Fast and low-complex frequency synchronization for OFDM

A fast and low-complex frequency synchronization method with wide acquisition range of frequency offset is proposed for orthogonal frequency division multiplexing (OFDM) systems. The training sequence is composed of two OFDM symbols, one for fine estimate and the other for coarse estimate of the frequency offset. The symbol for the coarse estimate is designed in such a way that the argument of the correlation of each subcarrier with the adjacent one and the predetermined difference component is proportional to the frequency offset. The coarse estimator requires only one correlation operation in the frequency domain, hence its computational complexity is similar to the conventional time domain methods. The maximum acquisition range of the frequency is M times the subcarrier spacing when M-ary phase shift keying (M-PSK) modulation is used for the subcarriers. Simulation results show that the error rate of the coarse estimate is very low and the proposed scheme reveals performance approaching the Cramer-Rao lower bound at reasonable signal-to-noise ratio (SNR) level