A
wise man once said, progress is the path from the primitive, via
the complicated to the simple. Thanks to Power-line
Communications (PLC), telephoning via the electricity supply
network from any power supply socket to any telephone in the
world is possible now.
"I need to send some
urgent e-mails. Where can I connect my PC to the network?"
Shahid Ali asked the receptionist shortly after his arrival at
his company’s freshly opened branch office. "I know that
when the building was being renovated it was planned to have a
communication socket in every room, but I cannot find one!"
The receptionist’s radiant smile quickly soothed the new
colleague, but her answer almost knocked him for six.
"Every power socket in this building is a communications
connection. And you not only have Internet access, you can
telephone as well."
Difficulties
Overcome
This
scenario could occur in every office building or household in
the not too distant future. Since what was once thought to be
impossible has become a reality: Telephoning via the electricity
supply network from any power supply socket to any telephone in
the world. For a long time even the experts doubted this
development. The objections against a universal network for
electricity supply and communications were overwhelming. The
electricity supply network is considered to be an extremely
demanding transmission channel. Since the signal, which is fed
into the network suffers attenuation on the long path from the
transmitter to the receiver. The greater the distance, the
greater the attenuation. Over and above this the electromagnetic
compatibility of PLC is regarded as a real challenge.
Interference must be avoided. Thus certain frequency bands are
disallowed for wire bound transmission procedures such as PLC,
depending on national regulations.
In principle, it is
possible today for every electricity socket to be turned into an
interface for a PC printer, telephone or other communications
devices. And solutions are available today that offer
communication over the electricity supply network. Vendors claim
that the transmission over the electricity supply network using
PLC is so good that for the first time voice traffic and high
speed data can be transmitted right from the transformer station
to every socket in the building.
The success potential of
the PLC approach does not, however, lie just in the technology
but also in the new services which can be implemented using it.
All devices that are powered from the mains supply are connected
to the same network. Hence diverse new service and applications
come to mind which will combine communications and IT devices
such as the telephone and the PC with traditional electrical
devices. Examples range from facility management, credit card
verification, the control of heating, air conditioning or
ventilation systems, through to electronic newspapers and tele-conferencing.
The broadband PLC system with which Ali’s company will soon be
equipped, permits access to the network from every room in the
building without the need to lay new cables.
The system functions as
follows: In the electricity supply company’s transformer
station, a PLC modem modulates the high frequency signal of the
telecommunications backbone network onto the low-voltage local
electricity supply network over which it is carried into the
building. According to vendors data rates of more than 1 Mbit/s
have already been achieved. This is 20 times the speed of ISDN,
which is 64 Kbit/s. It is important to note that the PLC
solution not only covers the path from the transformer station
to the building but can also connect the mains supply circuits
within the building. Every power socket in the building is thus
connected to the communications network. This brings tremendous
advantages, for example, for a company that needs to install a
local area network in an old building. After all, the in-house
PLC local area network for networking computers and peripheral
equipment can easily be based on the existing mains cabling.
The electricity supply
cables permit solutions with which transmission rates of up to
10 Mbit/s can be achieved. Every PLC modem provides two
transparent interfaces for TCP/IP so that the system can easily
be integrated into existing computer networks.
It is important to ensure
that the further development of PLC does nor result in
proprietary solutions. Rather, an open power-line platform must
be built up with interfaces, which are strictly defined. The
services that are to be offered over the low-voltage power
supply network are then "mounted" on this open
platform. Solutions should also take investment costs into
account. The interfaces of the PLC are oriented to existing
technologies and standards. PLC customers will get an
"Always On" service. It is for this reason that
packet-oriented solutions as used in the Internet, for example,
are used. Equally, the interfaces must also be the customary
ones (Ethernet, USB, etc.). It thus makes sense for PLC
solutions to be created through close cooperation between
electricity supply companies, telecommunications suppliers and
service providers. Then in future there will be: One network for
everything.
Courtesy:
Ascom