Research On Broadcast Phase Precoding And Detection Technology For Multi-user MIMO Systems

In recent years,with the progress of science and technology,the experience demand of information exchange is getting increasingly higher and higher,that is the effectiveness and reliability of communication system.Just as is the future vision of 5G communication,which the expected information can reach the place of your heart and you can get everything you need.And MIMO(Multiple Input Multiple Output,MIMO)technique is the key breakthrough technique for 5G.MIMO system improves the channel capacity and reliability of the system through the multi-antenna spatial multiplexing gain and the diversity gain without increasing the spectrum consumption.The multi-user MIMO technique can realize the information transmission with multiple users at the same time slot,which greatly increases the efficiency of spectrum.The multi-user MIMO systems need to code the signal at the base station or to detect the signals at the user node to remove the inter-user interferences and the data flow interferences.In this thesis,we focus on the precoding and detection techniques of the multi-user MIMO system in the broadcast phase.The base station is used to precode the transmitted signals to the users to remove the inter-user interferences.The detection operation is performed at the user node to delete the data stream interferences.In the case of full channel state information,the detection technique of multi-user is not different from single-user detection technique in the broadcast phase.Therefore,the detection technique of single-user MIMO system is studied deeply.The main research work in this thesis is as follows:(1)The single-user and multi-user MIMO system models and the capacity characteristics have been studied.(2)Several detection techniques for MIMO systems are studied.At the same time,the LLL algorithm is studied deeply.Based on the LLL algorithm,the LLL-MMSE detection technology gets a better performance because of the orthogonality improvement of the channel matrix in another spatial system(3)The single-user MIMO and multi-user MIMO precoding techniques have been studied.In the multi-user MIMO system,BD-MMSE-VP coding algorithm is proposed to improve the BER performance of the system by using the MMSE criterion to optimize the perturbation vector,and the system use QR technique to decompose BD channel matrix.