Performance improvement of the OFDM system based on fractional Fourier transform over doubly dispersive channels

Abstract

Traditional orthogonal frequency-division multiplexing (OFDM) loses its optimality in high-mobility scenarios, intercarrier interference (ICI) occurs and the Doppler shifts destroy the orthogonality of the subcarriers. Many solutions are introduced by using complicated equalizers in the receiver to overcome this problem. The fractional Fourier transform (FrFT) has been suggested to improve the performance of the OFDM over doubly dispersive channels that cannot be achieved with traditional OFDM even with complex equalizers. In this paper the performance of OFDM based FrFT is studied with multiple fractional orders at different Doppler shift. Simulation results demonstrate processing improvement due to using FrFT instead of Fourier Transform (FT) in OFDM system. The same bit error rate (BER) is achieved without increasing the transmitting signal to noise ratio (SNR) and processing improvements are gained up to 3 dB for different Doppler frequencies.

Waveform design and optimization for OFDM radar signal based on fractional Fourier transform

“…PAPR is an important parameter to measure the performance of radar systems [16][17][18][19] . The PAPR of FFT-based OFDM radar system is too large to easily cause signal distortion resulting in bad effects on radar's performance.…”