Research On Synchronization For OFDM System

Coherent demodulation is usually adopted in orthogonal frequency division multiplexing (OFDM) system to achieve better performance. It means accurate synchronization are needed.However, traditional preamble training sequence decrease substantially bandwidth utilization. In this thesis, a superimposed training scheme for synchronization is proposed for OFDM system, where training sequence are superimposed onto data stream Note that we added the m-sequence and guard interval in the time domain OFDM signal.In this thesis, we propose and analyze an efficient frequency offset synchronization method based on m-sequence of OFDM system. Repeated m-sequence is superimposed directly to OFDM frames in the time domain. By utilizing the autocorrelation characteristics of m-sequence, efficient synchronization can be achieved without imposing additional complexity. The frequency offset estimator are derived based on the maximum likelihood criterion both theoretical and simulated results are presented to verify the proposed frequency synchronization method.Also a new training sequence is proposed in this thesis we call it super imposed training sequence with zero added it was made to overcome the problem of high power of the transmitted signal. Simulation was made to compare between the two training sequence...