Orthogonal frequency-division multiplexing (OFDM) transmission has inter-subchannel interference (ICI) in fast fading environment. Several algorithms have been proposed to reduce the ICI effects. Among these algorithms, the ICI self-cancellation schemes [3, 4] needs not to estimate the multipath responses, and its performance doesn't depend on the signal-to-noise ratio (SNR). In , the pre-processor in the transmitter extends the original symbol interval to obtain diversity that can be used by the post-processor of the receiver to make ICI self-cancelled. When the original symbol interval is doubled and the multipath channels vary linearly with time within the extended symbol interval, this algorithm can completely the ICI. However, the complexity of the post-processor in  is not low. It needs N +1 parallel fast-Fourier transforms (FFT). Moreover, there is no performance comparison between  and . In this paper, we continue our work in  and propose an equivalent low-complexity post-processor that needs only one FFT. We also give analyze the variance of the residual ICI and derive an bit-error probability (BEP) upper bound. Furthermore, we compare the performance of our algorithm with Zhao's algorithm and give some related discussion.