Ofdm System Under The Selected Channel Synchronization Technology Research

OFDM has been widely used in wireless communication because it can support efficient and high-speed information transmission. In double-selective channels, a lot of technical bottlenecks need to be solved for OFDM transmission, such as the design of the frame structure and synchronization technology. Based on the project of "research on the high-speed communication system", the design of the frame structure and synchronization algorithms are studies in the thesis.On the basis of extensive literature, the following work is completed.First of all, the conventional synchronization algorithms have been simulated and studied. Limitations and improved methods of these algorithms are put forward.Secondly, in time-varing and multipath channels, some problems are brought in by conventional algorithms, such as multiple peaks, being sensitive to the length of cyclic prefix, the threshold setting and so on. A multiple-correlation algorithm is proposed. The algorithm is not sensitive to carrier frequency offset and takes full account of the effect of the cyclic prefix. There is only one peak in the new algorithm and only one threshold is needed for a certain range of SNR.Thirdly, a new frame structure is investigated for burst OFDM systems. Only two symbols are needed for synchronization and channel estimation. An improved Schmidl algorithm is proposed for the new frame structure. The symbol timing and carrier frequency estimation are more accurate than the Schmidl algorithm. The improved algorithm is simulated by MATLAB and CCS software. MATLAB simulation results show that the improved algorithm can work well in time-varing channels.CCS simulation results show that the error caused by fixed-point processing can be neglected.