modeling of the transfer function of the indoor power line channel stefano galli telcordia...

Modeling of the Transfer Function

of the Indoor Power Line Channel

Stefano GalliTelcordia Technologies [email protected]://www.argreenhouse.com/bios/sgalli

Copyright © 2006 Telcordia Technologies. All Rights Reserved.

Princeton University, ISS Seminars, April 20,2006Princeton University, ISS Seminars, April 20,2006

Telcordia Technologies Proprietary - Copyright 2006.2

Outline of presentation

1) Applications of Power Line Communications (PLCs)

2) Modeling the (indoor) transfer function

a) Time-domain and Frequency-domain models

b) Multi-conductor transmission line theory

c) The Symmetry Property

d) Experimental Results

3) Conclusions


• First applications date back to early 1920s, on HV lines.

• The first standard is the European CENELEC EN 50065, which mandates the use of the frequency range 3-148.5 kHz (1991).

• The first commercial attempt to use PLC for last mile access dates back to 1997, when Nortel announced the NorWeb partnership with United Utilities (a UK power utility company)

• Limited trials of broadband Internet access through power lines were conducted in Manchester and NorWeb prototypes were able to deliver data at rates around 1 Mbps.

• Cost and commercial viability became questionable and the pilot project was terminated few years later in 1999.

• In the past few years, interest in the technology has picked up again and possible applications have multiplied.

Power Line Communications


Power Line Communications – outdoor

(From ADVANCE, March 2005)



Power Line Communications – indoor


Power Line Communications – smart grid apps



Beyond Outdoor/Indoor…

• PLCs allows for easy in-vehicle networking:– In any vehicles (from automobiles to ships, from aircraft to space

vehicles), separate cabling is used to establish the PHY of a local command and control network which is becoming broadband

– The in-vehicle power distribution network may well perform double-duty, as an infrastructure supporting both power delivery and broadband digital connectivity.

– Weight, space and cost savings (aircraft, auto)

• PLCs as the enabler for truly pervasive and ad-hoc networks: Just look around… power is everywhere

– Traffic lights, lamp posts, etc. can easily become network nodes

– Smart appliances for better power utilization


From Brett Kilbourne, UPLC Conference, Sep. 2005


• Interference issues in the HF band• Better understanding is needed, theoretical and experimental work• Modulation and coding can help reducing interference

• There are very few channel models available: lack of general results in communications theory

• For the optimization of any communications system, it is imperative to understand the channel• Modeling the transfer function of the power line channel is non-trivial problem• Until recently, impossible to predict channel on the basis of the topology

• What is the “average” power line channel?• Many differences between countries in the mains grid• Plethora of grounding and wiring practices, wide variability of performance • Channel standardization needed

• High data rates with QoS, robustness, coexistence, security• More work in transceiver “robust” optimization needed • MAC issues for outdoor/indoor coexistence

Open Problems


• International:

– wiring system uses a star (e.g., a single cable feeds all of the wall outlets in one room only) or tree arrangement

– ground bonding at the main panel

• Europe: – two wire (ungrounded) or three wire (grounded) outlets – If three phase supply is used, separate rooms in the same

apartment may be on different phases

• UK exceptions: – special rings: a single cable runs all the way round part of a

house interconnecting all of the wall outlets; a typical house will have three or four rings.

– neutral not grounded in the home

– Old wiring: two-wire 1 phase, neutral and ground share common wire

Inside wiring environment


NM-B

BX



• Wiring and grounding come in many flavors, and this makes channel modeling (modem design) much more challenging.

• However, international harmonization is happening:

– Typical outlets have three wires: hot, neutral and ground

– Classes of appliances (light, heavy duty appliances, outlets, etc.) fed by separate circuits

– Neutral and ground separate wires within the home, except for the main panel where they are bonded

Although complex topologies may exist, today’s

regulations can simplify analysis of signal transmission



SERVICEPANELFEED

LIGHTING CIRCUITSNon-symmetric geometry

for B&W

RECEPTACLE CIRCUITS15-20 amps, branching, and

symmetric geometry for B&W

GROUNDBONDING

EMBEDDED APPLIANCES50 amps, non-branching, and symmetric

geometry for B&W

Wiring and Grounding Practices


RSB

BLK BLK

WHT WHT

GND GND

RTN HOT

RSB

L3 L2

CIRCUIT BREAKERS

SERVICE TRANSFORMER

SERVICE DROP

Wiring and Grounding Practices

Typical service panel, showing Typical service panel, showing bonding between the neutral and bonding between the neutral and

the ground cable through the ground cable through RRSBSB. .

