Nonlinear encoder and its method, nonlinear decoder and its method and data transmitting method through nonlinear channel

PURPOSE: To reduce effects of synergetic noise by making a transmission channel have a characteristic that is partially a nonlinear function, making flexion function almost an inverse function to the nonlinear function and impressing the sequence of a signal point that is flexed to the transmission channel. CONSTITUTION: Flexion is executed by multiplying a flexion multiplication factor that is generated according to a selected flexion function. That is, a nonlinear encoder 130 generates a flexion multiplication factor and gives it to multipliers 122 and 123. The multipliers 122 and 123 multiply, resultantly add a flexed value to a modulator 125 and generates a modulation line signal that represents the stream of the flexed signal points with a standard procedure. Next, the signal is added to a telephone channel of a voice band through a lead 130. This reduces noise that is caused by non-linearity in a trellis coding data transmission system and improves a signal point arrangement flexion system.