Motorola Corporation

Continental Automotive Systems Corporation

Temic Automotive of North America, Inc.

James Brian Piket

William Chunhung Yip

Christopher W Springfield

Daniel S Rokusek

Keith L Owens

Kyle K Iwai

David L Barron

Ernest Pei-Ching Chen

Tenkasi Vaideeswaran Ramabadran

Gerald V Piosenka

James A Stephens

David T Gustafson

Steven Peter Allen

Paul R Kennedy

Edgardo Manuel Cruz-Zeno

Marc Alan Newman

Bruce Edward Geren

Shirley Hsiao-Mei Lee

Daryl Leslie Bergstrom

Donald Fong Gee

Lance Foreman Amos

Holly Elizabeth Hall

An echo canceler circuit () and method attenuates at least post-echo canceler uplink data () to produce attenuated uplink data () in response to uplink echo return loss based attenuation data (). The echo canceler circuit () includes an echo return loss based attenuation data generator () and at least an uplink data attenuator (). The echo return loss based attenuation data generator () produces the uplink echo return loss based attenuation data () in response to echo return loss data (). The echo return loss data () is based on at least one of: attenuated downlink data (), pre-echo canceler uplink data (), and/or amplifier gain data (). The uplink data attenuator () attenuates the post-echo canceler uplink data () to produce attenuated uplink data () based on the uplink echo return loss based attenuation data ().

Echo canceler circuit and method

Received data is filtered to produce pre-noise suppression data. Noise is removed from the pre-noise suppression data to provide noise-suppressed data. At least one weighted filter coefficient is dynamically determined using at least the pre-noise suppression data and not the noise suppressed data. The determination occurs independently from and is not affected by removing the noise from the pre-noise suppression data. Removing the noise from the pre-noise suppression data occurs independently from and is not affected by dynamically determining the at least one weighted coefficient.

An echo canceling circuit comprising a double talk detector, an upper band signal filter configured to pass only near-end upper band signals to the double talk detector and remove lower band signals, an adaptive filter circuit, a control circuit operatively coupled to the double talk detector and to the adaptive filter circuit, and a threshold estimator configured to iteratively calculate an upper adaptive decision threshold value and a lower adaptive decision threshold value. The double talk detector declares near-end speech to be present if an estimated power level of the upper band signals exceeds the upper adaptive decision threshold value, and declares the near-end speech to be absent if the estimated power level of the upper band signals falls below the lower adaptive decision threshold value for a predetermined number of iterative cycles.

Method and apparatus for double-talk detection in a hands-free communication system

A method for reducing a computational complexity of an m-stage adaptive filter is provided by updating recursively forward and backward error prediction square terms for a first portion of a length of the adaptive filter, and keeping the updated forward and backward error prediction square terms constant for a second portion of the length of the adaptive filter.

Reduced complexity recursive least square lattice structure adaptive filter by means of limited recursion of the backward and forward error prediction squares

A method for reducing a computational complexity of an m-stage adaptive filter is provided by expanding a weighted sum of forward prediction error squares into a corresponding binomial expansion series, expanding a weighted sum of backward prediction error squares into a corresponding binomial expansion series, and determining coefficient updates of the adaptive filter with the weighted sums of forward and backward prediction error squares approximated by a select number of terms of their corresponding binomial expansion series.

Reduced complexity recursive least square lattice structure adaptive filter by means of estimating the backward and forward error prediction squares using binomial expansion

An echo canceller circuit () and method performs cascaded echo cancellation and noise suppression in a non-interfering manner. The echo canceller circuit () includes pre-noise suppression logic (), echo canceller coefficient logic (), noise suppression logic () and an echo canceller filter (). The pre-noise suppression logic () receives pre-echo canceller uplink data () and downlink data (), and in response produces pre-noise suppression uplink data (). The echo canceller coefficient logic () receives the pre-noise suppression uplink data () and the pre-echo canceller uplink data (), and in response produces filter coefficient data (). The noise suppression logic () receives the pre-noise suppression uplink data (), and in response produces noise suppressed uplink data (). The echo canceller filter () receives the noise suppressed uplink data () and the filter coefficient data () and in response produces final uplink data ().

