Design And Analysis On OFDM WLAN System And Its Synchronozation

OFDM is a key technology in B3G and even in 4G system . OFDM is a special kind of multicarrier modulate way, and also it is a high speed transmission technology to oppose ISI effectively. It divides a communication channel into a number of equally spaced frequency bands. Each subcarrier is orthogonal (independent of each other) with every other subcarrier, and frequency spectrum overlaps each other, which has improved the spectral utilization. OFDM symbol extends periodically, duplicates L pieces of sample behind each symbol to the front of the symbol to commit CP, which can reduce synchronization errors greatly for OFDM system, and can resist the damage of multipath delay effectively. At the same time WLAN is being paid more and more attention as a broadband wireless access technology at present, the construction and synchronous detection technique of OFDM WLAN subsystem is described in this paper studies, the main content is summarized as follows:? Beginning with OFDM and WLAN technical development, the advantages and the disadvantages over OFDM are proposed, and the certainty reason that the two combine is also described.? The transmitter and receiver work modules based on the OFDM WLAN subsystem are analyzed in this paper, and the produce procedure of 802.11a frame signal with simulation is described.? Synchronization problem of OFDM WLAN subsystem is analyzed, an efficient frame detection synchronization technique suitable for OFDM WLAN system is presented in this paper. This algorithm bases on the correlation technique with a threshold comparison mechanism and takes advantage of the cross correlation of short preamble. Averaging over several short symbols is applied to improve the precision of the algorithm. Finally, the performance of this algorithm is analyzed with computer simulation. Research on the present various kinds of synchronization algorithm at the same time is put on, and also the analysis of algorithm performance is described. This paper is supported by National Natural Science Foundation of China.