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Merits of Serving UAVs via Terrestrial Networks: A Vertical Antenna Radiation Study

Nesrine Cherif, Qurrat-Ul-Ain Nadeem

TL;DR

The paper tackles the challenge of providing reliable cellular connectivity to UAV-UEs by reusing terrestrial cellular networks and accounting for the 3D vertical radiation pattern of base station antennas. It develops a stochastic-geometry framework that models TBSs as a Poisson field and incorporates a Nakagami-$m$ LoS channel together with down-tilt $\theta_t$ and 3dB beamwidth $\theta_{3dB}$ to derive a closed-form UAV coverage probability $P^{cov}$. The main contributions include an analytic expression for $P^{cov}$ that depends on $h_{BS}$, $h_{UAV}$, $\lambda$, $P_T$, $\theta_t$, $\theta_{3dB}$, and sidelobe $A_V$, plus insights showing that increasing $\theta_{3dB}$ improves UAV coverage at low altitudes and that an optimal down-tilt around $13^{\circ}$ balances UAV and terrestrial user performance; the coverage saturates at large down-tilt due to sidelobe gain. The results offer practical guidance for configuring terrestrial networks to support aerial users and are validated against Monte Carlo simulations.

Abstract

Unmanned Aerial Vehicles (UAVs) are increasingly used in a plethora of applications such as shipping, surveillance, and search-and-rescue. For UAVs to operate safely, reliable cellular connectivity is essential. Utilizing the terrestrial networks for aerial connectivity has been proposed, but the 3D radiation pattern of base station antennas significantly affects the performance of aerial links.. To address this, we evaluate the coverage probability of cellular-connected UAVs, considering vertical antenna gain, by leveraging tools from stochastic geometry. We also analyze how the UAV hovering height, tilt angle and 3D antenna beamwidth influence the reliability of the communication link. Our results show that a down-tiled antenna does not only improve the connectivity of terrestrial users but also its cellularconnected UAVs counterpart. Moreover, the coverage probability of the UAV-UE becomes saturated at large down-tilt angles at the TBSs due to the antenna sidelobe gain at the serving and interfering TBSs. We also found that the significant increase of the vertical antenna beamwidth improves the UAV user coverage probability especially at relatively low hovering altitudes thanks to the increase of the desired signal strength compared to the interference power.

Merits of Serving UAVs via Terrestrial Networks: A Vertical Antenna Radiation Study

TL;DR

The paper tackles the challenge of providing reliable cellular connectivity to UAV-UEs by reusing terrestrial cellular networks and accounting for the 3D vertical radiation pattern of base station antennas. It develops a stochastic-geometry framework that models TBSs as a Poisson field and incorporates a Nakagami- LoS channel together with down-tilt and 3dB beamwidth to derive a closed-form UAV coverage probability . The main contributions include an analytic expression for that depends on , , , , , , and sidelobe , plus insights showing that increasing improves UAV coverage at low altitudes and that an optimal down-tilt around balances UAV and terrestrial user performance; the coverage saturates at large down-tilt due to sidelobe gain. The results offer practical guidance for configuring terrestrial networks to support aerial users and are validated against Monte Carlo simulations.

Abstract

Unmanned Aerial Vehicles (UAVs) are increasingly used in a plethora of applications such as shipping, surveillance, and search-and-rescue. For UAVs to operate safely, reliable cellular connectivity is essential. Utilizing the terrestrial networks for aerial connectivity has been proposed, but the 3D radiation pattern of base station antennas significantly affects the performance of aerial links.. To address this, we evaluate the coverage probability of cellular-connected UAVs, considering vertical antenna gain, by leveraging tools from stochastic geometry. We also analyze how the UAV hovering height, tilt angle and 3D antenna beamwidth influence the reliability of the communication link. Our results show that a down-tiled antenna does not only improve the connectivity of terrestrial users but also its cellularconnected UAVs counterpart. Moreover, the coverage probability of the UAV-UE becomes saturated at large down-tilt angles at the TBSs due to the antenna sidelobe gain at the serving and interfering TBSs. We also found that the significant increase of the vertical antenna beamwidth improves the UAV user coverage probability especially at relatively low hovering altitudes thanks to the increase of the desired signal strength compared to the interference power.

Paper Structure

This paper contains 7 sections, 1 theorem, 15 equations, 8 figures, 1 table.

Table of Contents

  1. Introduction
  2. System Model
  3. Vertical Antenna Pattern
  4. Channel Model
  5. Coverage Probability
  6. Simulation Results
  7. Conclusion

Key Result

Theorem 1

The coverage probability for a typical UAV-UE is given by eq. (eq:Pcov) provided at the top of next page, where $f_{r_0}(r)$ is the probability density function (PDF) of the distance between the nearest TBS and the typical UAV-UE which is given by chetlur2019coverage:

Figures (8)

  • Figure 1: Illustration of 3D vertical angle between the UAV-UE and the TBS.
  • Figure 2: Vertical antenna radiation pattern of TBS.
  • Figure 3: Coverage probability versus the UAV-UE altitude.
  • Figure 4: Impact of TBSs antenna down-tilt on coverage probability.
  • Figure 5: Impact of TBSs antenna down-tilt and sidelobe gain $A_V$ on coverage probability.
  • ...and 3 more figures

Theorems & Definitions (1)

  • Theorem 1