Research On OFDM Communication Key Technique Of Multi-mode In Dual-band Broadband Wireless Mobility Network

Wireless LAN not only has the same transmission rate like LAN, but also has wireless network's motion connected competence, and it also has characteristic that it needn't dispose wire and makes up of network easy. So wireless LAN has been developed into one of the most important direction of the computer network research.Multi-mode in Dual-band is the outcomes of WLAN development. It works in the segment of 2.4/5.8 GHz, And permit various work modes, such as 802.11a/b/g. OFDM technique is not only the core technique of multi-mode in dual-band WLAN, but also is the core contents that the core of 4G This paper mainly did analysis and research to OFDM technique on Multi-mode in Dual-band WLAN.The mainly research is followed:1. This paper analyze characteristics of the mold OFDM channel, including wireless channel's fade, multi-path effect and Rayleigh fade, slow-fade and fade Storage, multi-path spread and coherent bandwidth;And built up mathematics model to the wireless channel;and analyze the ISI, ICI etc;finally, studying how OFDM system overcome ISI and ICI.2. This paper research the modulation technique and the MIMO technique. In modulate technique, this paper mainly study PSK, QPSK, QAM. This paper analyze the BER and the speed of data transmission of BPSK, QPSK and 16-QAM in Systemview and Matlab, and pointing out QAM modulate Technology is a way effectively of high speed of data transmission.3. To raise the speed of data transmission, in addition to improve modulate technique, adopt MIMO technique. The MIMO technique make use of several antenna to deliver and to accept abundantly, and can become doubly exaltation channel capacity in case that don't need to increase frequency resources and antenna's sending power. This study the basic principle of MIMO-OFDM, giving the model of the MIMO-OFDM system, and analyze and studied some keytechniques of MIMO-OFDM, such as spatial multiplexing, diversity, Space-Time Coding and Space-frequency Coding, and equalization.4. In addition to the speed of data transmission, an important aspect of OFDM system is the research of PAPR. This paper analyze statistic characteristic of OFDM system, and give two types of technique which reduce PAPR-SLM and PTS. In the end, this paper give the simulation of PTS method and its improve method and show the effect of PTS and its improve method for reducing PAPR.The research of theory and simulation express: The OFDM system what adopt QAM mapping can increase the speed of data communation evidencely, especially in QAM mapping;And the OFDM system in SLM and PTS may depress PAPR, and in advanced PTS can make signal communication quality stability and make PTS easily.