German Researchers Work on Controlling Drones via Cellular Voice Channels

Using cellular data channels to maintain reliable connections to drones often fails, but voice channels are everywhere and highly reliable.

According to, German researchers at the Fraunhofer Heinrich-Hertz Institute (HHI) in Berlin have found an alternative to using the unreliable, frequently interrupted data connections of cellular networks to remotely control drones, by taking advantage of their voice channels, instead. Increased drone implementation in city environments will require dependable connections between operators and their unmanned aerial vehicles, and this solution proposes opting for cellular networks’ voice channels, which provide more continuous connection, than their data-centric counterparts, which frequently drop out.

While there have been alternative proposals to solve this issue, such as Hangar and Vapor IO’s data centers that would provide cities with the necessary computing power to manage mass amounts of autonomous drones, the Heinrich-Hertz Institute’s solution takes advantage of pre-existing infrastructures without the need to build one from scratch. 

“A major advantage is that – unlike the data connections – the voice channels are available almost everywhere and they’re highly reliable, too,” explained HHI research associate Tom Piechotta. “Even in areas where there is only a limited data connection, or even none at all, there is usually still network coverage for voice channels.” 

Though commands such as directing a drone or asking it to relay its location back to an operator aren’t very data-heavy, they’ll still need to be converted from their digital, electronic format to an audio-only version. The obvious question, then, quickly becomes apparent: how does one transmit data through voice? 

“Relatively speaking, the control commands and positioning information are fairly small amounts of data, but they must nevertheless be transmitted reliably,” said Piechotta. “We convert the commands into audio signals, in much the same way as modems used to. A small module on the drone then translates the audio signal back into a command. Transmitting the information in this way is extremely favorable given that it works in real-time and is highly resilient to failures and connection disruptions.”

While we’re on the subject of extremely favorable aspects to this audio-centric approach, the fact that all the tools and technological requirements necessary for this to work are already in place is a huge bonus. The HHI’s method, as described, is merely making ingenious use of the instruments we have at our collective disposal. “Another advantage is that no new radio standards or infrastructure are required; the requisite technology is already available today – all over the world,” said Piechotta. To his point, mobile networks are ubiquitous across the globe, and connecting to a drone through that infrastructure is as technologically basic as making a phone call. Utilizing the voice channels is merely a way to eliminate a huge swath of unnecessary data traffic. 

Piechotta added that his team has rarely encountered dead spots where the cellular voice connection drops out, and in the infrequent instances that they do, the system simply switches from one mobile standard such as LTE or GSM, to another such as UMTS. In the worst-case scenario, a call-back or return home feature, as standardized by your affordable hobby drone, takes over. Additionally, basing a system like this on a mobile network’s voice channel, in Piechotta’s opinion, is a foolproof strategy that will stand the test of time, regardless of inevitable tech innovation.

“Mobile communications standards come and go – but voice channels are a permanent feature,” he explained. “Mobile networks will always provide voice channels and, as long as this remains the case, the system we propose is a reliable and affordable alternative to conventional data connections.” 

Modern drone technology is filled with potential. From reducing carbon emissions and automating deliveries or inspections, to aiding in emergency services and surveying distant planets, the possibilities are endless. Though the industry is currently very much focused on developing thorough unmanned traffic management (UTM) systems in order to handle increasing aerial traffic, establishing secure, continuous connections like the one proposed by HHI is arguably just as necessary to do so. Besides, using the proverbial backdoor by opting for the voice channel instead of the assumed go-to data route is not only clever, but the kind of “cool” that science innovations are made of.