| OFDM (Orthogonal Frequency Division Multiplexing) technology is developing fast recently. The major reason is that the longer symbol duration, which reduces the amount of dispersion in time caused by multi-path delay spread. Therefore OFDM has been applying widely in many digital communication systems such as DVB ( Digital Video Broadcast ) , WLAN(Wireless Local Network), and UWB (Ultra Wide Band). How to realize efficient OFDM system has been an important hot issue for either academic or industry.In this thesis the OFDM model and its principle are introduced firstly in brief, then strengthens and weakens of OFDM are discussed, further more is the synchronization issue, especialy focuses on the OFDM time synchronization model directly based on the dispersion signal channel. And then it analyzes the performances of two kinds of synchronization technologies, which based on the training sequences and cyclic prefix, under different signal noise ratio conditions and different channel impulse responses. Based on the reference of the main algorithm and Protocol of current stage,one scheme is submitted that one kind of synchronization technologies is suitable for the transmit system which is happened abruptly, it is not only including the improved frame structure and header design, the frequency synchronization ways, as well as signal/frame synchronization, but also including the detail synchronization procedures. Its function is intention aiming at running and is verified in the present simulation system. From the comparing results , under this synchronization scheme,BER performance is approaching with the performance, which is under ideal circumstance, it indicates the synchronization quality is more satisfied. At last, an application of IEEE802.11a WLAN is analyzed in this thesis. |
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