Equalisation is the technique of removing the effect of dispersive channel that causes ISI. The very heart of the problem of ISI is that the current symbol is effected by symbols that are transmitted before and symbols that that are to be transmitted next.There are many to EQUALISE
1)use pilot sequence to estimate channel
2)use algorithms like LMS,NLMS etc. if desired signal is known.
3)use blind equalisation if desired signal not known.
Blind equalisation is done using
1)Higher order statistics
2)constant modulus algorithm etc.........