Empirical Studies of Propagation Characteristics and Modeling Based on XL-MIMO Channel Measurement: From Far-Field to Near-Field
Haiyang Miao, Jianhua Zhang, Pan Tang, Lei Tian, Weirang Zuo, Qi Wei, Guangyi Liu
TL;DR
This work addresses how XL-MIMO channels propagate across near-field and far-field regimes and the need for accurate NFRC modeling in 6G. It develops a broadband XL-MIMO channel sounding platform and conducts indoor 1600-element and outdoor 320-element measurement campaigns, enabling NFRC analysis from near-field to far-field. Using the high-resolution SAGE algorithm for MPC estimation, it quantifies spatial non-stationarity and proposes adaptive subarray division to capture array- and distance-related variations. The results provide near-field and NF-FF channel insights and offer modeling guidance for 6G standardization, including the near-field boundary described by the Rayleigh distance $2D^2/\lambda$.
Abstract
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.