Inter carrier interference cancellation in OFDM systems

Abstract

In the area of wireless communications, the demand for high data rate transmission is rapidly increasing. Orthogonal frequency division multiplexing (OFDM) is known to be a promising technique for high-rate transmission that can overcome the inter symbol interference (ISI) which results from the time dispersive nature of wireless channels. For OFDM communication systems the orthogonality is lost among the sub-carriers due to frequency offset which results in Inter carrier Interference (ICI). This ICI rapidly degrades the performance of OFDM system. We have so many ICI cancellation methods like time windowing and frequency equalization to improve the BER performance of OFDM systems. In this an efficient ICI cancellation methods termed ICI self-cancellation (SC) scheme, extended Kalman filter (EKF) method and another ICI cancellation scheme, named Total ICI Cancellation scheme are proposed. However the total ICI cancellation scheme has does not lower the transmission rate or reduce the bandwidth efficiency. It is shown that for high values of the frequency offset and for higher order modulation schemes, the EKF method perform better than the SC method. The Total ICI Cancellation scheme takes advantage of the orthogonality of the ICI matrix and offers perfect ICI cancellation and significant BER improvement at linearly growing cost. Simulation results in AWGN channel confirm the superb performance of the Total ICI Cancellation scheme in the presence of frequency offset or time variations in the channel compared with other two schemes.