Abstract
First generation digital codecs for speech have been the subject of worldwide studies since the sixties. Speech quality very close to that of the standard 64 Kbit/s PGM, the ability to carry voice band data all at reasonable complexity and cost are the main objectives of candidate coding techniques. This work deals with the subjective performance evaluation of two types of reduced bit-rate encoding techniques operating at 32 Kbit/s, for inclusion into business satellite communication systems. They are CVSDM and ADPCM, which are both capable of doubling the existing transponder capacity available in business satellite systems. The aim has been to determine transmission planning figures for their quality in terms of Richards' Q-factor. The work is also involved with the implementation of different ADPCM algorithms using digital signal processor (DSP) single chips which is fairly new to the field of telecommunications. Throughout the work the replacement of 64 Kbit/s PCM coder by 32 Kbit/s coder in satellite communication systems has been the theme. The achievement of acceptable subjective quality being the major objective.