Calibration of NYURay for Ray Tracing using 28, 73, and 142 GHz Channel Measurements conducted in Indoor, Outdoor, and Factory Scenarios

TL;DR

This work introduces NYURay, a 3D mmWave/sub-THz ray tracer, and demonstrates a fast, closed-form calibration method using an angle-independent reflection model to align simulated channels with real measurements at 28, 73, and 142 GHz across indoor, outdoor, and factory environments. Calibration relies on decibel-domain least-squares optimization of per-material reflection and penetration losses, achieving directional-power prediction errors with standard deviations as low as ~2–3 dB and good agreement for RMS delay/angular spreads overall. The study also documents material-property estimates and shows that incomplete environmental maps contribute to modest underpredictions of dispersion metrics, highlighting the impact of accurate scene maps on ray-tracing accuracy. The results indicate that calibrated NYURay can generate realistic synthetic channel data for machine learning and sensing applications in next-generation wireless systems.

Abstract

Site-specific wireless channel simulations via ray tracers can be used to effectively study wireless, decreasing the need for extensive site-specific radio propagation measurements. To ensure that ray tracer simulations faithfully reproduce wireless channels, calibration of simulation results against real-world measurements is required. In this study we introduce NYURay, a 3D ray tracer specifically tailored for mmWave and sub-THz frequencies. To reliably generate site-specific wireless channel parameters, NYURay is calibrated using radio propagation measurements conducted at 28, 73, and 142 GHz in diverse scenarios such as outdoor areas, indoor offices, and factories. Traditional ray tracing calibration assumes angle-dependent reflection, requiring slow iterative optimization techniques with no closed form solution. We propose a simpler and quicker novel calibration method that assumes angle-independent reflection. The effectiveness of the proposed calibration approach is demonstrated using NYURay. When comparing the directional multipath power predicted by NYURay to the actual measured power, the standard deviation in error was less than 3 dB in indoor office environments and less than 2 dB in outdoor and factory environments. The root mean square (RMS) delay spread and angular spread was underpredicted by NYURay due to incomplete environmental maps available for calibration, however an overall agreement between the measured and simulated values was observed. These results highlight the high level of accuracy NYURay provides in generating the site-specific real-world wireless channel, that could be used to generate synthetic data for machine learning.

Figures (15)

• Figure 1: When a ray is incident on a scattering surface, NYURay generates scattering rays (represented by black arrows) that propagate along the vertices of a half-icosahedron.
• Figure 2: Block diagram of channel sounder used for propagation measurements. Details of the LO signals, IF signals, filters and upconverters used are provided in Rap13aMac17aXing19a
• Figure 3: The 3-D antenna pattern of the horn antenna with a HPBW of 10.9° operating at 28 GHz is obtained by rotating the 2-D horn antenna pattern about the boresight axis (the x-axis). A symmetric antenna pattern was assumed in the vertical plane.
• Figure 4: Map of the indoor office environment displaying the TX and RX locations where channel measurements were conducted at 28 and 142 GHz. 33 TX-RX location combinations were measured at 28 GHz and 22 TX-RX combinations were measured at 142 GHz Mac15bJu_2021. The TX locations are depicted by stars, the RX locations are depicted by circles. RX locations paired with a TX location are denoted in the same color. The links measured at both frequencies are depicted by a checkerboard texture, while links only measured at 28 GHz are depicted by a solid texture Mac15bJu_2021.
• Figure 5: Map of the outdoor environment where the 28 GHz measurements were conducted, displaying the TX and RX locations Rappaport_2015.