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

Hossein Amininasab, Huda Farooqui, Dmitri Moltchanov, Sergey Andreev, Michele Polese, Mikko Valkama, Josep M. Jornet

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.

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

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.
Paper Structure (11 sections, 9 equations, 6 figures, 1 table)

This paper contains 11 sections, 9 equations, 6 figures, 1 table.

Table of Contents

  1. Introduction
  2. Related Work
  3. Measurement Campaign
  4. Measurement Setup
  5. Description of Experiments
  6. Data Processing
  7. Power Delay Profile
  8. MPC Detection
  9. Channel Metrics
  10. Results and Discussion
  11. Conclusions

Figures (6)

  • Figure 1: Block diagram of the NU channel sounder and the equipment in use for the channel sounding measurements.
  • Figure 2: Channel sounding measurement environment (UNLab, EXP Building, 7th floor) resembling a classroom, showing the cross-shaped trajectory, distances between tables, and the NU channel sounder setup.
  • Figure 3: Measurement points along the cross-shaped trajectory. Black circles indicate coarse sampling with 10 cm spacing, while green and red ribbons denote fine and ultra-fine regions with 1 cm (from position 5 toward 15) and 2.5 mm (from position 15 toward 5) spacing, respectively.
  • Figure 4: Max-directional PDPs at the center and four endpoints of the trajectory (positions 15, 1, 20, 21, and 30; see Fig. \ref{['fig:cross_shaped_trajectory']}), showing the discrete MPCs resolved within the observation window.
  • Figure 5: K-factor, RMS delay spread, and RMS angular spreads versus position index along 30 measurement points. Background colors denote coarse (blue), fine (green), and ultra-fine (yellow) spacing intervals.
  • ...and 1 more figures