The Uplink Transmission Technology Research For Large-Scale Wireless MIMO Systems

As the key technology of the fifth-generation mobile communication system (5G), large-scale wireless multiple-input multiple-output (MIMO) can provide significant improvements in performance and capacity. Then, it is a hot research area in wireless communication. In large-scale MIMO system, as the dimension of channel matrix is very large, the complexity of the joint data processing in base station (BS) is also very high. Therefore, this thesis focuses on the complexity reduction techniques for large-scale MIMO wireless communication system in uplink communication.First, we review the research status and development trends for large-scale wireless MIMO communi-cation technology, which leads to the research contents of this thesis.For the large-scale multi-cell multi-user MIMO cellular system model, we analyze the multiple access with the ideal uplink channel, including matched filter (MF), zero-forcing (ZF), minimum mean square error (MMSE) receiver. Then, the uplink Turbo iterative receiver is introduced for large-scale MIMO systems to approach the capacity. When the base station is aware of perfect channel state information of uplink com-munication, simulation results show that the simple receiver can achieve excellent performance with low transmitted power in large-scale MIMO system.In large-scale MIMO system, one of the most serious problems is pilot contamination. Thus, the Turbo it-erative receiver for uplink transmission is investigated in large-scale multi-cell multi-user MIMO system with channel estimation, mainly including the following areas:(1) we introduce the MMSE filter based iterative soft interference cancellation (ISDIC) algorithm for uplink receiver; (2) Taking into account the complexity of the algorithm, two soft-input soft-output (SISO) detection iterative algorithms, which avoid matrix inversion, are proposed:a soft interference cancellation algorithm for the polynomial expansion linear detector (PELD) and a SISO detector based on singular value decomposition (SVD); (3) MF-SISO is given as a special case of PELD-SISO. The simulation results show that if there is no iterative algorithm in base station, PELD obtains greater performance gains for the large-scale MIMO systems with the comparison to MF detection. And if iterative detection is exploited in receiver, MF-ISDIC can achieve the performance of the MMSE-ISDIC. In a word, matrix inversion should be avoided in iterative receiver for large-scale MIMO system.Additionally, the complexity reduction of uplink transmission is investigated for large-scale distributed antenna system (DAS). In single-cell multi-user large-scale DAS, we introduce a simple random pilot reuse to reduce the pilot overhead, and asymptotic sum capacity is given in theoretically with the infinite number of antennas. As the space access point of large-scale DAS increases distinctly, we present a method to reduce the signal processing complexity by using spatial channel matrix sparsification. Simulation results show that the proposed method can achieve impressive performance with low complexity. Moreover, the optimal orthogonal pilot number of large-scale DAS is given by Monte Carlo simulation.