Height-Dependent Spectrum Activity Measurements and Modeling: A Case Study with FM Radio Bands

TL;DR

This paper introduces a height-dependent spectrum activity model validated through extensive measurements and a case study on FM radio bands, improving spectrum prediction accuracy for aerial wireless systems.

Contribution

It presents a novel altitude-dependent propagation model incorporating NLoS to LoS transition, validated with real measurements and applicable to aerial communication spectrum management.

Findings

Model outperforms standard FSPL in urban environments

Identifies a specific altitude threshold for NLoS to LoS transition

Provides a practical framework for altitude-aware spectrum prediction

Abstract

The increasing demand for wireless connectivity necessitates advanced spectrum modeling to enable efficient spectrum sharing for next-generation aerial communications. While traditional models often overlook vertical variations in signal behavior, this paper proposes a height-dependent propagation model using a helikite-mounted software-defined radio (SDR). We collected extensive measurement data across the 88 MHz to 6 GHz range in both urban and rural environments. As a case study to validate our methodology, we focus on the FM radio band, which allows us to use publicly available transmitter locations and transmit power levels to facilitate comparisons between analytical with measurement results. We identify a clear transition from non-line-of-sight (NLoS) to line-of-sight (LoS) regimes at a specific altitude threshold and propose an altitude-dependent path loss model that incorporates this transition. Our results demonstrate that the proposed model significantly outperforms the standard free space path loss (FSPL) model in complex urban topologies, providing a more accurate framework for altitude-aware spectrum prediction and management across emerging aerial wireless technologies and bands.