Editing Power-line communication (section)

== Medium frequency (100&nbsp;kHz) ==

These systems are often used in countries in which it is illegal to transmit signals that interfere with normal radio. The frequencies are so low that they are unable to start radio waves when sent over the utility wiring.

=== Home control (narrowband) ===

Power-line communications technology can use the electrical power wiring within a home for [[home automation]]: for example, remote control of lighting and appliances without installation of additional control wiring.

Typically home-control power-line communication devices operate by modulating in a [[carrier wave]] of between 20 and 200 [[kHz]] into the household wiring at the transmitter. The carrier is modulated by digital signals. Each receiver in the system has an address and can be individually commanded by the signals transmitted over the household wiring and decoded at the receiver. These devices may be either plugged into regular power outlets or permanently wired in place. Since the carrier signal may propagate to nearby homes (or apartments) on the same distribution system, these control schemes have a ''house address'' that designates the owner. A popular technology known as [[X10 (industry standard)|X10]] has been used since the 1970s.<ref>{{cite web |title= The history of X10  |author= Edward B.Driscoll Jr. |url= http://home.planet.nl/~lhendrix/x10_history.htm |access-date= 22 July 2011 }}</ref>

The [[universal powerline bus]], introduced in 1999, uses [[pulse-position modulation]] (PPM). The physical layer method is a very different scheme than the X10.<ref>{{cite web |title= What is Univeral (sic) Powerline Bus? |publisher= Powerline Control Systems, Inc |url= http://pulseworx.com/UPB_.htm |access-date= 22 July 2011 |archive-date= 18 July 2011 |archive-url= https://web.archive.org/web/20110718042743/http://www.pulseworx.com/UPB_.htm |url-status= dead }}</ref> [[LonTalk]], part of the [[LonWorks]] home automation product line, was accepted as part of some automation standards.<ref>{{cite news |title= Echelon Announces ISO/IEC Standardization of LonWorks® Control Networks |publisher= Echelon Corporation |work= News release |date= 3 December 2008 |url= http://www.echelon.com/company/press/2008/lonworksISO.htm |access-date= 22 July 2011 |url-status= dead |archive-url= https://web.archive.org/web/20120407150936/http://www.echelon.com/company/news-room/2008/lonworksISO.htm |archive-date= 7 April 2012}}</ref>

=== Low-speed narrow-band ===

Narrowband power-line communications began soon after electrical power supply became widespread. Around the year 1922 the first carrier frequency systems began to operate over high-tension lines with frequencies of 15 to 500&nbsp;kHz for telemetry purposes, and this continues.<ref>{{cite journal|first=K|last=Dostert|year=1997|title=Telecommunications over the Power Distribution Grid- Possibilities and Limitations|journal=Proc 1997 Internat. Symp. On Power Line Comms and Its Applications|pages=1–9|url=http://www.isplc.org/docsearch/Proceedings/1997/pdf/0563_001.pdf}}</ref> Consumer products such as baby alarms have been available at least since 1940.<ref>{{cite conference|first=R.|last=Broadridge|title=Power line modems and networks|conference=Second IEE National Conference on Telecommunications|year=1989|pages=294–296|location=London UK|url=https://ieeexplore.ieee.org/document/20724}}</ref>

In the 1930s, ripple carrier signaling was introduced on the medium (10–20 kV) and low voltage (240/415&nbsp;V) distribution systems.

For many years the search continued for a cheap bi-directional technology suitable for applications such as remote meter reading. French electric power ''[[Électricité de France]]'' (EDF) prototyped and standardized a system called spread frequency shift keying or S-FSK. (See [[IEC 61334]]) It is now a simple, low cost system with a long history, however it has a very slow transmission rate. In the 1970s, the [[Tokyo Electric Power Company]] ran experiments that reported successful bi-directional operation with several hundred units.<ref>{{cite conference|first=M|last=Hosono|title=Improved Automatic meter reading and load control system and its operational achievement|conference=4th International Conference on Metering, Apparatus and Tariffs for Electricity Supply|pages=90–94|date=26–28 October 1982|publisher=IEE}}</ref> {{As of|2012}} the system was widely used in Italy and some other parts of the EU.

S-FSK sends a burst of 2, 4 or 8 tones centered around the time when the AC line passes through zero voltage. In this way, the tones avoid most radio-frequency noise from arcing. (It is common for dirty insulators to arc at the highest point of the voltage, and thus generate a wide-band burst of noise.) To avoid other interference, receivers can improve their signal-to-noise ratio by measuring the power of only the ''1'' tones, only the ''0'' tones or the differential power of both. Different districts use different tone pairs to avoid interference. The bit timing is typically recovered from the boundaries between tones, in a way similar to a [[UART]]. Timing is roughly centered on the zero crossing with a timer from the previous zero crossing. Typical speeds are 200 to 1200 bits per second, with one bit per tone slot. Speeds also depend on the AC line frequency. The speed is limited by noise, and the jitter of the AC line's zero crossing, which is affected by local loads. These systems are usually bidirectional, with both meters and central stations sending data and commands. Higher levels of the protocols can have stations (usually smart meters) retransmit messages. (See [[IEC 61334]])

