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Power Line Communication
(also sometimes referred to as Power Line Carrier) is a technology which modulates high frequencies onto
existing low voltage (110V – 240V) or medium voltage (1KV – 30KV) power lines.These digital signals can
carry the information and communications that is mostly done with standard Ethernet – TCP/IP protocols.
PLC Modems are capable to modulate and demodulate the signals on the power lines and have specially
designed coupling units to deal with the often harsh conditions on power grids or the electrical cabling
in buildings, which are otherwise more robust and capable of carrying more data than the twisted pairs of
fine copper wire in general use by the telcos.
PLC’s digital signals can be injected
either solely in buildings, to connect and network the electronics in our home
or office through the existing power lines as an Indoor Solution. Additionally,
the signal can be injected in the electricity grid of the utility company
resulting in an Outdoor Solution which then is an access method for the
building owner and a competitive last mile solution. Indoor and Outdoor
solutions can not only be easily combined - they also can co-exist cost
effectively.
In simple terms, the electricity cables are pieces of copper wire of higher carrying capacity than
conventional phone lines in the buildings and PLC is the technology to use
these wires for telecommunication purposes.
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Popular PLC Applications are |
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| High
Speed Digital Internet:
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Fast and secure surfing on the Internet, e-commerce, e-mail, e-banking, and IP-Telephony, a powerful telephone connection using the Internet that offers security and good speech quality. One can also send and receive fax messages. |
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Smart
Homes: |
Remote maintenance and in-house control of Internet enabled household appliances like refrigerators, heating systems, smoke and fire alarm systems. |
| Security
Surveillance Systems: |
With both visual and motion detectors, fire and smoke alarms that can be monitored by the occupants and a security service. |
| Health
Care Services: |
Monitor your children and people who are in need of regular help from any internet connection. |
| Utilities'
Support: |
Online reading of meters for easy up-to-date billing, switching of street lights or ripple control cost effectively and to the ultimate advantage of consumers. |
PLC applications have been around for
decades. Construction workers building high voltage transmission grids were
using telephone devices to communicate in between the poles in the late 1950s.
Utilities round the world have PLC equipment installed for tariff switching and
ripple control. Most popular for the public was the baby phone which came on the
market in the late 1960s in the US and a few years later in Europe and other
countries. This was a little device to be plugged in a power outlet in the
baby’s bedroom picking up the noise via a microphone. A corresponding device
with a speaker could be plugged in somewhere in the house where the parents
where. This way they could monitor the sleep of the baby and got an early alarm
if something was wrong.
When a decade ago world wide the
telecommunication market started to be deregulated, incoming communications
companies sought new methods of distributing data. The founder of Powerline
Communications Ltd achieved patents on the carriage of communications in
proximity to the end users, on powerlines, in the UK and several British
Commonwealth countries.
Following the telecommunications
deregulations the energy sector likewise
commenced deregulation and utilities in Europe, mainly in Germany, started to
look for new revenue channels. At this time the first projects where launched to
develop high speed PLC technology. An early leader was NorWeb a joint venture of
Nortel and United Utilities in Great Britain. They developed the first outdoor
system providing 2Mbps of band width with trial installations in the UK and
Germany. However, for various reasons NorWeb vanished in 1999. At this time the
leading organization was RWE in Germany with its Swiss based partner ASCOM. At
CeBit 1999 they presented a PLC demonstrator installed in a little township in
northwest Germany. This was the starting point of the PLC hype and many
utilities in Europe launched their own projects charmed by the potential of
gaining additional revenues not only out of their existing infrastructure but
also from an already established customer base. At the time many potential
hardware manufacturers entered the scene providing PLC solutions and field
trials were installed all over Europe. After CeBit 2000 featured a huge show
with all the key players being involved in PLC it became popular also in other
countries. First trial installations were done in South America and some Asian
countries. The major breakthrough came after the International
Telecommunications Union (ITU) developed a recommendation to all members how to
deal with PLC from a frequency regulation stand point of view. Following that
PLC was legalised in Europe early 2001 and trial installations moved to commercialization.
Today PLC is a matured technology being
available around the world. Executives and engineers from Powerline
Communications Ltd have been involved in the entire development process not only
in Europe but also in South America and Asia. As a result this company is the
leading service provider in this emerging industry that has worldwide potential
to cost effectively improve communications services.
How does it work?
PLC digital signals are modulated on the
electricity lines of your local utility. The modulation schemes vary depending
on the manufacturer of the PLC hardware and whether it is a broad band or
narrow band connection. For broadband systems today the OFDM modulation scheme
is most widely used. For the outdoor environment, frequencies between 1 - 10
Mhz are used and the data is coded on multiple channels to ensure the highest
possible band width. The number of channels used and the exact coding algorithms
vary with the manufacturers.Depending on the applications desired Powerline
Communications Ltd. chooses different hardware vendors.
