| Orthogonal frequency division multiplexing (OFDM) have been paid extensive attentions due to its high spectral efficiency, high data rate and well anti-multipath ability. And it has become the key technique in broadband wireless access and the next generation (Beyond 4G) mobile communication system. OFDM is very sensitive to both timing synchronization error and carrier frequency offset due to its main character, which is the orthogonal multicarrier modulation. So accurate symbol timing and carrier frequency synchronization are important for OFDM system.The paper studies the synchronization algorithms based on training symbols. At first, development, properties and key technology of OFDM are introduced simply; the fundamental principles of OFDM and some influences on the performances in OFDM by carrier frequency offset, symbol timing offset and sampling clock offset are described generally. Then some common synchronization algorithms are introduced simply.Second, the paper studies the synchronization algorithms using training symbol in whole, which includes Schmidl algorithm and H.Minn algorithm and Yun HeeKim algorithm. The training symbols and algorithms are improved in the paper and the improved algorithm can overcome the peak value plateau which occurs in Schmidl algorithm and multi-peak value which occurs in H.Minn algorithm. The paper uses Matlab to simulink under the AWGN channel and multipath channel. The mean and variance of timing offset are utilized to weigh the performance of the algorithm. In integer frequency offset estimation, the paper use the Yun HeeKim's differential coding structure in the frequency domain in one training symbol. The paper only uses one training symbol to achieve fraction frequency offset estimation and integer frequency offset estimation.At last, the simulation results show that the improved frequency offset estimation algorithm possesses better frequency synchronization performance than Schmidl algorithm and Yun HeeKim algorithm. |
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