Ericsson Gmbh

Ericsson Ge Mobile Communications Inc.

Robert Allen Zak

Torbjorn Wilson Solve

Jim A Rasmusson

Torbjon W Solve

A method and apparatus for reducing the echo in a hands-free digital cellular communications system is presented. Acting upon speech signals being present in the downlink, uplink speech frames generated by the hands-free communication device are attenuated to prevent the downlink speech signals from being transmitted at full volume back on the uplink as an echo. Added to the attenutated uplink speech frame is a noise frame generated by the hands-free communication device, which provides a consistent level of background noise to the person at the other end of the call. The noise codeword is further randomly ordered to prevent any modulative effects from the process.

Method and apparatus for echo reduction in a hands-free cellular radio

The present invention provides a battery-powered radio transceiver for transmitting and receiving digital signals and method of operation for reducing electrical power consumption and thereby improving battery life between recharges. The radio transceiver includes an operator interface and a transmitter, electrically connected to a microphone in the operator interface, to convert speech signals into digital radio frequency (RF) signals for transmission. A receiver is electrically connected to a speaker in the operator interface to receive digital RF signals and to convert the RF signals into audio signals from the speaker. A microprocessor electrically connected to the operator interface, the transmitter and the receiver controls the operation of these components in processing telephone calls. An electrical storage battery is electrically connected to the microprocessor to supply electrical power to the microprocessor, the operator interface, the transmitter and the receiver via the microprocessor. An antenna assembly is connected to the transmitter and the receiver for transmitting and receiving the RF signals. The transmitter comprises a digital signal processor which is programmed to de-energize at least some of its components and to generate an artificial noise signal for transmission when speech is not being received by the microphone.

Reducing electrical power consumption in a radio transceiver by

A method and system are provided for adaptively reducing noise in frames of digitized audio signals that may include both speech and background noise. Frames of digitized audio signals are processed to determine what attenuation (if any) should be applied to the current frame of digitized audio signals. Initially it is determined whether the current frame of digitized audio signals includes speech information, this determination being based upon an estimate of noise and on a speech threshold value. An attenuation value determined for the previous audio frame is modified based on this determination and applied to the current frame in order to minimize the background noise which thereby improves the quality of received speech. The attenuation applied to the audio frames is modified gradually on a frame-by-frame basis, each sample in a specific frame is attenuated using the value calculated for that frame. The adaptive noise reduction system may be advantageously applied to telecommunication systems in which portable radio transceivers communicate over RF channels because the adaptive noise reduction technique does not significantly increase data processing overhead.

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Raleigh, NC, United States of America

Robert Allen Zak