A voice transmission quality improvement scheme for personal communication systems-super mute scheme

To improve the ADPCM voice quality in slow fading channels, this paper proposes the super-mute (S-Mute) scheme by using the probability distribution of ADPCM code without error bits and the error patterns. With consideration of characteristics of voice and channel error patterns, it makes it possible to reduce the code error significantly compared with conventional muting, which has only two replacement code patterns. Furthermore, this paper shows the adaptive replacement of ADPCM code against the grade of burst degradation by applying the channel quality estimation scheme, the ADPCM code detection (ACD) scheme. As a result, when the proposed scheme is employed, the mean opinion score (MOS) improves by 0.6 points compared to the conventional muting scheme.