A downlink activity and double talk probability detector and method for an echo canceler circuit () improves the stability of an echo canceler adaptive filter () and improves the attenuation of post-echo canceler uplink data (). The echo canceler circuit () includes a downlink activity and double talk probability data generator () and an echo canceler stage (). The downlink activity and double talk probability data generator () receives pre-echo canceler uplink data () and downlink data () and in response produces double talk probability data () and downlink activity data (). The echo canceler stage () receives the downlink data (), the pre-echo canceler uplink data (), the double talk probability data () and the downlink activity data (), and in response produces uplink data ().

Downlink activity and double talk probability detector and method for an echo canceler circuit

A double talk activity detector () and method for an echo canceler circuit () improves the probability of detecting a double talk condition based on at least pre-echo canceler uplink data (). The echo canceler circuit () includes a double talk activity probability data generator () and an echo canceler stage (). The double talk activity probability data generator () receives pre-echo canceler uplink data () and in response produces double talk activity probability data (). The echo canceler stage () is coupled to the double talk activity probability data generator () and receives downlink data (), pre-echo canceler uplink data () and the double talk activity probability data () and in response produces attenuated uplink data ().

Double talk activity detector and method for an echo canceler circuit

A bi-directional hands-free communication device includes a microphone for transmitting a signal along a transmit path and a speaker receiving a signal transmitted along a receive path and outputting a corresponding output signal. An echo canceller, positioned in the transmit path and the receive path, cancels echo signals induced by the microphone from the speaker and outputs a corresponding cancelled signal along the transmit path, and a transparency circuit distributes state-dependent additional loss derived from the noise floor margin to the transmit path and the receive path to reduce residual echo signals output from the echo canceller. The transparency circuit measures a noise floor and inserts an artificial noise signal to the transmit path, and optionally to the receive path, at a predetermined level in relation to the measured noise floor, and dynamically adjusts the speaker to compensate for changing environmental conditions by dividing a range of an expected ambient noise power into adjacent consecutive bins, and controlling a volume of the speaker responsive to ambient noise changes only when measured noise power moves into an adjacent bin.

Full-duplex hands-free transparency circuit and method therefor

The step sizes for tap positions of an adaptive filter ( ) in an echo canceller ( ) for canceling an echo signal are individually selected based upon a profile of the echo environment. A training signal ( ) is injected into the echo canceller and to the echo path during a training interval, or period. The adaptive filter profiles the echo path during the training interval. Respective step sizes &agr;&lsqb;k&rsqb; for the tap positions are generated as a function of the echo profile so generated.

Method and apparatus for setting a step size for an adaptive filter coefficient of an echo canceller

A communications transmitter which operates as a mobile telephone incorporates a noise suppressor ( FIG. ) which reduces the background noise in the transmitted voice signal. An external voice activity detector ( ), which operates in conjunction with a noise suppressor ( ) estimates the signal power of the incoming voice signal and compares this to an estimated noise floor. As a result of this comparison, a voice activity factor is applied to an updated noise floor estimate to create a voice activity threshold estimate. The voice activity threshold estimate is then used to decide whether or not to the force noise suppressor ( ) to perform an update of a noise content estimate of the incoming voice signal.

Method and system for noise suppression using external voice activity detection

A hands-free communications unit employs a downlink peak power memory element ( , FIG. ), a downlink voice activity detector ( ), and an uplink voice activity detector ( ). The downlink voice activity detector ( ) evaluates the incoming signal to determine if the signal includes voice. In a similar manner, the uplink voice activity detector ( ) determines if an outgoing signal includes voice. In the event that the incoming signal includes voice and the energy of the outgoing signal exceeds a threshold calculated from the peak power of the incoming signal, the uplink voice activity detector ( ) indicates that a double-talk condition exists ( , FIG. ). In the event that the incoming signal does not include voice, the uplink voice activity detector ( ) compares the uplink signal to a voice threshold above a noise floor to determine if the outgoing signal includes voice.

Echo canceler and double-talk detector for use in a communications unit

A technique and method that efficiently and simultaneously transfers both voice and data information over a single communications link (11). The technique and method utilizes a multi-rate vocoder (12) for providing voice information at a plurality of different rates. Accordingly, the vocoder may be dynamically adjusted during transfer of information to meet channel bandwidth requirements. The technique and method also utilizes a bit-control protocol for inserting voice information within a stream of data information by the use of inserting flags having predetermined bitstreams. Accordingly, voice information is dynamically inserted into an existing bitstream of data information such that voice information is transferred only upon demand and when needed. This prevents the transfer of useless information, such as voice information when a speaker is silent and, thus, allows for very efficient utilization of system bandwidth.

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Gilbert, AZ, United States of America

James Brian Piket