Research Of Performance Of OFDM Transmission System In Mobile And Multipath Enviroment

Orthogonal frequency division multiplexing (OFDM) technology has been a core technology forB3G and4G communication systems with high spectrum efficiency, resistance to multipath fadingand has been widely applied in communication filed. At the same time, High-speed transmission ofbusiness data between the mobile terminal and a base station or a mobile terminal has become moreand more popular because of the rapid development of mobile Internet technology. However，asOFDM systems are very sensitive to frequency offset，it has a poor performance in mobilemultipath environment. Therefore, technology for OFDM system to eliminate multipath andDoppler effect needs to be improved so that it can play a great role in the mobile and multipathwireless communications environment.Firstly, the paper introduces the development of OFDM technology, characteristics and modelof mobile multipath channel and the model of classic OFDM system. Meanwhile, it studies andsimulates the causes and effects of inter-symbol interference system (ISI) and carrier interference(ICI) from multipath and Doppler effect when OFDM system running in the mobile and multipathenvironment. Secondly, the paper analyzes algorithm steps, applicable conditions, advantages anddisadvantages of channel estimation and equalization based on pilot, carrier frequency offsetestimation and ICI self-cancellation technologies which are used to improve performance of OFDMsystems in the mobile and multipath environment.Thirdly, the paper proposes a improved ICI self-cancellation technology. The improvedtechnology has better ICI self-cancellation performance. While the complexity of the algorithm ofthe technology will be increased, the ultimate complexity of the algorithm is not too high by takingadvantage of the system feature. The feature is that many datas transported in this system are zeros.Finally, the paper proposes a improved adaptived OFDM system which combines cognitiveradio and cross-layer scheduling technologies. The improved system becomes more intelligent dueto the use of cognitive radio technology and more efficient and practical due to the use ofcross-layer scheduling technology.