How to handle the vanishing radio spectrum: Share frequencies

Researchers say one way to alleviate the upcoming radio frequency crunch is to share public safety frequencies temporarily with secondary users, such as IoT sensors.

How to handle the vanishing radio spectrum: Share frequencies
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With the billions of Internet of Things (IoT) devices projected to come on-stream over the next few years, questions are arising as to just where the bandwidth and radio channels are going to come from to make it all work.

The sensors need to send their likely increasingly voluminous data back to networks wirelessly to be processed.

But there’s a finite amount of radio spectrum available, and much of it is already allocated to incumbent primary users, such as public safety agencies. Other spectrum is dedicated to mobile network operators who have licensed chunks of it. Some is leftover in the millimeter frequencies, which is thus far pretty much untested in the real world — it’s going to be used for 5G in the future.

Then add the fact that you can’t physically share distinct frequencies locally at the same time without causing interference, and the scenario reads trouble ahead — radio spectrum will ultimately run out.

Sharing radio frequencies when not occupied by primary users

Scientists, however, say there might be a solution to this potentially serious problem. Indeed, IoT’s wide-reaching success could be foiled if it isn’t solved.

They say a system should be devised that allows incumbent radio users to share traditional, individual frequencies when they’re not being used with the sensor newcomers. That's not easy to do. You would have to detect when the legally allocated, licensed primary user wasn’t occupying bandwidth during its down times and then jump in.

“There’s a need for sensors and computational techniques that can detect and use the available spectrum when it’s not engaged by primary users,” says Columbia University’s Data Science Institute in a press release.

The researchers there think they know how to approach the problem. With algorithms, and the like, they plan to develop a way to identify when, say, a public safety emergency channel is in use (during a disaster or drill) or not in use (most the time) and allocate it temporarily to “mobile and wireless-device users.” One could interpret that to mean smartphones or whatever comes next, such as voice-first devices, robots or IoT sensors.

The researchers just received a grant from The National Science Foundation to help them figure out how to achieve the task.

“At some point in the future, as we keep using more and more mobile devices, the [radio] spectrum will run out of space,” says John Wright, an electrical engineering professor and main researcher on the project.

Identifying unoccupied RF spectrum

The team uses the photography analogy of a “snapshot” to explain the direction they want to go with the project.

One of the group members, who “specializes in analog and radio-frequency (RF) integrated circuits, will design circuits that can create ‘snapshots’ of a large portion of the spectrum,” the release continues.

They’ll then use some of the depictions to “design algorithms to reconstruct the spectrum” and help plan the sensor architecture. The sensor will predict unocupied spectrum. Energy-efficiency improvements are also promised, and elements of the group are already working on that part.

“We’ll use all the data science tools we possess — machine learning, neural networks, algorithms and advanced computation techniques — in conjunction with new hardware devices to sense pieces of the RF spectrum as they become available,” says Wright.

Those frequencies would then be temporarily allocated to secondary users, the sensors, and if it works, could be a clever way to alleviate a potentially commercially disastrous, looming spectrum crunch.

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