  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.
