To support high throughput and massive connectivity, next-generation mobile networks are expected to utilize extremely large-scale antenna arrays. This would result in wireless communications occurring in the near-field region. Leveraging the unique channel characteristics of near-field propagation presents both opportunities and challenges, hence we critically appraise near-field communications (NFC). We commence by determining the boundary that distinguishes NFC and conventional far-field communications. Furthermore, some of the key challenges of NFC, including its spherical wavefront-based channel modeling and channel estimation, near-field beamfocusing, hardware design, as well as wireless sensing, are covered based on a comprehensive survey of existing progress. Two case studies demonstrate the potential of NFC in improving the spatial multiplexing gain and positioning accuracy in the near field. Finally, a suite of open issues are identified for motivating future research, such as dealing with spatial non-stationarity, and the potential of stacked intelligent metasurface-based transceiver design.

中文翻译：

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近场通信：研究进展、潜力和挑战


为了支持高吞吐量和大规模连接，下一代移动网络预计将使用超大规模的天线阵列。这将导致在近场区域发生无线通信。利用近场传播独特的信道特性既带来了机遇，也带来了挑战，因此我们对近场通信（NFC）进行了严格的评估。我们首先确定区分 NFC 和传统远场通信的边界。此外，基于对现有进展的全面调查，涵盖了 NFC 的一些关键挑战，包括基于球面波前的信道建模和信道估计、近场波束聚焦、硬件设计以及无线传感。两个案例研究证明了 NFC 在提高近场空间复用增益和定位精度方面的潜力。最后，确定了一系列开放问题以激励未来的研究，例如处理空间非平稳性以及基于堆叠智能超表面的收发器设计的潜力。