By Contributing Editor, Barry Flynn
TV White Spaces (TVWS) technology could be incorporated into future smart TVs to improve their wireless connectivity, according to Andrew Stirling, a leading TVWS expert.
Stirlingâ€™s comments come in the wake of a decision by the UK regulator Ofcom to open up â€˜licence-exemptâ€™ access to TV White Spaces â€“ gaps in the frequencies used by television that can be shared to offer new wireless applications.
WiFi currently uses licence-exempt spectrum at 2.4GHz band and 5GHz. However, a new standard approved a year ago, IEEE 802.11af, which is closely related to the current 802.11ac variant, can be used in the TV frequencies located between 54 and 790 MHz, which contain the white spaces Ofcom has just licensed. These lower bands offer much better coverage and penetration of buildings than the higher ones.
Stirling is the managing director of the Larkhill Consultancy, which led the successful TVWS trial in Cambridge in partnership with Microsoft, and also chairs the Centre for White Space Communications at the University of Strathclyde, which has conducted separate TVWS trials in Glasgow and the Isle of Bute.
Stirling singles out the provision of rural wireless broadband (trialled on the Isle of Bute) as â€œa very good fitâ€ for the technology, noting that TV frequencies â€œhave very good coverage efficiency for capital input, which makes it very attractive. And, of course, if youâ€™re looking at areas where youâ€™ve got marginal viability of networks, anything that gets the cost of the capital down means that you can actually cover more people for the same amount of public or commercial funds available. So the density of population that you can then support becomes lower.â€
Stirling also believes that â€œone of the good [TVWS applications] for driving the business case of silicon is [â€¦.] in-home or in-office access points, where being able to service all of your gaps means that potentially you donâ€™t need to deploy another extender point.â€
Taiwanese semi-conductor firm MediaTek has already supplied a triple-band WiFi unit to the Glasgow TVWS trial where the third band (in addition to 2.5 and 5GHz) operates in the TV UHF frequencies.
â€œItâ€™s interesting, of course, what sort of future that could mean for TVs with broadband connectivity, which already have UHF hardware,â€ Stirling speculates. â€œWe might see the TV white spaces growing up as part of the WiFi equipment within the set.â€
This could, for example, be used to stream high-resolution video much more reliably to TV sets around the home than it can be at present. Indeed, one of the TVWS trials Ofcom is supporting includes one where Google and London Zoo are using the white spaces to stream live video of the Zoo’s meerkats, Asian otters and giant Galapagos tortoises to YouTube, with a view to helping conservationists monitor and protect endangered animals across the globe.
Quite apart from the new applications Ofcomâ€™s move could engender, it creates â€œa whole new way of accessing spectrum,â€ says Stirling. â€œBasically it provides you with opportunities for sharing spectrum that is otherwise unused, and we know that in Europe there are particularly large amounts of spectrum that are unused for much of the time in many, many places. [TVWS] gives you the potential to unlock those sorts of bands.â€
The way TVWS spectrum can be shared while managing the risk of interference for current users is through the use of geo-location databases which identify locations, frequencies and times where white space devices will not affect them. The databases then tell the devices wanting to use the spectrum what the technical constraints are that they must operate within, applying rules set by the regulator, which put limits on the power levels they can operate at.
This approach allows spectrum to be managed very dynamically, concludes Stirling. â€œYou bring your band, add it to the database, and then the devices have got the capability of working in that new band, and they know which channels they can use and what power level and so on, and itâ€™s very easy to grow the portfolio of spectrum thatâ€™s available for sharing.â€