说明：   结合理论课讲解基于Matlab仿真OFDM信号，绘制OFDM符号星座图，时域、频域曲线；  绘制发送端、接收端低通滤波器的幅频特性； 分析AWGN信道条件下OFDM系统的误码率性能
( combined with the theory of lesson based on Matlab simulation OFDM signal, drawing OFDM symbol constellation, time domain, frequency domain curve  draw the transmitter, receiver low-pass filter amplitude and frequency characteristics Analysis of Bit Error Rate Performance of OFDM System under AWGN Channel)