| In the past century, wireless communication has developed into a significant component in communication engineering, while mobile communication has experienced 1G, 2G and 3G's commercial availability on a wide scale. The research and application of 4G are also in a positive process. As a technology of broadband wireless access, WLAN compensates the shortage of Ethernet and provides the customers information with large amounts of data. When the development of mobile communication meets a cross-generation period, WLAN acts as a role of a service complement as well as an excellent application.This paper begins with the introduction of the broadband wireless access and then gives a general idea of the relevant mainstream technology. Afterwards, a detailed analysis on the IEEEE802.11 WLAN infrastructure was given. The paper introduces the important modulation technology called OFDM, which is used in the physical layer of 802.11a.The detailed information of how to realize 802.11a's baseband is also presented. The research starts with the simulation of system's transmitter, receiver and the channel it experienced. Several suggested synchronization algorithms are thoroughly researched and discussed. By analyzing on theory and simulation, the advantages and shortages are given.On that basic, some new algorithms, say, local short symbols cross correlation algorithm and changing-window correlation algorithm are realized and tested.Considering the complexity and performance, the new algorithms are feasible and easy to implement.As the frequency offsets estimation, a maximum likelihood estimation on timing and frequency offsets is analyzed. The paper puts emphasis on the frequency synchronization on the time domain.The simulation gets the results expected.On the MAC layer, the basic mechanism and backoff algorithm are researched and meanwhile some changes are made to the binary exponential backoff algorithm. Simulation results and analysis are presented. |
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