Near-Field Communications for 6G:
Fundamentals, Challenges, Potentials, and Future
Directions
主办方: The 2024 IEEE 100th Vehicular Technology Conference (VTC-2024 Fall）
主讲人：Linglong Dai
时 间: 10月7日 9:00-12:00 （美国华盛顿时间）
10月7日 21:00-24:00 （北京时间）
地 点: Continental A, Ronald Reagan Building and International Trade Center, 1300 Pennsylvania Avenue, NW Washington DC, 20004
摘要
The promising technologies for 6G including ultra-massive multiple-input-multiple-output (UM-MIMO), reconfigurable intelligent surface (RIS), and terahertz (THz) communications share a common feature: A very large number of antennas is required to achieve their expected performance, i.e., extremely large antenna arrays (ELAA) are essential for these different promising candidate technologies for 6G. ELAA for 6G not only means a sharp increase in the number of antennas but also results in a fundamental change in the electromagnetic (EM) characteristics. The EM radiation field can generally be divided into far-field and near-field regions. The boundary is determined by the Rayleigh distance, which is proportional to the product of the square of the array aperture and the carrier frequency. With the significant increase of the antenna number and carrier frequency in future 6G systems, the near-field region of ELAA will expand by orders of magnitude. Therefore, near-field communications will become essential for future 6G networks.
In this tutorial, the near-field communication techniques for 6G will be discussed. Specifically, the fundamental difference between far-field and near-field communications will be clarified at first, where we explain the principle to determine the boundary of near-field and far-field regions for MIMO communications and RIS-aided communications. Then we investigate the near-field communication techniques that are designed to compensate for the performance loss of far-field techniques in the near-field region. Moreover, we also introduce the techniques that exploit the nature of near-field spherical wavefront for capacity enhancement and accessibility improvement. Finally, several open problems and future research directions are pointed out.
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