Analytical Channel Models for Millimeter Wave UAV Networks Under Hovering Fluctuations

Abstract

The integration of unmanned aerial vehicles (UAVs) and millimeter wave (mmWave) wireless systems has been recently proposed to provide high data rate aerial links for next generation wireless networks. However, establishing UAVbased mmWave links is quite challenging due to the random fluctuations of hovering UAVs which can induce antenna gain mismatch between transmitter and receiver. To assess the benefit of UAV-based mmWave links, in this paper, tractable, closedform statistical channel models are derived for three UAV communication scenarios: (i) a direct UAV-to-UAV link, (ii) an aerial relay link in which source, relay, and destination are hovering UAVs, and (iii) a relay link in which a hovering UAV connects a ground source to a ground destination. The accuracy of the derived analytical expressions is corroborated by performing Monte-Carlo simulations. Numerical results are then used to study the effect of antenna directivity gain under different channel conditions for establishing reliable UAV-based mmWave links in terms of achieving minimum outage probability. It is shown that the performance of such links is largely dependent on the random fluctuations of hovering UAVs. Moreover, higher antenna directivity gains achieve better performance at low SNR regime. Nevertheless, at the high SNR regime, lower antenna directivity gains result in a more reliable communication link. The developed results can therefore be applied as a benchmark for finding the optimal antenna directivity gain of UAVs under the different levels of instability without resorting to time-consuming simulations.

Federated Learning in the Sky: Joint Power Allocation and Scheduling with UAV Swarms

“…1(b), due to the impact of wind, payload, and nonideal mechanical and control systems, the angle of the UAVs will randomly fluctuate and deviate from the initial angle setting. Based on the central limit theorem, we model the angle deviation for each UAV as a Gaussian random variable [10]. Moreover, we consider a squared cosine function to capture the antenna aperture of UAV j ∈ I ∪ {L} when communicating with UAV l ∈ I ∪ {L}/j as follows [11]:…”

Performance, Fairness, and Tradeoff in UAV Swarm Underlaid mmWave Cellular Networks With Directional Antennas

“…Different from the traditional cellular networks in band below 6 GHz (sub-6 GHz), mmWave cellular networks have high path loss due to the effect of sensitivity to blockages. To compensate the path loss and enhance the security, a common solution is to deploy highly directional antenna array to perform the directional beamforming in the existing works [16]- [22], which consider either an ideal 2D directional antenna array omitting elevation [16]- [19] or an ideal 3D directional antenna array [20]- [22]. The gain of these ideal directional antenna arrays is constant for radiation angles inside the beamwidth, and small value or zero outside.…”

“…But the existing works on mmWave directional antenna array mainly focus on the 2D one in terrestrial mmWave cellular networks without UAV [16]- [19]. Recently, some works in [20]- [22] propose 3D mmWave directional antenna arrays to model the antenna gain in mmWave links from UAVs to ground BSs/UEs. The antenna gain in all these works [16]- [22] is assumed to be a constant for radiation angles inside the beamwidth, and small value or zero outside.…”

“…Furthermore, a consecutive time period optimization is proposed to formulate the spectrum management architecture which considers the issues of interference, energy consumption, and UAV mobility. To evaluate the benefit of mmWave links associated with UAVs, the authors in [20] derive analytical channel models for three scenarios: a link from UAV to UAV, an aerial relay link consisting of a UAV source, a UAV relay and a UAV destination, and a relay link in which a UAV serving as relay for a ground source and a ground destination. These channel models are further assessed utilizing outage probability.…”

Outage Analysis for Millimeter-Wave Fronthaul Link of UAV-Aided Wireless Networks

“…Fluctuations in the orientation of UAV, due to wind loading effects, mechanical and control system resolutions, antenna and DU payload, that lead to beam misalignment are here not considered. These effects are described in [25]. For tractability of analysis, we approximate the antenna pattern by a sectored antenna model [15].…”