说明：   This script simulates the classical turbo encoding-decoding system. It simulates parallel concatenated convolutional codes. Two component rate 1/2 RSC (Recursive Systematic Convolutional) component encoders are assumed. First encoder is terminated with tails bits. (Info + tail) bits are scrambled and passed to the second encoder, while second encoder is left open without tail bits of itself. Random information bits are modulated into +1/-1, and transmitted through a AWGN channel. Interleavers are randomly generated for each frame. Log-MAP algorithm without quantization or approximation is used. By making use of ln(e^x+e^y) = max(x,y) + ln(1+e^(-abs(x-y))), the Log-MAP can be simplified with a look-up table for the correction function. If use approximation ln(e^x+e^y) = max(x,y), it becomes MAX-Log-MAP.