Varsha Mohite Tejas Kandgaonkar

ABSTRACT
After evolution of wireless technology, classical Public Switched Telephone Network (PSTN) suffered through the drastic change. As a result of it, approximate 80-90% wired telephone networks are replaced by wireless network. But due to wireless network humans are nowadays facing various problems such as sleep disturbances, heart palpitations, migraines, and general poor health due to electromagnetic radiations. So there is need to switchover towards some existing wired network for communication. This leads to a new approach of green computing by using the existing power lines for the communication. This paper covers the working mechanism of power line communication, its modulation techniques and its applications. This paper will also give the general idea about the components for PLC based network elements.
KEYWORDS
Green Computing, PLC, Power Line Communication, Power Line Networking, Green Networking
INTRODUCTION TO POWER LINE COMMUNICATION
Power Line Communication (PLC) is a technology for the communication which provides the facility to send and receive data over existing wired network of power lines [1]. It is sometimes called as Internet over Power Line (IPL).
Fig 1 Power Line Communication

Power Line Communication is now became a need of today’s modern digital era due to following reasons:

Slackening of telecommunication.
Deregulation of electricity utilities.
Increasing growth of digitization in every premise.
Power grid control.

PCL categorized into two categories as Narrowband PLC and Broadband PLC as follows [2],

Narrowband PLC

Narrowband PLC works at very low frequency range of 3-500 KHz with data rates from few 100s of kbps to several kilometers. Due to the application of narrowband PLC in smart grid technology, nowadays it is area of interest of many researchers.

Broadband PLC

Broadband PLC is last-mile solution for internet and networking through power lines. It has very high data rate and no any additional wiring is required for it, as it uses existing wired network. Thus this technology is serving as effective technology for Home Area Network (HAN).
This way of communication through existing wired network of power lines provides following features:

Lower cost for construction as it is using existing wired communication media.
Provides high speed, high capacity, and long distance communication.
It cannot be affected by electric fields or magnetic fields.
It can be used for protection, system control and equipment automation.

DEVELOPMENT PHASES
The leading company in the field of power line communication based devices and services KEPKO KDN [5] has given the brief business record as below:

Power line communication (PLC) trial service (Nov. 2004 ~ Jul. 2005, Remote metering, transformer monitoring, and internet service for 1,500 households in Daegu and Daejeon regions)
Energy saving system construction using PLC technology (Feb. 2005 ~ May. 2005, Constructed street lights and in-building lights control system for Korea South-East Power and Bundang Combines Cycle Thermal Plant)
Constructed integrated metering network based on power line communication (PLC) technology (Oct. 2005 ~ Dec. 2005, Electricity and gas remote metering system for 190 households in Gyeongnam region)
PLC lighting control system for Younghung Thermal Power Plant (Dec. 2005 ~ present, Constructed lighting control (street light, turbine building, and high pressure building) system for Korea South-East Power Co Younghung Thermal Plant)
Established industry-university online education infrastructure based on PLC technology (Dec. 2006 ~ Dec. 2007 Constructed and PLC home network for Korea Polytechnics education infra, and provided education and training support)
Power line communication (PLC) based second remote metering trial service (Aug. 2007 ~ Dec. 2007, Constructed PLC based remote metering system for 5,000 household in Uijeongbu and three other regions)
Constructed Power line communication (PLC) based integrated remote metering system (Aug. 2007 ~ Sept. 2007 Electricity, water, and gas metering system for 100 households in the South Seoul Business Unit (Mokdong)
Lighting energy saving system expansion construction using power line communication (Sept. 2007 ~ Dec. 2007 Constructed expansion system in Busan Combined Cycle Thermal Plan of Nambu Power Plant (main control building, chemical building, CWP building, material building)
PLC long distance transmission equipment supply (Apr. 2007 ~ Sept. 2007, Delivered couplers for long distance communication using high voltage lines for six business premises including KEPCO Jeju branches)

PROBLEMS WITH PLC AND PROPOSED SOLUTION
The current power lie networks are not designed for communication. PLC has the impairments like high attenuation, significant potential interference and the noise which is generated by all loads connected to the grid. With the application of OFDM modulation scheme these problems can be minimized. Encoding technique should be applied to achieve high data rates.
PLC NETWORK ELEMENTS

PLC Modem

PLC modem is used to connect you communication device with the power line as a transmission medium. It performs the similar functionalities of the general modem.

PLC Base Station

A PLC base station is used to connect PLC to its backbone network.
Other than this PLC gateways, repaters and coupling are also essential.
OPERATING MECHANISM
Like normal communication process, in Power Line Communication also sender modulates data and sends towards the receiver through the transmission media. At the receiving end receiver demodulates the received signal to read it. But only change is that the communication medium is the power line. PLC does not require any kind of extra cabling mechanism. By using PLC virtually all power-plugged devices can be controlled or monitored.
From the network oriented point of view, 7-layered OSI reference model consideration is essential. Some PLC chips serves as only physical layer. It can be also used as Digital Signal Processor (DSP) with a clean software consciousness of the Medium Access Control sub layer and Physical Layer.

MODULATION TECHNIQUES
Various modulation techniques can be used in PLC such as Orthogonal Frequency Shift Keying, Binary Frequency Shift Keying, Frequency Shift Keying and Spread Frequency Shift Keying. In the table below these modulation techniques are compared by using two important parameters, complexity and bandwidth.

OFDM gives highest data rates and FSK offers lowest complexity. Thus current trend is to move towards the combination of OFDM and FSK.
APPLICATIONS
Earlier, we saw that PLC is widely used in the Smart Grid and in micro-inverters. PLC can be used in other applications like lighting (e.g. traffic light control, LED dimming), industrial (e.g. UPS communicating to a network device, irrigation control), machine-to-machine (e.g. vending machines, a hotel’s reception-to-room communication), telemetry (e.g. offshore oil rigs), transport (e.g. Electronics in cars, trains and airplanes) and indeed, applications of PLC are only limited by one’s creativity.
The major applications of power line communication [5] include:

High-speed internet and Home Network

High-speed internet
Home network
VoIP
Integrated metering (electric, water, gas, hot water, heating)
Security, alarm

Power IT

Remote metering
Distribution automation
Street light control
Unmanned substation surveillance
Underground utility conduit monitoring
SCADA
Air conditioner control
Energy saving lights control for power plant

Misc Applications

Traffic signal control
Road monitoring
Emergency phone
Forest fire monitoring
Elevator control

SUMMARY AND CONCLUSION
REFERENCES
[1] DOSTERT, K. Powerline Communications. Prentice-Hall PTR, 2001, ISBN 0-13-029342-3.
[2] AHOLA, J. Applicability of power-line communicationsto data transfer of on-line condition monitoring ofelectrical drives. Thesis for the degree of Doctor ofScience (Technology). Lappeenranta University ofTechnology, Lappeenranta 2003, ISBN 951-764-783-2,ISSN 1456-4491.
[3] KOSONEN, A. Power line communication in motorcables of variable-speed electric drives − analysis andimplementation. Thesis for the degree of Doctor ofScience (Technology). Lappeenranta University of Technology, Lappeenranta 2008, ISBN 978-952-214-641-0, ISBN 978-952-214-642-7 (PDF), ISSN 1456-4491, 2008.
[4] HRASNICA, H., HAIDINE, A., LEHNERT, R.Broadband Powerline Communications Networks.England: Wiley, 2004. 275 pp. ISBN 0-470-85741-2.
[5] https://www.kdn.com/home3/we/gs/WEGS_0106.jsp?toMenuNum=510