Power Line Carrier Communication (PLCC), is an approach to utilize the present power lines for the transmission of knowledge. In today’s world each house and building has properly put in electricity lines. By using the present AC power lines as a medium to transfer the knowledge, it becomes straightforward to attach the homes with a high speed network access purpose while not putting in new wirings.
This technology has been in wide use since 1950 and was mainly used by the grid stations to transmit info at high speed. currently a days this technology is finding wide use in building/ home automationas it avoids the necessity of additional wiring. the information collected from completely different sensors is transmitted on these power lines thereby conjointly reducing the upkeep price of the extra wiring. In some countries this technology is additionally used to give net connection.
The idea of using an existing medium to send the communication signals is as recent because the telegraph itself. however it had not been possible till the recent decades. the primary vital step within the field was once 2 patents were issued to american telephone and Telegraph Company within the name of ‘Carrier Transmission over Power Circuits’ in 1920. when four years later in 1924 2 different patents were filed for the systems sending and receiving communication signals over 3 part power lines.
Harsh characteristics of the power cables were the key problem in additional development. Researchers were involved to overcome the unpredictable characteristics of the ability lines. Since the first 1980, spread spectrum cable communication was the most focus of the analysis. This technology is currently developed much better than that initial improvement and is promising a reliable utilization in home automation and security systems.
Applications of PLCC
PLCC technology may be deployed into differing types of applications so as to supply economic networking solutions. thence merging with alternative technologies it proves helpful in several areas. These area unit few key areas wherever PLC communications are utilized:
- Transmission & Distribution Network:PLCC was first adopted in the electrical transmission and distribution system to transmit information at a fast rate.
- Home control and Automation: PLCC technology is used in home control and automation. This technology can reduce the resources as well as efforts for activities like power management, energy conservation, etc.
- Entertainment:PLCC is used to distribute the multimedia content throughout the home.
- Telecommunication:Data transmission for different types of communications like telephonic communication, audio, video communication can be made with the use of PLCC technology.
- Security Systems:In monitoring houses or businesses through surveillance cameras, PLCC technology is far useful.
- Automatic Meter Reading– Automatic Meter reading applications use the PLCC technology to send the data from home meters to Host Central Station.
The communication device used for the communication over the power lines could be a electronic equipment, normally called power line modem (PLM). It works as each transmitter and receiver, i.e., it transmits and receives knowledge over the facility lines. an influence line electronic equipment not solely modulates the info to transmit it over the facility lines and however conjointly demodulates the info it receives from the facility lines. By using modulation techniques, binary knowledge stream is keyed on to a carrier signal so coupled on to the power lines by PLM. At the receiver finish another PLM detects the signal and extracts the corresponding bit stream.
The above image shows the working of a PLCC system. data is processed before transmission on power lines consistent with the on top of figure. initial knowledge is modulated & filtered and so by using couplers, it’s sent over the facility lines.
PLC Transceiver is that the key part of a PLCC system. it’s the device that transmits & receives information to & from the ability lines and acts as a hub between the ability stations and our Computers/Network utilization devices. they’re wired with the electrical voltage lines reception or business and work on 2 modes – transmit mode and receive mode. In transmit mode, they simply receive information from receiver finish put in on an equivalent network and any transmit them. In receive mode, they work the other approach.
A number of companies provide PLC transceivers and other networking devices for PLCC communication. A PLC transceiver is shown in the following image.
Modulation & Superimposition
As mentioned earlier, characteristics of the power line channel continuously vary with time and load. therefore standard modulation techniques like ask, FSK or PSK can’t be utilized with them. PLCC desires a way that may influence the unpredictable attenuation and section shifts.
Modulation techniques that prefer lower frequency ranges of thirty five kc to ninety five kc will perform higher as compared to those using the complete obtainable band. OFDM (Orthogonal Frequency Division Multiplexing) is that the modulation technique that’s utilized in HomePlug specification network appliances. In OFDM, data is modulated on to multiple carriers, wherever every carrier occupies its own frequency within the vary of four.3 to 20.9 MHz. Incoming bit stream is demultiplexed into N range of parallel bit streams every with 1/N of original bit rate that are then modulated on N orthogonal carriers. By using multiple carriers at a time, the modulation technique uses the obtainable spectrum most with efficiency. throughout the transmission, every frequency is monitored and if any interference, noise or information loss happens, the responsible frequency is removed. but this system doesn’t perform well once an oversized attenuation and jam happens within the channel, however still it may be terribly economical relatively.
How signals are superimposed on Power Lines?
There are two different ways by which we can connect a PLC unit with the power lines – capacitive coupling and inductive coupling.
In capacitive coupling, a capacitor is used to put the modulated signal on to the network’s voltage wave form. differently is inductive coupling that employs an inductor to couple the signal with the network’s wave form.
No physical connection is needed to ascertain inductive coupling. This makes it safer as compared to capacitive coupling. but this methodology has higher tendency to lose the signal throughout coupling.
Important Technical Parameters in PLC Communication
Noise on Residential Power Circuit (RPC):
A variety of noises may occur during the communication caused by the home appliances. Following are some of the types:
1. Noise synchronous to the power system frequency (50Hz or sixty Hz) – this kind of noise is generated because of completely different quite shift devices.
