Digroup data reduction techniques

This report describes a study made to determine the best speech data compression system to use in compressing the output of two T1 carrier systems down into the transmission rate normally occupied by one T1 system. The study contains a review of previously proposed speech compression techniques, a more detailed consideration of three candidate systems for this application and the rationale for selecting ADPCM/TASI as the most suitable system. ADPCM/TASI is a combination of Adaptive Differential Pulse Code Modulation (ADPCM) and Time Assignment Speech Interpolation (TASI). Computer simulation was the primary technique used to evaluate the systems.