Capacity Analysis And Key Technologies Of Millimeter Wave Massive MIMO Systems

In order to cope with the challenge that the future mobile communication system needs to provide human beings with ubiquitous information services,new breakthroughs are urgently needed to make in wireless transmission technologies.By utilizing the abundant spectrum resources available in the millimeter wave band and combining the large-scale antenna array technology,millimeter wave massive multiple-input multiple-output(MIMO)technology can meet the requirements of future mobile communication systems,such as,ultra-high data transmission rate,ultra-low communication delay,and stronger communication security.Millimeter wave massive MIMO becomes one of the key technologies of the next generation mobile communication system.However,millimeter wave massive MIMO still faces many technical problems,such as,beam blockage,high hardware cost and complexity,hardware impairments from radio frequency components,and so on.To address some of these problems,in this dissertation,we investigate the millimeter wave massive MIMO technology from the aspects of the ergodic capacity,the initial access phase's beam training,the uplink transmission performance,and the system prototyping.Firstly,the ergodic capacity of point-to-point millimeter wave massive MIMO systems under finite-dimensional channels is investigated.The sparse characteristics of the millimeter wave channel make it difficult to directly utilize the conventional random matrix theory in calculating the ergodic capacity of a millimeter wave system.To break this bottleneck,we propose to employ the theory of majorization and order statistics,and derive closed-form expressions of the tight ergodic capacity approximations under finite-dimensional channels.Furthermore,several Jensen's approximations and bounds of the ergodic capacity are also derived.The results indicate that the ergodic capacity seems to increase logarithmically with the number of antennas,the transmit signal-to-noise ratio(SNR)per antenna,and the eigenvalues of the steering matrix products.After that,high-SNR ergodic capacity,high-SNR slope,and power offset are also analyzed.It indicates that for a finite-dimensional channel,the maximum multiplexing gain increases with the number of paths instead of the number of antennas in Rayleigh channels.Numerical results reveal that all the ergodic capacity approximations,the Jensen's approximations,and the high-SNR capacity exhibit great tightness,and hence can be used to provide guidance for subsequent millimeter wave prototyping system design.Secondly,the beam training performance of millimeter wave MIMO systems with carrier frequency offset(CFO)is analyzed,and a simplified Newtonized orthogonal matching pursuit algorithm(NOMP)-based compressive beam scanning and CFO estimation method is proposed.Given that beam training always occupies much time overhead in millimeter wave systems,especially in the initial access phase,compressive beam scanning shows its superiority when compared with the exhaustive beam scanning and the hierarchical beam scanning,in terms of the time overhead.Nevertheless,compressive beam scanning is sensitive to CFO.For the purpose of improving the robustness of the compressive beam training,we propose a simplified NOMPbased compressive beam scanning and CFO estimation method.Numerical results show that the proposed method can effectively improve the performance of the compressive beam training,and thus can provide good beam training performance for the base station and users in initial access phase for millimeter wave systems.After that,the uplink transmission performance of multi-user extra-large massive MIMO systems with spatial non-stationarities(i.e.,visibility region,VR)is investigated,and an effective implementation scheme for multi-user extra-large massive MIMO systems is proposed.Since the hardware cost and complexity of the extra-large scale massive MIMO system increase sharply with the increase of the number of antennas,two low-cost subarray-based system architectures are firstly proposed.Then,tight closed-form uplink spectral efficiency(SE)approximations with linear receivers are derived.These approximations reveal that users with their VRs covering different subarrays or VRs with less overlap should be scheduled simultaneously under maximum ratio combining(MRC)receiver,while as many users as possible should be selected under linear minimum mean squared error(LMMSE)receiver.With the objective of maximizing the system sum achievable SE,schemes for subarrays' phase coefficient design are proposed.Moreover,to further exploit the spatial non-stationarities,two statistical CSI-based greedy user scheduling algorithms are developed.Numerical results verify the effectiveness of the SE approximations and demonstrate the great performance of the subarray phase coefficient design.These results exhibit that the switch-based subarray system architecture cooperating with the statistical CSI-based greedy joint user and subarray scheduling algorithm and the LMMSE receiver seems to be a promising effective low-cost implementation for the extra-large massive MIMO system.Finally,a novel system architecture that can be leveraged to rapidly establish wireless communication prototyping systems is proposed,and a real-time millimeter wave massive MIMO prototyping system based on phase-shifter network is designed and partially constructed.Aiming at the barriers of long programming and long compile time that existing millimeter wave FPGA-based prototyping systems constantly suffer from,a novel rapid prototyping(RaPro)system architecture by combining FPGA-privileged modules from a software defined radio(or FPGA-coprocessor)and high-level programming language for advanced algorithms from multicore general purpose processors,is proposed.On the basis of the RaPro architecture,the system architecture of a real-time phase-shifter network-based millimeter wave massive MIMO prototyping system is also designed.The proposed system architecture exhibits excellent flexibility and scalability in the development of prototyping systems.As a proof of concept,a multi-user16-antenna full-dimension(FD)MIMO system and a subsystem of the millimeter wave massive MIMO prototyping system are implemented,which lays a great foundation for the verification of the practical performance of millimeter wave algorithms.