Mitel Networks Corporation

Zarlink Semiconductor Limited

Mitel Knowledge Corporation

Mitef Networks Corporation

Xin Xu

Mirjana Popovic

Celtic Tech Jet Limited

Dieter Schulz

Renee Johnston

Yonghua Fang

Jan Radecki

Andrew Wu

Logendra Naidoo

Edward Peter Gancarcik

Dean Swan

Roger Bastin

Rob McLeod

Chi Keung Leung

Dieter Schultz

A communication system with a noise cancellation (NC) assembly providing adaptive or dynamic noise cancellation. The NC assembly includes a localizer module determining, during a communication session (active speaking or during idle times), a location of the active talker. The NC assembly includes a beam generator forming a beam in the determined direction of the active talker to enhance the active talker speech. Once the NC assembly has determined the position of the active talker, the NC assembly assigns a microphone of the microphone array or generated beam in that active direction to be the 'active signal' source. The NC assembly assigns a second microphone or beam to be the noise source for NC purposes, and this source may be selected to be in acoustic shadow of the first microphone used as the active signal source or may be the farthest away in its position from the active talker's position.

Adaptive noise cancelling for conferencing communication systems

Technology for dynamic characterization of a communication device is disclosed. One method comprises sending an acoustic characterization excitation signal to be output by an acoustic transducer in the communication device. A received acoustic coupling signal that is received by a microphone of the communication device in response to the output of the acoustic transducer is measured. An acoustic signal conditioning algorithm is applied to at least one of the microphone or the acoustic transducer to reduce an amplitude of the acoustic signal or the received acoustic coupling signal to a level below a selected threshold.

Dynamic characterization of a communication device

An echo canceling system has an adaptive filter connected to an echo source, for canceling echo from an echo path. A fixed echo conditioning filter is connected in series with the adaptive filter, intermediate the echo source and the adaptive filter. The fixed echo conditioning filter cancels the constant part of the echo path using a measured impulse response of the echo path.

System for conditioning echo response of loop start trunk line

An echo canceller comprising a first adaptive filter having N_long coefficients for converging to an echo path, a non-adaptive filter representing a direct echo path portion captured by the first adaptive filter and having N_short default coefficients, where N_long&#x3e;N_short, for quick convergence of the echo canceller at start-up, wherein the default coefficients are replaced by the first N_short coefficients from the first adaptive filter responsive to an improvement in echo return loss enhancement (ERLE) of the first adaptive filter, a second adaptive filter having N_short default coefficients for modeling the direct echo path and providing an indication of double-talk and echo path changes, decision logic for receiving error signal outputs from the first and second adaptive filters and the non-adaptive filter and in response distinguishing between echo path changes and double-talk, and a non-linear processor for attenuating signals responsive to input from the decision logic.

Method and apparatus for detecting echo path changes in an acoustic echo canceller

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.

Narrow band tone detection in echo canceling system

A method of selecting an optimum impedance for a loop start trunk line, comprising successively applying respective ones of a plurality of impedance settings to the loop start trunk line, for each impedance setting measuring the impulse response of the trans-hybrid echo path by applying audio test signals to obtain a time-domain trans-hybrid transfer function and deriving a frequency-domain spectrum representative of trans-hybrid loss, and then calculating figure of merit of the transfer function based on the power spectrum. Once all impedance settings have been tested, the optimum impedance is selected as the impedance setting associated with the highest calculated figure of merit.

Method for selecting impedance setting for loop start trunk line

A method of determining residue-echo threshold for the trans-hybrid echo path of a loop start (LS) trunk line, comprising the steps of estimating the impulse response of the trans-hybrid echo path, passing a speech-like signal through the LS trunk circuit and collecting the echo signal. The collected echo signal is compared to the convolution of the speech-like signal with the estimated impulse response. The difference between the convolution result and the collected echo signal is the residue echo, which represents the effect of nonlinearity. With different levels of excitation signal, a curve of residue echo power level against input signal level is obtained, and the distortion characteristics are derived from this curve.

