Near-Field User Localization and Channel Estimation for XL-MIMO Systems: Fundamentals, Recent Advances, and Outlooks
<|reference_start|>Near-Field User Localization and Channel Estimation for XL-MIMO Systems: Fundamentals, Recent Advances, and Outlooks: Extremely large-scale multiple-input multipleoutput (XL-MIMO) is believed to be a cornerstone of sixth-generation (6G) wireless networks. XL-MIMO uses more antennas to both achieve unprecedented spatial degrees of freedom (DoFs) and exploit new electromagnetic (EM) phenomena occurring in the radiative near-field. The near-field effects provide the XL-MIMO array with depth perception, enabling precise localization and spatially multiplexing jointly in the angle and distance domains. This article delineates the distinctions between near-field and far-field propagation, highlighting the unique EM characteristics introduced by having large antenna arrays. It thoroughly examines the challenges these new near-field characteristics pose for user localization and channel estimation and provides a comprehensive review of new algorithms developed to address them. The article concludes by identifying critical future research directions.<|reference_end|>
@article{lei2024near-field,
    title={Near-Field User Localization and Channel Estimation for XL-MIMO Systems:
  Fundamentals, Recent Advances, and Outlooks},
    author={Hao Lei, Jiayi Zhang, Zhe Wang, Huahua Xiao, Bo Ai, Emil Bj"ornson},
    journal={arXiv preprint arXiv:2407.10147},
    year={2024},
    archivePrefix={arXiv},
    eprint={2407.10147},
    primaryClass={eess.SP cs.IT math.IT}
}