Channel estimation in OFDM systems is an issue of research interest. Characterization of mobile radio channels is very complex, so the estimates of the channel parameters also encountered many difficulties. We can only apply an estimation method is to insert symbols Pilot navigation.
In fact under the influence of AWGN noise and fading is very large, normally we can not recover if the data has not used any method for estimating how, to compensate for vibrations and rotation phase signal at receiver than at the transmitter signal.