Line-of-Sight Probability for mmWave-Based UAV Communications in 3D Urban Grid Deployments

Abstract

The network operators will soon be accommodating a new type of users: unmanned aerial vehicles (UAVs). 5G New Radio (NR) technology operating in the millimeterwave (mmWave) frequency bands can support the emerging bandwidth-hungry applications facilitated by such aerial devices. To reliably integrate UAVs into the NR-based network infrastructure, new system models that capture the features of UAVs in urban environments are required. As city building blocks constitute one of the primary sources of blockage on the links from the UAV to its serving base station (BS), the corresponding line-of-sight (LoS) probability models are essential for accurate performance evaluation in realistic scenarios. We propose a LoS probability model in UAV communication setups over regular urban grid deployments, which is based on a Manhattan Poisson line process. Our approach captures different building height distributions as well as their dimensions and densities. Under certain characteristic distributions, closed-form expressions for the LoS probability are offered. Our numerical results demonstrate the importance of accounting for the building height distribution type as well as the orientation of the UAV with respect to its BS. By comparing our model with the standard ITU and 3GPP formulations, we establish that the latter provide an overly optimistic approximation for various deployments.Index Terms-3D LoS probability, urban grid deployment, mmWave radio, UAV communication, 5G NR technology I. INTRODUCTIONAccording to recent studies, millimeter-wave (mmWave) communication promises to support connectivity between unmanned aerial vehicles (UAVs) and their serving radio infrastructure [1], [2]. With larger available bandwidths, mmWave transmission enables UAV-based applications and services that require high data rates, such as real-time video transfer, area surveillance, and many more. As mmWave bands are embraced by 5G New Radio (NR) access technology, the latter is expected to accommodate a new type of UAV users [3]- [5]. However, the incorporation of specific UAV features, such as their three-dimensional (3D) mobility, introduces further challenges and requires modifications to the existing channel models [6], [7].One of the essential roadblocks for arranging seamless UAV support in mmWave-based 5G NR systems is the blockage of line-of-sight (LoS) radio propagation paths. As UAVs are envisioned to be utilized in city deployments [8], buildings

Closed-Form UAV LoS Blockage Probability in Mixed Ground- and Rooftop-Mounted Urban mmWave NR Deployments

“…Recently, the authors in [ 21 ] proposed a detailed and versatile UAV LoS blockage probability that accounts for most critical parameters including different UAV and BS heights, different building height distribution, and various widths of streets and building blocks. The standard city deployment is however limited to the regular one and captured by the Manhattan Poisson line process (MPLP).…”

“…In particular, the probability that a LoS path is blocked by an obstacle depending on relative positions of obstacles with respect to each other leading to complex expressions for coverage/outage probabilities that cannot be provided in closed-form. When dealing with such deployments the results are often provided in product form either having infinite sums [ 20 ] or involving integration [ 21 ]. An alternative approach is to utilize field measurements of LoS blockage, see, e.g., [ 22 ].…”

3D Uplink Channel Modeling of UAV-based mmWave Fronthaul Links for Future Small Cell Networks

“…Although UAV-assisted channel modeling has been investigated in recent studies [7]- [10], these works are mainly limited to sub-6 GHz frequency bands which cannot be directly employed to UAV-based mmWave communication systems. Meanwhile, most of the prior studies on mmWave channel modeling [11]- [13] do not address the presence of UAVs, with the exception of a few recent works in [14]- [28]. For instance, a new LoS probability model for UAV to ground BS links is offered in [14] over realistic urban grid deployments in which the effects of building height distributions along with their densities and dimensions are considered.…”

A Tutorial on Mathematical Modeling of Millimeter Wave and Terahertz Cellular Systems

“…In addition to blockage by small dynamic objects such as humans or vehicles, propagation paths in mmWave and THz systems can be blocked by large static objects such as buildings [125], [126], [127], [128], see Fig. 7.…”

“…The ITU-R model has been extended to 3D deployments by the authors in [126]. Although the model has been originally developed for UAV LoS blockage it can also be applied to the case of BS to terrestrial UE communications.…”