Research On The Channel Estimation In MIMO-OFDM System

The MIMO-OFDM system which combines OFDM and MIMO can improve the performance of the wireless communication system. In order to realize the excellent transmission performance, accurate channel estimation is very necessary in the receiver. This brings out the target of this paper: the author investigates the channel estimation based on pilot-symbol-aided for the MIMO-OFDM system.At the first, the author discusses the system design of the MIMO-OFDM system, introduces the principles of OFDM and MIMO systems, especially researches the system structure and encode decode principle of the Space-time Block Coded OFDM. Then, the channel estimation technique based on pilot-based channel estimation methods is investigated. The estimation algorithms of different pilot arrangement in nowadays is analyzed, including of the estimation of the channel response of pilot sub-carriers, the interpolated estimation based on the comb-type pilot, the LS estimation based on the block-type pilot and the Wiener Filter algorithms based on the two dimension pilot. The author compares the simulation results of each technique in the Space-time Block Coded OFDM system and analyzes the performances and characteristics of these algorithms.The improved MMSE estimation is given, which can work in the systems when the statistics character of channel isn't known. According to the shortages of the low performance of LS estimation and the high computational complexity of MMSE estimation, the author improves the algorithms. The improved LS estimation which is using the change between the time and frequency fields can reduce the effect of additive noises, improve the performance and reduce the computational complexity. According of the simulation results, it shows that the improved algorithms have a better performance and a lower computational complexity, and is easy to realize.