Power Line Communication (Power Line Communication, English abbreviation PLC) technology is the use of Power Line transmission data and media a way of Communication signals. The technology is the high frequency load carrying information on current and then wire transmission accept information adapter to separate from high frequency current and transmitted to the computer or phone in order to realize information transfer.
Power Line communication full name is the Power Line Carrier (Power Line Carrier - PLC) communication, is refers to the use of high voltage Power Line (in the field of Power Carrier) usually refers to more than 35 kv voltage grade, medium voltage Power Line (10 kv voltage level) or low voltage distribution lines) as the medium of information transmission (380/220 v for voice or data transmission is a kind of special communication mode.
Power cat "power line communication Modem", namely the broadband Internet access via the power line Modem commonly known as. Use a home or office existing powerline and formed into a network socket, to connect to PC, ADSL modem, set-top boxes, audio equipment, monitoring equipment, and other intelligent electrical equipment, to transmit data, voice and video. It has the characteristics of plug and play, can pass the ordinary families power line transmission network IP digital signal.
The development Phases
In the past
Power line communication technology appeared in the early 1920 s. Application instance of power line transmission signal, as is power line phone, its application range is within the same power supply circuit of transformer, the electrical signal from a powerline filter down. In 1991, the electronics industry association identified three family bus, power line is one of them. In October 1997, Northern Telecom company announced a digital wire technology development, the technology will make the electric power company can transport on the power line at a rate of 1 MBPS data and voice services. Later, Siemens PLC technology will power bus family is extended to the village of telecommunication access network port, and can transmit data at a rate of about 1 MBPS.
Technological progress has accelerated. By cisco, Intel, HP, panasonic and sharp 13 companies and established "family plug Alliance" (HomePlugPowerline Alliance), is committed to create a common household electrical wiring network communications technology standard.
Europe is not weakness. Information technology show in Hanover, Germany, the German power industry giant RWE power company introduced a new technology named power network, this new transmission technology will be able to all kinds of Internet data transmission via power line signals, thus greatly promote the popularity of the Internet. Users only need to take a few minutes, the special modem with the ordinary wire into the socket, you can surf the web, the speed can also be at 2 million MBPS broadband standard. The Bundestag parliament's upper house recently passed a bill, approved for use to make the Internet information through the power line and power socket on the wall transmission technology.
Japan will make a connection in the 2001 years of technical standards. Kyushu electric power company and the Tokyo electric power company and mitsubishi electric, Fujitsu, panasonic and other cooperation, the development of transmit and receive image through the power line technology, practical products and is scheduled for 2001 years.
In China, in the 1940 s has Japanese production of carrier machine running in the northeast of China, as a long distance scheduling methods of communication. Since 1999, China began to research institute for the high speed PLC is studied, and in August 2001, established the first experiment network in shenyang. Again since December 2001, guodian communications center began to organize the domestic and foreign manufacturers of PLC application experiment in the residential area in Beijing these companies include South Korea Xeline ASCOM (14 Mb/s system), Switzerland company (4.5 Mb/s) system, the Leap (14 Mb/s), the Spanish company DS2. Fujian electric power test research institute (10 Mb/s systems), as well as electricity institute (14 Mb/s system), etc. China's fujian province electric power test research institute developed "digital transmission technology" of the core products - power modem and multiple related products, its transmission rate up to 10 m. The guodian communications center USES the power line communication (PLC) network equipment at home and abroad, a living community in Beijing lnternet access tests have been carried out successfully, and get the ideal effect. With the deepening of the research, PLC also develops to a higher rate. To increase the rate to 100 Mb/s, for example, or even 200 Mb/s. At the appointed time, high speed PLC will make a greater contribution for broadband communications.
