Research On MIMO Technology In LTE-Advanced System

As the smooth evolution of the Long Term Evolution (LTE) system, LTE-Advanced system inherits the key technologies of LTE system, such as Multiple-Input Multiple-Output (MIMO) and Orthogonal Frequency Division Multiplexing (OFDM). And as the IMT-Advanced candidate technology that 3rd Generation Partnership Project (3GPP) submits to the International Telecommunication Union (ITU), LTE-Advanced is required to meet or exceed the performance target of IMT-Advanced. The MIMO technologies playes an important role in LTE-Advanced system. Firstly, the single-user MIMO (SU-MIMO) technology improves the single-user peak rate and cell peak spectral efficiency. Secondly, the Multi-user MIMO (MU-MIMO) technology can improve the cell average spectral efficiency. Last but not least, the network-MIMO technology improves the cell edge spectral efficiency.The goal of this paper is studying the MIMO technologies of LTE-Advanced downlink. Research the improved algorithm schemes of MIMO technology based on the existing technology, find out the optimal algorithm scheme of all kind of MIMO technologies through analysis and simulation. Then research the integrative application of three kind of MIMO technologies, and propose a MIMO technology application scheme in LTE-Advanced system. The main work of this paper is following.The system overview, key technologies and channel processing of physical layer in LTE-Advanced system is studied.The standardization progress of SU-MIMO technology in LTE-Advanced System is summarized, and the signal detection algorithm of receiver is studied. Because of the existing algorithms can not be applied to spatial multiplexing and transmit diversity at the same time, a improved algorithm is studied, and it not only overcomed the deficiency of existing algorithms, but also its bit error rato performance was nearly 1 dB better than the Combination and Maximum Likelihood algorithm.The MU-MIMO technology scheme in LTE-Advanced system is studied. The simulation results indicate that Block Diagonalization (BD) scheme with perfect feedback can obtain optimal performance. Due to it need large feedback overhead, a improved scheme of BD scheme with limited feedback is studied. Compared with BD scheme with perfect feedback, it reduced feedback overhead of more than 10 times but little performance lost. The Network-MIMO technology scheme in LTE-Advanced system is studied. Based on the idea of using spreading technology to improve the signal noise ratio performance in TD-SCDMA system, a improved Network-MIMO technology scheme is studied. The simulation results show that the improved shceme can obtain better performance than existing schemes.The integrative application of three kind of MIMO technology is studied. The MIMO technology application scheme in LTE-Advanced system is proposed.