Grounding and bonding has been completely

ignored in indoor PLC modeling


B

0.3 FREQUENCY ( MHz) 30.0

LOS

S

3dB

/DIV

Ground bonding introduces non negligible resonant modes due to pair-mode excitation.

Effects of Grounding on Signal Propagation

Same topology with bonding

Topology without bonding


Two-Conductor Transmission Line Model Hooijen - ISPLC’98

• Straightforward approach, follows TPC/coax modeling• Frequency domain model• Transfer function can be computed a priori

• Limitations:• Knowledge of whole topology is needed • Accuracy of results depend on accuracy of cable models• Incomplete model, presence of third wire not included so that wiring and grounding practices not explicitly accounted for• Some aspects of signal propagations cannot be explained with this model

Channel Modeling Approaches


B

0 5 10 15 20 25 30-25

-20

-15

-10

-5

0

5

Frequency in MHz

Mag

nitu

de o

f Tra

nsfe

r Fu

nctio

n (d

B)

LOS

S

4dB

/DIV


Current Models(no bonding)

Measurements(when bonding present)

Effects of Grounding on Signal Propagation


Multipath ModelPhillips, and Dostert & Zimmermann - ISPLC’99, T-COM’02

The multipath nature arises from the presence of several branches and impedance mismatches that cause reflections.


X A1(f)

A2(f)

LAB

LAY

A

B

Y

B(f)

LXA

Direct path XAY (i=0):

10

0

1 A

AYXA

g

LLd

Secondary paths XABA(BA)i-1Y(i>0):

Bi

ABAA

AYABXA

ig

LiLLid

1221 11

2


The multipath model is a good model, but has some limitations: • modeling is based on parameters that can be estimated only after the actual channel transfer function has been measured

• wiring and grounding practices not explicitly accounted for, but “phenomenologically” included

• computational cost in estimating the delay, amplitude and phase associated with each path (time-domain model) drawback for some indoor/in-vehicle channels.


gi: is a complex number that depends on the topology of the link;

(f) is the attenuation coefficient (skin effect and dielectric loss);

i is the delay associated with the ith path;

di is the path length;

N is the number of non-negligible paths.

N

i

dffji

ii eegfH1

)(2)(



X A1(f) A3(f)

A2(f) C(f)

LAB

LAC

A C

B

Y

B(f)

LCY LXA

Direct path (i=0):

CA

CYACXA

g

LLLd

11 10

0

Secondary paths of Type 1 (i>0):

CBi

ABAA

CYACABXA

ig

LLiLLid

111

21

221

Secondary paths of Type 2 (j>0):

Cj

ACA

CYACXA

ig

LLjLid

11

12

31

Secondary paths of Type 3 (i, j>0):

Cj

ACABi

ABA

CYACABXA

ig

LLjiLLid

111

122

321

21

Adding discontinuities, the computational cost of the multipath model grows very fast


Multi-Conductor Transmission Line ModelGalli & Banwell - ISPLC’01, T-PD’05 Part I and II

• Based on Multi-conductor Transmission Line Theory and Modal Decomposition: takes into account multi-conductor nature of PL cables, as well as wiring and grounding practices.

• Transfer function can be computed a priori• Frequency domain model (limited computational complexity)• Allows to unveilunveil interesting and useful properties of the PLC, e.g.

superposition of resonant modes, isotropy of channel.

• Limitations:• Knowledge of whole topology is needed• Accuracy of results depend on accuracy of cable models

Recent Results on Channel Modeling: MTL



Three-conductor Analysis

• A three-conductor cable supports six propagating modes (TEM approximation): three spatial modes (differential, common and pair) each for two directions of propagation:

• The differential mode current, generally the desired signal.

• The common mode current Icm represents overall cable

current imbalance, which creates a current loop with earth ground. Lossy mode, can be neglected.

• The pair-mode current (flowing between ground and the white/black wires “tied together”). This mode is excited due to certain wiring and grounding practices.

