Networking

Peter Cochrane's Blog: Aerial bombardment

Our laptops and mobiles have become a battleground for competing antennas…

Written at a hotel in Taunton, UK, and dispatched via another free wi-fi service that needed no password - a trend that seems to be catching on

The competition for antenna space on our laptops and mobile devices is getting critical. Talk to any designer of radio systems for military applications and they will immediately regale you with their ongoing competition for physical space.

If you look closely at all their platforms you will see what I mean - aircraft, vehicles and ships that look like pin cushions, with antennas bolted onto every conceivable location.

The demand for wireless systems has mushroomed over the past 50 years, and nowhere has it become more critical than in defence. And while superficially the problem might appear to be a simple competition for space, it is of course far more complex.

High and low power, line-of-sight VHF, UHF and SHF, plus non-line-of-sight LF, MF and HF systems, have to be squeezed onto the limited platform presented by a warship, with ideally the ability for everything to be operational at the same time.

Once the desired antenna propagation characteristics have been achieved, then it is usual that some closely located system causes interference on one kind or another. This really is a mega problem that is subject to significant engineering and operational limitations.

In extreme cases systems cannot be simultaneously operated and facilities become time- and space-limited.

Does this world seem a remote one? Well, hang onto your hats. It is rapidly heading our way as more and more wireless facilities are included on laptops and mobile devices.

While we quietly said goodbye to the IRDA, floppy drive and the dial-up telephone modem slots, we have already seen the rapid inclusion of Bluetooth and wi-fi. And on the horizon we have WiMax, 3G, 4G, TV and radio.

Each requires its own antenna space - yet the laptop and mobile device is far more of a physical challenge that any military platform.

When we think of antennas we tend to see something like a single wire or TV design - but the reality is very different. Over the past 50 years antenna technology has blossomed beyond recognition with fixed and multi-frequency designs based on regular planar and fractal geometry patterns.

But looking to the future some of our space problems might be solved in part by programmable wireless technologies that will see all the functionality reduced to a single set of adaptable hardware and software.

This technology will allow us to use the same electronics and antenna for wi-fi and WiMax, for example, and also possibly for 2.5/3/4G where it is unlikely that simultaneous operation will be needed.

But Bluetooth, FM, DAB and TV present a different subset. In short, the likelihood is that we will require at least two or three simultaneously operational wireless systems that may preclude antenna sharing.

One solution from the past, which is both efficient and on the same scale as the laptop form factor, is the use of slots. Strange as it might seem, a wire loop antenna has a mirrored alternative - a plate with a hole in it.

In the case of a laptop that might just be the bezel around the screen, or the hand-rest surrounding the keyboard, or even an expanded logo plate in the lid. This form of antenna is often used for broadcast transmitters and on high-speed aircraft where any form of protrusion poses aerodynamic problems.

Whatever solution is selected in the short term for laptop and mobile is almost certainly going to be suboptimal and we will have to suffer wildly different performance between platforms. But in the much longer term we should see software programmable devices capable of doing everything we need at the same time on a single chip set.

As I travel I often find myself on the edge of a cell site or hotspot and have to resort to tricks to stay connected. These include the application of an earth wire to the frame of my laptop and mobile, or an external antenna coupled directly or indirectly to the main unit. But year on year I have seen this need diminish as wireless coverage becomes all-pervasive.

Of course, there is an obvious and final solution. 4G networks might just see contiguous coverage with real bandwidth capable of carrying all we need over a single IP channel. Until that day, we will have to continue the struggle for antenna real estate and sufficient signal quality.

About Peter Cochrane

Peter Cochrane is an engineer, scientist, entrepreneur, futurist and consultant. He is the former CTO and head of research at BT, with a career in telecoms and IT spanning more than 40 years.

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