The Research Of Wireless Network Technology Based On OFDM

Wireless LAN has been developed into one of the most important parts of the computer network research with the increasing demands for broadband wireless communication. It is the successful establishment and consecutive development of IEEE802.1l protocol that causes WLAN become he reliable and flexible network connection scheme in the places which can not be accessed by wired network.Orthogonal Frequency Division Multiplexing (OFDM) is a special case of multicarrier transmission, in which a single high rate datastream is transmitted using a number of lower data rate subcarriers. In July 1998, the IEEE standardization group selected the OFDM modulation technique for their new IEEE802.1l a standard, targeting data transmission from 11 up to 54 Mbps.Meanwhile, this new IEEE standard is the first one to use OFDM in packet based communications.(Before the proposal of this standard, use of OFDM was limited to continuous systems)In this paper, the author firstly presents the technical characteristics and the typical application of wireless local area network (WLAN), analyzes its topology structure, the network configuration and etc. Then the author illustrates the Media Access Control and the operation and frame structure of physical layer. Consequently, the author presents the basic principle of OFDM, and the process how to utilize the certain technology based on FFT & IFFT to realize the OFDM system. Through the simulation analysis of OFDM system by MATLAB, the author probes into the influence from modulating reflection, protection interval and sub-carrier wave on OFDM system, which is quite significant to the designing process of OFDM system.Furthermore, in this paper, the author advocates that the wireless AP hardware of Broadcom chip is be adopted as the solution, and then the author highlights in detail the functions and structures of some of the major chips. The same time the author makes tests on the wireless AP properties of the connectionand its penetrating among the wireless clients, or between the wireless and the wire clients. The results of the testing prove that the system compare with DSSS takes great advantages over others on the aspects of the rate of transmitting data, its stabilization and its possibility of expanding.