| Summary: | 碩士 === 國立臺灣大學 === 電信工程學研究所 === 91 === In this thesis, we develop a coarse frequency offset estimator to estimate an integral frequency offset between the oscillators in the receiver and transmitter for OFDM system. In this approach, a frequency offset estimation is realized by transmitting specific training polynomials as the preamble of OFDM frames. With the properties of these training polynomials, we can obtain the carrier frequency offset by means of a simple shift register circuits. Under the consideration of the practical noisy environments, three decision rules are proposed to deal with the noise effects. Simulation results show that either in an AWGN channel or a multi-path channel, our estimator provides the better performance than the conventional PN-sequence-based estimation techniques do. Furthermore, in order to obtain more accurate timing information, we propose a fine timing synchronizer to estimate the timing offset in the frequency domain. Finally, in the residual frequency tracking step, a frequency -domain adaptive filter is proposed to perform the residual frequency offset tracking process in the presence of phase noise. The simulation results also verify that the proposed approach outperforms the conventional method.
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