A precise frequency offset estimator for OFDM system

In this paper, we proposed a new frequency synchronization method for orthogonal frequency division multiplexing (OFDM) system by using PN sequences. It is an improvement of Tufvesson's method. In the new method the frequency offset is estimated in two steps. First a small step (span of the correlation) is used for estimation of frequency offset which will result in a larger estimation range but is less precise. After the frequency offset has been compensated, the second estimation is conducted which is a large step. The new algorithm has large estimation range and the estimation is more precise. Performance of the new estimator is improved drastically compared to that of the old one. In AWGN channels, the Cramer-Rao bound of the new method is achieved and it coincides with the Cramer-Rao bound of Schmidl's method.