EYE ON THE FUTURE

Telecommunications Journal of Australia, Spring 2005 by Corner, Stuart

AN OCCASIONAL COLUMN BY INDUSTRY NOTABLES

Everybody's knows Moore's Law: the prediction by Intel founder Gordon Moore at the dawn of the integrated circuit era in 1965 that the number of transistors able to be crammed onto a single silicon chip would double roughly every two years.

This year marked the 40th anniversary of the formulation of the law, generally dated to the publication on April 19 1965 of an article by Moore in the journal 'Electronics'. Over the years it has proved a remarkably accurate prediction of the exponential growth in the power of semiconductor technology.

One consequence of this has been to drive a similar exponential growth in demand for throughput in communications networks. Remember the 300-baud acoustically-coupled modems of the early '80s? And the predictions are that this growth will continue unabated.

But here's a difference: Moore's law defines progress in a technology looking for problems to solve: the exponential growth forecast for bandwidth predicts a problem looking for a solution. What technologies will deliver the throughput that this extrapolation predicts?

The answer in part is obvious: optical fibre. A fibre optic network today could deliver sufficient bandwidth to meet the most optimistic projections for demand growth, but of course a fibre optic network on its own can only ever provide communications to a device that is tethered to it. And it is quite clear that we are now demanding to devices that are fully mobile communications services that are on par with those to devices tethered to an optical or electrical cable.

Wireless communications today cannot match the throughput of wired networks in any practical and economic way. But what of the future? Well there is another law that has something to say about this. It's far less well known than Moore's Law and unlike Moore's law, when first promulgated it carried the authority of basing its predictions on almost a century of historical development.

It's Cooper's Law, formulated by the 'father' of cellular telephony Martin Cooper, who observed that, on average, the data-carrying capacity human ingenuity has been able to extract from the radio frequency spectrum, per unit area, has doubled every 2.5 years since Marconi's first wireless transmission at the end of the 19th century: a trillion-fold improvement in the past 100 plus years.

And he sees every reason why this trend should continue for another 100 years!

Any radio engineer will tell you that the information carrying capacity of a simple radiofrequency signal is limited by another law, Shannon's Law, promulgated by Bell Labs engineer Claude Shannon in 1948. It says in part that the higher the frequency the more information the signal can carry. So one way that engineers have been able to fulfil Cooper's Law is by developing technologies able to use ever higher frequencies for communications.

For example, researchers and standards setting bodies are now working on chips for wireless local area networks operating at 60 GHz with data rates somewhere between 1 and 10 Gbit/s. When? In only about five years.

They will also achieve a significant lift in 'per unit area' performance. 60 GHz signals are heavily attenuated by air and building materials, so will not have a usable range greater than a few metres. The upside is that they will be very small, basically one chip, and very cheap. So you'll be able to plug one into every power point and they will operate as a mesh providing a multi-gigabit wireless local area network.

At lower frequencies where attenuation levels are lower and radio signals usable (or a source of interference) over hundreds of metres or more, realising the predictions of Cooper's Law has been much more challenging.

As we all know only too well, try to carry too much information on the radio spectrum in the same area, and you get interference. One of the great leaps forward in overcoming this limitation was cellular technology. Cooper reckons it brought about approximately a 50-fold increase in our ability in information carrying capacity.

What next? Well Cooper's current company, ArrayComm, whose technology drives Personal Broadband's iBurst wireless access network, uses 'smart antenna' technology which effectively focuses the radiofrequency energy on each user as they need it, thus enabling more information to be delivered to more users in the same area.

A well-known phenomenon in radio communication is multipath interference: RF signals bounce off buildings and other obstacles, and the receiver picks up several signals carrying the same information at different times: this is what causes 'ghosting' on TV pictures.

Since the dawn of the wireless era multipath interference has been a problem to be mitigated and a limiter of throughput. Today, thanks to the enormous processing power of microchips, these multiple paths can each be used to carry usable information thus increasing overall throughput.

And this is not just a laboratory phenomenon. You can take advantage of it for a few hundred dollars by buying a MIMO (multiple input multiple output) wireless local network for your home or office. One such product is the NetGear RangeMax. At short distances (7 metres) it is claimed to give a throughput three times that of the 802.11g wireless LAN standard. But where it really shines is at longer ranges, with a claimed throughput 10 times that of 802.11 g at 130 metres.