The indoor systems are very similar and most manufacturers are starting to use ITU
recommended frequencies in between 10 – 30 Mhz. Such systems usually
provide encryption and VLAN features to ensure security. Outdoor and Indoor
systems can be installed independently and can work together with other
telecommunication services like DSL, Cable, WLL etc. without any problems.
Narrow band systems work in the CENELEC band. The usable frequencies differ from
country to country. For example in Europe frequencies in between 20Khz and 148Khz
are allocated where as in the US the frequencies go from 20Khz to 500Khz. Narrow
band systems are also widely available and usually operate with the FSK modulation scheme.
PLC Services are available in various ways.
Ideally using the power lines to bring the Internet and other communications
services to your home or office from a Powerline Internet Service Provider
utilizing the power grid of the local electricity provider through a PLC Home
Gateway, distributing Internet, telephony or other services into your home or building
to all electrical outlets. A Powerline Home Gateway is a device that enables
communication through the electrical system in a home or office. Each of the computers
and appliances that are plugged in can be networked or access the Internet as well as
power. Physically every power outlet in the building becomes a communication port.
However, alternatively the communication
services might come to the building through DSL, Cable, Satellite, Microwave or
what ever else is available in the area. Also in this case you would have a
Powerline Home Gateway picking up the data from the desired services and inject
it into the electricity cables in the building. Again services can be made
available at every power outlet in the building. Such enables the networking of
all your computers, gaming consoles, TV, Stereos and intelligent appliances.
You are also able to assign single services to predefined devices.
Another feature which becomes available
with PLC is neighborhood networking. This can be enabled by the Powerline Service
Provider if wanted by neighbors to enable kids playing games on their consoles
from one house to the other or if certain equipment will be shared by
businesses or private households to reduce cost.
Today PLC solutions are installed in many countries around the world. Some of them are still in trials but mainly in Europe the roll out is in the commercial phase with huge numbers of subscribers. For that reason Europe is probably the best place to see PLC in action.
However, depending on where you are Powerline Communications Ltd. can provide you with information about the closest point for you to go for a visit. In some European countries or the US you can also find PLC hardware for home networking in electronic or department stores. No matter whether you want to go to Europe or at some other place closer to where you are located we will be glad to arrange a visit or provide you with local contact details.
Is it dangerous?First of all and most important, no not at all. All PLC equipment has gone through extensive testing and complies with the most rigorous safety regulations of the US and Europe. Powerline Communications Ltd. will never use any equipment which is not FCC and / or CE certified. The equipment on the electricity grid and your PLC Home Gateway will be installed by highly trained specialists and certified electricians. The PLC modems you can use for your computer or which ever other device to be networked in the house are as safe as plugging in any other electrical device in your household. In the very unlikely event of a malfunction of the PLC equipment your normal power supply will not be affected and continue as normal. The faulty unit can be exchanged or replaced without interruption to your electricity supply.
What is about radiation?Nowadays the harm of electromagnetic radiation also called electro smog is widely discussed and has created public confusion. Even experts give different views and no long term study has been made to find out the effects of the various frequencies and any resulting radiation. We know for sure that some rays which are used for radar or x-rays have an impact on our health. Also you can be sure to get fried if you position yourself in front of a powerful radio beam operating in the Gigahertz bands. The discussion is also fueled by the question of whether mobile phones are a risk or not.
When it comes to PLC systems by all what we know today and all the studies being undertaken by various laboratories and universities we can say it is absolutely harmless. First of all the frequencies in which the PLC systems operate are not considered to be harmful by present regulatory standards and secondly the PLC systems operate on such a low emission level that the signals can hardly be detected. The electrical wires are usually covered and run through the walls of a building which shields any emission. Equipment in your home like TV’s, computer monitors, microwaves etc. expose you to much higher radiation than PLC hardware does.
Outdoor systems are of no concern where there is underground cabling. Again the signal is completely shielded since the cables are dug into the ground. In the case of overhead cabling there is some emission but signals can only be detected in the very close vicinity of the power line. This is a very different level of emission to cell phone repeaters and other long range wireless systems.
Since the current PLC systems were mainly developed to be first available on the European market they comply with the rigid emission regulations developed by the standards authority ETSI, especially for PLC.
Regulatory IssuesFor narrow band systems world wide the CENELEC band is clearly defined and the frequencies were allocated a long time ago. Although, a legal system from the US would not comply with regulations in Europe and the Pacific region because of the much more liberal approach of the FCC to the subject. Some parts of Asia do have the same frequencies allocated as the US but before installing any system the regional frequencies have to be carefully checked. However, it can be said that European systems can be installed everywhere because they are generally operating in frequencies which are legal everywhere.
