On the Spatial Consistency of Sub-Terahertz Channel Characteristics for Beyond-6G Systems

TL;DR

This study experimentally investigates the spatial consistency of sub-THz channel characteristics in an indoor environment, revealing that certain properties remain stable over tens of centimeters, which can simplify modeling efforts.

Contribution

The paper provides empirical data on sub-THz channel stability over large distances, aiding efficient ray-tracing modeling for beyond-6G systems.

Findings

Channel characteristics change only slightly over tens of centimeters.

Mesh grid size can be 10-50 wavelengths in LoS directions.

Finer resolution and interpolation are needed in non-LoS regions.

Abstract

Ray tracing is a versatile approach for precise sub-terahertz (sub-THz, 100-300 GHz) channel modeling when designing new mechanisms for beyond-6G cellular systems. Theoretically, wireless channels may exhibit variations over wavelength distances. In the sub-THz band, close-to-millimeter wavelengths thus require extremely large computational efforts for ray-tracing modeling. However, in practice, channel characteristics may remain quantitatively similar over much larger distances, which can drastically decrease computational efforts. The aim of this study is to experimentally characterize the degree of spatial consistency in sub-THz channel characteristics. To this end, we performed a large-scale measurement campaign in the 140-150 GHz frequency band in an indoor-hall (InH) environment and characterized the channel at separation distances from 2.5 mm up to 1 m. Our results show that channel characteristics including delay spread, angular delay spread, and K-factor change only slightly over multiple tens of centimeter distances. This implies that, in the considered InH environment, the mesh grid can be in the range of 10-50 wavelengths (at 145 GHz) along stable line-of-sight (LoS) directions, while a finer resolution is needed in regions not dominated by LoS. For coarser grids, advanced interpolation is required to capture rapidly varying scattered components.