BROADBAND POWER LINE

COMMUNICATION

Submitted by:

Praveen Mittal (2013JTM2532)Manish Bhumarkar (2013JTM2524)

Why not use electrical lines…..!!!!

OUTLINES Introduction Motivation Types of PLC Architecture PLC Technology Background OFDM basics Network Architechture Advantages Important Issues International Standards References

INTRODUCTION Power Line Communications (PLC) is a disruptive communications technology that enables power line infrastructure landlords to deliver a suite of Internet Protocol (IP) based services using their existing power distribution infrastructure.

This technology offers an alternative means for :

• High speed internet access• Voice over Internet Protocol (VoIP)• Video Streaming • Home Networking • Home Automation• Home Security Systems • Telemedicine Applications

Evolution Of PLC :PLC technology developed in 1928 by AT&T Bell Telephone

Laboratories

In the 1990s, development began on broadband over power line (BPL)

MOTIVATION :• The birth and growth of the Internet has accelerated the

demand for digital telecommunications services to almost every premises.

• as Broadband Power Line Access (BPL), is the latest technology to provide broadband Internet access through existing house wiring.

• Every outlet in the home becomes a high-speed Internet access point. Access from the in-home network.

• This technology has the potential to offer benefits relative to regular cable, DSL or wireless connections.

TYPES OF PLC ARCHITECTURE

PLC

POWER BASED

HIGH VOLTAGE PLC

MEDIUM VOLTAGE PLC

LOW VOLTAGE PLC

FREQUENCY BASED

BROADBAND PLC

ACCESS NETWORK

HOME NETWORK

NARROWBAND PLC

PLC TECHNOLOGY BACKGROUND :

BPL systems function by coupling radio frequency energy to the existing electrical power lines .

For deliverance of high speed data communication to customers, technology is based on high density advanced modulation using :

• Orthogonal Frequency Division Multiplexing (OFDM) • Code division multiple access (CDMA)• Forward error correction (FEC)

OFDM MODULATION :• frequency multiplexing scheme utilized as a digital multi carrier

modulation method .

• A large number of closely spaced orthogonal subcarrier signals are used to carry data on several parallel data stream or channel

• Each subcarrier is modulated with a convention modulation scheme.

• Each subcarrier is orthogonal to each other.

frequency

Conventional FDM

frequency

OFDM

OFDM Mechanism :

OFDM Transmitter :An OFDM carrier signal is the sum of a number of orthogonal sub-carriers, with base band data on each sub-carrier being independently modulated commonly using some type of quadrature amplitude modulation (QAM) or

phase-shift keying (PSK).

9

OFDM Mechanism :

OFDM Receiver:The receiver picks up the signal r(t), which is then quadrature-mixed down to baseband using cosine and sine waves at the carrier frequency. This returns N parallel streams, each of which is converted to a binary stream using an appropriate symbol detector. These streams are then re-combined into a serial stream, , which is an estimate of the original binary stream at the transmitter.

OFDM Spectrum

-6 -4 -2 0 2 4 6

-0.2

0

0.2

0.4

0.6

0.8

Normalized Frequency (fT) --->

Nor

mal

ized

Am

plitu

de --

->

OFDM Basics To maintain orthogonality where

= sub-carrier spacing = symbol duration

If N-point IDFT (or FFT) is used Total bandwidth (in Hz) :

fTs

1

fsT

fNW Time

T

Base frequency = 1/TT= symbol period

Advantages of OFDM in BPL : • Severe channel conditions • Narrowband interference• Frequency selective fading

Disadvantages :• High sensitivity inter-channel interference, ICI• OFDM is sensitive to frequency, clock and phase offset• The OFDM time-domain signal has a relatively large

peak-to-average ratio• tends to reduce the power efficiency of the RF

amplifier• non-linear amplification destroys the orthogonality of

the OFDM signal and introduced out-of-band radiation

NETWORK ARCHITECHTURE :

Data Transmission over power line

ACCESS BPL BUILDING BLOCKS : Access BPL equipment consists of:

Injectors: BPL signals may be injected onto MV power lines with the injectors.

Extractors: Provide interface between the medium power

lines & the customers . BPL extractors are usually located at each LV distribution transformer feeding a group of homes

Repeaters: For long runs of MV power lines, repeaters are employed to maintain the required signal strength.

Bridge

Coupler

Backhaul Point

Coupler

BPL MODEM : The signal is received by a power line modem that plugs into the wall.

BPL modems use silicon chipsets specially designed to handle the work load of pulling data out of an electric current.

BPL modem has roughly the size of a commonpower adapter.

It plugs into a common wall socket, and an Ethernet cable running to your computer finishes the connection

ADVANTAGES :• High Speed Internet Access to Rural areas as well.

• There would be no need to build a new infrastructure. Anywhere there is electricity there could be broadband. So cheaper.

• Secure data-encryption: The signals are not in the air where neighbours or others could potentially snoop your service. Power line adapters are sold with encryption turned on . Secured network through a simple password setting process.

• Improves the competitiveness of the market for broadband services.

• One wire offers both power and your high-speed communications needs.

BPL ISSUES :• Interference issue: The system is expected to use frequencies of 1

to 30 MHZ which has been used by radio operators. Power lines are shielded & have potential to interfere with radio communications.

• Harmonics & Intermodulation: The interference caused by BPL harmonics is not reduced even if the fundamental frequency is notched. Intermodulation products are frequently encountered in power lines at bad joints, which readily produce mixing.

• Noise: The power lines are inherently a very noisy environment. Every time a device turns on or off, it introduces a pop or click into the line.

• BPL signals cannot readily pass through transformers, as their high inductance makes them act as low-pass filters.

• The system is based on shared bandwidth, in part due to the tree design of the infrastructure.

INTERNATIONAL STANDARDS

• IEEE 1901, Broadband Power Line Standards.• ITU-T G.9960 Standards.• CENELAC Standards.• ETSI Standards.