Channel Estimation With Spreading Code For MIMO-OFDM System

The combination of OFDM with space-time coding has received much attention recently to combat multi-path delay spread and increase system capacity over wireless links. Channel parameters are needed in order to coherently decode the transmitted signal. In this paper, we discuss the principle of MIMO-OFDM system based on the introduction of fading channels. Furthermore, the channel estimation technique in MIMO-OFDM system is investigated, with the emphasis on training sequence-based and pilot-based channel estimation methods, and also several basic and improved algorithms are given respectively.The channel estimation of MIMO-OFDM can be simplified to independent single-input single-output OFDM(SISO-OFDM) channel estimation by the comb-pilot tone scheme. But it results in decreasing the data transmission speed. Spreading code is introduced to pilot tone in order to take advantage of the orthogonality of the spreading codes to restrain the noise. The scheme can not only convert the channel estimation of MIMO-OFDM to independent channel estimation of SISO-OFDM, but also improve the accuracy of the channel estimation and reduce the impact of noise. Finally, the analysis and comparison of these algorithms are made by computer simulation.