完成M=4的正交信号的数字通信系统的蒙特卡罗仿真。分析其在加性高斯白噪声下误码率与信噪比之间的关系，绘出误码率-信噪比曲线图，并和物理曲线进行比较。-The completion of M = 4 orthogonal signals in Monte Carlo simulation of digital communication systems. Analysis of the additive white Gaussian noise bit error rate and signal