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The challenges of in-building wireless coverage
Is it less of a black art now?
By Bryan Betts, Techworld | Techworld
Published: 01:00 GMT, 08 July 08
Attempts to make buildings more energy-efficient in terms of heating and cooling could backfire badly on the networking front, if radio expert Daniel Lewing is to be believed.
Lewing is technical director at Innova Wireless, and a specialist in in-building radio frequency (RF) coverage. He says people will end up having to install additional radio hardware of their own - plus additional wired uplink capacity to support it. But he adds that if done right, this could be a good thing rather than a cost-sink.
"Environmental codes - insulation for energy efficiency and so on - mean RF will get worse," he explains. "For instance, K-glass windows can heavily attenuate signals, as can the sticky films that prevent glass from shattering.
"I don't think building owners know yet that by making buildings energy-efficient, your RF coverage is worse. So you need to install in-building coverage and fund that."
"In-building coverage is still something of a mystery - people are afraid of it," he adds. "Typically they'd go in and install a cellular system for the four network operators, then an FM system, then maybe TETRA... So you're seeing a lot of [wireless] traffic going through, and your roof looks like a porcupine."
The next problem is the huge range of wireless frequencies in use and affected. Lewing says it's not quite as bad as in tunnels (another of his specialist areas - he was lead architect on projects for the London DLR and Heathrow Express) where "you can have everything from 200MHz to 1.5GHz," but it's pretty complex, and getting more so.
That's partly because as wireless technologies evolve, they're having to use what spectrum they can get - and while the technologies are typically international standards, the spectrum allocations are not. Instead, a specific technology might be allocated a few MHz here and a few MHz there, with the specific frequencies varying from country to country.
As an example, Lewing highlights the band planning - or lack of it - for US cellular telephony. "It's all over the place!" he exclaims. "PCS is five [separate] blocks, 850MHz is another seven blocks... And now you can have mobile repeaters too, on trains for instance, which means you have to change blocks at a border."
He argues though that in-building coverage doesn't have to be the RF equivalent of spaghetti cabling - and it could even become a commercial advantage.
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