Abstract: 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.

Abstract: A processing system time compresses a voice message before transmission, and processing system time expands the message after reception. To process the message the processing systems perform at least one of: (a) randomizing the order of a sequence of samples form a silent portion of the message after reception thereof before blending the sequence with a last portion of the expanded message; (b) selecting the sequence of samples from the silent portion of the message after reception thereof, the sequence selected being poorly correlated with the last portion of the expanded message, before blending the sequence with the last portion of the message; and (c) compressing the dynamic range of the message before transmission, by an amount dependent upon the signal-to-noise ratio of the message, and aggressively expanding the dynamic range of the message after reception, by a fixed amount.