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Orthogonal frequency division multiplexing (OFDM) is the projected modulation of choice for fourth-generation broadband multimedia wireless systems. However, for mobile applications, channel variations during one OFDM symbol introduce intercarrier interference (ICI), which degrades the performance. This gets more severe as mobile speed, carrier frequency or OFDM symbol duration increases. In this paper, we first analyze the ICI caused by time-variant channel in terms of the complex weighting coefficients, which give the contribution of each transmitter subcarrier to each demodulated subcarrier. Then, we propose a high efficiency intercarrier interference cancellation scheme to reduce the effects of Doppler frequency shift. Finally we derive the signal-to interference power ratio (SIR) for the proposed OFDM system. From the comparison between the normal OFDM and the proposed system, we can see that such an ICI cancellation scheme gives more than 5 dB SIR improvement. The simulation results confirm the analysis and show the SIR improvement.