Extremely large-scale multiple-input-multiple-output (XL-MIMO), which offers vast spatial degrees of freedom, has emerged as a potentially pivotal enabling technology for the sixth generation (6G) of wireless mobile networks. With its growing significance, both opportunities and challenges are concurrently manifesting. This paper presents a comprehensive survey of research on XL-MIMO wireless systems. In particular, we introduce four XL-MIMO hardware architectures: uniform linear array (ULA)-based XL-MIMO, uniform planar array (UPA)-based XL-MIMO utilizing either patch antennas or point antennas, and continuous aperture (CAP)-based XL-MIMO. We comprehensively analyze and discuss their characteristics and interrelationships. Following this, we introduce several electromagnetic characteristics and general distance boundaries in XL-MIMO. Given the distinct electromagnetic properties of near-field communications, we present a range of channel models to demonstrate the benefits of XL-MIMO. We further discuss and summarize signal processing schemes for XL-MIMO. It is worth noting that the low-complexity signal processing schemes and deep learning empowered signal processing schemes are reviewed and highlighted to promote the practical implementation of XL-MIMO. Furthermore, we explore the interplay between XL-MIMO and other emergent 6G technologies. Finally, we outline several compelling research directions for future XL-MIMO wireless communication systems.

中文翻译：

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6G 超大规模 MIMO 教程：基础知识、信号处理和应用


超大规模多输入多输出 (XL-MIMO) 提供巨大的空间自由度，已成为第六代 (6G) 无线移动网络的潜在关键支持技术。随着其重要性的不断增强，机遇与挑战并存。本文对 XL-MIMO 无线系统的研究进行了全面的综述。我们特别介绍了四种 XL-MIMO 硬件架构：基于均匀线性阵列 (ULA) 的 XL-MIMO、利用贴片天线或点天线的基于均匀平面阵列 (UPA) 的 XL-MIMO，以及连续孔径 (CAP) -基于XL-MIMO。我们全面分析和讨论它们的特点和相互关系。接下来，我们介绍 XL-MIMO 中的几个电磁特性和一般距离边界。鉴于近场通信独特的电磁特性，我们提出了一系列信道模型来展示 XL-MIMO 的优势。我们进一步讨论和总结了 XL-MIMO 的信号处理方案。值得注意的是，对低复杂度信号处理方案和深度学习赋能信号处理方案进行了回顾和重点介绍，以推动XL-MIMO的实际落地。此外，我们还探讨了 XL-MIMO 与其他新兴 6G 技术之间的相互作用。最后，我们概述了未来 XL-MIMO 无线通信系统的几个引人注目的研究方向。