说明：  在OFDM系统 中，宽带信道被分割相互重叠的窄带子信道，如果各子信道 的带宽比信道的相干带宽要小，那么信号传输就有可能在无 频率选择性衰落或者平坦衰落的信道进行。
(In OFDM system The wideband channel is divided into narrowband sub-overlapping, if each sub- The bandwidth is less than the coherence bandwidth of the channel, the signal transmission is possible without Frequency selective fading or flat fading channels.)