面向6G无线网络的全息多输入多输出技术综述

The future Sixth-Generation (6G) wireless communication systems are required to support ultra-large-scale user demands, with increasing demands for spectrum efficiency and energy efficiency. In this context, Holographic Multiple-Input Multiple-Output (HMIMO) technology has gained increasing attention due to its potential for intelligent reconfigurability, electromagnetic tunability, high directional gain, cost-effectiveness, and flexible deployment. In holographic MIMO system, large amount small and cheap antenna units are integrated tightly, thus realize high directional gain at a low hardware cost and flexible adjustment of electromagnetic wave at the same time, thereby effectively enhancing the performance of wireless communication. A brief introduction to holographic MIMO technology is provided at the start of this paper, covering its current status, development process, classification, and key characteristics. Subsequently, the channel model for holographic MIMO in line-of-sight scenarios and non-line-of-sight scenarios with spatially smooth scattering is presented. Finally, the challenges and future trends faced by holographic MIMO technology are described, and the article is concluded.