What is TV White Space?
Latest news for TV White SpaceTelevision is transmitted in chunks of radio signal which have gaps in between, to stop them interfering with each other.
In the UK, TV uses the Ultra High Frequency (UHF) radio band from 470MHz to 790MHz, and for Freeview, channels are grouped together in ‘multiplexes’ (or ‘muxes’) about 8MHz wide.
With more than 400MHz to play with and just six muxes, that should be lots of free space, but Freeview has a patchwork of multiplexes spread across the whole UHF TV band, so that the BBC, ITV, Channel 4 and Channel 5 can have regional news and advertising.
The only other users are radio microphones for live performances and TV, which have a small slice of the UHF TV band set aside.
The UHF frequencies are extremely valuable because they can travel long distances and penetrate into buildings, so there’s lots of demand to use them for other things like mobile broadband. That’s why some Freeview space above 800MHz is being sold to 4G mobile broadband operators, and some frequencies above 700MHz could be sold for 5G in 2018.
It’s also possible to use the space between Freeview muxes at low power, so there’s no interference with our TV pictures.
This is TV White Space Spectrum, but it needs a careful approach to make sure white space devices don’t cause problems.
What can TV White Space be used for?
The most obvious candidate is broadband, especially in rural areas where it’s very expensive to lay fibre-optic cables to remote homes and businesses, but white space radio could reach them cheaply.
Electricity, gas and water providers would also like to use white space devices to transmit automatic meter readings, or to report faults on the network or at the customer’s property. They don’t need very high data rates, so they can transmit at low power.
In urban areas, white spaces could be used for city-wide wireless hotspots, carried via WiFi or 4G LTE mobile.
White space WiFi at very low power is also an ideal candidate for home and office local networks, and for wireless HDMI to replace cables between your TV and digital TV box, Blu-ray player or games console.
How will TV White Space devices work?
UK communications regulator Ofcom has decided that White Space Devices could go ahead if they’re smart enough to find the white space and set a power level that won’t interfere with Freeview.
Ofcom (and their counterparts in other countries) has proposed an online directory of legitimate UHF radio users, which a white space device could check against a GPS location fix to see which frequencies and power levels are free to use.
The database will break the UK down into 100m squares also be automatically updated by other white space devices on a first come, first served basis.
White space device manufacturers won’t need a licence, but they will need to meet a specification and pay a registration charge to access the white space databases approved by Ofcom.
In most situations there will be ‘master’ white space devices, such as broadband routers or hot-spot hubs, and ‘slave’ devices such as mobile phones or TVs. The master device will check the database to work out its frequency and power settings, then transmit it for slave devices to pick up and set themselves up.
Signals between master and slave devices will have to be encrypted, and the master device will be able to send a ‘kill switch’ signal to shut down slave devices if there are reports of interference. Slave devices will also shut down if they lose contact with the master, but they will be able to communicate with other slaves as long as the master device is active.
When will TV White Space devices and services begin?
After this, there will be further consultation with European regulators and the existing UHF users to draw up the final technical specifications for white space devices, while the first white space spectrum databases are set up and approved by Ofcom.
If it all goes smoothly, the first devices and services could be available by the end of 2013.
- Google, Microsoft and BT take lead roles in UK’s White Space broadband trials
- Ofcom’s Freeview white space broadband pilots aim for national launch in 2014
- TV White Space broadband could go live in late 2013
- White space wireless trial points the way to smart dustbins and faster rural broadband
- BT to test drive ‘white-space’ broadband in Cornwall
The gaps between Freeview signals could be filled with new broadband services by the end of 2013.
Communications regulator Ofcom has set out rules for devices which can use the space between Freeview broadcasts for services from rural broadband to automatic meter readings.
Called TV White Space, it’s a potential goldmine for new devices that can sniff out unused radio frequencies and transmit without interfering with Freeview.
Ofcom has been working on White Space technology since 2007, and hopes the rules will open up some of the most useful frequencies in the radio spectrum.
“Location-aware wireless devices, assisted by databases which provide information on white space availability taking into account existing licensed use, offer the promise of opportunistic access to under-utilised frequency bands around the United Kingdom for innovative and useful services,” said Ofcom’s TV White Spaces consultation.
“We believe that such database-assisted operation can also be a key enabling technology for the efficient and dynamic sharing of spectrum in a variety of frequency bands.”
BT has been testing white space rural broadband technology as part of the Superfast Cornwall project, while the BBC, Sky, BT, Microsoft, Nokia, Samsung, and Virgin Media took part in a 10-month trial of the technology in Cambridge.
If the plans win public and industry approval in the UK, and get a green light from European regulators, the white space devices and services could launch in late 2013.
November 23, 2012 (image John Steven F./Flickr)