ICI Cancelation in OFDM using Windowing Method in Time Varying Channel

Orthogonal Frequency Division Multiplexing (OFDM) is a hopeful technique for attaining high data rates in mobile environment because of its multicarrier modulation. As the sub carriers are orthogonal in OFDM, the spectrum of each carrier has a null at the center frequency of each of the other carriers in the system. But in time varying channel the orthogonality between subcarriers are distorted due to Doppler Spread (DS) which introduces the Inter Carrier Interference (ICI) that diminishes the system performance. To enhance the OFDM system performance over time varying channels, an ICI self-cancellation scheme driven with the transmitter Hamming and Hanning windowing are implemented. The time domain Hamming and Hanning windows immediately after Inverse Fast Fourier Transform (IFFT) cancel the ICI fractions from adjacent subcarriers significantly. As a result, the frequency domain channel matrix reshaped by the Hamming and Hanning windowing can be closely approximated to a strictly banded matrix. The estimation of the channel matrix is done with the assistance of the pilot tones in the Complex Exponential Basis Expansion Model (CE-BEM). The CE-BEM channel estimation performance is evaluated in terms of bit error rate for proposed system and compared with cyclic prefix OFDM system with time varying channel.