Research Of The Technology Of OFDM Used In WLAN Based On IEEE 802.11a

When the mobile communication has been developed to the third generation (3G), as the data flow increased and the needs of broad band multimedia service, the network needs broad band connected faculty. By using OFDM technology in WLAN, it has highly increased the transmission speed and achieved high bandwidth efficiency. OFDM technology has many advantages, such as defending the multipath fading and high bandwidth efficiency, which are suitable for the high-rate data transmission in wireless enviroment.This paper introduces some basic conception of WLAN, the protocol standards involved, and also the working principle and several key technologies of OFDM system. It describes the OFDM data frame format and the system simulation based on IEEE 802.11a protocol detailedly. The paper focus on the research of channel estimation method in OFDM system. Firstly, it gives the classifiable explanation and deeply studied some typical channel estimation methods. Then on the basis of being familiar with the propagation characteristics of wireless channel, it proposes two channel estimation methods which separate the time-delay estimation to the amplitude estimation. The new methods decrease the number of pilot frequency, improve the bandwidth efficiency. The paper emulates the periodic channel estimation method and the adaptive channel estimation method with matlab. In the end, the comparison analyses to the emulation result are given.