PURPOSE: To demodulate reception data with high reliability even when the fluctuating speed of a communication path is high by operating adaptively a maximum likelihood system estimation device based on predicted communication path impulse response.

CONSTITUTION: A reception signal is inputted to an input terminal 100, and is inputted to a maximum likelihood system estimation circuit 101, and a reception signal reproducing filter 102. The circuit 101 performs the processing of maximum likelihood system estimation, and outputs a result to an output terminal 104 and the filter 102. At the filter 102, the replica of the reception signal is generated based on an estimation result and the internal state of the result. Furthermore, the reception signal is compared with the replica of the signal, and the internal state is updated so as to reduce an error, and also, an update result is outputted to a communication path impulse response estimation circuit 103. At the circuit 103, future communication path impulse response is predicted based on the change of the inputted internal state of the filter 102, and the result is outputted to the circuit 101. At the circuit 101, the internal state is changed based on the result predicted from the circuit 103, and the demodulation with high reliability can be attained.