中文说明：详细描述了16QAM调制解调的过程，包括星座图，误码率-SNR曲线，升余弦滤波器，抽取，采样信号，信号的基带调制及解调 等。
English Description：
The process of 16QAM modulation and demodulation is described in detail, including constellation diagram, BER SNR curve, raised cosine filter, decimation, sampling signal, baseband modulation and demodulation of signal, etc.