wise man once said, progress is the path from the primitive, via the complicated
to the simple.
Thanks to Power-line CommunicationsÂ
(PLC), telephoning via the electricity supply network from any power
supply socket to any telephone in the world is possible now.
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.”
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
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
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.