Research On Channel Estimation In MIMO-OFDM System

The Wireless Local Area Network (WLAN) technology is the result that the computer network technology and wireless communication technology combined together. Now, the popular WLAN technology mainly includes IEEE 802.11 standards, HiperLAN (high performance radio local area network) standards, Bluetooth, infrared system technology and HomeRF technology and recently the ITU determined that the IEEE 802.16a would be the standard of the WMAN. But, with the continuous increase of society requirements in the information times in 21th centry, the type service and transfer rate offered by the existing technological products are still far from meeting people's demands. Thus, people need develop a new WLAN technology with higher speed and supporting more business kind.The orthogonal frequency division multiplexing (OFDM) system is multicarrier systems and usually used to combat frequency selective fading or narrowband interfere. But in order to increase the systematic capacity further, raise the systematic transfer rate, only use OFDM technology broadband wireless communication means to need to increase the quantity of the sub signal carrier simply in a large amount, and this kind of method will increase systematic complexity by a wide margin, and take up the systematic bandwidth in a large amount, certainly will be very difficult to adapt to the limited bandwidth and power wireless LAN at present. But multiple input multiple output (MIMO) systems could improve the capacity of the communication system and spectral utilization ratio at double in case of not increasing bandwidth. Therefore, combing these techniques to form a MIMO-OFDM system is a promising scheme for achieving high data rates for the future broadband wireless networks in frequency selected channel.The principle of MIMO-OFDM system based on the introduction of fading channels will be discussed in this paper. Furthermore, the channel estimation technique in MIMO-OFDM system is investigated, with the emphasis on trainingsequence-based and pilot-based channel estimation methods, and also several basic and improved algorithms are given respectively. Finally, the analysis and comparison of these algorithms is made by computer simulation.The structure of this paper is as follows:Chapter one reviewed the development of the wireless communication and introduced the main idea of the research briefly. And then recommended every chapter arrange of this paper.Chapter two introduced the characteristic of the wireless mobile channel in mobile communication at first, and the fading effect caused. Secondly, analyzed the model of the wireless channel and then simulated it. It introduced the principle of OFDM and MIMO and the structure and principle of MIMO-OFDM system. And a real MIMO-OFDM system was shown in the last part.Chapter three introduced the model of the signal and channel of training sequence-based in MIMO-OFDM system and analyzed the LS and MMSE estimation in the same system. Finally it was simulated.Chapter four introduced the principle of pilot-based technology including the interring and chosen, the method of the attaining of information from the receiver. The mathematics model was shown. The development of estimation of channel based on MMSE and several approximate methods were introduced. The conclusion was shown by simulation.