Adaptive frequency offset estimator without priori signature code synchronization in DS-SS systems

An adaptive frequency offset estimator without a priori signature code synchronization for DS-SS systems is proposed. First, we derive a maximum-likelihood (ML) estimation criterion, then the parabola method is applied as adaptive estimator to solve the optimization problem, and the estimation range is widened by introducing a forward-backward strategy. The analysis and simulation results show that the adaptive estimator is effective in low SNR, robust to frequency offset, and the estimation range amounts to 80% of symbol rate.