试说明卷积编解码的工作原理。

请用Simulink仿真卷积编码，并用Viterbi译码的方法进行解码，其中的编解码全部自己编写代码(S-Function方式)，在加性白高斯噪声信道中，画出比特信噪比与误码率的关系曲线。

-Descr iption Convolutional codec test works. Please use Simulink simulation of convolutional coding and Viterbi decoding method used to decode, which codec to prepare all their own code (S-Function mode), in the AWGN channel, drawn-noise ratio and bit error rate curve.