The Reaserch Of Channel Estimation In OFDM System Based On IEEE802.11a Standard

Since the 1980s, wireless communication technologies have been Obtained the rapid development, Each advanced method is introduced unceasingly, like the OFDM technology,MIMO technology,free time coding technique,the soft decision technology and so on ,in order to achieve a higher use of the spectrum rate, more access to rich business capabilities, more flexible bandwidth allocation method. OFDM technology has gained interest for its high bandwidth efficiency and robust performance in multipath dispersive environment, as the core of next-generation wireless communications technology, not only in the broadcasting digital audio and video has been used widely, it already become the standard of wireless local area network.OFDM technology is a special form of Multi-carriers modulation technology, its key technologies, including time-domain and frequency domain synchronization,channel estimation,channel coding and intertexture,Reduces the peak-to-average power ratio and equalization. Channel estimation is one key technology in OFDM system. The accuracy of the channel estimated has decided system's transmission accuracy directly. This paper presents pilot-based channel estimation algorithms in OFDM systems.This article first reviewed the OFDM technology development history, then expound the wireless channel model and the ODFM system basic principle, Nest analyzes the channel estimation methods, discusses basic pilot-aided channel estimation methods, and provides comparisons of some typical channel estimation methods and their computer simulation results. Simulation results demonstrate that LMMSE algorithm is more efficiency than US algorithm. But the LMMSE algorithm is so complicated. Moreover needs to know the channel'statistical property in advance and the real-time SNR, This has been limited in the practical application.