2. Noise with a sleek spectrum – The sources of such style of noise are the appliances that don’t seem to be in operation synchronously with the ability line frequency. for instance the little motors with many windings will generate such style of noise.
3. Single Event Impulse Noise – shift of devices, that contain a electrical device, generates such style of noise. the rationale is sudden discharge of the capacitor within the RPC.
4. Periodic Noise – the kind of noise is generated by fluorescent lights, tv receivers etc.
These are some ways to reduce the noise in between the communication over power lines:
a. Implementation of Forward Error Correction (FEC) codes with interleaving will reduce the noise in class one, 2 and 3.
b. Frequency Hopping with the FEC coding is implemented to deal with the unknown frequencies.
c. Whereas modulating the signal on to the power lines, tv line frequencies ought to be avoided.
Signal to Noise Ratio:
Signal to Noise Ratio (SNR) is a measurement of quality of the signal. It indicates the amount of the noise in a signal. SNR can be formulated in the following way:
SNR = Received Power / Noise Power
Increasing SNR suggests that increasing the performance of the communication system. By applying noise filters on unit appliances, the noise going in the power system is reduced. but it’ll increase the price of the appliances however could be a higher resolution to boost overall performance.
Signal attenuation is largely the reduction in strength of the signal. a proof attenuation of about 100dB/Km happens for low voltage power lines and 10dB/km for top voltage lines. It creates a necessity of continuous repeaters over a fixed distance. variety of things that are responsible for signal attenuation include distance, time, frequency of the signal, etc.
Automatic Meter Reading using PLCC technology is sort of helpful because it saves loads of human efforts and additionally makes the complete system a lot of economical. the automated meter reading system consists of 3 parts, namely, Multifunction Node (MFN), Concentrator & Communication Node (CCN) and Operation & Management System (OMS).
Different components and their inter-connections are shown in the figure.
MFN is a unit installed in household meters, either incorporated within the meter itself or externally connected to that. Its perform is to require reading of the meter on an hourly basis and store it during a memory chip. CNN is another half that manages all MFNs at intervals a selected space and collects meter readings from all MFNs. it’s typically put in on substations and desires a pc. the pc is put in with Operation and Management System (OMS) that more manages all the info and meter readings from CNNs.
PLCC Technology in Home Automation
In modern homes, there’s a huge demand of causing digital info, audio, and video everywhere the house. Running new wires to support this may increase the burden and price of maintenance. to beat this, PLCC is that the right option to implement home automation construct. Home automation or additionally called good Home technology may be a assortment of systems and devices in a home that have a capability to act with one another or perform on an individual basis so as to be optimized in best means. using PLCC technology, existing power wirings of the home is wont to connect home appliances with one another moreover like web.
Architecture of a PLCC primarily based home automation system is shown within the higher than image. varied home appliances are connected within a loop through the prevailing power cables. This technology will connect every device with the network that is connected to an AC outlet. All appliances are connected with a centralized panel that controls them.
Proper standardization makes a technology comprehensive and deployable. A few standards pertaining to PLCC exist in different parts of the world.
- European Committee for Electrotechnical Standardization (CENELEC) Countries from the Western Europe formed customary|a typical|a regular|a customary} referred to as CENELEC standard to standardize the problems and issues associated with power cable communication. This commonplace defines standards for allowed frequency ranges and output voltages for the communication over power lines.
A frequency range of 3 to 148.5 KHz is allowed for the communication and this range is further divided in 5 sub-bands. These are according to the following table:
|3KHz – 9KHz||This range is restricted to the Energy Providers.|
|A-Band||9KHz-95KHz||Restricted to the energy providers and their concession holders|
|B-Band||95KHz-125KHz||Restricted to the energy providers customers. There is no access rule defined for this frequency range.|
|C-Band||125KHz-140KHz||Restricted to energy providers customers. Simultaneous operations on multiple systems are possible for this frequency band, A protocol named Carrier Sense Multiple Access Protocol is defined for this using a frequency of 132.5KHz.|
|D-Band||140KHz-148.5KHz||Restricted to customers. No access protocol is defined for this band.|
- Federal Communications Commission (FCC)
FCC standardizes the frequency ranges and transmitted power ranges for the power line communications in North America. The allowed base frequencies range from 0 to 530 KHz.
- HomePlugPowerline Alliance HomePlugPowerline Alliance is a group of corporations dedicated to boost the technology for the networking and communication over power lines. In Gregorian calendar month 2001, 1st specification named HomePlug one.0 was launched. the quality uses a physical layer protocol (PHY) supported 128 equally divided carrier OFDMs (Orthogonal Frequency Division Multiplexing) from a frequency vary of zero to 25MHz. It uses concatenated Viterbi and Reed Solomon writing for payload information, Turbo product codes for management information and BPSK, DBPSK, DQPSK or ROBO modulation with a cyclic prefix for modulation of the info.
- IEEE 1901
Institute of Electrical and electronics Engineers (IEEE) expressed a regular named IEEE 1901 for prime speed power line communications. This cluster was shaped in 2005 and gave its 1st customary in 2010 which includes 2 completely different physical layers, 1st one supported OFDM modulation and also the alternative one supported riffle modulation. Network devices that use only OFDM physical layer won’t be practical with the device that employ wavelet physical layer.