Powerline Communications: Channel Characterization and Modem Design

Powerline Communications:Channel Characterization and Modem Design

Yangpo Gao

Helsinki University of Technology

[email protected] 2005-10-18

Powerline Communications: Channel Characterization and Modem DesignPowerline Communications: Channel Characterization and Modem Design22 Yangpo Gao,Yangpo Gao, 2005-10-18 2005-10-18

Thesis Contents

Table of ContentsIntroduction

PLC Technology Background

Channel Measurement and Modeling

Disturbance over PLC

DMT Based PLC Modem Design

Conclusion

Reference

This thesis is part of project “ PLC controlled LEDs for general lighting system”, which is sponsored by TEKES

Introduction


History of PLC and Motivation of Thesis

What is PLCPLC – Powerline CommunicationsUsing powerline as transmission medium for data communication

History of PLCFrom high voltage (HV) low voltage (LV)Low data rate high data rateControl application multimedia data applications

MotivationCheap “the last mile” solutionHowever, worse channel than other wired networkChannel characterization reliable communications

PLC Technology Background


PLC Technologies

Three network levelsHigh voltage (110–380 kV) Medium voltage (10–30 kV) Low voltage (230/400 V, in the USA 110 V) (my thesis range)

Efficient couplingInductive couplingConductive coupling

Modulation and error correctionOFDM, DMTCDMAFEC


EMC Issues

EMC --Electromagnetic compatibilityThe ability of a device or system to function satisfactorily in its electromagnetic environment without introducing intolerable electromagnetic disturbances in the form of interferences to any other system in that environment, even to itself.

Electromagneticcompatibility (EMC)

electromagneticemission (EME)

Electromagneticsusceptibility (EMS)

Conductedemission (CE)

Radiatedemission (RE)

Radiatedsusceptibility (RS)

Conductedsusceptibility (CS)


Standardizations

PLC standardization bodies

IEC Committee

TC 77 CISPR Product Committees

ITU ISO CENELECAisa and Pacific

organizations FCCRA RegTP

InternationalInternational

RegionalRegionalNationalNational

Channel Measurement and Modeling


Transmission Line Theory

A piece of mains cable can be modeled as following figure

( , )i z tR z

L z

Gz

C z

( , )i z z t

( , )v z t ( , )v z z t

zz z z

R : resistance . L : inductance.G : conductanceC : capacitance

0 0( ) ( ) ( ) z zV z V z V z V e V e

0 0( ) ( ) ( ) z zI z I z I z I e I e

( )( )j R jwL G jwC

00

0

V R jwL R jwLZ

I G jwC G jwC

Attenuationconstant

phaseconstant Characteristic

impedance

Propagationconstant


Channel Measurement Setup

Equipment:Network Analyzer (NA)

Coupling Circuit

Coupling circuitConductive coupling

High pass filter

Galvanic isolation

Over Voltage protection

NA

Cou

pler

Cou

pler

PLCchannel

Transmittest head

Receivetest head

C1

C2

D1

D2 D3 D4

D5To

powerl i neTo measurement

devi ce

T1


10-1

100

101

102

-14

-12

-10

-8

-6

-4

-2

0

2

Frequency (MHz)A

tten

uatio

n (d

B)

1. 0.75mm2 Vulcanize rubber cable

2. 1mm2 Vulcanize rubber cable

3. 0.75mm2 PVC/PVC cable

4. 0.5mm2 PVC/PVC cable

Fluctuation at high frequency

(2)

(3)

(1) (4)

• Rapid fluctuation caused by impedance mismatch

• Maximum of 4 dB attenuation difference @ 100 MHz

rR

rR

Cable transversal

PLC Cable Measurements

Cable Type Size (mm2)

Vulcanize rubber cable (three-wire) 0.75

Vulcanize rubber cable (three-wire) 1

PVC/PVC cable (three-wire) 0.75

PVC/PVC cable (two-wire) 0.5


PLC Channel Measurements

Scenario 1: Internet access and distribution

Scenario 2: Home networking

0 20 40 60 80 100-30

-25

-20

-15

-10

-5

0

Frequency (MHz)

Am

plitu

de A

tten

uatio

n (d

B)

1. socket 12. socket 23. socket 34. 20 m cable

(1 )

(2 )

(4)

(3)

Scenario 1: Network topology is known, or easy to estimate. Channel is simple, and

has few multipath components Scenario 2: Network topology is unknown

or it is hard to define. Channel acts as

black box. A lot of multipath components


Channel Responses

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8-0.2

-0.1

0

0.1

Time (us)

Am

plitu

de

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8-0.015

-0.01

-0.005

0

0.005

0.01

0.015

0.02

Time (us)

Am

plitu

de

0 20 40 60 80 100-25

-20

-15

-10

-5

0

Frequency (MHz)

Ch

an

ne

l att

en

ua

tion

(d

B)

0 20 40 60 80 100-30

-25

-20

-15

-10

-5

Frequency (MHz)

Ch

an

ne

l att

en

ua

tion

(d

B)

FrequencyDomain

TimeDomain

Scenario 1 Scenario 2


PLC Channel Modeling

According to PLC channel multipath phenomenon, channel can be modeled as:

3hL

2

0g 1g 2g 3ghLg

I nput

Output

. . .

