Study On Channel Estimation In MIMO-OFDM System Based On Pilots

Orthogonal Frequency Division Multiplexing (OFDM) can divide a frequency selective fading channel into a number of parallel flat fading channels. This technology can overcome the adverse of multi-path effects, and achieves high spectral Efficiency. Multiple-Input Multiple-Output (MIMO) systems, employing multiple transmitting antennas and multiple receiving antennas, can not only multiple channel capacity, but also multiple the spectral efficiency without increasing the bandwidth and transmit power. Combining OFDM and MIMO will achieve high rate and large capacity in limited bandwidth. Recently, MIMO-OFDM technology has become a research hotspot.In MIMO-OFDM systems, many techniques such as coherent demodulation, STBC decoding, multi-user detection can not be independent from the channel state information. So, as the core technology of MIMO-OFDM; channel estimation will play an important role in the whole system. Channel estimation methods can be classified into the pilot-based channel estimation, blind channel estimation and semi-blind channel estimation. Pilot-based channel estimation will have higher accuracy and more practical application value.In this paper, the characteristics of wireless channel and the principles of MIMO-OFDM system are presented. Then, sever typical pilot-based channel estimation algorithms are introduced, including LS channel estimation algorithm, MMSE channel estimation algorithm and the DFT-based channel estimation algorithm, and their performance are compared and analyzed. Then, it focuses on the DCT-based channel estimation algorithm and an improved algorithm is proposed for the high computational complexity the original. The theoretical analysis proved that the improved algorithm reduces the computational complexity and compared the original algorithm, it has a lower mean square error (MSE) and bit error rate (BER), In the 802.11n channel simulation environment, the superiority of the algorithm is verified.