Research On The Adaptive Technique Based On OFDM System

Orthogonal Frequency Division Multiplexing (OFDM) has high spectrum efficiency and capability to mitigate the side-effect of multipath channel. So it has been regarded as a key technology for high data rate transmission.In this paper, adaptive transmission technology based on the OFDM system is studied. First, a brief introduction of the basic principles of OFDM is presented.The advantage,the disadvantage and the applied scene of the OFDM system is pointed out. Secondly, we focus on adaptive transmission technology for OFDM system,which related with the estimation techonolgy of the Channel Impulse Response (CIR) and the Signal to Noise Ratio (SNR).After searching relevant papers and algorithms both in English and Chinese,we study the performance of common adaptive algorithm.The channel estimation algorithm including LS,LMMSE,intervene,DFT and MST are simulated. The snr estimation algorithm including ML,MM,EVM and MMSE is simulated.Third, Wireless Local Area Network(WLAN),namely IEEE802.11a,is presented. Based on the scene of WLAN,we simulate the adaptive algorithm proposed above,and compare their performance.Considering the given physical parameters and the channel models,better adaptive algorithms is choosed.Finally, a software simulation platform based on IEEE 802.11a standard is designed and constructed. Then the adaptive algorithm is loaded and tested in the platform. And an analysis of performance is described.