The paper discusses the scaling up of MIMO (Multiple-Input Multiple-Output) technology, particularly focusing on very large arrays with an order of magnitude more antennas than currently used. The authors highlight the benefits and challenges of this approach, including improved data rates, link reliability, and the ability to serve a larger number of terminals simultaneously. They also address the increased complexity and energy consumption associated with more antennas, as well as the physical space required for the antenna arrays. The paper delves into the theoretical aspects of very large MIMO, including information-theoretic performance limits, practical algorithms, and the impact of channel properties. It explores the asymptotic behavior of random matrix theory and the optimal processing techniques for very large arrays, such as maximum-ratio transmission and reception. The authors also discuss the practical constraints and engineering difficulties, such as pilot contamination and the need for low-power consumption. In the antenna and propagation aspects, the paper examines how more antennas can improve spatial focusing and reduce interference between users. It also analyzes the effects of antenna correlation and mutual coupling on system performance, providing numerical simulations to illustrate these impacts. The authors conclude by discussing the potential of very large MIMO in addressing the limitations of point-to-point MIMO and the challenges of implementing large arrays in real-world scenarios.The paper discusses the scaling up of MIMO (Multiple-Input Multiple-Output) technology, particularly focusing on very large arrays with an order of magnitude more antennas than currently used. The authors highlight the benefits and challenges of this approach, including improved data rates, link reliability, and the ability to serve a larger number of terminals simultaneously. They also address the increased complexity and energy consumption associated with more antennas, as well as the physical space required for the antenna arrays. The paper delves into the theoretical aspects of very large MIMO, including information-theoretic performance limits, practical algorithms, and the impact of channel properties. It explores the asymptotic behavior of random matrix theory and the optimal processing techniques for very large arrays, such as maximum-ratio transmission and reception. The authors also discuss the practical constraints and engineering difficulties, such as pilot contamination and the need for low-power consumption. In the antenna and propagation aspects, the paper examines how more antennas can improve spatial focusing and reduce interference between users. It also analyzes the effects of antenna correlation and mutual coupling on system performance, providing numerical simulations to illustrate these impacts. The authors conclude by discussing the potential of very large MIMO in addressing the limitations of point-to-point MIMO and the challenges of implementing large arrays in real-world scenarios.