Decoupled maximum likelihood blind carrier offset estimator for OFDM systems

In orthogonal frequency division multiplexing (OFDM) communication systems, the loss of orthogonality between the sub-carriers due to carrier-frequency offset can degrade the performance of the system. It must be compensated before the discrete Fourier transform-based demodulation. The estimation procedure based on the traditional maximum likelihood (ML) criterion usually relies on the excess cyclic prefix (CP) symbols of OFDM system, hence reduces the bandwidth efficiency of the system when multipath channel is involved. In this paper, we present a decoupled maximum likelihood blind estimation method, which does not rely on the structure of CP. This method is suboptimum. However, it is shown that the performance of the proposed method is better than the existing blind carrier offset estimation methods. This method works well even if the SNR is very low.