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How to build a national cellular wireless network for £50m
|22 апреля 2011|
A team of 20 developers in Cambridge wants to build a new radio network covering the entire country, but plans to cut costs by only offering connectivity to silicon-based customers.
The team has set up a company called Nuel with plans to make use of unused TV frequencies ("white spaces"), and is busy designing base stations for national deployment. The idea is to connect up all the electricity meters, cars, e-readers and suchlike over a new national network that the team reckons can be built for around the same amount that O2 spends on its network every couple of weeks.
White Space kit uses the same frequencies as terrestrial digital television, branded Freeview in the UK, but only in locations where they aren't being used to send TV pictures. Freeview can only reuse frequencies with huge geographic separations, so a band filled with TV in London can't be reused in Oxford, but a low-power transmitter in Oxford can use that same frequency for a different application without bothering the Londoners.
Professional wireless microphones have been doing that for decades (in the analogue TV bands before DTV) which is why the PMSE (Programme Making & Special Events) crowd are so upset about exploitation of white space. But despite complaints from Dolly Parton and the Church of England, regulators around the world are dead set on making use of it, with most following the US model of unlicensed devices coordinated through online databases of available frequencies.
How those databases are to coordinate with each other is still under discussion in the US, and the UK hasn’t yet decided who's going to run such a thing, but Nuel's CTO William Webb wrote the book on radio spectrum management and is confident that Ofcom will sort it all out in the next year or two which fits the company's schedule well.
White Space is often presented as being like Wi-Fi, only better, but that's a result of clever marketing by proponents rather than any technical or applicable similarity. White space refers to a series of geographically-restricted radio frequencies rather than any technical standard that requires interoperability; white space bands may be used by everything from TV remotes to broadband internet access, without any potential for them to be compatible.
Broadband internet is the poster child for white space applications, since it only requires two compatible devices (one at each end), but if standard technologies can be adopted then the frequencies have a much greater potential.
Neul is well aware of that, and plans to set up a Special Interest Group (SIG) later this year with a view to defining those standards. The idea is for a client device, embedded in a car, e-reader or washing machine, to listen on various predefined slots within the white space frequency range. The device will only transmit in response to a poll from a fixed base station, that station then uses the online databases to be sure there aren't any local TV transmissions to interfere with.
Enter the £1,000 base station
Nuel reckons it can get the cost of a base station down to £1,000 a pop, multiplied by ten to cover the antenna, installation and backhaul and you've got base stations costing ten grand. Transmission power is limited to one watt, making cells small by TV standards but big compared to phone networks, and putting the cost of a national network well under £50m.
One watt won't give you much in the way of bandwidth, kilobytes rather than megabytes, which is why the company is sticking to machine-to-machine (M2M) connections, though existing operators also want to play in that market.
GSM networks are already being used for M2M connections, exemplified by Amazon's Kindle and its accompanying Whispernet connectivity. But GSM is poorly suited to low power applications, requiring complicated, and continuous, registration and paging signals. Nuel is confident that its meagre energy requirements and simplicity of silicon will win the day, especially as the number of devices goes up and the cost of embedded phones in every one becomes economically impossible.
Not that Neul is just about white space - it also has its eye on the 600MHz band which no one seems to know what to do with. The UK government is set on getting some local TV services into that area, but no one wants to run or watch them. Once that plan dies off the spectrum should pop up for auction and Nuel could well be in the bidding, though that might prove expensive.
This is important as Nuel dosen't have much in the way of money. The company was only set up last year and is still raising first-round funding.
The utility of a national network for M2M communications is hard to deny, but who gets to run that network is more difficult judge. What we can't afford is multiple incompatible networks, as they'll interfere with each other and reduce the utility for all, but the alternative might be an equally objectionable monopoly.
Ofcom seems pretty unsure what to do with the whole ex-TV radio bands, other than those slices which have been harmonised around the world for mobile telephony - thus ensuring cheap kit, and expensive frequencies. The regulator has a new consultation out last Wednesday on that very subject, asking what people think might fit well in the spaces where we used to watch TV.
We might not need talking fridges or connected cars, but they're certainly more interesting than more local TV.