The Research On Channel Estimationalgorithms In MIMO Wireless Communication Systems

The goal of mobile wireless communication is to achieve the purpose of instant communication, that is, anybody or anything can communicate anytime in any ways in any places. Because of the high spectrum efficiency and the resistance of multipath effect, OFDM realizes the rapid transmission of data, so is the core technology of high speed wireless local area network.MIMO greatly enhances the system capacity and reliability by taking advantage of multipath,bying developing new resources from the spatial and using three kinds of diversity techniques--frequency, time and space, without extra frequency resources and improving the transmitted power.Therefore, MIMO-OFDM is the most promising technology in wireless broadband mobile communication system, is the key technology of cellular communications, wireless personal area networks, wireless local area network and broadcast.An important way to obtain high communication efficiency and reliability of MIMO-OFDM system is accurate channel estimation, and the space-time decoding and signal detection are required channel state information, therefore, the main research is the channel estimation algorithm of MIMO-OFDM system based on pilots in time domain and frequency domain.In this paper, according to the MIMO-OFDM system, based on MIMO channel model, first of all, the channel is estimated in frequency domain using of training sequences of comb structure, and scattering model make MIMO system be equivalent to a combination of several independent SISO system, so the SISO channel estimation algorithm can extend to MIMO. Then,this paper discusses the least square channel estimation algorithm based on comb pilots in time domain and derives the optimal pilot sequences and placement. Finally, this paper proposes channel estimation algorithms of LMMSE and RLS method in time domain and compared with the classical LS algorithm, analyses the algorithm’s estimation accuracy and complexity. LMMSE improves the accuracy of parameters of channel estimation, reduces the error rate and mean square error of estimation,and the receiving detection performance is more close to perfect estimation performance. RLS algorithm can track the slow channel’s dynamic change effectively and improves the system performance further.