Research On Parametric Channel Estimation Algorithm For MIMO-OFDM System

Orthogonal Frequency Division Multiplexing (OFDM) becomes the core technology of fourth-generation mobile communication system, which has strong capacity of anti-multipath spread and frequency selective fading. The multi-input and multi-output (MIMO) system uses multiple antennas to carry out multi-sending and multi-receiving transmission to make full use of space resources. Without the increase of the system bandwidth and total transmission power of the antennas, the effect of wireless channel fading is effectively avoided, and the spectrum efficiency and channel capacity of the communication system are greatly improved. Therefore, the MIMO-OFDM system combined by OFDM and MIMO technically gives full play to their strengths and becomes the most promising core technology of a new generation of wireless mobile communication systems. Because channel estimation is an indispensable part of the MIMO-OFDM system, therefore, the research of the channel estimation technique is very critical for the MIMO-OFDM system.In this paper, MIMO-OFDM wireless communications system channel estimation algorithms have been theoretical analysis and simulation. Respectively, for the traditional estimation algorithm error in small SNR and the estimated diffusion length of channel mismatch problem, the two channel estimation algorithm has been improved.Firstly, this article analyzes OFDM system channel estimation classic algorithms, mainly for the conversion domain channel estimation algorithm. Theoretically analysis the relationship and the advantages and disadvantages between the discrete Fourier transform (DFT) estimated algorithms and discrete cosine transform (DCT) estimated algorithms. To avoid emerging and high-frequency error-aliasing distortion, get a better estimation performance in the non-integer multiple sampling channel environment and effectively suppressing impact of white Gaussian noise (AWGN) and inter-carrier interference (ICI).Secondly, this article introduces the principle and key technologies of MIMO system. On this basis of it, this article focuses on MIMO-OFDM system framework, as well as channel estimation technologies. In order to independently identify MIMO channel, different transmission antennas require orthogonal pilot sequences. For different orthogonal pilot the comparion of DCT estimate to the simulation.Finally,according to the characteristics of DCT and the time-domain characteristics of multi-path channels, the separation of the volumes of signals and noise in time domain is analyzed pertinently, for problem of estimates diffusion length of channel mismatch in time-domain, two parameter estimation algorithms are put forward, and the algorithm has an idea that multipath interference of the channel is eliminated maximumly by self-adaptive changes of the sampling points of time-domain channel impulse response, so that the system can adjust the length of channel impulse response according to the change of the channel environment in a self-adaptive mode in order to obtain better estimation performance. Improved algorithm solves the deviation of the estimated in small SNR and the problem of the mismatch of channel correlation. In this paper, for the noise interference in time-domain diffusion length, the second improved algorithm combines with de-noising method of limiting to achieve the purpose of avoiding noise in the further. At the end of this article, simulation comparison and theoretical analysis verify the feasibility of the proposed algorithm. Compared with the original DCT estimation algorithm, the improved estimation algorithm maximumly eliminates noise interference, and the channel estimation performance is improved.