Directional Measurements and Analysis for FR3 Low-Altitude Channels in a Campus Environment

TL;DR

This study provides detailed low-altitude channel measurements at the FR3 band in a campus environment, revealing propagation characteristics and modeling insights crucial for mid-band communication system design.

Contribution

It offers new empirical data and analysis on low-altitude propagation, highlighting the limitations of existing models and the impact of environmental factors on channel behavior.

Findings

Path loss models outperform 3GPP models in this environment

Ground reflections significantly influence signal behavior at low altitudes

Propagation varies with environmental conditions and obstacles

Abstract

In this paper, we present detailed low-altitude channel measurements at the FR3 band in an outdoor campus environment. Using a time-domain channel sounder system, we conduct two types of measurements: path loss measurements by moving the transmitter (Tx) at one-meter intervals along a 26-point rooftop path, and directional power angular spectrum measurements through antenna scanning at half-power beam width intervals. The path loss analysis across different Rx shows that the close-in model outperforms conventional 3GPP models and height-corrected variants, with path loss exponents close to free space values indicating line-of-sight dominance. The power angular spectrum measurements show that propagation behavior varies significantly with environmental conditions. Closer Rx exhibit stronger sensitivity to ground reflections during downward Tx tilting, while obstructed links display uniform angular characteristics due to dominant scattering effects, and corridor environments produce asymmetric power distributions. These results indicate that low-altitude propagation is characterized by complex interactions between Tx height and ground scattering mechanisms, providing fundamental insights for channel modeling in emerging mid-band communication systems.