Variable Step Size Acoustic Echo Cancellation
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Solution Overview
Problem
In acoustic echo cancellation systems, the adaptive filtering algorithm's convergence speed is hindered by spectral leakage due to small adaptive sub-filter sizes, leading to increased algorithmic delay and uneven data processing loads, which affects system performance.
Innovation Solution
A method is introduced to vary the step size of the adaptive filter based on echo leakage, using a processing block with a receiver module, adaptive filtering module, and variable step size module to compute averages and estimate echo leakage, allowing for dynamic adjustment of the step size within a maximum allowed step size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the size of adaptive sub-filters is decreased to reduce block processing delay, then processing delay is reduced, but spectral leakage increases which lowers convergence speed
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the step-size parameter of the adaptive filter based on echo leakage detection. When echo leakage is detected, the step-size is reduced to prevent divergence, and when echo leakage is absent, the step-size is increased to accelerate convergence. This dynamic parameter adjustment resolves the contradiction by allowing the filter to converge quickly when conditions permit while maintaining stability when echo leakage occurs.
2Speed
If the size of adaptive sub-filters is increased to increase convergence speed, then convergence speed is improved, but block processing delay increases
Solution Approach 1:
The patent implements dynamics by making the step-size parameter dynamic rather than fixed. The step-size adapts in real-time based on the detected echo leakage conditions, allowing the system to optimize convergence speed when possible while preventing divergence when echo leakage is present. This dynamic adjustment mechanism resolves the contradiction between convergence speed and processing delay.
3Device complexity
If fixed step-size is used for adaptive sub-filters, then algorithmic complexity is reduced, but convergence performance deteriorates due to echo leakage
Solution Approach 1:
The patent applies feedback by detecting echo leakage in the error signal and using this information to adjust the step-size parameter. The echo leakage detector monitors the error signal and provides feedback to the adaptive filter, enabling it to adjust its step-size accordingly. This feedback mechanism improves convergence performance and reliability without significantly increasing algorithmic complexity, as the detection and adjustment logic is integrated into the existing filter structure.
Data Source
AI summary
A method and system for acoustic echo cancellation varies a step size of an adaptive filter in an acoustic echo canceller. Far-end data is received and echo estimate data is calculated using the received far-end data. Microphone data is received and error data is calculated using the received microphone data and the echo estimate data. A first average of the microphone data and a second average of the error data are computed over a predefined number of samples. An echo leakage is estimated using the first average and the second average wherein the echo leakage indicates an extent to which the far-end data is present in the error data, and the step size of the adaptive filter is varied based on the echo leakage and a maximum allowed step size.