Blind carrier frequency synchronization for the uplink of interleaved OFDMA systems

In this letter, a novel blind CFO estimation algorithm for the uplink of an OFDMA system is proposed. The proposed method exploits the inherent redundant information in OFDMA symbols and does not require additional pilot of preamble overhead. Since it is a post-FFT estimator, it does not use filter banks to separate the desired user's signal from the others in the time domain. Hence, the subcarriers of a certain user are not restricted to be clustered in the frequency domain. Therefore, the proposed estimator can be applied to OFDMA systems with an arbitrary subcarrier assignment over the entire bandwidth, including IEEE 802.16e, to obtain sufficient frequency diversity in a frequency selective fading channel. The proposed method can be efficiently used for continuous tracking of all active users' CFOs only with two FFT windows within a single OFDM symbol. From simulation results, the performance of the proposed scheme is shown better than that uses preamble symbols.