Research on frequency synchronization algorithms for OFDM in WLAN

Once the carrier frequency offset (CFO) exists, the orthogonality among subcarriers will be destroyed, which will cause inter-carrier interference (ICI). The effect of frequency offset for OFDM is analyzed, and three classical algorithms for CFO estimation based on the structure of IEEE 802.11 is summarized, that is, maximum likelihood (ML) algorithm based on cyclic prefix, time-domain correlation algorithm based on short training sequences, and frequency-domain correlation algorithm utilizing based on pilots. Then a combined estimation algorithm based on both short training sequences and pilots is proposed in the paper. Simulation result shows that proposed algorithm outperforms the three classical algorithms in both the estimation range and accuracy, especially when the initial frequency offset is large, which is required in practice.