Frequency synchronization and tracking in COFDM systems

A computationally and memory efficient technique to achieve frequency synchronization and tracking in COFDM systems is presented. Previously proposed methods rely on the filtered phase information of pilots in two consecutive symbols demodulated at the same estimated frequency. To continuously update the demodulation frequency, these estimation techniques require two demodulators to determine two symbols at each symbol period. The proposed method allows the frequency to vary using one demodulator. The frequency estimates are evaluated based on previous pilot information. Since the phase information between two consecutive pilots includes the frequency difference when the pilots were evaluated, appropriate filtering must be added. This paper derives the FIR filter that must be included in the loop. The estimator bias and variance of the frequency estimate, and the performance of the filter are evaluated.