The design dilemma of "What will be different between near-field communications (NFC) and far-field communications (FFC)?" is addressed from four perspectives. 1) From the channel modelling perspective, the differences between near-field and far-field channel models are discussed. A novel Green's function-based channel model is proposed for continuous-aperture antennas, which is contrasted to conventional channel models tailored for spatially-discrete antennas. 2) From the performance analysis perspective, analytical results for characterizing the degrees of freedom and the power scaling laws in the near-field region are provided for both spatially-discrete and continuous-aperture antennas. 3) From the beamforming perspective, far-field beamforming is analogous to a "flashlight" that enables beamsteering, while near-field beamforming can be likened to a "spotlight" that facilitates beamfocusing. As a further advance, a couple of new beamforming structures are proposed for exploiting the new characteristics of NFC. 4) From the application perspective, new designs are discussed in the context of promising next-generation technologies in NFC, where our preliminary numerical results demonstrate that distance-aware target sensing and enhanced physical layer security can be realized in NFC. Finally, several future research directions of NFC are discussed.

翻译：针对“近场通信（NFC）与远场通信（FFC）之间究竟有何不同”这一设计难题，本文从四个视角展开探讨：1）从信道建模视角，讨论了近场与远场信道模型的差异。针对连续孔径天线提出一种基于格林函数的新型信道模型，并与适用于空间离散天线的传统信道模型形成对比。2）从性能分析视角，为空间离散天线和连续孔径天线提供了表征近场区域自由度与功率缩放定律的解析结果。3）从波束赋形视角，远场波束赋形类似于实现波束导引的“手电筒”，而近场波束赋形则可类比为支持波束聚焦的“聚光灯”。作为进一步推进，提出若干新型波束赋形结构以利用近场通信的新特性。4）从应用视角，在近场通信相关的新一代前瞻技术背景下探讨新型设计，初步数值结果表明近场通信可实现距离感知的目标探测与增强的物理层安全。最后，讨论了近场通信的若干未来研究方向。