Frequency offset estimation in an OFDM system

The orthogonal frequency division multiplexing (OFDM) system has recently attracted increasing interest for its robustness of frequency selective fading, and is believed to be an important technique for future high-speed wireline and wireless communications, including cellular mobile communication systems. However, a well-known problem of such a multi-carrier modulation is its vulnerability to synchronization errors. The frequency offset, which results from a Doppler shift, due to mobile movement, as well as the inherent instability of the transmit and the receive reference, causes a loss of orthogonality between the subcarriers, and hence, produces intercarrier interference (ICI). To solve this problem, we trade on the correlation of the samples at the output of the discrete Fourier transform (DFT) to estimate the frequency offset by using the extended Kalman filter (EKF), which blindly tracks the frequency offset via a recursive procedure. Simulation results are given to illustrate the tracking performance of this algorithm.