Path Loss Analysis for Low-Altitude Air-to-Air Millimeter-Wave Channel in Built-Up Area

TL;DR

This paper develops a comprehensive path loss model for low-altitude air-to-air millimeter-wave channels in urban environments, considering obstacles, multipath effects, and beam misalignment, validated against 3GPP standards.

Contribution

It introduces an analytical model for low-altitude A2A mmWave channels in urban areas, accounting for LOS probability, multipath, and beam misalignment effects, validated through simulations and comparisons.

Findings

The model accurately predicts path loss in urban low-altitude scenarios.

Beam misalignment significantly impacts path loss fluctuations.

The proposed model outperforms existing 3GPP models in urban environments.

Abstract

Communications between unmanned aerial vehicles (UAVs) play an important role in deploying aerial networks. Although some studies reveal that drone-based air-to-air (A2A) channels are relatively clear and thus can be modeled as free-space propagation, such an assumption may not be applicable to drones flying in low altitudes of built-up environments. In practice, low-altitude A2A channel modeling becomes more challenging in urban scenarios since buildings can obstruct the line-of-sight (LOS) path, and multipaths from buildings lead to additional losses. Therefore, we herein focus on modeling low-altitude A2A channels considering a generic urban deployment, where we introduce the evidence of the small-size first Fresnel zone at the millimeter-wave (mmWave) band to approximately derive the LOS probability. Then, the path loss under different propagation conditions is investigated to obtain an integrated path loss model. In addition, we incorporate the impact of imperfect beam alignment on the path loss, where the relation between path loss fluctuation and beam misalignment level is modeled as an exponential form. Finally, comparisons with the 3GPP model show the effectiveness of the proposed analytical model. Numerical simulations in different environments and heights provide practical deployment guidance for aerial networks.