Nortel Networks Corporation

Conexant Systems, Inc.

3Dsp Corporation

Wei-Jei Song

Kan Lu

Chiang Yeh

Mike Tomlinson

A method and apparatus for canceling a near-end echo of a far-end signal for each channel of a voice over packet multi-channel communications gateway. The invention applies 'off-the-shelf' coding mechanisms as well as novel coding schemes to provide fixed compression rate and with options to maintain perfect speech integrity on certain processing components, such as network echo canceller, acoustic echo canceller, Voice Activity Detector, Comfort Noise Generation, etc. The off-the-shelf compression algorithm includes LPC-10, G.723.1, G.729A. The alternatives are Wavelet transform, DPCM, and ADPCM, etc.

Coefficient domain history storage of voice processing systems

A communication device and method for detecting an infinite return loss (IRL) condition and temporarily halting or bypassing operations of an echo canceller in response to detecting that condition. The echo canceller includes an IRL detection module that analyzes the echo return loss and the echo return loss enhancement measured from the far-end and near-end signals. Based on the analysis, the IRL detection module determines whether to bypass the subtraction of the estimated echo in the outgoing near-end signal or continue normal operations.

Method and apparatus for infinite return loss handler for network echo canceller

A method, apparatus and system employing such for adapting the Beta factor in a echo cancellation adaptive filter by using echo loss return enhancement (ERLE) as a metric to determine the setting of the Beta factor. In addition, a method and apparatus for determining the optimum number of filter taps used in an adaptive filter by dividing a filter array into blocks of taps, finding for each tap the sum of squares of the coefficients therein and then comparing the sum to an average block energy. Based on this comparison, a block is deemed to either contribute significantly to the operation of the filter or not. Starting with the tail end block of the array, the optimum filter order is found by determining when the first contributing block is found.

Heusristics for optimum beta factor and filter order determination in echo canceler systems

An echo canceller is described with improved performance. The echo canceller is capable of maintaining audio quality with less consumption of processor cycles by initially segmenting coefficients corresponding to successive audio samples of a delay line into a predetermined number of segments. The coefficients are used in computing an echo estimate. Upon segmenting the coefficients, certain segments are assigned to a first segment group, where the coefficients of that group are updated more frequently than coefficients assigned to one or more of the remaining groups. In one embodiment, this grouping is achieved by periodically computing a cumulative magnitude of the coefficients of each segment for all coefficients of the segments and subsequently placing a lesser number of segments with the highest cumulative coefficient magnitudes into the first segment group. Of course, in lieu of cumulative magnitude calculations, the energy of the coefficients may be computed. In any event, the remainder of the segments may be placed into a second segment group or multiple groups that are updated less frequently than the first segment group.

Method and communication device for optimizing echo cancellation

An echo canceler including a processor to adjust a dynamic clipping amplitude threshold for use in determining whether or not to clip outgoing audio. The dynamic clipping amplitude threshold is increased when the ratio of residue echo over echo is decreased over a prescribed period of time. The residue echo is taken as a difference between a true echo and an estimated echo initially emulated by the echo canceler. Likewise, when this ratio is increased over the prescribed period of time, the dynamic clipping amplitude threshold is decreased.

Adaptive nonlinear processor for echo cancellation

A method and an apparatus is provided for acquiring satellite signals to establish the exact spatial position of a cellular radiotelephone, in order to perform a timely dropoff or smooth handoff to another base station or frequency. The cellular radiotelephone is equipped with its own positioning system which uses satellite data to determine its spatial position. The communication system is preferably a Code Division Multiple Access (CDMA) system, and the positioning system is preferably a Global Positioning System (GPS). The method of the present invention may be used to determine the base station closest to the cellular radiotelephone. In the alternative, it may be used to compute a distance between the cellular radiotelephone and a location where the quality level of the cellular radiotelephone communication signal is predicted to be less than the predetermined value, and to determine from the computed distance whether the cellular radiotelephone should be handed off.

Method and an apparatus for positioning system assisted cellular radiotelephone handoff and dropoff

A method for speech encoding and decoding usable in a Digital Telephone Answering Machine/Voice Memo for a cellular radiotelephone is provided. The apparatus uses parameter-based speech compression and decompression modules. These modules perform decimation of standard-type speech parameter frames before storing the message, and interpolation before playing the message, in order to substantially reduce the number of parameter bits in parameter frames of the stored speech signal. The result is a decreased demand for storage space and increased speed of speech compression and decompression.

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Aliso Viejo, CA, United States of America

Wei-Jei Song