Research on Channel Estimation Techniques in MIMO-OFDM Systems
|Course||Signal and Information Processing|
|Keywords||MIMO OFDM Channel Estimation Least Square|
The mobile communication technology has become the fastest growing and hottechnology in communication field. Currently, the third-generation mobilecommunication systems have been used in a wide range of countries around the world,which include WCDMA, CDMA2000and TD-SCDMA systems. The third-generationcommunication systems only provide basic data and multimedia services， but will beless than the ability to meet the high-speed mobile multimedia services. The newchallenge is to achieve the higher rate, the better service quality and the seamlessintegration.The communication systems which based on the technology of OrthogonalFrequency Division Multiplexing (OFDM) and Multiple Input and Multiple Output(MIMO) are the main development trend in future4G telecommunications. As acombination of OFDM with space-time coding technique, it has been widely concernedand studied by researchers in communication field. In wireless communication systemsthe MIMO-OFDM technology can not only effectively enhance the transmission rateand capacity of the systems, but also can effectively combat multi-path fading andinterfere. Channel estimation is a key technical issue of the MIMO-OFDM systems.Therefore, this (paper) thesis mainly investigates the channel estimation technique inMIMO-OFDM systems. First, the thesis introduces the background, significance andresearch status of MIMO-OFDM technology both at home and abroad (in domestic andoverseas), and then the basic characteristics of wireless channels are (also) introduced，including the wireless channel fading，multipath effect and time variability. Secondly,the thesis discusses the core principle and technology of MIMO and OFDM systems,and not only researches the MIMO-OFDM systems, but also sets up a simulationplatform for MIMO-OFDM system. We mainly analyze the STBC-OFDM system. Atlast, the channel capacity of SISO and MIMO systems and the performance ofSTBC-OFDM system are analyzed through Matlab simulation.The channel estimation is a key technical issue of the MIMO-OFDM systems.Therefore, the channel estimation technique in MIMO-OFDM systems is investigated,with the emphasis on training-assisted channel estimation methods. Basic principles ofseveral traditional channel estimation algorithms are discussed, which include the LS,MMSE, LMMSE, SVD-LMMSE and EM algorithms. Finally, the performance of various algorithms is provided through Matlab. Because the least square (LS) channelestimation method takes into account both the complexity and accuracy, it is applicablein the practical systems. Thus, the thesis mainly analyzes this algorithm. Finally, the LSchannel estimation algorithm bases on optimal training sequences is researched. Thestimulation results indicate that the new improved approach can decrease the computingcomplexity without the deteriorating of estimation accuracy.