High quality 16 kb/s voice transmission

In this paper, we discuss how adaptive predictive coders employing pitch and coefficient predictors perform when combined with adaptive multilevel quantizers to transmit speech at 16 Kb/s. Performance curves based on fixed point simulations provide a quantitative signal-to-noise analysis as a function of predictor complexity, quantizer adaptation strategy and channel error rate. For example, a fourth order adaptive predictor with pitch loop and adaptive 8-level quantization provides reconstructed speech that is perceptually indistinguishable from the original 2500 Hz band limited input. With channel errors, performance is found to be both a sensitive function of quantizer adaption strategy and predictor complexity. While complex predictors are superior to CVSD at error rates below 10^-4, CVSD degrades less rapidly as channel errors increase, At 10^-2BER and above, CVSD outperforms the other techniques studied.