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Floating Cell Towers Are the Next Step for 5G

Terrestrial 5G networks will support high-altitude balloons and drones, and could someday merge with them

3 min read
Photograph of a Loon balloon in the air.
Photo: Loon

As the world races to deploy speedy 5G mobile networks on the ground, some companies remain focused on floating cell towers in the sky. During the final session of the sixth annual Brooklyn 5G Summit on Thursday, Silicon Valley and telecom leaders discussed whether aerial drones and balloons could finally begin providing commercial mobile phone and Internet service from the air.

That same day, Alphabet subsidiary Loon, a balloon-focused graduate of the Google X research lab, unveiled a strategic partnership with Softbank’s HAPSMobile to leverage both solar-powered balloons and drones to expand mobile Internet coverage and aid in deploying 5G networks. No high-altitude network connectivity services have taken off commercially so far, but some Brooklyn 5G Summit speakers were optimistic that it would happen soon. 

“The opportunity is in our hands in terms of truly leveraging 5G in conjunction with the massive paradigm shift when it comes to UAS—drones—and also satellites,” said Volker Ziegler, CTO at Nokia Bell Labs.

Nobody expects the high-flying Loon balloons and HAPSMobile’s drones to compete directly with ground-based 5G networks in the near future. Until recently, it hasn’t been easy to develop a balloon or drone platform that is cost-effective enough to even consider using for telecommunications, said Salvatore Candido, principal engineer at Alphabet and CTO of Loon. But such high-flying platforms may help fill the gaps when coverage is lacking in rural or otherwise under-served communities. (Even rural parts of the United States may miss out under current 5G network deployment plans.)

Fleets of balloons and drones could also provide coverage on a temporary basis, such as during a major pre-planned event like the Super Bowl or in the wake of a natural disaster. Nokia previously partnered with Alphabet’s Loon when the latter deployed its experimental balloon fleet to provide basic Internet service to 200,000 people in Puerto Rico after the U.S. island territory was left devastated by Hurricane Maria in 2017. The balloons carried LTE technology from Nokia as part of a broader coalition involving AT&T and T-Mobile. 

“There’s a billion people in the world who don’t have sufficient connectivity, whether that’s temporary because of a hurricane or just because of where they live,” Candido said. “I think all these new technologies coming together makes it possible to create networks that might begin to cover huge numbers of those people.”

Loon has not yet begun deploying 5G equipment on its balloons—though the partnership with Softbank’s HAPSMobile suggests that could someday be possible. But the advent of terrestrial 5G networks could also make it easier for companies to deploy Internet drones or Internet balloons. Nokia’s Ziegler pointed out that 5G offers advantages over 4G LTE when implementing a relay system that bounces the signal around between groups of balloons or drones to extend coverage well beyond the ground station where the signal originates.

“There’s a billion people in the world who don’t have sufficient connectivity.”

The availability of 5G network technology could also make it easier from an air traffic control standpoint, to track and manage a large group of drones, said Giuseppe Loinno, an assistant professor in electrical and computer engineering at the New York University and director of the Agile Robotics and Perception Lab.

When the time comes, it will be important for telecommunications companies to create demand for high-flying mobile phone and Internet services by showing what they can do for communities or customers, said Dallas Brooks, director of the Raspet Flight Research Laboratory at Mississippi State University and associate director of the ASSURE FAA UAS Center of Excellence. He invited Brooklyn 5G Summit attendees to collaborate with him and other universities participating in the Federal Aviation Administration’s research and testing program for integrating drones into U.S. national airspace.

Loon may be among the first to take that advice with its balloons—even if they won’t deliver 5G service in the beginning. The company’s stratospheric balloons have already won their first commercial contract with Telkom Kenya to provide mobile phone service for some of Kenya’s almost 50 million citizens. But Loon certainly won’t be alone in trying to make such projects work in the 5G era. “There is no shortage of people trying to create pseudosatellites in the stratosphere,” Candido said.

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Metamaterials Could Solve One of 6G’s Big Problems

There’s plenty of bandwidth available if we use reconfigurable intelligent surfaces

12 min read
An illustration depicting cellphone users at street level in a city, with wireless signals reaching them via reflecting surfaces.

Ground level in a typical urban canyon, shielded by tall buildings, will be inaccessible to some 6G frequencies. Deft placement of reconfigurable intelligent surfaces [yellow] will enable the signals to pervade these areas.

Chris Philpot

For all the tumultuous revolution in wireless technology over the past several decades, there have been a couple of constants. One is the overcrowding of radio bands, and the other is the move to escape that congestion by exploiting higher and higher frequencies. And today, as engineers roll out 5G and plan for 6G wireless, they find themselves at a crossroads: After years of designing superefficient transmitters and receivers, and of compensating for the signal losses at the end points of a radio channel, they’re beginning to realize that they are approaching the practical limits of transmitter and receiver efficiency. From now on, to get high performance as we go to higher frequencies, we will need to engineer the wireless channel itself. But how can we possibly engineer and control a wireless environment, which is determined by a host of factors, many of them random and therefore unpredictable?

Perhaps the most promising solution, right now, is to use reconfigurable intelligent surfaces. These are planar structures typically ranging in size from about 100 square centimeters to about 5 square meters or more, depending on the frequency and other factors. These surfaces use advanced substances called metamaterials to reflect and refract electromagnetic waves. Thin two-dimensional metamaterials, known as metasurfaces, can be designed to sense the local electromagnetic environment and tune the wave’s key properties, such as its amplitude, phase, and polarization, as the wave is reflected or refracted by the surface. So as the waves fall on such a surface, it can alter the incident waves’ direction so as to strengthen the channel. In fact, these metasurfaces can be programmed to make these changes dynamically, reconfiguring the signal in real time in response to changes in the wireless channel. Think of reconfigurable intelligent surfaces as the next evolution of the repeater concept.

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