SELF-CORRECTING DIFFERENTIAL PCM

Abstract

Differential PCM (DPCM) systems are characterized by an accumulation of transmission errors in the signal regenerated in the receiver. The use of a normalization procedure before transmission appears to permit suppression of these errors. This normalization must be carried out with respect to the limit value toward which the signal is evolving. The error reduction is not immediate, but is a function of signal value and signal activity. For constant signals there is no reduction. Reduction is more rapid the more widely the signal varies, and is also more rapid as the frequency of signal reversals increases. This method of coding requires adaptation to each application, since the basic quantization interval varies with signal magnitude.