Soft decision value generation circuit to reduce calculation amounts and hardware scale

A device comprising

• circuitry configured to:
• rotate, as a phase rotation process, a phase of a received symbol after coherent detection;
• calculate, by using the phase-rotated received symbol, absolute values of soft decision values for soft decision value candidates, wherein a number of the soft decision value candidates, of a number of possible soft decision value candidates, is restricted by the circuitry in advance of the absolute value calculation;
• select a minimum value out of the absolute values of the soft decision values;
• and
• assign, as a sign reflection process that is based on the phase of the received symbol after the phase rotation, a sign to the minimum value to generate a soft decision value.

A soft decision value generation method, comprising:

• rotating a phase of a received symbol after coherent detection;
• calculating, by using the phase-rotated received symbol, absolute values of soft decision values for soft decision value candidates, wherein a number of the soft decision value candidates, of a number of possible soft decision value candidates, is restricted in advance of the absolute value calculation;
• selecting a minimum value out of the absolute values of the soft decision values;
• and
• assigning, based on the phase of the received symbol after the phase rotation, a sign to the minimum value to generate a soft decision value.