Toward UAV Control via Cellular Networks: Delay Profiles, Delay Modeling, and a Case Study Within the 5-mile Range

While some unmanned aerial vehicles (UAVs) can operate with a given degree of autonomy (e.g., path following, obstacle avoidance, auto return, and other flight modes), many civilian drones have a safety pilot standby all the time for abnormal conditions. This is typically done within line-of-sight (LOS) due to regulations. While flying within LOS, radio frequency communication remains a popular alternative for retail pilots. For beyond line of sight operations, given the availability of cellular technologies, the UAV community has explored the possibility of using the cellular network instead, which could bring benefits such as an additional channel for control and telemetry, extension of range, and allowing the UAV to interact with cloud services while it flies, via a data connection. With the current prevalence of data supporting communication over 3G and 4G networks, the following representative technologies have been used for long-distance control-short message service (SMS), transmission control protocol (TCP), message queue telemetry transport (MQTT), and the so-called “protocol-independent” service PubNub. While the safety of drone flights is highly prioritized by regulators, the issue becomes even more highlighted when control commands are transmitted via cellular network channels (e.g., 4G long-term evolution, SMS) which can introduce time delays in communication chains and degrade pilot's ability to properly control UAVs. This article reviews common UAV communication protocols over cellular links and presents a technique for measuring and modeling delays over such channels. The quality-of-fit for the proposed models is measured for different communication protocols, short versus long-range communication, and different UAV operation modes. Finally, details are presented for a system that manipulates a drone via the cellular network and latency is measured for such system.