Research On Channel Information Acquisition And Pre-Coding Technology In Massive MIMO Multiple -Antenna Systems

With the coming of the era of mobile Internet and big data, people’s demand to access the information quickly and reliably is increasingly higher and higher. The massive MIMO multiple-antenna technology attracts much attention because of its high spectral efficiency and energy efficiency. The channel state information (CSI) acquisition and downlink pre-coding technologies in massive MIMO systems are studied in this thesis.Firstly, the principles of traditional MIMO and massive MIMO systems are introduced. The CSI acquisition and downlink pre-coding technologies in both traditional MIMO and massive MIMO systems are summarized.Secondly, the thesis focuses on the analysis of the capacity of massive MIMO systems. The asymptotic expressions of achievable rate in both single-user and multi-user massive MIMO systems are obtained. The pilot pollution is investigated in non-cooperative multi-cell massive MIMO systems. The theoretical analysis and simulation results show that the massive MIMO systems are operating in a purely interference-limited regime.Thirdly, the technology of the downlink CSI acquisition in frequency division duplexing massive MIMO systems is studied. The optimal structures of the training sequences corresponding to different channel estimation criterions are derived. A design of downlink training sequences is proposed to reduce training overhead through exploiting the channel spatial correlation. The optimal structure and length of training sequences are obtained. The simulation results show that the trade-off between the accuracy of channel estimation and system achievable data rates is achieved in the proposed design.Finally, the linear and nonlinear downlink pre-coding technologies in massive MIMO system are investigated. The performance of linear pre-coding schemes is evaluated in terms of the achievable rate, spectral efficiency and energy efficiency by simulations. The vector perturbation (VP) pre-coding is improved by using lattice reduction and the LR-ZF-VP and LR-MMSE-VP pre-coding schemes are proposed. The LR-ZF-TVP pre-coding algorithm based on LR-ZF-VP pre-coding is proposed, in which the balance between the system performance and computational complexity is obtained.