Standardization of the selectable mode vocoder
S.C. Greer, A. DeJaco · 2002
The migration from the first generation of cellular telephony to the second has included a transition from an analog speech channel to a digital channel that employs digital speech codecs. As the deployment of these second-generation systems matures, system capacity concerns have increased the pressure for a more efficient encoding of speech. In addition, market pressures have contributed to the contradictory requirement of improved voice quality provided by these wireless systems. This paper presents the motivation for, and the execution of, a program of standardizing a new variable-rate speech codec for the cdmaOne/cdma2000 wireless system. Several codecs have previously been standardized. This new codec, known as the selectable mode vocoder or SMV, offers a significant improvement in voice quality over that of existing codec standards as well as the flexibility of allowing the system operator to make tradeoffs between voice quality and system capacity.