Motorola Corporation

Daehyoung Hong

Michael D Kotzin

Anthony P Van Den Heuvel

Steven C Jasper

Kenneth J Crisler

Lawrence M Mohl

Mark R Poulin

Theodore Saltzberg

Douglas A Carlone

Variable hangover time is provided for a speech coder (105). Voice activity within a speech message is detected (209) using a voice activity detector (VAD) (107), and a signal-to-noise ratio is calculated. A variable hangover time is calculated (215) and appended to the time in which voice activity is detected, producing an extended voice detection period. The speech coder (105) is enabled only during the extended voice detection period, thus saving power.

Variable hangover time in a voice activity detector

A convolutional decoder which assigns bit metrics to at least one bit of a symbol in a multilevel system. This decoder uses soft-decision Viterbi decoding with channel state information of a convolutionally-encoded communication transmitted using multilevel modulation.

Convolutional decoder using soft-decision decoding with channel state

A harmonic signal is created from a limited spectral representation of a voice signal. The harmonic signal is combined with the at least a portion of the limited delayed spectral signal to provide a reconstructed speech signal having perceptually improved audio quality.

Speech quality improvement for voice coders and synthesizers

An subband coding system encoder is provided for improving the quality of a reconstructed speech signal. Briefly, the improved subband coding system encoder includes means for improving the selection of the waveform/noise fill gain factor. The improved selection method, according to the invention, is based on the quasi-stationary characteristic of speech, that is, that the short-time frequency spectrum of a speech signal varies slowly with time. Moreover, the amount of fill energy is adaptively determined for each subband according to the shape of the frequency spectrum for each speech frame.

Subband decoding method and apparatus

A communication system that provides TDM and FDM communications between communication units. At least two control slots are provided in each TDM frame window to provide communication control information such as channel assignment information.

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Hanover Park, IL, United States of America

Daehyoung Hong