The Research Of Channel Estimation And Detection Technology In MIMO-OFDM Systems

Multiple-input multiple-output (MIMO) technology can effectively improve the system capacity and performanceOrthogonal Frequency Division Multiplexing (OFDM) technology can eliminate the delay effect of frequency-selective channel.MIMO-OFDM system organically combined MIMO and OFDM technology ,it can significantly improve the channel capacity and transmission speeds , effective resistant to multipath fading and inhibite of interference and noise in Wireless Communication System.Thus it is considered to be the most promising program in the future system for mobile communications (B3G/4G) .The accuracy of parameter estimation and data detection is essential to the performance of the MIMO-OFDM system. This thesis focuses on channel estimation and data detection in space-time coded MIMO-OFDM system and carries out work in the following aspects:The thesis carries out in-depth studies of the principles of MIMO technology and OFDM technology and analyzies MIMO system and the key issues need to resolve; The paper also discusses the application of the space-time coding technology in MIMO systems, and describes the wireless channel model and the mathematical model of MIMO-OFDM system.This thesis studies the basic principles of channel estimation in MIMO system ,then it carries out in-depth research on an iterative method of channel estimation which based on the EM algorithm and applied it to the space-time coded MIMO-OFDM system.This channel estimation can reduce the complexity of computing.And the simulation shows that the performance of MIMO-OFDM system which use iteratived EM algorithm for channel estimation is better than the one which uses simplified LS channel estimation algorithm.This paper presents a channel estimation method based on the RLS algorithm in space-time coded MIMO-OFDM system, combined with maximum likelihood (ML) method of detecting data, the algorithm can instantly track and estimate the time-varying channel parameters through pilots and iterative method ,without any priori statistical information of channel. Simulation shows RLS channel estimation method combining ML detection method can resist multi-path effects of the Channel very well. Its BER and MSE performance has a substantial increase when compared with the LMS and LS method, so this algorithm is suitable for space-time coded MIMO-OFDM systems .In this paper, the hardware implementation of MIMO signal detection on FPGA is researched. The paper analyzies and simplifies the iteratived PIC-MMSE algorithms for signal detection from the hardware perspective , and described the hardware architecture,design elements, and methods of fixed-point design and simulation.