With the existing telephone networks evolving towards Integrated Services
Digital Networks, there is a specific need to transmit high quality wideband
(0-7 kHz) speech at 64 kbps or below for special services like voice
channels in teleconferencing, commentary channels for broadcasting etc.
In this thesis, a computer simulation study of digital coding of wideband
speech at 64 kbps using relatively simple coding techniques is first
presented. The performance of ADPCM coders employing fixed or adaptive
prediction, with or without noise spectral shaping, and 2-band subband
coders is examined under ideal as well as noisy channel conditions. While
preserving the quality of the 64 kbps recovered speech, the transmission
bit rate is reduced to 56 kbps so that 8 kbps data can be accommodated
within 64 kbps channel....cont'd.
A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University.