Cross Far- and Near-Field Wireless Communications in Terahertz Ultra-Large Antenna Array Systems
Cross Far- and Near-Field Wireless Communications in Terahertz Ultra-Large Antenna Array Systems
复制标题
太赫兹超大型天线阵列系统中的远场和近场交叉无线通信
DOI：
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发表时间：
2023
影响因子：
12.9
通讯作者：
L. Dai
中科院分区：
文献类型：
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作者：
Chong Han;Yuhang Chen;Longfei Yan;Zhimin Chen;L. Dai
太赫兹（THz）频段具有丰富的数十GHz带宽，能够支持每秒太比特的无线通信，这是6 G及更高系统的支柱技术。利用亚毫米长天线，具有数千个阵列元件的超大规模（UM）-MIMO和反射智能表面（RIS）系统可以有效地对抗有前途的THz超大天线阵列（ULAA）系统的距离限制和阻塞问题。作为波长和阵列孔径的组合效应，由此产生的THz系统的覆盖范围从近场到远场，导致跨场通信的新范例。虽然已经分别针对远场和近场研究了信道模型、通信理论和组网策略，但是仍然缺少实现高频谱效率和低复杂度的跨场通信的统一设计。在这篇文章中，THz ULAA跨场通信的挑战和特点进行了研究。在此基础上，从球面波和平面波混合信道模型、交叉场信道估计和宽间距多子阵混合波束形成三个方面提出了交叉场解决方案，其中子阵是THz ULAA系统的基本单元。这些设计的信道建模精度，频谱效率和估计误差的近似误差进行了数值评估。最后，作为THz ULAA跨场通信的路线图，多个开放的问题和潜在的研究方向进行了阐述。
The Terahertz (THz) band with abundant multiten-GHz bandwidth is capable of supporting terabit-per-second wireless communications, which is a pillar technology for 6G and beyond systems. With sub-millimeter-long antennas, ultra-massive (UM)-MIMO and reflective intelligent surface (RIS) systems with thousands of array elements can be exploited to effectively combat the distance limitation and blockage problems of a promising THz ultra-large antenna array (ULAA) system. As a combined effect of wavelength and array aperture, the resulting coverage of THz systems ranges from near-field to far-field, leading to a new paradigm of cross-field communications. Although channel models, communications theories, and networking strategies have been studied for far-field and near-field separately, the unified design of cross-field communications that achieve high spectral efficiency and low complexity is still missing. In this article, the challenges and features of THz ULAA cross-field communications are investigated. Furthermore, cross-field solutions in three perspectives are presented, including a hybrid spherical- and planar-wave channel model, cross-field channel estimation, and widely-spaced multi-subarray hybrid beamforming, where a subarray as a basic unit in THz ULAA systems is exploited. The approximation error of channel modeling accuracy, spectral efficiency, and estimation error of these designs are numerically evaluated. Finally, as a roadmap of THz ULAA cross-field communications, multiple open problems and potential research directions are elaborated.