Single DSP implementation of a 16 kbps sub-band speech coder for portable communications

The authors present a real-time single DSP prototype of a 16-kb/s subband speech coder, using a single digital signal processor, for application to digital portable radio communications. The system architecture, coding algorithm, firmware, and hardware of this coder are addressed. Careful attention has been given to the many special design requirements for interfacing to a time-division multiple-access radio link. The coder uses nonlinear quantization improvement in speech quality with negligible added complexity. A single-board full-duplex prototype, based on a TMS320C25, has been designed and delivers good speech quality