Core Concepts
This work systematically investigates the channel measurements and modeling for the emerging near-field radio communications (NFRC) in extremely large-scale MIMO (XL-MIMO) systems. It provides empirical insights and modeling approaches for the spatial non-stationary characteristics of XL-MIMO channels from near-field to far-field.
Abstract
This paper presents a comprehensive study on XL-MIMO channel measurement and modeling from near-field to far-field.
First, the authors designed and validated a massive MIMO channel measurement platform based on high-speed electronic switching. This platform enables efficient XL-MIMO channel measurements covering the mid-band frequency range.
Second, the authors conducted indoor XL-MIMO channel measurements with 1600 array elements and analyzed the near-field channel characteristics. They observed significant spatial non-stationary (SnS) properties along the antenna array, including variations in power, delay spread, and angular spread. Polynomial models were developed to capture these SnS effects.
Third, the authors carried out outdoor XL-MIMO channel measurements with 320 array elements, covering the transition from near-field to far-field. They investigated the SnS characteristics of path loss, delay spread, and angular spread across the transmit-receive distance and antenna array. Compared to the receiving end, the SnS of angular spread at the transmitting end was found to be more prominent in the modeling.
The authors hope this work will provide valuable references for near-field and far-field research in 6G wireless communications.
Stats
The maximum power difference across array elements is only 0.12 dB in the near-field region.
The largest difference in angle-of-departure (AOD) across the array is over 10°.
The RMS delay spread fluctuates in the range of 6 ns to 20 ns along the array in the near-field.
The path loss follows a logarithmic distribution with distance and a linear distribution along the array in the near-field and far-field.
The standard deviation of angular spread follows a quadratic distribution with increasing transmit-receive distance.
Quotes
"The spatial non-stationary characteristics of angular spread at the transmitting end are more important in modeling."
"Compared with the angular spread at the receiving end, the spatial non-stationary characteristics of angular spread at the transmitting end are more important in modeling."