Since the mid-1980s, there has been a surge of interest in using the potential of digital communications techniques and [[digital signal processing]]. The drive is to produce a reliable system that is cheap enough to be widely installed and able to compete cost effectively with wireless solutions. But the narrowband powerline communications channel presents many technical challenges, a mathematical channel model and a survey of work is available.<ref>{{cite journal|last=Cooper|first=D. |author2= Jeans, T. |title= Narrowband, low data rate communications on the low-voltage mains in the CENELEC frequencies. I. Noise and attenuation|journal=IEEE Transactions on Power Delivery|date=1 July 2002|volume=17|issue=3|pages=718–723|doi=10.1109/TPWRD.2002.1022794}}</ref>

Applications of mains communications vary enormously, as would be expected of such a widely available medium. One natural application of narrow-band power-line communication is the control and [[telemetry]] of electrical equipment such as meters, switches, heaters and domestic appliances. A number of active developments are considering such applications from a systems point of view, such as [[demand side management]].<ref>{{cite journal|last=Newbury|first=J.|title=Communication requirements and standards for low voltage mains signalling|journal=IEEE Transactions on Power Delivery|date=Jan 1998|volume=13|issue=1|pages=46–52|doi=10.1109/61.660847}}</ref> In this, domestic appliances would intelligently co-ordinate their use of resources, for example limiting peak loads.

Control and telemetry applications include both ''utility side'' applications, which involve equipment belonging to the utility company up to the domestic meter, and ''consumer-side'' applications which involve equipment in the consumer's premises. Possible utility-side applications include [[automatic meter reading]] (AMR), dynamic tariff control, load management, load profile recording, credit control, pre-payment, remote connection, fraud detection and network management,<ref>{{cite conference|first=T J|last=Sheppard|title=Mains Communications- a practical metering system|conference=7th International Conference on Metering Applications and Tariffs for Electricity Supply|pages=223–227|date=17–19 November 1992|location=London UK|publisher=IEE}}</ref> and could be extended to include gas and water.

[[Open Smart Grid Protocol]] (OSGP) is one of the most proven narrowband PLC technologies and protocols for smart metering. There are{{as of?|date=August 2021}} more than five million smart meters, based on OSGP and using BPSK PLC, installed and operating around the World. The OSGP Alliance, a non-profit association originally established as ESNA in 2006, led an effort to establish a family of specifications published by the European Telecommunications Standards Institute (ETSI) used in conjunction with the ISO/IEC 14908 control networking standard for smart grid applications. OSGP is optimized to provide reliable and efficient delivery of command and control information for smart meters, direct load control modules, solar panels, gateways, and other smart grid devices. OSGP follows a modern, structured approach based on the OSI protocol model to meet the evolving challenges of the smart grid.

At the physical layer, OSGP currently uses ETSI 103 908 as its technology standard. This uses binary phase shift keying at 3592.98 BAUD, using a carrier tone of 86.232&nbsp;KHz +/- 200ppm.<ref>{{cite web |title=ETSI TS 103 908 V1.1.1 |url=https://www.etsi.org/deliver/etsi_ts/103900_103999/103908/01.01.01_60/ts_103908v010101p.pdf |website=ETSI Delivery |publisher=ETSI |access-date=16 August 2021}}</ref> (Note: The bit clock is almost exactly 1/24 of the carrier.) At the OSGP application layer, ETSI TS 104 001 provides a table-oriented data storage based, in part, on the ANSI C12.19 / MC12.19 / 2012 / IEEE Std 1377 standards for Utility Industry End Device Data Tables and ANSI C12.18 / MC12.18 / IEEE Std 1701, for its services and payload encapsulation. This standard and command system provides not only for smart meters and related data but also for general-purpose extension to other smart grid devices.

A project of EDF, France includes demand management, street lighting control, remote metering and billing, customer-specific tariff optimization, contract management, expense estimation and gas applications safety.<ref>{{cite journal|first=G|title=Applications of power-line carrier at Electricite de France|journal=Proc 1997 Internat. Symp. On Power Line Comms and Its Applications|pages=76–80|last=Duval}}</ref>

There are also many specialized niche applications that use the mains supply within the home as a convenient data link for telemetry. For example, in the UK and Europe a TV audience monitoring system uses powerline communications as a convenient data path between devices that monitor TV viewing activity in different rooms in a home and a data [[concentrator]] which is connected to a telephone modem.

