Waveform encoding of voiceband data signals

This is a tutorial paper on encoding the waveform of voiceband data signals into digital form for digital transmission. The encoding algorithms covered are PCM, DPCM, and DM with and without quantizer adaptation. Coder bit rates from 16 to 64 kb/s are considered. Most digital Codec´s on voiceband channels are designed primarily for speech and their performance with speech is well known. However, since many voiceband channels may contain other signals such as voiceband data, adequate performance with such signals is a necessity. Much of the paper is a summary and an interpretation of previous work in encoding data signals. Some new perspectives and material are presented, especially for DPCM. Topics covered include the sampling phase effect, fast and slow acting quantizer adaptation algorithms, comparison between speech and data performance, dual-mode coders, network considerations, and the effect of quantizing noise on the phase integrity of data signals.