Semi-blind Channel Estimation Approach For MIMO-OFDM Systems

Utilizing the multi-path scattering environment in Wireless channel, multiple-input multiple-output(MIMO) technology can increase significantly the channel capacity without the band-width increasing. Orthogonal frequency division multiplexing (OFDM) technology uses between adjacent sub-carrier orthogonality can be effective against frequency-selective multipath fading wireless channel. And recently, MIMO-OFDM wireless communications system will be combined MIMO and OFDM technologies, can significantly improve the wireless communication system channel capacity and transmission rate, the key to the generation mobile communication technologies.Channel estimation is the focus of the study for MIMO-OFDM system. In this paper,we discuss the principle of MIMO-OFDM systems, point out that the channel estimation is one of the most important elements for the performance of the systems. Details describes the two kinds of channel estimation method which are Pilot-aided channel estimation and blind channel estimation algorithm based on second-order-statistics have been introduced in paper. Further more, a subspace-based sim-blind channel estimation algorithm and its improved algorithm have been investigated. The proposed method exploits both receive diversity and statistical property of the received signal based on the iterative algorithm. To reduce the effect of residual error affecting the accuracy of the noise subspace, a measure called the Hermitian angle is introduced. In addition, To track the channel variation, the forgetting factor is used to consider a time-varying channel.