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Zenneck Waves Keep Wearable Tech Wireless Communications 'Close to the Vest'
Wearable Tech World Feature Article
February 05, 2013

Zenneck Waves Keep Wearable Tech Wireless Communications 'Close to the Vest'

By Tony Rizzo
TMCnet Senior Editor

Typically, when people talk of wearable technology today, they tend to refer to a single device that a user might wear - a watch, or a monitor/sensor of some sort, usually something that is bulky enough to sport a transmitting radio of some kind - "typically" Wi-Fi.

In turn, that device or sensor communicates with some external receiver - a tablet or smartphone or a medical device, for example.

But let's advance the state of wearable technology just a bit, and consider the possibility of wearing more than one tech device – perhaps a video display-enabled set of eyewear, and perhaps a tiny little video camera that might sit somewhere entirely separated from the eyewear.

How about if we add a tiny wearable video recording device to the mix to make it even more interesting?

Well then, how might three such devices communicate directly with each other while also ensuring that they remain hugely energy efficient? We wouldn't want to connect them through actual wires - that would be so 1990s and utterly crude. Wi-Fi certainly remains an option, as does Bluetooth. But each of these wireless communications methods have their own issues.

Wi-Fi is not exactly super energy efficient, and Bluetooth can succumb to all sorts of interference issues as soon as we create three devices in need of close proximity handshaking.

Enter the idea of surface waves, also known as, among other things, Zenneck Waves, named after Jonathan Zenneck, who did the initial work in understanding their properties.

Here’s the beginning of an introduction from a physics paper dating back to 1996:

Jonathan Zenneck in 1907, was the first to analyze a solution of Maxwell's equations that had a "surface wave" property. This so-called Zenneck wave is simply a vertically polarized plane wave solution to Maxwell's equations in the presence of a planar boundary that separates free space from a half space with a finite conductivity. For large conductivity – this depends on the frequency and dielectric constant, too – such a wave has a Poynting vector that is approximately parallel to the planar boundary. The amplitude of this wave decays exponentially in the directions both parallel and perpendicular to the boundary (with differing decay constants).

We don't really need to understand the above, any more than we really need to understand how semiconductors work. But it's enormously interesting.

Here is what Wikipedia has to say:

Surface or ground waves can be of mechanical or electromagnetic nature. In physics, a surface wave is a mechanical wave that propagates along the interface between differing media. A surface wave can also be an electromagnetic wave guided by a refractive index gradient. In radio transmission, a ground wave is a surface wave that propagates close to the surface of the Earth.

That’s almost as obtuse as the first definition, granted, but we're getting a bit closer. Note that now we are at least talking about "radio transmission" (i.e. communication) traveling close to the earth's surface.

It's a wave that remains at the interface between the surface of an object (the earth, for instance) and the air. It doesn't travel through open space (as you might imagine Wi-Fi to do).

Taking this to its logical conclusion for our discussion, rather than the earth providing the surface, imagine a fabric fashioned into wearable tech providing the surface. The question then becomes one of how to actually harness this surface for communication between wearable devices.

This is where Roke Manor Research Ltd (or simply Roke), a Chemring Group company based in the United Kingdom, comes into play.

Real Science, Not Fiction

Roke is an electronics engineering company that primarily provides contract research, product development and manufacturing for a wide range of U.K. and international customers. Its team currently comprises more than 350 engineers focused on developing advanced sensors, communications systems and network solutions for a diverse range of applications. Aside from working on real-world networking and communications solutions for clients, the company also does original research to problems that may not yet have practical real world implications but that soon are likely to - such as, for example, wearable tech communications such as what we've described above.

It turns out that some of those engineers, led by a colleague, Janice Turner, have in fact created a demonstration system that uses Zenneck waves to send high-definition video over a short length of material. It has a bandwidth of up to 1.5 GBPS (roughly three times faster than is currently available through high speed Wi-Fi).

The key to the technology, relative to what we wrote earlier, is that the signal between the devices doesn't travel "through" the material itself (as one might think would be the case with a fabric containing a woven conductive thread) but rather wirelessly and literally over its surface.

Such a wireless signal is what the Roke demonstrates delivers, and currently that signal is able to travel roughly several inches. Pretty amazing.

It is difficult to get one's head around this perhaps, but what we are talking about here is essentially the ability to deliver HD-quality video over the span of several inches wirelessly from one wearable device to another using the fabric a user is wearing to create the surface waves that establish the wireless link.

An IEEE paper by Turner and her colleagues is available for purchase ($19) for anyone interested in the deeper details.

Turner and her colleagues have based the demo system on a fabric that includes a dielectric-coated conducting material that creates the surface waves that deliver the wireless data. Returning to our hypothetical example above of a video camera, display and a miniaturized recording device, imagine then a vest made of this material that allows these wearable tech devices to wirelessly communicate with each other bi-directionally.

It is the ultimate in a "wearable wireless personal network."

There’s more to it than what we've described with our three device scenario. In fact, the way the system can work is that multiple devices can be attached or unattached simply through proximity to the fabric.

A smartphone, for example, might simply be attached to the personal wireless network simply by placing it in a pocket made of our hypothetical vest.

Zenneck wave-based devices do not necessarily need to be wearable tech-focused - that simply happens to be our specific interest. Such wireless networks would also have applications in numerous other industries. How about your smartphone being able to connect with an airline passenger seat made up of Zenneck wave-enabled fabric?

As soon as you sit in your seat you can simply be wirelessly connected to a plane's video entertainment system. Use smart eyewear that provides an expansive image instead of video displays cramped into the back of your fellow passenger's seat, and earphones that connect wirelessly - all controlled through a smartphone app that you agreed to download - again wirelessly connected through your seat.

It isn't science fiction but rather science reality. Zenneck wave-enabled devices, Janice Turner suggests, may very well be far enough along to hit the market within 24 months. We're looking forward to it!

Edited by Braden Becker

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