Method of measuring distortion and determining residue-echo threshold in loop start trunk circuits

A method for detecting echo path changes in an echo canceller using the statistics of the echo canceling behavior (i.e. signal and performance information), to distinguish between new line and double talk conditions. A moving counter is incremented or decremented based on monitored levels of ERL (Echo Return Loss), ERLE (Echo Return Loss Enhancement), noise and signal energies. When the counter reaches a predetermined threshold value indicative of sustained poor echo cancellation performance, a determination is made that there is a probable new line condition (i.e. echo path change). This echo path change information is then passed to the echo canceller to enable re-convergence.

Method for detecting echo path changes in echo cancellers

An echo canceller comprising a digital filter having adaptive coefficients which are updated to simulate an echo response, a temporary register for storing default coefficients, and a controller for monitoring ERLE and in the event the ERLE is greater than a first predetermined threshold then enabling the digital filter and replacing the default coefficients in the temporary register with the adaptive coefficients, and in the event the ERLE is less than a second predetermined threshold then disabling the digital filter and replacing the adaptive coefficients with said the default coefficients from the temporary register.

Echo canceller employing H-register and storage register

Method of selecting impedance setting for loop start trunk line

A method of suppressing an echo signal in a communication path such as acoustic coupling between a speaker and a microphone in a telephone device handset includes the steps of monitoring a transmitted signal supplied to the communication path to determine an attribute thereof; generating a leaky mask based on the determined attribute and an attribute of a received echo signal; and partially cancelling the received echo signal using the leaky mask.

Echo cancellation/suppression and double-talk detection in communication paths

A method of determining when to save default coefficients in an echo canceller so as to ensure that the capture of coefficients that correspond to the best possible echo cancellation in a current condition. Coefficients are saved at varying times depending on the amount of echo removed by the echo canceller. More particularly, the present method involves constantly monitoring the error signal to the echo canceller and comparing it with the error signal that would be obtained if default coefficients were to be used instead of the current coefficients. This ensures that the default coefficients are upgraded each time the current set of coefficients is better than the saved default coefficients.

Method of capturing constant echo path information in a full duplex speakerphone using default coefficients

A method for suppressing echo signals generated in a communication path such as acoustic coupling between a speaker and a microphone in a telephone device handset includes the steps of monitoring signals supplied to the communication path to determine an attribute thereof and masking signals received from the communication path as a function of the determined attribute of the monitored signals thereby to suppress echo.

Echo cancelling/suppression for handsets

An echo cancellation system for detecting and canceling echo from a network speech path, comprising a pool of echo locators for detecting pure echo delay and dispersion of time, a pool of echo cancellers, a pool of line watchdogs for detecting presence or absence of echo in the network speech path, and a control system for (i) locating and applying an echo locator from the pool of echo locators to the network speech path for detecting the pure echo delay and dispersion of time of any echo in the network speech path, and thereafter returning the echo locator to the pool of echo locators; (ii) locating and applying an echo canceller from the pool of echo cancellers to the network speech path for canceling the echo using the pure delay and dispersion time, and thereafter returning the echo canceller to the pool of echo cancellers; and (iii) locating and applying a line watchdog from the pool of line watchdogs to the network speech path for detecting said presence or absence of echo, and in the event the presence of said echo is detected then re-executing (i).

Line echo cancellation system

An echo cancelling system for cancelling echoes in a communication path includes an echo locator and an echo canceller. The echo locator is coupled to the communication path and locates the positions of echo signals received from the communication path. The echo canceller is also coupled to the communication path and cancels echo signals received therefrom. During echo cancellation, the echo canceller becomes active in regions corresponding to the positions of echo signals in response to the echo locator.

Growing community of inventors

Ottawa, Canada

Mirjana Popovic