The status
Electric power communication network is in order to guarantee the safe and stable operation of power system and arises at the historic moment. It with the power system security and stability control system, dispatching automation system are collectively known as power system safe and stable operation of the three pillars. It is the marketization of power grid dispatching automation, network operations and the basis of the modern management; Is to ensure that an important means of power grid security, stability, economic operation; Is one of the important infrastructure power system. Due to the electric power communication network reliability, protection and control of communication information transmission and the quickness and accuracy of strict requirements, and the power sector has special resource advantage for the development of communication, therefore, most countries in the world of power companies are established in the form of self-built primarily for power system communication network. [1]
Traditional power line carrier communication (PLC), which make use of high voltage transmission line as the high frequency signal transmission channel, limited to transmit voice, remote control signal, such as narrow application range, transmission rate is low, cannot satisfy the demands of the development of broadband networks. PLC is to develop in the direction of large capacity, high speed, at the same time to communication with low voltage distribution network carrier, realize the home users using the powerline phone, Internet and other business. Abroad, such as the United States, Japan, Israel and other countries are carrying out a research into the low voltage distribution network communication and test. By the 3 com, Intel, Cisco, Japan panasonic, 13 companies jointly set up using power line as the transmission medium of Home network to promote group, "Homeplug PowerlineAlliance", has put forward Home (Home) plug-in socket plan, aimed at promoting power line as the transmission medium of digital family (DigitalHome).
There are two problems to be further study:
(1) Hardware platform: mainly includes the selection of proper communication, the communication network structure optimization selection, etc. Way of spread spectrum and OFDM technology and multi-dimensional grid coding modes have their own advantages, which is suitable for DiYaWang remains to be seen, or it can use the idea of software radio for the three ways to provide a unified platform. Power grid structure is very complex, network topology, how to optimize the network structure is also worth studying problem.
The basic principle
When sending, use of modulation technology to user data modulation, the high frequency load carrying information on current, and then transmitted on power line; At the receiving end, take out modulation signal through the filter, after demodulation, can get the original signal, and transmitted to the computer or phone, in order to realize information transfer. PLC end and modem equipment bureau, bureau of end with internal PLC modem communication and connection with the external network. In communication, from the user data into the modem modulation, through user distribution circuit transmission to office equipment, office end to signal demodulation, and then transferred to the outside of the Internet. Concrete two-way transmission power line carrier module design idea: by the modulator, oscillator, power amplifier, T/R in parts, such as switches, coupling circuit and the modem transmission module, the oscillator is a carrier signal for modulator. When firing data, momentum after the issue of the signal from the TXD modulation by the modulator, then modulated signal to the amplifier amplification, after T/R to switch and the modulated signal coupling circuit load to the power line. When receiving data, emission module to send the modulated signal by coupling circuit and T/R to switch into the modem, the modem to extract the original signal after demodulation, and the original signal from the RXD end to the next level of digital devices.
Interface type
Power line communication equipment commonly used interface is as follows:
RJ - 45
RJ - 45 interface is the most commonly used interface, Ethernet RJ - 45 is a commonly used name, refers to the standardization of IEC 603-7 (60), using the defined by the international standard connectors of eight (8) needle position modular jack or plug.
USB
USB (Universal Serial Bus) Universal Serial Bus (USB) is made by Intel, Microsoft and Compaq, IBM, NEC, launched several big manufacturers such as a new type of peripheral interface standards. USB1.1 transmission speed of 12 MBPS, USB2.0 is up to 480 MBPS; The maximum length of 5 meters cable. USB cable with 4 lines, of which 2 line, 2 power cords, can provide 5 v power supply. USB cable is shielded and unshielded two, shielded cable transmission speed can be up to 12 Mbps, more expensive and not shielded cable speed of 1.5 Mbps, but cheap; USB can connect up to 127 by way of series equipment; Support plug and play and hot plug.
Modulation method
Power line communication usually adopts the debugging method for OFDM, namely orthogonal frequency division multiplexing. OFDM is under severe electromagnetic interference of communication environment, technical measures to guarantee the stability of data transmission complete HomePLUG 1.0 specification covers 4-21 MHZ communication frequencies, in this frequency division within the 84 OFDM communications channel. The principle of OFDM is a few communication channel according to the 90 degree phase frequency division, the result is that when a particular channel wave passing zero when the waveform of the adjacent channel is right is the maximum amplitude, thus ensure the channel between the waveform will not overlap, crosstalk by outside interference.