6. 在三条径的瑞利信道中，对于OFDM：
(1)　　请设计一种具体的导引辅助的信道估计方法，用Simulink进行仿真。画出比特信噪比与信道估计均方误差的关系曲线和比特信噪比与误码率的关系曲线。
(2)　　设频率已同步，请设计OFDM一种具体的采用循环前缀进行时间同步方法，用Simulink进行仿真，画出比特信噪比与捕获概率的关系曲线。
(3)　　设时间已同步，请设计OFDM一种具体的采用循环前缀进行频率同步方法，用Simulink进行仿真，画出比特信噪比与频率同步误差的关系曲线。(6. In the three-path Rayleigh channel, for OFDM:
(1) please design a specific navigation-assisted channel estimation method and use Simulink for simulation.The relation curves of bit signal-noise ratio and channel estimation mean square error and the relation curves of bit signal-noise ratio and bit error rate are drawn.
(2) if the frequency has been synchronized, please design a specific method of time synchronization using cyclic prefix in OFDM. Simulink is used for simulation to draw the relationship curve between bit-snr and acquisition probability.
(3) if time has been synchronized, please design a specific method of frequency synchronization using cyclic prefix in OFDM. Simulink is used for simulation to draw the relationship curve between bit signal-to-noise ratio and frequency synchronization error.)