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Inside Ames: Drones map cellphone signals

Are cellular signals strong and reliable enough to control and monitor drones in the skies? Researchers at Carnegie Mellon University's Silicon Valley campus are using a revamped ambulance and drones of their own to find out.

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So Bob, we’re in this really cool van. Can you tell me what it does?
This van is a mobile radio laboratory.

Bob Iannucci is a professor of computer engineering at Carnegie Mellon University. He built a full cellular network into this old ambulance.

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Bob Iannucci
Professor, Carnegie Mellon University
Director, CyLab Mobility Research Center
So we have the ability to go anywhere, set up a big antenna, create what we call a cellular bubble of coverage. And connect that via satellite back to the Internet.

The group is trying to measure and predict how cellular signals cover an entire area, not just the ground, so they can better understand how ground-based cell networks communicate with small drones in the air.

Today’s cell networks are designed for users on the ground and their coverage- and reliability- in the air is not well-known.

I got a tour of the ambulance and was impressed by how each storage cabinet was retrofitted to make a mobile RF lab. Like this compartment designed to store oxygen tanks. It now holds the pneumatic mast that puts up a cellular antenna to connect to the Internet.

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Ours, we had the oxygen bottle removed and we put a telescopic mast and a compressor there so we can raise and lower the mast just by flipping switches. That one brings it down.

Inside the ambulance, a rack of servers and radio gear generates the cell signal.

Iannucci and his students are using the ambulance and customized drones to investigate how cellular signals travel through the air and reflect off the ground and other objects.

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One of the things that we did recently that’s pretty cool, I’ll show you on this quadcopter, we make some of our own parts for these quadcopters. This part right here that’s grey was actually 3D printed.

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The group travels to a remote area to operate an experimental radio system. Students climb up onto the roof of the ambulance and fly their drones, capturing information about the cellular signal.

Through these experiments, Iannucci’s team has discovered that getting a reliable cell signal a hundred meters off the ground isn’t easy.

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The big surprise was that the signal strength up there didn’t match what people expected at all. In fact, you know the Verizon guy, who used to walk around, can you hear me now? If he were able to fly around, there would be a lot of places up there where you wouldn’t be able to hear them.

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This information could present a challenge for companies that are interested in flying drones and using the cell network to control them. Companies like Amazon and Google, which want to fly delivery drones over distances too great to be able maintain contact with the drones using WiFi.

The group recently partnered with the U.S. Geological Survey to get detailed laser-scans of the surrounding terrain. The idea being to use radio measurements and terrain map to create software that can more accurately stimulate cell coverage in any given location.

This research might help future drone services and give us a better signal here on the ground.