A Tutorial on Extremely Large-Scale MIMO for 6G: Fundamentals, Signal Processing, and Applications

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 concu...

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Bibliographic Details
Published in:IEEE Communications surveys and tutorials 2024, Vol.26 (3), p.1560-1605
Main Authors: Wang, Zhe, Zhang, Jiayi, Du, Hongyang, Niyato, Dusit, Cui, Shuguang, Ai, Bo, Debbah, Merouane, Letaief, Khaled B., Poor, H. Vincent
Format: Article
Language:English
Subjects:
6G mobile communication
Antenna arrays
Antennas
channel modeling
deep learning
Electromagnetic properties
Hardware
Linear arrays
MIMO communication
Near field communication
near-field communications
Patch antennas
Signal processing
Surveys
Wireless communication systems
Wireless networks
XL-MIMO
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Summary: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.
ISSN:1553-877X
2373-745X
DOI:10.1109/COMST.2023.3349276