Carrier frequency offset estimation of OFDM systems based on complementary sequence

As a key point of orthogonal frequency division multiplexing (OFDM) technology, carrier frequency offset (CFO) has a significant effect on OFDM system performance. This paper proposes a CFO estimation method by using complementary sequence (CS) as training sequence. The proposed CS-based method can operate integer CFO and fractional CFO estimations on the basis of the same training sequence. The fractional CFO can be effectively estimated by exploiting repetition properties of training symbol in time domain, which is similar to traditional methods. In order to increase the acquisition range and estimation accuracy of integer CFO, we design aperiodic zero correlation zone for training sequence in frequency domain. Combining the ideal autocorrelation property of CS with zero-inserting operation, integer CFO estimation can be perfectly performed. Simulation results show that mean square error of CFO estimation is close to Cramer-Rao lower bound for the fixed detection threshold and better performance can be obtained for flexible detection thresholds at different signal-to-noise ratios.