The Sky Is Not the Limit: LTE for Unmanned Aerial Vehicles (1707.07534v2)

Abstract: Many use cases of unmanned aerial vehicles (UAVs) require beyond visual line-of-sight (LOS) communications. Mobile networks offer wide area, high speed, and secure wireless connectivity, which can enhance control and safety of UAV operations and enable beyond visual LOS use cases. In this article, we share some of our experience in Long-Term Evolution (LTE) connectivity for low altitude small UAVs. We first identify the typical airborne connectivity requirements and characteristics, highlight the different propagation conditions for UAVs and mobiles on the ground with measurement and ray tracing results, and present simulation results to shed light on the feasibility of providing LTE connectivity for UAVs. We also present several ideas on potential enhancements for improving LTE connectivity performance and identify fruitful avenues for future research.

• The paper presents LTE as a viable solution for UAV command/control and data communication, specifying needs like 100 kbps for control and 50 Mbps for data.
• It examines unique propagation challenges including LOS/NLOS variations and increased interference from favorable aerial conditions affecting both UAVs and ground users.
• The study proposes enhancements—such as CoMP, improved handover strategies, and aerial UE identification—to optimize network performance for expansive UAV deployment.

LTE for Unmanned Aerial Vehicles: Technical Considerations and Future Directions

The paper "The Sky Is Not the Limit: LTE for Unmanned Aerial Vehicles," authored by X. Lin et al., explores the technical challenges and feasibility of utilizing LTE networks for providing connectivity to unmanned aerial vehicles (UAVs), specifically focusing on low altitude small UAVs.

Key Insights and Findings

The adoption of UAVs has been expanding rapidly across various sectors, necessitating reliable communication frameworks. The paper posits LTE networks as a promising solution due to their ability to offer wide-area, secure, and high-speed connectivity, essential for safe operational control and the deployment of beyond visual line-of-sight (LOS) use cases.

Connectivity Requirements

The paper outlines two primary connectivity purposes:

1. Command and Control: Requires data rates up to 100 kbps with a packet error rate below 0.1% within a 50 ms latency bound.
2. Data Communication: Use cases like aerial photography necessitate up to 50 Mbps data rates.

The LTE networks face distinct challenges when accommodating UAVs due to differences in propagation conditions compared to terrestrial user equipment.

Propagation Characteristics

The paper highlights unique aspects of wireless channels for UAV communication, focusing on LOS vs. non-LOS (NLOS) and large-scale pathloss models. Existing pathloss models are limited in addressing UAV altitudes, prompting the authors to propose the use of ray tracing and empirical measurements for better characterization.

Technical Feasibility and Challenges

Simulation results suggest that while UAVs can be feasibly supported by LTE networks, there are notable challenges:

• Interference: UAVs experience more favorable propagation conditions which may lead to increased interference, impacting both UAV and ground user equipment (UE) performance.
• Coverage: Down-tilted base station (BS) antennas may limit coverage, necessitating enhancements to cater to aerial UEs.
• Mobility and Handover: The aerial UEs face fragmented cell associations due to unique SINR patterns, which could result in more handovers and associated failures.

Potential Enhancements

To mitigate these issues, several enhancements are proposed:

• Interference Mitigation: Use of Coordinated Multipoint (CoMP) transmission, better uplink power control, and dynamic radio resource management could reduce interference.
• Mobility Enhancements: Improved handover mechanisms and strategies to manage fragmented cell associations are essential.
• Aerial UE Identification: The network needs efficient mechanisms to identify and manage aerial UEs distinctly from terrestrial devices.

Implications and Future Research

The paper implies that while current LTE networks can support the initial proliferation of UAV operations, as UAV deployment becomes more ubiquitous, enhanced strategies are imperative. The findings point towards several future research areas:

1. UAV-to-UAV Communication: Exploring LTE’s potential in facilitating direct communication for collision avoidance and navigation.
2. Higher Altitude Connectivity: Extending LTE and possibly 5G networks to support high altitude UAVs demands new link budget analysis and beamforming technologies.
3. 5G Integration: With enhanced capacity and low-latency capabilities, 5G appears poised to address UAV connectivity requirements, promising ubiquitous coverage across diverse operational altitudes.

The paper effectively positions LTE connectivity as a viable enabler for UAVs while acknowledging the need for palliative measures and ongoing research to optimize performance alongside terrestrial users.