Employing Simple FFT-Interpolation for Improved Complex Tone Detection and Fine Estimation

Frequency offset estimation is an important task in mobile communication receivers. FFT-based approaches have been shown to have a very good performance at low signal-to-noise ratios (SNR). They usually consist of two steps: A coarse estimation by searching for the maximum FFT-value and a subsequent fine estimation for whichmany different approaches exist. In this paper, we demonstrate how simple interpolation in frequency domain can be used to improve the search for the maximum FFT-value without having to rely on zero-padding. The concept is then applied and tested in an acquisition scheme where large frequency offsets occur. Further, the interpolation scheme is used to reduce the complexity of a previously proposed frequency offset estimator. The basic idea of the interpolation scheme is that the spectrum can be evaluated at any position just by using the FFT-coefficients. Since most of the energy is stored in the coefficients close to the actual position, it is sufficient to consider a few of them.