4.　　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，其中的编码、译码全部是自己编写代码(S-Function方式)，不是调用Simulink的已有编码、译码函数。请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。-4 Explain the working principle of convolutional encoding and decoding. Please use the Simulink simulation convolutional coding and Viterbi decoding method used to decode, in which the encoding, decoding all write your own code (S-Function mode), instead of calling the Simulink existing encoding and decoding functions. In additive white Gaussian noise channel, signal to noise ratio and bit error rate to draw the curve.