5 ways to prepare your advertising infrastructure for disaster

Next year Londoners will get access to 72MHz of unlicensed radio spectrum, all in the prime sub-1GHz band, as Ofcom prepares to open the TV airwaves to anyone with a database handy.

Ofcom's new consultation on opening up White Space frequencies shows London as the biggest winner thanks to the presence of the Crystal Palace transmitter, which blats out TV to most of the capital, leaving the frequencies used by neighbouring towns empty. Less well structured is Glasgow, where the primary transmitter is too far from the centre and leaves only 60 per cent of Glaswegians with the 27MHz of shiny new radio spectrum that will be available to nine in 10 UK households early next year.

But that's not to be sniffed at. The 2.4GHz Wi-Fi band is 83MHz wide and has changed how we perceive mobility. Three runs a national mobile network with only 74.1MHz, so the prospect of a similarly-sized chunk of radio falling into public hands early next year is exciting stuff.

Not that it will be entirely open to all: White Space radios use frequencies which are being used somewhere else, but are locally empty – so some management is necessary. The frequencies used to transmit TV in Slough are different from those used at Crystal Palace, to avoid interference, so the Slough frequencies are empty in Islington where they can be used for short-range wireless or point-to-point links.

A White Space access point, on booting up, contacts Ofcom to ask for a list of approved databases, then contacts a database with its location and the radio protocol it would like to use. The database responds with a suitable frequency and power level which the access point passes on to connecting devices.

It sounds complicated but it works; White Space devices, and the associated databases, have been operating in the US since early this year. The UK is a lot smaller and more reliant on Freeview (digital terrestrial TV) which stands to lose most if it all goes wrong. So the industry has been waiting to see how conservative Ofcom would be in permitting the use of TV White Space, and it turns out Ofcom isn't feeling very conservative at all.

In the consultation [PDF, readable for the first 20 pages or so] Ofcom outlines the power it's minded to permit, and how it will protect Programme Makers and Special Events (PMSE, aka the luvvies) from being interfered with. PMSE users have been lurking in the TV White Spaces for decades, and are wary of the newcomers – so they'll get priority access. That means anyone living near Wimbledon or Wembley should be aware that their White Space allocation will reduce significantly during Special Events. Ofcom reckons the UK has 24 such events annually, so perhaps it's not the ideal technology for streaming sports coverage.

White Space users will also be banned from approaching within 14 meters of a PMSE user (their device will have to switch frequencies, or switch off) which should keep them outside the studio/theatre/set.

One might reasonably ask what happens when someone tweaks their White Space kit to use the whole band, knocking out TV reception and radio mics alike, but in reality that's already happening. White Space kit is required to be tamperproof and resistant to replacement firmware, which might make it slightly harder to modify than (for example) existing Wi-Fi routers. Hacked Wi-Fi offers better range and capacity, but few people bother. Your correspondent's own radio kit features an "obey regulatory rules" checkbox which makes flaunting the restrictions trivial, but still illegal.

Ofcom's more relaxed approach is, of course, down to the temporary nature of White Space allocations. Londoners might start off with 72MHz of prime radio spectrum to play with, but if the luvvies kick up a fuss or Freeview goes on the blink then Ofcom will send word to the databases and within three hours the bands and power levels will have been adjusted downwards.

Over the next six months Ofcom will be running trials, in London and elsewhere, to see just how much interference these White Space devices kick out, and – perhaps more importantly – whether anyone cares. If all goes well, the UK could be enjoying a spectral bonus by March next year. Now we just have to think of something worth doing with it all. ®

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