=== Medium-speed narrow-band ===

The Distribution Line Carrier (DLC) System technology used a frequency range of 9 to 500&nbsp;kHz with data rate up to {{nowrap|576 kbit/s}}.<ref>{{cite web |title= Distribution Line Carrier System |publisher= Power-Q Sendirian Bhd |url-status=dead |url= http://www.powerq.com.my/telecommunication/distribution-line-carrier-system |archive-url= https://web.archive.org/web/20090520004013/http://www.powerq.com.my/telecommunication/distribution-line-carrier-system |archive-date= 20 May 2009  |access-date= 22 July 2011 }}</ref>

A project called Real-time Energy Management via Powerlines and Internet (REMPLI) was funded from 2003 to 2006 by the [[European Commission]].<ref>{{cite web |title=Real-time Energy Management via Powerlines and Internet |work=official web site |url-status=dead |url= http://www.rempli.org/ |archive-url= https://web.archive.org/web/20090214043341/http://www.rempli.org/ |archive-date= 14 February 2009 |access-date= 22 July 2011 }}</ref>

More modern systems use [[OFDM]] to send data at faster bit rates without causing radio frequency interference. These utilize hundreds of slowly-sending data channels. Usually, they can adapt to noise by turning off channels with interference. The extra expense of the encoding devices is minor compared to the cost of the electronics to transmit. The transmission electronics is usually a high-power operational amplifier, a coupling transformer and a power supply. Similar transmission electronics is required on older, slower systems, so with improved technology, improved performance can be very affordable.

In 2009, a group of vendors formed the PoweRline Intelligent Metering Evolution (PRIME) alliance.<ref>{{cite web |title= Welcome To PRIME Alliance  |work= Official web site |url= http://www.prime-alliance.org/ |access-date= 22 July 2011 }}</ref> As delivered, the physical layer is [[OFDM]], sampled at 250&nbsp;kHz, with 512 [[differential phase shift keying]] channels from 42–89&nbsp;kHz. Its fastest transmission rate is {{nowrap|128.6 kbit/s}}, while its most robust is {{nowrap|21.4 kbit/s}}. It uses a [[convolutional code]] for error detection and correction. The upper layer is usually [[IPv4]].<ref>{{cite book|chapter-url=http://www.lit.lnt.de/papers/isplc_2011_hoch.pdf|last=Hoch|first=Martin|title=2011 IEEE International Symposium on Power Line Communications and Its Applications |chapter=Comparison of PLC G3 and PRIME |doi=10.1109/ISPLC.2011.5764384|pages=165–169|year=2011|isbn=978-1-4244-7751-7|s2cid=13741019|access-date=16 May 2012|archive-date=10 August 2017|archive-url=https://web.archive.org/web/20170810045448/http://www.lit.lnt.de/papers/isplc_2011_hoch.pdf|url-status=dead}}</ref>

In 2011, several companies including [[distribution network operator]]s ([[Électricité de France#Distribution network (RTE and Enedis)|ERDF]], Enexis), meter vendors ([[Sagemcom]], Landis&Gyr) and chip vendors ([[Maxim Integrated]], [[Texas Instruments]], [[STMicroelectronics]], [[Renesas]]) founded the G3-PLC Alliance<ref>{{cite web |title= G3-PLC Official Web Site |work= Official web site |url= http://www.g3-plc.com/ |access-date= 6 March 2013 }}</ref> to promote G3-PLC technology. G3-PLC is the low-layer protocol to enable large scale infrastructure on the electrical grid. G3-PLC may operate on CENELEC A band (35 to 91&nbsp;kHz) or CENELEC B band (98&nbsp;kHz to 122&nbsp;kHz) in Europe, on ARIB band (155&nbsp;kHz to 403&nbsp;kHz) in Japan and on FCC (155&nbsp;kHz to 487&nbsp;kHz) for the US and the rest of the world. The technology used is [[OFDM]] sampled at 400&nbsp;kHz with adaptative modulation and tone mapping. Error detection and correction is made by both a [[convolutional code]] and [[Reed-Solomon error correction]]. The required [[media access control]] is taken from [[IEEE 802.15.4]], a radio standard. In the protocol, [[6loWPAN]] has been chosen to adapt [[IPv6]] an internet network layer to constrained environments which is Power line communications. [[6loWPAN]] integrates routing, based on the [[mesh network]] LOADng, header compression, fragmentation and security. G3-PLC has been designed for extremely robust communication based on reliable and highly secured connections between devices, including crossing Medium Voltage to Low Voltage transformers. With the use of IPv6, G3-PLC enables communication between meters, grid actuators as well as smart objects. In December 2011, G3 PLC technology was recognized as an international standard at [[ITU]] in Geneva where it is referenced as G.9903,<ref>{{cite web |title= G.9903 ITU-T Web Page  |work= Official web site |url= http://www.itu.int/rec/T-REC-G.9903-201210-I/en |access-date= 6 March 2013 }}</ref> Narrowband orthogonal frequency division multiplexing power line communication transceivers for G3-PLC networks.

=== Transmitting radio programs ===
{{main|Carrier current}}

Sometimes PLC was used for transmitting radio programs over powerlines. When operated in the AM radio band, it is known as a [[carrier current]] system.