Enhancement in the 32-kbit/s ADPCM algorithm for FSK voice-band data signals
Nevio Benvenuto, G. Bertocci · IEEE Transactions on Communications · 1988
Due to the feedback architecture of the standard CCITT and ANSI 32-kb/s ADPCM (adaptive digital pulse-code modulated) coders, large transitional errors occur when characteristics of the input signal suddenly change. This particularly holds for FSK modems that transmit a single-frequency signal between actual characters. A mechanism that identifies these transitions and reduces errors is presented.>