Pair-mode has been completely neglected in previous models


IZV O

IZV O

PROPAGATING MODES

WHERE

MTL Modal Decomposition

C

111

11

02

1

2

1

BIIII 111

gnd

wht

blk

cm

pair

dif

I

I

I

I

I

I

C

12

1

2

1

12

1

2

1

011

AVVVV 111

gnd

wht

blk

cm

pair

dif

V

V

V

V

V

V

Parameters describes shielding by the ground conductor

Parameter describes asymmetry between the hot and return wires, with respect to the ground conductor


SERVICEPANEL

MAINS

BLK BLK

WHT WHT

GND GND

RTNHOT

RS

SERVICE PANEL BONDING

MTL Modeling: bonding


RS

MAINS

GND

DISTRIBUTION

RTN

HOT

MTL Modeling: Measurements



BLK

WHT

VDIFF PULSE GEN

R1

GND

VGND

R1

R2 RSB

7.6m 7.6m

R3

TEST CABLE

TEST CABLE


TTo

T BYBYZAρ shshV112

000

0148

4

148

12

0148

12

148

1

22

22

2

difprSB

pr

difprSB

pr

difprSB

dif

difprSB

dif

ZZR

Z

ZZR

ZZZR

Z

ZZR

Z

(SB)Vρ


dif

pr

dif

SBSB

dif Z

Z

Z

R22)( ε1

4

ε1

81

1

The reciprocal of the scalar reflection coefficientexhibits a simple linear dependence on RSB.


BONDING

FAULT

-1/

dif

Resistance RSB ohms

MTL Modeling: measurements


BLK

GND

WHT

BLK

GND

WHT

1+

1-

1-

Z dif Z dif

Z pr Z pr

Z cm Z cm

I dif

I pr

I cm

1+

1-

1-

I BLK

I WHT

I GND

(Idif + Vdif/Zdif)e-dif

(Ipr + Vpr/Zpr)e-pr

(Icm + Vcm/Zcm)e -cm

Parameters describes shielding by the ground conductor

Parameter describes asymmetry between the hot and return wires, with respect to the ground conductor

MTL Modeling: Modal Decomposition Validation


MTL Modeling: SPICE simulation


MTL Modeling: Measurements

TIME (nsec/div)

DIF

FE

RE

NT

IAL

VO

LT

AG

E (

18

00

mV

/div

) P

AIR

-MO

DE

VO

LT

AG

E (

20

0m

V/d

iv )

EXCITATION

DIFFERENTIAL SHUNT

BONDING/FAULT

IMBALANCE

DIFFERENTIAL SHUNT

GND SHUNT (400mV/div)

FAULT

BONDING


MTL Modeling: Modal Transformer

RSB

Zdif1

I dif1

Vdif1

I pr1

Zpr1

Zdif2

I dif2

Vdif2

I pr2

Zpr2

Zdif3

I dif3

1:2

Vdif3

I pr3

Zpr

HOT

RTN

GND Vpr1 Vpr2 Vpr3

PHANTOM

Differential and pair modes can be modeled as two independent networks of simple two-conductor TLs

strongly coupled at one location through a modal transformer


From MTL Modeling to 2PNs

• MTL was the starting point for the modeling, but it is not a convenient tool for communications engineers.

• The full model requires knowledge of both and .• We can assume =0 since this parameter primarily affects EMC.

• An “average” must be estimated form measurements.

• If we assume symmetry between hot and return with respect to the ground cable along the whole PL link, then we can neglect and no preliminary measurements are then necessary.

• We have shown that this approximation:• still allows for accurate channel modeling

• allows for a convenient representation in terms of 2PNs and transmission matrix formalism

S. Galli, T. Banwell, “A Deterministic Frequency-Domain Model for the IndoorPower Line Transfer Function,” IEEE JSAC Special Issue on PLCs, July 2006



The proposed channel model requires crossing several layers of abstraction:

• Derive the differential mode and pair mode circuit models of power line link • Tie the two modes through a transformer• Describe each circuit models as cascaded two-port networks• Obtain transfer function using transmission matrices

Treat with same formalism

both grounded and ungrounded links


Modeling the PL channel: ABCD matrix modeling

Two-port network (2PN) and ABCD matrix notation:

2

2

2

2

1

1I

VT

I

V

DC

BA

I

V

Two-Port Network

A BC D

ZS

ZLVS V1 V2

I2I1

SLSL

L

S DZZCZBAZ

Z

V

VfH

2)(


Modeling a transmission line as a 2PN:

1) A=D for any frequency;

2) BC for any frequency;

3) Unitary determinant: det(T)=AD-BC=1 (reciprocal 2PN);

4) Recalling the convention on positive currents, T=T –1.

