Adaptive Filter Coefficient Oscillation for Tone Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing echo cancellation systems, particularly those using NLMS adaptive filtering, struggle to effectively detect tones which can interfere with other components and worsen echo issues due to poor performance with highly correlated signals like those in telephony tone dialing systems.
Innovation Solution
A method is introduced to detect tones in an echo canceling system by monitoring the oscillation of adaptive filter coefficients, where if the coefficients oscillate, the system is alerted to the presence of tones, using a threshold-based analysis to differentiate between tone presence and other conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If NLMS adaptive filtering is employed for echo cancellation, then echo removal effectiveness is improved, but tone signal detection capability deteriorates due to poor performance with highly correlated signals
Solution Approach 1:
The system segments the signal analysis function by separating tone detection from the NLMS adaptive filtering process. A dedicated tone detector monitors the adaptive filter coefficients independently, allowing the NLMS algorithm to continue optimizing echo cancellation while tone detection operates in parallel without interference from the highly correlated signal conditions that degrade NLMS performance.
Solution Approach 2:
The adaptive filter coefficients serve as an intermediary signal for tone detection. Instead of directly analyzing the original highly correlated tone signals which NLMS handles poorly, the system monitors the filter coefficients that result from NLMS processing. These coefficients contain oscillation patterns that indicate tone presence, providing an indirect but effective detection mechanism that bypasses NLMS's limitations with correlated signals.
2Measurement precision
If tone detection is added to the echo canceling system, then tone identification capability is improved, but device complexity increases
Solution Approach 1:
The adaptive filter, originally designed solely for echo cancellation, is made multi-functional by also serving as a tone detection mechanism. The existing NLMS adaptive filter structure is repurposed to provide dual functionality: maintaining echo cancellation performance while simultaneously enabling tone signal detection through monitoring of its coefficient oscillations, thereby avoiding the need for completely separate detection hardware.
Solution Approach 2:
The echo canceling system performs self-diagnosis by monitoring its own adaptive filter coefficients for oscillation patterns. The system uses its internal state (filter coefficients) to detect external tone signals, eliminating the need for separate external detection devices. This self-service approach allows tone detection to emerge from the existing system infrastructure without adding significant external complexity.
Data Source
AI summary
The present invention relates generally to tone detection in echo canceling systems, and more particularly to a method of monitoring oscillations of adaptive filter coefficients for narrow band tone detection in echo cancellation systems. The invention is directed at improving communication in a telephone communication network having one or more hybrid connections. A method for detecting continuous tones in an echo canceling system having an adaptive filter is provided. Continuous tones have a deleterious effect on the performance of adaptive filters. In the present invention, the adaptive filter coefficients are monitored. Oscillation of those coefficients indicates continuous tone presence.