Original URL: http://www.theregister.co.uk/2013/02/21/at800/

So you won a 4G licence. The Freeview interference squad wants a word

Next-gen mobe broadband threat to 2 MILLION tellies

By Bill Ray

Posted in Media, 21st February 2013 13:32 GMT

The team to turn to when high-speed mobile broadband knocks out your Freeview signal has kicked off negotiations with this week's 4G auction winners. It's hoped that Brits will get four weeks of notice before up to two million TV screens go dark.

The recently established body managing interference from new 4G services is called Digital Mobile Spectrum Limited (DMSL), and it now has a shiny website with a new logo. It also prefers to be known as AT800. Under that name it undertakes to contact every home at risk of losing Freeview reception at lest four weeks ahead of time, and provide mitigation to those who want it.

The new 4G licences, auctioned off earlier this week, occupy the space where analogue TV used to be, adjacent to Freeview's digital transmissions. In most cases that won't be an issue: the leakage from 4G into Freeview will be minimal, but where the viewer is receiving a weak Freeview signal, and using a cheap signal booster, then the effect of boosting both will knock out Freeview reception.

AT800 is funded by an £180m charge tacked onto* the 4G auction's £2.3bn revenue, most of which will go on filters fitted in homes to remove the 4G signal before boosting. But the filter has to go between the ariel and the booster, and where that's impossible (such as both being within the roof of a block of flats) then AT800 has the authority to spend up to £10,000 per household ensuring they get some sort of free-to-view TV service.

No one knows quite how big the problem will be nor where it's going to happen. Right now we don't even know which of the auction winners will be most likely to interfere - the amount of spectrum has been decided, but exactly which bands will be used is still being negotiated, and the interference issue will play a significant part in those negotiations.

The operators could probably make the problem disappear by fitting better filters on their base stations, and they'll get any left over cash as a motivator for installing that kit, once the shiny logo, website, letters, home filters and so forth have been paid for.

The big issue is that no one knows how much this is going to matter. Ofcom's original estimate was 760,000 houses impacted, and 30,000 losing Freeview entirely, but set-top boxes have improved since then and AT800 is keeping busy testing lots of gear and talking to the operators about roll-out plans.

We do know that Channel 60 will be the Freeview frequency most affected, and UK Free.tv has a useful map showing which Freeeview transmitters are using that slot, but until the networks start deploying we won't know how bad the problem is, or if £180m will be enough to fix it. ®

* AT800 has been in touch to point out that, in a late change to the 4G licence process, its funding was tacked onto the auction prices, so the £180m spending pot will be collected from winning mobile telcos in addition to the £2.3bn in 4G licences.