Motorola Corporation

Martin Thuo Karanja

Chin Pan Wong

Patrick Joseph Doran

Richard B Nicholls

Nader Rizq

David J Graham

Christopher L Johnson

Mark R Poulin

Michael W Loos

Scott D Gleason

A communication device employs a method and apparatus for transmitting and receiving information in a time slot. When transmitting, the communication device generates user information symbols and positions the symbols in a first portion of the time slot. The first portion of the time slot occupies less time than the time slot. The communication device then transmits the user information symbols during the first portion of the time slot only. When receiving, a communication device decodes and then encodes a received time slot, presuming the received time slot is not a truncated time slot. The communication device determines an error metric for the encoded time slot and, based on the error metric, determines whether the encoded time slot is a truncated time slot. When the encoded time slot is a truncated time slot, the communication device processes the user information symbols in the received time slot.

Method and apparatus for transmitting and receiving information in a time slot

A portable communication device (,), such as a cellular telephone, is operable in a speakerphone mode. The communication device uses a digital communication scheme, and both receives and generates vocoded signals. The speakerphone provides half duplex operation to eliminate echo. When voice activity is detected, the device activates a speaker and mutes a microphone to avoid echo. When no voice activity is detected in the received signal, the speaker is muted and the microphone activated. To determine when speech activity is present in the received signal, a novel voice activity detection (VAD) algorithm is used which takes advantage of parameters provided as part of the received vocoded signal. The new voice activity algorithm includes calculating a staggered average of the frame energy value for a sequence of received frames, and determining if the staggered average value exceeds a threshold. The algorithm also includes adjusting the threshold level by basing the threshold level on the voicing value of the present vocoded frame.

Using vocoded parameters in a staggered average to provide speakerphone operation based on enhanced speech activity thresholds

A digital signal processor (100) receives a digitally vocoded signal (102), and calculates a staggered average value (404) from the frame energy of each received frame, or the product of the frame energy and a voicing value. While the staggered average value is above a threshold voice indicator value, speech is declared present.

Method for detecting speech in a vocoded signal

In a communication device, a decoded audio signal is evaluated by a detection function (112). Two portions of the decoded audio signal spectrum are evaluated, a ringback band (206), and the remaining band(s). The signal strength in the ringback band is measured against a preselected ringback energy threshold level and the non-ringback signal strength is measured against a voice energy threshold level. Only if the ringback energy is above the ringback energy threshold level and the non-ringback band energy is below the voice energy threshold level will a ringback filter be applied to the audio signal.

Method and apparatus for reducing false ringback detection

In a mobile communication system (400) where a handover results in a momentary interruption of a signal between the mobile communication device (402) and the fixed network equipment(404, 410), the effect of muted portion (306) of the signal can be reduced by storing a segment (308) of the signal that is received just prior to the occurrence of the handover, and re-using the stored segment by attenuating the segment, playing the segment, and repeating the attenuating and playing (208, 210) until the handover is complete.

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Plantation, FL, United States of America

Martin Thuo Karanja