  Orthogonal Frequency Division Multiplexing (OFDM) has recently been used
widely in wireless communication systems. OFDM is very effective in combating
intersymbol interference and can achieve high data rate in frequency selective
channel. For OFDM communication systems, the frequency offsets in mobile radio
channels distort the orthogonality between subcarriers resulting in Inter
Carrier Interference (ICI). ICI causes power leakage among subcarriers thus
degrading the system performance. A wellknown problem of OFDM is its
sensitivity to frequency offset between the transmitted and received carrier
frequencies. There are two deleterious effects caused by frequency offset one
is the reduction of signal amplitude in the output of the filters matched to
each of the carriers and the second is introduction of ICI from the other
carriers. This research work investigates three effective methods for combating
the effects of ICI: ICI Self Cancellation (SC), Maximum Likelihood (ML)
estimation, and Extended Kalman Filter (EKF) method. These three methods are
compared in terms of bit error rate performance and bandwidth efficiency.
Through simulations, it is shown that the three techniques are effective in
mitigating the modulation schemes, the ML and EKF methods perform better than
the SC method.
