rx_estimate_channel

代码说明：

  OFDM频域算法，根据WLAN前导的长训练符号完成所有对子载波的信道频率响应的简单有效的估算，这两个长训练符号内容是一样的，因此二者的平均可以改进信道估算的质量。(OFDM frequency-domain algorithm, according to leading WLAN long training symbols to complete all the pairs of channel-carrier frequency response of simple and effective estimate, the two long training symbols is the same as the content, so they can improve the average quality of channel estimation.)