. . .

. . .

. . .

1

1

( ) ( )hL

i ii

h t g t

1

( ) ( )hL

i ii

H f r t

( )( , ) id f l

i ir f l a e 0

1 20

( ) ( ) ( )

2 2

R Gd f d f d f

GZRv f v f

Z

0 1( ) ( )d f c c f

Disturbance over PLC


PLC Noise

Noise Classification:Colored background noise

Narrowband noise

Periodic impulsive noise, asynchronous to the main frequency

Periodic impulsive noise, noise, synchronous to the main frequency

Asynchronous impulsive noise

Our concentrationColored background noise

Asynchronous impulsive noise


Noise Measurement setup

Equipment:Oscilloscope

Spectrum Analyzer

Coupler

PLC

chan

nel

Cou

pler

Spectrumanalyzer

(frequency domain)

Oscilloscope(time domain)


Colored Background Noise

Quasi-Static behavior

Statistic information is extracted in table

Can be modeled as:

0 20 40 60 80 100-130

-120

-110

-100

-90

-80

-70

-60

-50

-40

-30

Frequency (MHz)

Bac

kgro

und

Noi

se P

SD

(dB

m)

1. Maximum background noise PSD2. Average background noise PSD3. Minimum background noise PSDCurve fitting

(1) (2)

(3) ( ) 10 (W/Hz)cs b fN f

s b c

Max -94 -80 -0.4

Min -124 -100 -0.6

Average -105 -90 -0.5


Random Impulsive Noise

Caused by frequency bursts generated by electrical devices connected to the powerline.

Statistic information is extracted

0 2 4 6 8 10 12 14 16 18 20 -0.5

-0.4

-0.3

-0.2

-0.1

0

0.1

0.2

0.3

0.4

0.5

Time (ms)

Impu

lsiv

e no

ise

am

plitu

de (

v)

0 200 400 600 800 1000 1200 1400 1600 1800 2000-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

Time (us)

Impu

lsiv

e n

ois

e am

plitu

de

(V)


Other Disturbance

NEXT (Near End crosstalk)

FEXT (Far End crosstalk).

ELFEXT FEXT Cable Attenuation

0 20 40 60 80 100-120

-100

-80

-60

-40

-20

0

20

Frequency (MHz)

FE

XT

Att

enua

tion

(dB

)

1. PLC FEXT2. Cable Attenuation3. PLC ELFEXT4. xDSL FEXT

(2)

(1)

(3)

(4)

Transmi t

Recei ve

NEXT

NEXT Formation

FEXT Formation

Transmi t

Recei ve

FEXT



DMT Technology

Discrete Multi-tone Modulation (DMT)

Advantages:Multicarrier technology – combat frequency selective fading

Dynamic bit loading based on SNR – efficient spectrum utilization

High channel capacity

EncoderConstel l at i on

mappi ng and Toneshuffl e

I FFTCycl i cprefi x

P/ STransmi tter

fi l ter

DecoderConstel l at i onde-mappi ng andTone shuffl e

FFTCycl i cprefi xremove

S/ PRecei verfi l ter

PLC ChannelNoi se



Simulation environment:MATLAB SimuLink

MATLAB DSP Blockset

Simulated channel response

Expected resultBit Error Rate (BER)

0 20 40 60 80 100-30

-25

-20

-15

-10

-5

Att

enua

tion

(dB

)

Frequency (MHz)

Simulated channelMeasured channel

BitSource

AdaptiveLoading

Algorithm

DMTModulator

SpectrumObservation

SpectrumObservation

PLC Channel

NoiseGenerator

DMTDemodulator

BERComparison


Simulation and Performance

0 32 64 96 128 160 192 224 2560

5

10

15

Channel Number

Num

ber

of b

its p

er c

hane

l

0 10 20 30 40 5010

-7

10-6

10-5

10-4

10-3

10-2

10-1

100

SNR (dB)

BE

R

DMT over AWGN channelDMT over PLC channel

Optimized bit loading algorithm

Signal spectrum before PLC channel

Signal spectrum after PLC channel

Modem performancePLC vs AWGN

Publications Related to My Thesis


Publications

More information can be found in my publications:

“Channel modeling and modem design for broadband

power line communications”, Proceeding of ISPLC 2004,

April, Spain

“Broadband characterization of indoor powerline channel”,

Proceeding of ISPLC 2004, April, Spain

“Broadband Characterization of Indoor Powerline Channel

and Its Capacity Consideration”, Proceeding of ICC 2005,

May, Korea

Any Questions?

Thank You!

Documents

Powerline Communications: Channel Characterization and Modem Design