Decoding device and decoding method

A decoding method comprising:

• an equalization step of performing, on an input signal, partial response equalization involving convolution of a partial response coefficient, the equalization step being an adaptive equalization step of performing adaptive equalization to cause the partial response coefficient to adaptively follow a characteristic of the input signal;
• and
• a maximum likelihood decoding step of performing maximum likelihood decoding on an equalized signal, which is a resultant signal obtained by equalization of the input signal in the adaptive equalization step, and of outputting a decoded value, the maximum likelihood decoding step being an adaptive maximum likelihood decoding step of causing an identification point of the maximum likelihood decoding to adaptively follow a characteristic of the input signal,
• the decoding method further comprising:
• a target waveform generation step of, by convoluting the partial response coefficient into the decoded value, generating an equalization target waveform of the adaptive equalization which is performed in the adaptive equalization step;
• an error signal generation step of generating, as an equalization error signal, an error signal between the equalization target waveform and the equalized signal;
• and
• a coefficient updating step of, through least-square-method computation for minimizing a correlation between the decoded value and the equalization error signal, updating the partial response coefficient which is used to generate the equalization target waveform in the target waveform generation step.