Design of a medium rate linear-predictive speech coder for digital portable radio communications

A 16 kb/s speech-coding algorithm is described. Ways of mitigating the effects of transmission errors due to slow-fading channels are discussed. The coder yields near toll-quality speech with moderate delay and complexity. It is assumed that the portable radio link uses an error detection code. For mitigation of error effects in the received speech, through objective analysis and subjective evaluation, the critical speech parameters whose error could result in very undesirable speech degradation are identified. Then a method for altering these critical parameters when errors are detected in them is considered. Experiments were run with this method using several conceivable error detection arrangements for the radio link. Results show that it eliminates the loud and annoying pops and pings arising from errors in the critical parameters, and replaces them with subjectively more preferable silence or low-level buzzes. >