PURPOSE: To perform the transmission of a voice band data signal at high speed, by constituting an adaptive prediction filter in such a way that a variable zero filter of arbitrary order, a variable pole filter of arbitrary order, a fixed pole filter of arbitrary order, and an offset elimination filter are cascade- connected.
CONSTITUTION: The variable zero filter 65 and the variable pole filter 71 of the adaptive prediction filter 54 output predicted values for an input signal whose frequency component changes corresponding to the lapse of time. Also, the fixed pole filter 73 outputs the predicted value for the input signal whose frequency component is almost constant in point of time. Furthermore, the offset elimination filter 68 is operated so as to eliminate the offset component of the input signal. Therefore, the predicted value of the adaptive prediction filter becomes the one with superior predictive capacity, and also, no deterioration in a quantizing characteristic for a modem signal occurs. Also, it results the variation of a bit rate, and it is possible to respond to application on a DSI sufficiently. In such a way, it is possible to realize the fast transmission of the modem signal, and to respond to a method to solve the shutout of a call used in a DSI system generally.
KAWAGUCHI SHINJI
SHINPO ATSUSHI
YOKOTA KIYOSHI