In respect to broadband systems, regulations initially were lacking. The unregulated frequency band in between 1 – 30Mhz as now used by PLC systems could freely be assigned by national regulators for whatever service applied for it. In some countries frequencies are occupied by services which no longer exist, or some vital services needing protection are operating in this band. Also in the early 90s, in a project called TETRA, international efforts were made to renew the radio systems from police forces, emergency services etc. from analog to digital. For that purpose the frequency band between 1 – 30 Mhz was targeted. The problem with this band however was that many radio controlled devices like your remote control garage door opener or the remote control toys of your children are also operating in this band. Further, the remote door locks from some car manufacturers are operating in this band. Additionally it came up at the time that some intelligence services tried to occupy frequencies in this band. Therefore it became obvious that the band needed regulation by the international authority.
In 1999 the ITU (International Telecommunication Union) which has representatives from most countries forwarded the first recommendation to national regulators for the frequency band 1 – 30Mhz. This recommendation also included PLC systems. Since at that time Europe was the place where most PLC systems were on a trial, the lobby of the big electricity companies put significant pressure on the politicians. Accordingly it was ETSI (European Telecommunication Standardization Institute) which clearly defined a regulation for PLC. Based on the regulation of ETSI, Germany was the first country to legalise PLC and today many other countries followed that example. However, before installing PLC systems in a country Powerline Communications Ltd. will always approach the national regulator to find out whether it will adapt the ETSI regulation and if there are any exceptions. If necessary the PLC systems can be configured in a way that certain frequencies will not be used if they are protected in that particular country.
Is it used commercially?Yes it is. Germany was the first country in the world starting commercial roll outs of PLC systems. Today many tens of thousands of households all over that country have a broad band PLC internet service. It is also used in schools, universities and other public buildings. Now commercial roll outs can also be seen in Italy, France, Sweden and other countries. Also first attempts for commercialisation are made in South America mainly in Brazil. Furthermore Powerline Communications Ltd is working with utilities preparing to provide commercial systems in some Asian countries which will be launched in the near future.
What band width can I have?The bandwidth discussion is not as easy as it might appear at first glance. This can easily be seen when looking to a connection with a standard 56Kbps modem. It is rare, when dialling up your ISP that the modem will connect with 56Kbps. Depending on the quality of the phone lines the connection speed is much less. Also only the download channel has the theoretical speed of 56Kbps, the return channel operates only at the maximum speed of 33Kbps.
PLC systems have to deal with many obstacles and the sometimes very harsh environments on electricity lines. The operation of your hair dryer in the house can change the performance. Although the majority of the PLC systems deal with the problems very well and can be customized to achieve the maximum bandwidth, the speed can vary from network to network. The differences are not significant but can definitely be measured.
Powerline Communications Ltd. will always install the PLC system that best suits the applications which appropriate for the needs of the end user. If for instance only an Internet connection is wanted it doesn’t make a lot of sense to install a powerful 20Mbps system because neither your ISP nor the Internet itself is capable of that speed. However, PLC systems run as a shared media and therefore the total bandwidth will always be higher than the bandwidth provided to the end user. Also it can be expected that over a 24 hour period slight variations in bandwidth can be measured due to varying noise levels on the power lines. Under normal circumstances the end user won’t recognize these variations.
Narrow band systems today can provide anything up to 300Kbps in full duplex mode which is sufficient for many applications like telephony, fax, alarm, remote control and even Internet if compared to the 56Kbps analog connection provided by a normal modem.
Current broad band systems start at 1Mbps. Most widely used are systems providing between 2 – 10 Mbps depending on the grid conditions and the type of system chosen. If desired, high speed systems up to 40Mbps capable of supporting multi media services like VoD or TV broadcasting, can be installed.
Prior to an installation Powerline Communications Ltd. strongly recommends analysis of the grid conditions in terms of signal to noise ratio. Such enables choice of the right solution which ensures the service applications required are supported by the system and sufficient bandwidth is delivered.
What new developments are pending?Powerline Communications Ltd is working with
manufacturers who are on the cutting edge of producing chips and other technology to
improve capacity and delivery techniques. The industry is fast moving as giants like
Philips and Cisco devote substantial resources to what they know to be an emerging
mainstream industry.
Executives and engineers of Powerline Communications Ltd, both individually and in
association with other research and development agencies have patents pending on the
extension of PLC into the field of short range wireless transmissions so that
battery operated devices such as laptops, PDAs, cell phones and the like, can
connect to each other and to the data on the powerlines within the walls of the
buildings, wirelessly.
© Powerline Communications Ltd. 2002
