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Correction of OFDM Signal Form in Time Domain to Reduce ICI Due to the Doppler Spread and Carrier Frequency Offset
Gagik MKRTCHYAN Kazuo MORI Hideo KOBAYASHI
IEICE TRANSACTIONS on Communications
Publication Date: 2005/01/01
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Section on Multi-carrier Signal Processing Techniques for Next Generation Mobile Communications--Part 1)
Category: Interference Canceller
OFDM, DFT, ICI, Doppler spread, carrier offset,
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This paper analyzes the immediate cause of the ICI in OFDM systems due to the Doppler spread and carrier frequency offset. As shown, ICI occurs because of the using DFT (FFT) and IDFT (IFFT) for signal conversion from time domain into frequency domain, and vice versa, when the sampled signal has limited duration. Proposed method 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. 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 than PCC-OFDM and up to the 100 times less BER than conventional OFDM, which allows using of the OFDM in the mobile communication for vehicle speed up to the 500 km/hr.