Research On Channel Estimation Of MIMO-OFDM System Based On Compressed Sensing Greedy Algorithm

At present,with the overall development of technology in various fields,the traditional measure of communication quality is no longer applicable in the field of communication.Modern communication is developing in the direction of high quality and high speed.In this rapid development of the environment,the traditional communication technology must be a breakthrough to improve the traditional technology or find new method meeting the key technologies at this stage of communication.With the MIMO-OFDM system as the framework of the modern communication system,using the antenna overdraft technology,the system has many advantages meeting the current stage of high-quality,high-speed communication transmission standards.But in the actual signal transmission process will be affected by the surrounding environment and the impact of obstacles,resulting in varying degrees of fading and delay,resulting in inter-symbol interference,affecting the transmission quality of the signal.In this paper,we focus on the MIMO-OFDM system as a framework,and using the new compression sampling technique to study the sparse multipath channel.In order to achieve a more accurate CSI,to enhance the quality of communication transmission and the purpose of the rate.In this thesis,the main work and achievements are as follows:(1)The model of MIMO-OFDM system is studied,The coding and beamforming techniques in multiuser MIMO-OFDM systems are summarized and their channel capacity is analyzed.And the fading characteristics and the pilot structure of the channel are studied.Based on the fading characteristics of the signal in the wireless transmission process,the pilot-based LS,MMSE and DFT-based algorithms are analyzed and studied in the MIMO-OFDM system.Based on the pilot channel estimation algorithm,the advantages and disadvantages are analyzed.(2)The multi-user channel estimation is analyzed,and the key technologies of multi-user MIMO-OFDM system are summarized.Because the multi-user has the interference problem between users,the channel state information obtained by the system is incomplete.This paper uses the time delay envelope characteristic of the channel to make the channel state information step by step accurate on the basis of the MMSE algorithm.The simulation results show that the improved algorithm has improved the channel estimation in the multi-user MIMO-OFDM system.(3)Theoretical analysis and experimental results show that the channel has sparse characteristics,and the channel estimation of greedy algorithm based on CS theory is applied to the characteristics of the channel.This paper discusses several greedy algorithms based on compression perception: OMP,ROMP and SP algorithm,and gives the experimental simulation comparison.Based on the research of CoSaMP algorithm,which is improved based on the weak selection criterion of atoms,and proposing the improved CoSaMP algorithm based on threshold.The simulation shows that the improved algorithm is based on the sparse degree and complexity of the compression perception algorithm.Improve the rate of the algorithm.