升余弦滚降的误码率和信噪比曲线，取样时间无偏差，但信道是多径信道，衰减系数0.5 傅立叶变换及反变换参见t2f-and-f2t-Raised cosine roll-off of the bit error rate and signal to noise ratio curve, sampling time deviation, but the channel is a multipath channel, the attenuation coefficient of 0.5 Fourie