WiFi has created an international market, spanning office infrastructure, home consumer equipment and public hotspots - and all based on a small grubby piece of open-access spectrum. Regulators have been pondering whether they can repeat that success by offering more spectrum for people to use as they will.

"Look at what we've achieved in 2.4GHz," says Michael Coci, director of technical marketing at wireless switch vendor Trapeze. "There's a huge ecosystem for the use of licence-exempt spectrum, that is worth billions of dollars, all from a small, dirty slice of spectrum."

WiFi was a $2.4 billion market in 2006, and will be worth $4.3 billion by 2010, according to Infonetics Research. It's boosting economies and having social benefits too, says Coci.

The vast majority of that activity is in a small bit of spectrum around 2.4GHz, originally designated for non-commercial "industrial, scientific and medical" usage. Although loosely called "unlicensed" the band is actually "licence-exempt", which means that regulators apply basic requirements - the most onerous being to keep below a power-level that (mostly) ensures that equipment won't interfere with other users' activities.

Anyone can use any technology there. So, amazingly enough, 2.4GHz also accommodates the very healthy Bluetooth ecosystem, currently installed on millions of devices, and coming more frequently into use as people get the hang of hands-free and other applications.

That's not bad for a left-over bit of spectrum. And the spectrum regulators have learned a lesson from this - to regulate as little as possible.

The UK's regulator has said that all spectrum it releases from now on will be "technology neutral", and this is in line with European policy "Offering spectrum on a technology neutral basis is all part of EU
spectrum liberalisation," says commentator Steve Kennedy.

The first technology neutral spectrum to be auctioned was the "DECT guard bands" originally kept clear to prevent interference, but now available. In principle this could be used for anything, but in practice is will be used for low power GSM.

More licence exempt spectrum

But the regulator also wants to expand the commons where people can play with radio, by offering more licence-exempt spectrum.

On one level, this may seem premature, since WiFi is already poised on expanding into a less-crowded license-exempt band near 5GHz, driven by 802.11n. But regulators see that other technologies could emerge, as radios become more intelligent, and more spectrum to play in would definitely help.

The trouble is, there isn't that much spectrum about that isn't already in use. And, if any is opened up, it would be best if it were opened up globally to try and repeat the market.

Ofcom is therefore consulting on the whole issue of licence-exempt spectrum (read the Executive Summary, the full consultation document [PDF], and the plain English version [PDF]).

"Spectrum use should be licence-exempt if the value that is expected to be derived from the spectrum under such an approach is predicted to be greater than if spectrum use were licensed," Ofcom says in the introduction to this consultation. It also says: "where harmful interference is unlikely (e.g. where the demand for spectrum in a given frequency band is less than the supply), then licensing may present an unnecessary overhead and a licence-exempt model may be more appropriate."

The bottom line is value for money: "All the measures proposed in this document are intended to further enhance the efficiency of the licence-exempt use of spectrum, increasing the value that it generates for the UK."

But where is the new spectrum?

The main new territory is at high frequencies. There is about 100GHz available between 40GHz and 275GHz - and spectrum above 275 GHz is unused. This doesn't penetrate far, so it's likely to be used for short range communications. Although radiation at high frequencies tends to be absorbed there are "water windows" where water molecules allow radiation to pass, where sensible communications can be carried out.

There is also an already existing licence-exempt band around 60GHz in the US, set up by the FCC. That is already producing talk of a goldrush. Other people are proposing "Terahertz" radio, above 100GHz.

New principles

The consultation could establish new principles:

  • Should some spectrum be licence-exempt but not technology-neutral, ie reserved for WiFi or some similar technology?
  • When should spectrum be licence-exempt, and when should it be "light-licensed"?
  • Is there a frequency limit - say 275GHz - above which all spectrum use can be made exempt from licensing?

  • Is there a transmission power limit below which all emissions can be made exempt from licensing (allowing technology such as ultra-wideband?

"Ofcom will publish generic license conditions (and spectral masks etc) which need to be adhered to," says commentator Steve Kennedy. Alternatively, specific licences may be offered for some high power uses. For instance, radar systems give out lots of power - but unfortunately, due to the nature of radar, they have to be sensitive to low power signals, in order to pick up reflections.

There is also going to be some consideration of radio interference: "Low power stuff can produce harmonics and these cause interference," says Kennedy. "There are likely to be stringent radio regulations on the low power stuff - Ofcom don't want radios to crackle each time your UWB or other kit transmits."

Get your responses in

Responses have to be in by 21 June, and anyone involved in - or thinking of getting involved in - low-power radio should consider responding. Ofcom is influential in European circles, and a good European approach is needed to make sensible global markets for low-power equipment.