利用最小二乘法进行拟合多元非线性方程，ofdm系统仿真 含16qam调制 fft 加窗 加cp等模块，可以得到很精确的幅值、频率、相位估计。- Multivariate least squares fitting method of nonlinear equations, ofdm system simulation including 16qam modulation fft windowing modules plus cp, You can get a very accurate amp