Dual adaptive delta modulation for mobile voice channel and its DSP implementation

The objective of our work reported in this paper is to design a dual adaptive delta modulation (DADM) that can 1) transmit fairly good quality speech (as high as communications quality) at 16 kbps, 2) produce a graceful degradation in speech quality in the presence of channel bit errors of up to 1 percent, and 3) be implemented with a small-sized and economical digital hardware. Presented are: 1) basic characteristics of the algorithm proposed, including subjective assessment of voice quality, 2) optimization of system parameters using speech samples spoken by 4 males and 4 females, and 3) hardware realization of the DADM using a DSP and a PCM-Codec LSI chips for full-duplex operation.