Regulators in the United States and Europe are being lobbied by parts of the industry to reserve the 700Mhz White Space spectrum as another unlicensed band for use by Wi-Fi providers. The spectrum, currently used by analogue TV channels, could be used on an intermittent basis for Wi-Fi services, interleaved in the White Spaces between frequencies used by the TV broadcasters.
Stephen Rayment, CTO of Wi-Fi solutions provider BelAir Networks, argues that regulators should designate the 700Mhz band as unlicensed spectrum. If they do, he says, it will allow Wi-Fi providers to deliver a cost effective solution to meet the demand for broadband in rural areas, as well as enhance capacity for hard pressed mobile network operators in areas of high data demand.
Rayment believes that national regulators are interested in the proposal. ‘The Federal Communications Commission (FCC) in the US is keen for 700Mhz to be another unlicensed band. Before this we had the 2.4Ghz and then 5Ghz unlicensed bands and now we have the 700Mhz band – all of which can be looked at as unlicensed spectrum. I think Ofcom in the UK is also keen on the value of unlicensed spectrum too,’ Rayment told Wireless.
Ofcom has published two consultation papers on the subject and further paper is in the offing, but says it is minded to allow the use of 700Mhz White Space for Wi-Fi in the UK. ‘It’s about using the existing 700Mhz spectrum more efficiently in an intermittent and interleaved way,’ says an Ofcom spokesman.
One way is to use cognitive radio technology, where the device senses the available spectrum not in use at that point in time and at that location, and uses it. The technology is available, but Wireless understands no devices are on the market yet. The other is to set up a database listing available 700Mhz spectrum at any given place and time that could be used for Wi-Fi.
Rayment says that organisations such as Google, Dell and Microsoft are all in favour of bringing on more unlicensed band spectrum, as they are keen to promote more low cost connectivity, which the 700Mhz will provide.
Rayment points out that the use of the existing 2.4Ghz unlicensed Wi-Fi spectrum has grown enormously over the last few years as people realised its usefulness and the technology to exploit it has developed and improved.
‘Twenty years ago 2.4Ghz was considered junk spectrum – it was used for microwaves. But now all the Wi-Fi providers are in that spectrum and it’s being used to improve the user experience by providing unlicensed spectrum to augment the licensed spectrum,’ says Rayment.
Rayment happily admits that as a Wi-Fi solutions provider BelAir is eager to keep the 700Mhz spectrum unlicensed. ‘Our interest is in mobile broadband connectivity to provide the extra capacity where you need it in particular locations. The thing about Wi-Fi is that it doesn’t have the range the licensed band mobile spectrum does. But the great thing about the 700Mhz spectrum is that it can penetrate buildings much better than 2.4Ghz spectrum can.’
BelAir has undertaken Wi-Fi data offloads in New York’s Times Square, co-located with microcells. ‘Today we do our Wi-Fi offload co-located with the cell tower and get into some buildings, but 700Mhz will allow us to get into a lot more buildings,’ says Rayment.
The 700Mhz spectrum is being freed up to some extent as TV channels move from analogue to digital, but others will can continue to use it and that means there are some tricky issues still to be dealt with, according to Rayment.
‘The FCC has been working on it in the USA for some time,’ says Rayment. ‘The 700Mhz band is co-located with wireless microphones used by performers at concerts and some of the TV channels that use it are still in the process of transition from analogue to digital.’
The immediate stumbling block to allowing Wi-Fi providers to use the spectrum (presuming regulators agree to it) is the need to keep the present 700Mhz incumbents happy. TV broadcasters still using the spectrum are worried that Wi-Fi access points (APs) may interfere with their signal.
Rayment says the FCC in the US has said that Wi-Fi users will have to report the position of their APs to a database in the sky. That will tell incumbents if the position of Wi-Fi providers’ APs are interfering with their broadcasts.
Similarly, the FCC has made provisions in its current ruling to allow performers using wireless microphones at concerts to use them in certain places and at certain times.
The good news according to Rayment is that the UK has about 125Mhz of spectrum coming available: one and a half times the amount of spectrum currently available for Wi-Fi; and in the USA it is double that - 300Mhz of spectrum.
Rayment argues that the industry should follow the model used to standardise the current unlicensed band Wi-Fi and make it work for White Space 700Mhz band. ‘The advantage is that the spectrum is readily available, there is no vendor lock in and there is no cost in terms of license fees,’ adds Rayment.
‘There is a lot of vendor interest here,’ he continued, ‘and we want to try and recreate the success of Wi-Fi in White Space. But we need to let chip vendors know what to design and ensure interoperability – that’s the key – and hence, the need to establish a standard.’
Rayment reports that several bodies are working on the standard, but the Institute of Electrical and Electronics Engineers (IEEE) is taking the lead. The standard will be called 802.11AF. He says that the IEEE is looking at a very aggressive timeline and wants to get the standard in place by October 2011.
‘Our angle here is to provide infrastructure for Tier 1 providers,’ says Rayment. ‘They are looking for any means they can to augment licensed spectrum. If 1.5 times more unlicensed spectrum could come available in the UK it will help them solve capacity problems and provide better Wi-Fi penetration of buildings.’
Rayment adds that there is no stand-off between the claims for providing better mobile broadband in rural and capacity enhancement in urban areas. ‘There are not incompatible claims, they are complimentary,’ he says.