Reg comments

UK to make White Space devices legal

Can anyone can make them practical?

The feedback from Ofcom's consultation on White Space has convinced the regulator to push ahead of Europe and get deployments by 2013 – if the technology can be shown to work.

Ofcom received 25 non-confidential responses to its consultation, which was published in November last year. Based on those comments the regulator is to prepare a Statutory Instrument that will make the use of White Space licence-exempt – like 2.4GHz. But Ofcom will also take on board some of the comments and start thinking about how the supporting databases will be run and about who will run them.

Six companies apparently expressed interest in running databases, with varying degrees of enthusiasm. White Space use will be largely architected on a hub, or "access point" system, and the hub is required to check with an online database for a list of TV-broadcast frequencies which aren't being used locally. The database replies using a standard format – based on the hub location, height, and model (so the spectrum mask can be allowed for) – enabling the hub to pass that information onto its slaves and get a network operating.

Ofcom wants to see competitive databases which will offer the same data but will be differentiated by value-added services, but how that will be paid for remains a mystery. In the United States, Google offered to run a national database for free, but most companies reckon they'll get paid by manufacturers of White Space devices, who'll fold the cost into the retail price of the device.

That model prevents peer-to-peer communications, and makes mesh networks really hard to do. Several of the respondents reckoned something could be done about that, and Ofcom has promised to look into it.

The regulator will also be looking into incorporating a kill switch into the database protocol, so a device can be required to switch off when interference is detected. There's also the dodgy assumption that all wireless microphones are 1.5m (about 5ft) from the ground.

That assumption is important as what we call "white spaces" are actually very grey, already being used by the theatrical luvvies and Big Brother contestants alike for their wireless microphones. Ofcom's modelling assumes that such users don't propagate far as they are at ground level, but the PMSE (Programme Making & Special Events) crowd have pointed out that they have been known to mount scaffolding on occasion, so Ofcom has promised to think about that.

Mobile White Space users, on the other hand, will be able to ascend to any altitude as there's no reliable technology for monitoring their height (especially as slave devices won't necessarily have GPS, even if a signal were available within a tower block), so that's another thing for Ofcom to take on board.

What the regulator won't be doing is waiting for Europe to catch up. European standards on White Space are coming, but are expected to take a few years to put together. Neither the UK regulator nor the UK industry is prepared to wait that long, so Ofcom's response (31-page/255kb PDF, short but still surprisingly dull) explains that the regulator is now working to put the laws into place to make the use of White Space technology legal, while it continues to work out if it is actually practical. ®