主要用途是对抗多径衰落。由于多径衰落的存在，使得同一个帧由于路径不同，到达用户端的时延有先有后。在相关的频域上的会造成子载波之间的相互干扰，影响 性能。另外，由于有了循环前缀，使得IFFT FFT操作把原来的线性卷积变成循环卷积，大大简化了相应的信号处理复杂度-The main purpose is to fight against multipath fading. Due to the presence of multipath fading, the first after they have the same fr a me different paths to reach the client delay. Would cause mutual interference between sub-carriers in the frequency domain, affecting performance. In addition, thanks to the cyclic prefix, so IFFT FFT operation to the linear convolution of the original into a circular convolution, greatly simplifying the corresponding signal processing complexity