linear processing is added to suppress residual echo, then echo suppression performance improves, but device complexity and processing overhead increase
Solution Approach 1:
The patent introduces non-linear processing units as intermediary components that operate on the output of the linear echo canceller. These units apply non-linear transformations to further suppress residual echo without requiring complete redesign of the core cancellation mechanism, thereby improving performance with additive rather than multiplicative complexity
Data Source
AI summary
Traditionally, echo cancellation has employed linear adaptive filters to cancel echoes in a two way communication system. The rate of adaptation is often dynamic and varies over time. Disclosed are novel rates of adaptation that perform well in the presence of background noise, during double talk and with echo path changes. Additionally, the echo or residual echo can further be suppressed with non-linear processing performed using joint frequency-time domain processing.