초록 ▼

A system is disclosed for an adaptive rate voice system to provide improvements in coded operation over changing communication channel (50) conditions. This adaptive rate system efficiently determines optimal voice/channel coding rates , coding strategies and modulation/demodulation for optimum voic

A system is disclosed for an adaptive rate voice system to provide improvements in coded operation over changing communication channel (50) conditions. This adaptive rate system efficiently determines optimal voice/channel coding rates , coding strategies and modulation/demodulation for optimum voice quality and intelligibility. A system state estimator (100), channel status estimator (110) and channel status monitor (120) provides feedback in the system to optimize the communication channel. The system maintains a continuous link despite changing channel conditions and minimizes delays through the system. Even though simple in design, it provides relatively low complexity and powerful channel coding operation. Operating conditions are thus extended for CDMA and portable communication systems. Voice intelligibility is preserved in extremely noisy or even hostile channel conditions.

대표청구항 ▼

[ What is claimed is:] [1.] An adaptive voice coding communication system comprising a transmitter for transmitting voice coded signals through a communication channel, and a receiver for receiving the voice coded signals from the channel, wherein the transmitter comprises:a voice coder for compress

[ What is claimed is:] [1.] An adaptive voice coding communication system comprising a transmitter for transmitting voice coded signals through a communication channel, and a receiver for receiving the voice coded signals from the channel, wherein the transmitter comprises:a voice coder for compressing and digitizing audio signals from an audio source at a voice coding rate;a channel coder for encoding signals from the voice coder at a channel coding rate;a modulator for modulating and transmitting the voice coded signals provided by the channel coder at a symbol rate and modulation method; anda channel status monitor for changing the voice coding rate, the channel coding rate, the symbol rate and the modulation method in response to a channel status indicator provided by the receiver over a feedback channel, the transmitter providing system status bits to the receiver prior to changing the voice coding rate, the channel coding rate, the symbol rate and the modulation method, andwherein the receiver comprises:a demodulator for demodulating the voice coded signals at the symbol rate and a demodulation method that corresponds with the modulation method, the demodulator determining a symbol error rate from the received signal;a channel decoder for decoding signals provided by the demodulator at a channel decoding rate that corresponds with the channel coding rate, the channel decoder determining a bit error rate;a voice decoder for decompressing signals provided by the channel decoder and synthesizing audio signals in accordance with a voice decoding rate that corresponds with the voice coding rate, the voice decoder determining a spectral distortion indicator from the signals decoded by the channel decoder;a system state estimator for setting the symbol rate, demodulation rate, channel decoding rate, and voice decoding rate of the receiver in response to system status bits provided by the transmitter; anda channel status estimator for providing the channel status indicator to the transmitter's channel status monitor when a current channel state differs from a previous channel state, the system state estimator coupled to the channel status estimator and determining the current channel state by computing a new symbol rate, demodulation rate, channel decoding rate, and voice decoding rate from the symbol error rate, bit error rate, and spectral distortion indicator.