ICI Analysis for FRFT-OFDM Systems to Frequency Offset in Time-Frequency Selective Fading Channels

This letter presents the effects of frequency offset to orthogonal frequency division multiplexing systems based on fractional Fourier transform (FRFT-OFDM) in time-frequency selective fading channels. FRFT-OFDM systems generalize the OFDM systems based on discrete Fourier transform by the deployment of FRFT. The expressions of signal-to-interference ratio (SIR) due to ICI are derived in different fading channels. In a flat channel, the performances of both systems are the same. In a frequency selective channel, the FRFT-OFDM systems have superior SIR performances by choosing the optimal fractional factor, when Doppler spread is comparable to the inverse of the symbol duration or carrier offset exists in the system.