2

2

2

2

1

1I

VT

I

V

DC

BA

I

V

llZ

lZlT

lZ

C

lZB

lDA

o

o

o

o

coshsinh1

sinhcosh

sinh1

sinh

cosh



Modeling shunt impedances along the line:

[Ti+2] [Ti]

[T]

Zinbt

[Ti+2] Zinbt [Ti]

[Ti+1]=[Tbt]

1/1

01

inBTBT Z

T


DCZ

BAZZ

L

LinBT


Modeling series impedances along the line:

10

1 sese

ZT

Zse



The chain rule:

If a link is constituted of several sections, each of which can be modeled as a 2PN, the the overall ABCD matrix of the end-to-end circuit is obtained by multiplying the ABCD matrices of the single portions of the network.

)()2()1( ....... Nffff TTTT



MTL Channel Modeling


NLMains

LXYXY

XYXYXY TTTTTT

DC

BAT ........... 1

)(21

MTL modeling: ungrounded links


MTL modeling: grounded links

NLPanelMains

LXYXY

XYXYXY TTTTTTT

DC

BAT ........... 1

)()(21


1/1

01)(

PanelZT Panel



DCZ

BAZZ

L

LPanel

11

21

...1/1

01

...1/1

01

TTTZ

T

TTTZ

TDC

BA

LLinRight

NLLinLeft

Trans

Trans



25ft 14/2 25ft 14/2 25ft 14/2

25ft 14/215ft 14/2

60ft 6/2

SERVICEPANEL

( X ) ( Y )

MAINS

TX RCVR

Example


25 ft 25 ft

15 ft 25 ft

25 ft

60 ft

ZS=140

15 ft

25 ft

25 ft

25 ft

25 ft

VS

VY

VX

R4

R3

RY

4RSB

RSB

2Vpr

Vpr

FE

Vdif

½Vdif

DIFFERENTIAL-MODE MODEL

PAIR-MODE COMPANION MODEL

BONDING

Example

No ground

bonding

Telcordia Technologies Proprietary - Copyright 2005.

25 ft 25 ft

15 ft 25 ft

25 ft

60 ft

ZS=140

15 ft

25 ft

25 ft

25 ft

25 ft

VS

VY

VX

R4

R3

RY

4RSB

RSB

2Vpr

Vpr

FE

Vdif

½Vdif

DIFFERENTIAL-MODE MODEL

PAIR-MODE COMPANION MODEL

BONDING

Example

With ground

bonding


Transformer

25 ft, 14/2

60 ft, 6/2

25 ft, 14/2

15 ft, 14/2

50 ft, 14/2

25 ft, 14/2

25 ft, 14/2

15 ft, 14/2

25 ft, 14/225 ft, 14/2

YX

36ns 14036ns140

22ns140

36ns140

36ns 140

96ns50

140

21ns58

35ns 58

35ns 58 35ns 58

35ns58

VS

VY

VX

R1

R2

RY

R3

4RS

RS

2Vpr

Vpr

FE

Vdiff

½Vdiff

Example


Transformer

25 ft, 14/2

60 ft, 6/2

25 ft, 14/2

15 ft, 14/2

50 ft, 14/2

25 ft, 14/2

25 ft, 14/2

15 ft, 14/2

25 ft, 14/2 25 ft, 14/2

Y X

(A)

(B)

Vx

Zx

[T25] [T15(BTU)

]

[T25] [T25(BTU)

]

[T25][Tbrk(BT)][T60

(BTS)

]

Vy

(A)

ZB [2 -4][0 -0.5]

[T50(BTU)

]

[T25] [T25][T15(BTU)

]

(B)1/1

01

BZ

Example


XYXY

Y

X

YXY DZZCZBAZ

Z

V

VfH

)(

Applying the chain rule, we finally obtain a single 2PN:

