How new radio tech will solve the upcoming spectrum crunch

A new kind of twisted radio wave can send 10 HD movies in one second. If this and other new radio technologies work in the real world, we could solve our upcoming 5G spectrum crunch.

092414 twisted lead image
Credit: USC Viterbi School of Engineering

Research conducted a couple of years ago by a bunch of scientists showed it was possible to twist light beams to send data at high speeds. Well, that same group has now achieved similar results with radio.

The lab geeks, led by Professor Alan Willner at the University of Southern California’s Viterbi School of Engineering, reckon they have been able to get speeds of 32 GB-per-second. Or, roughly the equivalent of 10 90-minute HD videos sent wirelessly in one second. That’s 30-times LTE.

The USC engineers’ previous light-based experiment obtained speeds of 2.56 TB-per-second, or 2560 GB-a-second, obviously faster, but it used awkward light waves, not the more hardy radio, which takes advantage of wider waves.

Light waves have inherent disadvantages over radio, though, in that they need light. It’s not a great solution unless you can control the environment, like you can with a cable. We know data-via-light over cable as fiber optic. Radio is better than light over spaces. That’s why this new tech is more exciting.

How it works

Four radio beams, each carrying a unique data stream, are squirted through something called a "spiral phase plate." That device twists the radio waves into unique, statistically-independent, helical, or spiral shapes. Think DNA. The receiver then unscrambles, or untwists, the beams, thus recovering the data.

You can read the technical gobbledygook in a recent Nature article — it’s all to do with orbital angular momentum allowing multiplexing.

The experiment was conducted over 2.5 meters of free lab space.

What it means

Conceivably, if the experiment actually works over long distances in real-world environments, this twisting technology could help with future-gen 5G wireless because we’re running into a spectrum crunch.

You can add twisted radio to two additional avant-garde technologies that might help with spectrum, if they can be made to work properly. They are: millimeter-frequencies, and self-interference canceling algorithms.


Theodore S. Rappaport, Wonil Roh and Kyungwhoon Cheun, say in a recent spectrum crunch article titled “Smart Antennas Could Open Up New Spectrum For 5G” in the Institute of Electrical and Electronics Engineers’, or IEEE’s, Spectrum publication, that mobile traffic is doubling each year.

This is according to gear makers Cisco and Ericsson, who estimate that by 2020, the average mobile user could be downloading 1 TB of data annually—equal to about 1,000 films.

It’s only a matter of time before we run out of existing spectrum.

Rappaport et al point out that fixes, to expand capacity from 3G to current 4G, have included multiple antennas, smaller cells, and better coordination between devices. So we’ve done all that and are still projecting a crunch, due to the traffic surge, in about four to five years, according to them.

The authors reckon that millimeter-wave band might be the answer. That’s the extremely high-frequency band that spans 30 to 300 GHz and is way above our current, common microwave bands around 2 to 5 GHz.

Twisted radio also uses millimeter frequencies.

Millimeter-wave has historically been cost-prohibitive, and it’s been hard to get the signals to propagate well with movement—the higher the frequency, the shorter the wavelength and more prone it is to getting knocked around by variables like walls and trees. One good thing about it, though, is the antenna is tiny and it’s under-used.

Equipment makers are beginning to figure out how to make millimeter work, though, and are using it for data in line-of-sight transmissions. Two millimeter-wave standards are Wireless High Definition (WirelessHD) and Wireless Gigabit (WiGig).

Self interference-canceling algorithms

Self interference-canceling tech is based on the concept that it should be possible to second guess how a transmission is affected by the elements that cause self-interference, and then kill it. I’ve written about this one before.

Self interference means that you can’t send and receive at the same time on the same frequency. It’s a technical limitation with radio. Removing the need for two frequencies for send–and-receive makes spectrum available.

Where’s the bookie?

So that’s a triple-play of possible technologies that could be used to alleviate the next spectrum crunch.

We’ve got USC’s latest: its twisted radio waves. Add that technology to self-interference canceling algorithms and then throw in the somewhat already-functioning millimeter-frequencies, and we’ve got possibilities.

Anyone know where I can find a forward-thinking, tech-minded bookie?

Copyright © 2014 IDG Communications, Inc.

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