Research On Channel Estimation For MIMO-OFDM Systems

As a combination of MIMO and OFDM, MIMO-OFDM systems achieve space|, time and frequency diversities efficiently, which can not only greatly improved channel capacity and tansimission rate of wireless communication systems, but also efficiently combat multi-path fading and interference.In wireless communication systems, the radio channel is frequency selective and time-variant. Channel state information is required in MIMO-OFDM systems for combination diversity, coherent demodulation and space-time decoding. In MIMO-OFDM systems, correct decoding at receiver depends on correct channel state information, which means accurate channel estimation. The content of this dissertation are concentrated on channel estimation technologies in MIMO-OFDM systems.Firstly, introduced the situations of MIMO and OFDM technologies, and then, summarized advantages and problems of the combination of MIMO and OFDM, thereby, indicated the importance of channel estimation in MIMO-OFDM systems.Secondly, introduced the theory of space-time coding, analyzed OFDM and MIMO system models and their advantages and disadvantages, and presented the model of MIMO-OFDM systems.The dissertation deeply studied training sequence-aided channel estimation. Realized transmitter diversity by using space-time coding. Based on characteristics of the radio channel, studied basic LS channel estimation, STC-based LS channel estimation, simplified LS channel estimation and optimum training sequences, simulated the last two channel estimation algorithms, at last, we proposed a new optimum training sequences design.Lastly, studied 2-D pilot-symbol-aided channel estimation, mainly studied conventional 2-D pilot-symbol-aided channel estimation and low-rank pilot-smbol-aided channel estimation, and simulated the two channel estimation algorithms.