In the sixth-generation (6G), the extremely large-scale multiple-input-multiple-output (XL-MIMO) is considered a promising enabling technology. With the further expansion of array element number and frequency bands, near-field effects will be more likely to occur in 6G communication systems. The near-field radio communications (NFRC) will become crucial in 6G communication systems. It is known that the channel research is very important for the development and performance evaluation of the communication systems. In this paper, we will systematically investigate the channel measurements and modeling for the emerging NFRC. First, the principle design of massive MIMO channel measurement platform are solved. Second, an indoor XL-MIMO channel measurement campaign with 1600 array elements is conducted, and the channel characteristics are extracted and validated in the near-field region. Then, the outdoor XL-MIMO channel measurement campaign with 320 array elements is conducted, and the channel characteristics are extracted and modeled from near-field to far-field (NF-FF) region. The spatial non-stationary characteristics of angular spread at the transmitting end are more important in modeling. We hope that this work will give some reference to the near-field and far-field research for 6G.

翻译：在第六代移动通信（6G）中，超大规模多输入多输出（XL-MIMO）被认为是一项极具前景的关键技术。随着阵列单元数目及频段的进一步扩展，近场效应将更易出现在6G通信系统中。近场无线通信（NFRC）将成为6G通信系统的关键组成部分。众所周知，信道研究对于通信系统的发展与性能评估至关重要。本文系统性地研究了新兴NFRC的信道测量与建模问题。首先，解决了大规模MIMO信道测量平台的原理性设计问题。其次，开展了包含1600个阵列单元的室内XL-MIMO信道测量实验，提取并验证了近场区域的信道特性。随后，开展了包含320个阵列单元的室外XL-MIMO信道测量实验，从近场至远场（NF-FF）区域提取并建模了信道特性。其中，发射端角度扩展的空间非平稳特性在建模中尤为重要。本研究期望能为6G近场与远场研究提供一定参考。