Imagine surfing the web or playing multiplayer online games in your local park, a couple of hundred metres beyond the point where your Wi-Fi router signal dies.
Impossible? Right now, yes. But not if white space radio gets off the ground.
White spaces pop up wherever broadcasters fear a conflict with their neighbours. To prevent interference, each TV channel is broadcast at a different frequency within a chunk of the ultra-high frequency (UHF) region of the spectrum. Where two neighbouring cities 鈥� A and B 鈥� are broadcasting distinct channels, each must leave a gap 鈥� a white space 鈥� on its frequency plan corresponding to the other city鈥檚 frequency chunk, again to minimise interference.
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But city A could use city B鈥檚 frequencies at very low power for short-range use, say both the US and the UK鈥檚 broadcasting regulator . That would open the way for a new generation of UHF Wi-Fi routers which would extend the range of home networks, or let cities (PDF), say proponents in the US and UK.
Walls no obstacle
Most routers now transmit only a short distance, using radiation at a frequency of 2.4聽gigahertz 鈥� because that鈥檚 close to the frequency used in microwave ovens, boosting the signal strength to increase the range could pose a health risk. A white space router working at 400 to 800聽megahertz would pose less of a risk even with a stronger signal, while the longer waves produced at these frequencies 鈥� 75 centimetres rather than 12 centimetres 鈥� are better able to pass through walls and other obstacles.
However, although white-space technology has been gaining credence since early 2008, its development has hit a barrier: no one can yet guarantee that white-space devices won鈥檛 interfere with TV signals 鈥� or with the signals from other white-space devices.
The solution is to identify the usable white-space channels. But an early suggestion 鈥� 鈥渃ognitive radios鈥� built into white-space devices that 鈥渟niff鈥� the airwaves for free space 鈥� simply doesn鈥檛 work, says , technology director at Ofcom. The FCC has arrived at a similar conclusion, following tests it undertook on devices made by Intel, Motorola, Microsoft and Philips.
鈥淭he power level they had to detect with 99.9聽per cent accuracy to prevent interference was one-thousandth the power a mobile phone receives at the edge of a mast鈥檚 coverage area,鈥� says Webb.
They know where you live
Some technology firms think it鈥檚 too early to give up on the idea. Luke D鈥橝rcy, an engineer at Cambridge Consultants in the UK, says the company is developing smart technology it claims can detect ultra-weak signals. But Ofcom and the FCC are now pressing ahead with another solution: a white space 鈥済eolocation database鈥� run by the private sector.
In this scenario, every white-space device can connect to GPS to find where it is, and contacts an online database of free frequencies available in its area every time it is switched on. This database will allocate frequencies and power levels so devices do not interfere.
Running such a database could be a politically charged affair, however. In the US, for instance, Google is among the six firms that have applied to run the FCC鈥檚 white spaces geolocation database 鈥� but as the firm delivering YouTube, Gmail and other services to white-space devices, that may be deemed a conflict of interest.
The system could also infringe users鈥� privacy. 鈥淲e don鈥檛 know yet what information your white-space device should supply to the database, for instance,鈥� says Webb. 鈥淥r what information it will send back.鈥� Such issues are now being thrashed out at Ofcom, he told a conference in Reading, UK, in late April: a legal framework has to be established that will allow underperforming database operators to be taken off the job but will keep private data safe.
With these problems to be overcome, it looks like we won鈥檛 be logging on to our home networks from the park any time soon. 鈥淓stablishing the database and approving the white-space consumer devices is going to take until at least 2012,鈥� Webb predicts.
Read previous Innovation columns: Why labs love gaming hardware, Robots look to the cloud for enlightenment, iPad is child鈥檚 play but not quite magical, Only mind games will make us save power, Gaze trackers eye computer gamers, Market research wants to open your skull, Sending botnets the way of smallpox.
