NT internet access via electric lines problems
Streetlamps using the same power supply as Net surfers are acting as aerials and broadcasting downloaded data as high-frequency radio waves. Oops.
newscientist.com
The light programme
By Mark Ward
ultrafast internet access via the electricity
mains...it sounded too good to be true, and perhaps it
was. Trials of the scheme in Manchester have hit an
embarrassing
snag.
Streetlamps
using the same
power supply
as Net surfers
are acting as
aerials and
broadcasting
downloaded
data as
high-frequency
radio waves.
If the current
technology were to be widely used, experts fear that
sections of the radio spectrum could be swamped,
disrupting emergency communications, annoying
amateur radio buffs and interfering with the BBC
World Service. Britain's Department of Trade and
Industry (DTI) has stepped in to mediate between
users of the affected frequencies and NOR.WEB, the
company developing the system.
NOR.WEB is a joint venture between the British
energy supplier United Utilities and the Canadian
telecommunications equipment company Nortel. Its
Digital PowerLine system transfers data between
electricity substations and people's homes using a
1-megahertz carrier wave riding on top of the
50-hertz AC electricity supply (New Scientist, print
edition, 18 January 1997, p 18). The connection from
substation to the Internet is via a conventional
high-bandwidth optical fibre.
The system can download data about twenty times as
fast as the modems used by most domestic Net
useres, and also leaves phone lines free. NOR.WEB
is confident that it can bring about a revolution in Net
access. The company is marketing the technology
worldwide.
The Manchester trials delivered the impressive access
speeds that the system had promised. But the
company's engineers hadn't taken the physical
characteristics of streetlights into consideration. "If
you set out to design radio aerials to fit with this
system, they would look like streetlamps," says Nick
Long, chief engineer with Great Circle Design, a radio
systems consultancy based in Wincanton, Somerset.
"They are just the right vertical length of conductor."
As a result, data being downloaded by users of the
system are being broadcast as radio waves between 2
and 10 megahertz.
If the technology is not modified to remove this
interference, says Long, some sections of the radio
spectrum could become unusable. The online
activities of Net surfers using the system could also,
in theory, be tracked by monitoring the radio
transmissions, he adds.
British users of the affected radio frequencies include
the BBC, the Civil Aviation Authority and even
GCHQ, the government's electronic communications
nerve centre. "We are trying to gauge the level of
risk," says a GCHQ spokeswoman.
Robin Page-Jones of the Radio Society of Great
Britain fears that his members will be hit hardest. "It
could be very difficult in the long term to control
this," he says. "Regulations need to be nailed down
now."
The Radiocommunications Agency at the DTI has
been holding meetings with NOR.WEB and radio
users to resolve the problem, but a solution has not
yet been thrashed out.
Nevertheless, John Seddon, operations director for
NOR.WEB, is confident that the problem can be
solved. "The technology that will be deployed in
volume will be at low power levels in comparison to
the general radio noise that's already out there," he
predicts.
From New Scientist, 30 May 1998
c Copyright New Scientist, RBI Limited 1998 |
