Output peak powers of 15 filtering ports spaced evenly as a function of input peak powers ((a), (b), (c)). The corresponding quantization transfer function of the four-bit quantization scheme ((d), (e), (f)). Differential nonlinear error and integral nonlinear error with the filtering ports ((g), (h), (i)). The input pulses of panels (a), (d), and (h) are parabolic pulses. The input pulses of panels (b), (e), and (h) are hyperbolic-secant pulses. The input pulses of panels (c), (f), and (i) are Gaussian pulses.