pilot based estimation is like transmitting the known data in a frram and correlation is being perfomed at the reciever on the entir frame. The transmitted data will b effected by channel behaviour. when it will b compared by the same data at the rxer the channel effect can be calculated. The invesr of channel effect will be applied on the entire data to mnimize the channel effect. hece the data corrupted due to channel behaviour is recovered. it may be done in time domain and frequency domain as well. hope u will under stand.
best regards
zamir