Analysis of Two-Step Frequency Offset Estimators for OFDM

The conventional two-step carrier frequency offset (CFO) estimator using L identical parts is analyzed. It turns out that the conventional two-step CFO estimator is not optimal in terms of MSE. A novel two-step CFO estimator is proposed in this paper. In fist step, a fine estimate is obtained based on the principle of minimum variance. The fine estimation has ambiguity since its estimate range is limited. In second step, a coarse estimation is obtained which results in a larger estimate range but less precision. Using the coarse estimation, the ambiguity of fine estimation is resolved. Finally, the fine estimation resolved the ambiguity and the coarse estimation are optimally combined to improve the estimate performance. Analysis and simulation results demonstrate that the novel two- step estimator outperforms the conventional two-step estimator in terms of estimate performance and computational complexity.