This paper analyzes the immediate cause of the ICI in the OFDM systems due to the Doppler spread, As was shown, ICI occurs because of the direct using of the DFT (FFT) and IDFT (IFFT) for signal conversion from time domain into frequency domain, and vice versa, when the duration and bandwidth of signal are limited. It was proposed the method, which refines the spectral density function of subcarriers, when applied in the transmission side, and improves the characteristics of the DFT as a digital filter, when applied in the receiver side, Designed simulation includes, working under the same conditions, models of conventional OFDM, PCC-OFDM and proposed method Results of the simulation show that proposed method provides up to the 10 times less BER, compared with PCC-OFDM and up to the 100 times less BER, compared with conventional OFDM, which allows mobile communications for the vehicle speed at 500km/h and higher.
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