Power line communication |
Power line communication (PLC), also called Broadband over Power Lines (BPL) or Power Line Telecoms (PLT), is a wireline technology that is able to use the current electricity networks for data and voice transmission. The carrier can communicate voice and data by superimposing an analog signal over the standard 50 or 60 Hertz alternating current (AC). Traditionally electrical utilities used low-speed power-line carrier circuits for control of substations, voice communication, and protection of high-voltage transmission lines. One example of this technology is SCADA. More recently, high-speed data transmission has been developed using the lower voltage transmission lines used for power distribution. A short-range form of power-line carrier is used for home automation and intercoms.
= Types of PLC technology =
==Indoors/Short Range==
Indoors, the PLC equipment can use the household electrical power wiring as a transmission medium. This is a technique used in domotics for remote control of lighting and appliances without installation of additional control wiring. The HomePlug system is an example of this technology. The X10 (industry standard) home automation system uses power line communication at the zero crossing voltage point in the AC wave.
Typically these devices operate by injecting 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 either be plugged into regular power outlets or else 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.
There are also some very low-bit rate power line communication systems used for automatic meter reading.
==Outdoors/Long Haul==
Utility companies use special coupling capacitors to connect low-frequency radio transmitters to the power-frequency AC conductors. Frequencies used are in the range of 30 to 300 kHz, with transmitter power levels up to hundreds of watts. These signals may be impressed on one conductor, on two conductors or on all three conductors of a high-voltage AC transmission line. Several different PLC channels may be coupled onto one HV line. Filtering devices are applied at substations to prevent the carrier frequency current from being bypassed through the station apparatus and to ensure that distant faults do not affect the isolated segments of the PLC system. These circuits are used for control of switchgear, and for protection of transmission lines. For example, a protection relay can use a PLC channel to trip a line if a fault is detected between its two terminals, but to leave the line in operation if the fault is elsewhere on the system.
While utility companies use microwave and now, increasingly, fiber optic cables for their primary system communication needs, the power-line carrier apparatus may still be useful as a backup channel or for very simple low-cost installations that do not warrant a fibre drop.
==Automotive==
Power-line technology enables in-vehicle network communication of Data, Voice, Music and Video signals by digital means over Direct Current (DC) battery power-line. Advanced digital communication techniques tailored to overcome hostile and noisy environment are implemented in a small size silicon device. One power-line can be used for multiple independent networks. Prototypes are successfully operational in vehicles, using automotive compatible protocols such as CAN-bus[http://en.wikipedia.org/wiki/CAN-bus], LIN sub-bus[http://en.wikipedia.org/wiki/Local_Interconnect_Network] DC-bus[http://www.yamar.com/dc-bus.html]. Automotive Applications include Mechatronics (e.g. Climate control, Door module, Immobilizer, Obstacle detector). Telematics and Multimedia. *Benefits **Saving the Cost and Weight of Ordinary Wiring, **Flexible Modifications **Simplicity of Installation. **Operation over 12V up to 42V power networks
=Broadband over power lines=
Broadband over Power Lines (BPL) aka Powerband is the use of PLC technology to provide broadband Internet access through ordinary power lines. A computer (or any other device) would need only to plug a BPL Modem into any outlet in an equipped building to have high-speed Internet access.
BPL offers obvious benefits over regular s or sound systems, to hook up. However, variations in the physical characteristics of the electricity network and the current lack of IEEE standards mean that provisioning of the service is far from being a standard, repeatable process and the amount of bandwidth a BPL system can provide compared to cable and wireless is in question.
High-speed data transmission, or Broadband over Power Line uses the electric circuit between the electric Electrical substations and home networks. A standard used for this is ETSI PLT .
PLC modems transmit in medium and high frequency (1.6 to 30 MHz electric carrier). The symmetry speed in the modem is generally from 256 Kilobit per second to 2.7 Mbit/s. In the repeater situated in the meter room the speed is up to 45 Mbit/s and can be connected to 256 PLC modems. In the medium voltage stations, the speed from the head ends to the Internet is up to 135 Mbit/s. To connect to the Internet, public utility can use optical fiber backbone or wireless link.
Differences in the electrical distribution systems in North America and Europe affect the implementation of BPL. In North America relatively few homes are connected to each distribution transformer, whereas European practice may have hundreds of homes connected to each substation. Since the BPL signals do not propagate through the distribution transformers, extra equipment is needed in the North American case.
=Technology=
Technology will deliver speeds of up to 200 Mbit/s at the physical layer and 130 Mbit/s at the application layer using HomePlug AV standard (interoperable with HomePlug 1.0 or Intellon proprietary 85 Mbit/s Turbo mode, already available) or proprietary DS2 technology which is based on OFDM modulation with 1536 carriers and TDD or FDD channel access method. DS2 technology may operate between 1 and 34MHz. It provides a high dynamic range (90 dB) and offers frequency division and time division repeating capabilities. These characteristics allow the implementation of quality of service (QoS) and class of service (CoS) capabilities.
=Standards=
Several competing standards are evolving including the s Plug n Power system.
==HomePlug Powerline Alliance==
HomePlug 1.0
HomePlug 1.0 is the specification for a technology that connects devices to each other through the power lines in a home. HomePlug certified products connect PCs and other devices that use Ethernet, USB and 802.11 Wi-Fi technologies to the power line via a HomePlug bridge or adapter - some products even have HomePlug technology built-in. The HomePlug Alliance evaluated various powerline-networking technologies through an industry-wide, open evaluation process that incorporated theoretical analysis, lab testing and field trials. The criteria included 10 Mbit/s data rate, whole-house coverage, robustness and ease of implementation.
HomePlug AV
HomePlug AV was designed to support the high-bandwidth and low-latency demands of several simultaneous streams of HDTV and VoIP, made concurrently available in over 90% of power outlets in a home. The target applications are in-home distribution of audio-video in home-theater and data-networking environments. For this reason, in the given frequency range, HomePlug AV has pushed Shannon-Hartley_theorem to its limit and will provide a 200 Mbit/s class service at the PHY layer. After overhead considerations, the MAC layer will support over 100 Mbit/s.
HomePlug BPL
Broadband Power Line (BPL) refers to a to-the-home technology. Recently, the HomePlug Alliance announced the formation of the HomePlug Access BPL Working Group, whose first charter is to develop the Market Requirements Document (MRD) for a HomePlug BPL specification. Shortly after that announcement, the Alliance made an open invitation to utilities, ISPs, network operators and other interested parties from around the world, to participate in the development of or provide input for consideration in the MRD. In addition to being the roadmap for developing a BPL specification, the MRD will provide input into the resource sharing policy between In-home and BPL uses of powerline technology.
HomePlug Home Automation
Command-and-control applications.
==IEEE==
http://standards.ieee.org/ http://grouper.ieee.org/groups/ http://www.comsoc.org/
IEEE P1901 - Draft Standard for Broadband over Power Line Networks: Medium Access Control and Physical Layer Specifications http://grouper.ieee.org/groups/1901/index.html
The project will develop a standard for high speed (>100 Mbit/s at the physical layer) communication devices via alternating current electric power lines, so called Broadband over Power Line (BPL) devices. The standard will use trannsmission frequencies below 100 MHz. This standard will be usable by all classes of BPL devices, including BPL devices used for the first-mile/last-mile connection (|
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