Frequency synchronization in OFDM Could you please help me understanding how the null sub-carriers can be used to estimate the carrier frequency offset and thus performing frequency Synchronization at the receiver?
That depends, but usually rough frequency correction in an OFDM receiver is done by simply looking at which carriers have significant energy, which don't; you can do that, for example, by comparing the sum of all non-null carriers' energies to that of all null-carrier energies, and shifting that around until the ratio maximizes. Pretty simple idea!