Multiband Characterization of Radio Propagation Into and Inside Vehicles

In-vehicle subnetworks are envisioned to support localized, high-performance connectivity for 6 G systems. Vehicle structures, materials, and confined interiors create distinctive propagation conditions, making multiband characterization of in-vehicle and O2V channels essential for link design and interference assessment. This paper presents multidimensional channel measurements across sub-6 GHz, mid-band, mm-wave, and sub-THz frequencies in several real-world car models. We analyze attenuation, fading, angular and delay dispersion, under the measured antenna and polarization configurations, and derive an extension of the 3GPP O2V penetration-loss model to sub-THz frequencies. The results provide experimental insights for reliable 6 G vehicular system design, including link budgeting, antenna placement, and robustness.