Example

Two-Port Network TXY

A B C D

ZX

ZY VX V1 V2=VY

I2 I1

)(252525

)(1525

)(60

BTUbrk

BTUXY TTTTTTTT BTS

Telcordia Technologies Proprietary - Copyright 2006.520 5 10 15 20 25 30

-25

-20

-15

-10

-5

0

5

Frequency in MHz

Mag

nitu

de o

f Tra

nsfe

r Fu

nctio

n (d

B)

MTL Approach: Better Accuracy

Current models (no bonding)MTL model

LOS

S

4dB

/DIV


B


Channel property: Symmetry

Let us define the forward and backward ABCD matrices:

2

2

2

2

1

1I

V

I

V

DC

BA

I

Vf

T

Two-Port Network

A BC D

ZS

ZLVS V1 V2

I2I1

1

1

1

1

2

2

I

VT

I

V

AC

BD

I

Vb

b

TT fSLSL

Lbf DZZCZBAZ

ZfHfH

)()(



The overalloverall forward and backward ABCD matrices are:

)()2()1( ....... Nffff TTTT

)1()1()(1 ....... fN

fN

ffb TTTTT

However, Tf = Tb iff they share all common eigenvectors

If Tf=Tb, then forward and backward transfer functions are the same: Hf(f)=Hb(f)



oo ZuZu 21 ,

Eigenvectors of ABCD matrices depend on Zo:

Although counterintuitive, cascading two sections of different cables yields to different overall forward and backward matrices !!

Nevertheless, it can be shown that the forward and backward transfer functions of the power line channel are the same regardless of topology if and only if ZS=ZL.(IEEE Trans. on Power Delivery, Part II, July 2005)



0

-20

-10

-30

TR

AN

SM

ISS

ION

GA

IN (

dB

)

FREQUENCY ( MHz)

HXY HYX


• Plethora of grounding and wiring practices, but harmonization of regulations can simplify analysis of signal transmission

• Wiring and grounding practices must be taken into account !

• We have now a better understanding of the physics of channel propagation and predict the channel on the basis of its topology

How do we characterize the “average” link?

Average Channel

Statistical or deterministic approach?


• Several groups are pursuing methods to deduce relevant statistical behavior from ensembles of physical models (Dostert, Zimmerman,etc.).

• Other groups are instead following a deterministic approach based on precise channel models (Sartenaer, Issa, Esmailian, Galli, Banwell, etc.).

• Statistical models do not require knowledge of the link topology nor of the cable models, but require extensive measurement campaign.

• Deterministic models require detailed knowledge of the link topology and of the cable models, but do not require extensive measurements.

• A statistical approach should preserve inherent determinism as much as possible, including correlations between differential and companion (pair mode) models.

• It is likely that several topology elements will be associated with regular features of the transfer function: the ability to correlate these elements with their effect on the transfer function will be helpful in generating good statistical models.

This important property can be obtained by combining both statistical and deterministic models

Deterministic versus Statistical Models


• On the basis of engineering rules, regulatory constraints, it is possible to generate (randomly) a “realistic” topology. This sample topology would represent “a house”.

• For a given topology, we can again randomly generate possible terminating impedances. These variations of the basic topology representing a house represent the variations that can be found within a home.

• We now compute, using a deterministic model, the transfer functions of the sample topology with the sample terminating impedances for every pair of plugs.

• We compute the “capacity” of all the computed transfer functions between pair of power plugs (nodes)

• We can now build a CDF with the rates per home, as a function of the percentage of plugs within the home.

• We can then average again over the homes, and extract meaningful statistics, e.g. delay spread, attenuation, etc.

Hybrid procedure


Concluding Remarks

• We have today a better understanding of the PL channel

• PL channel more deterministic than originally thought– Determinism should be exploited for transceiver optimization

• Plethora of grounding and wiring practices, but harmonization of regulations can simplify analysis of signal transmission

– Wiring and grounding practices must be taken into account

• Lack of traditional research funding has kept PLC research out of academia, so that most work has been done within an industrial environment and has been directed towards winning skepticism

– Lack of a solid theoretical approach

• System modeling and optimization is challenging– Wide variability of environment

– PLCs is one of the most inter-disciplinary fields we have


8-3SUB-PANEL

FEED

1:3 SPLIT

1WAY2×3WAY

4-WAYRELAY

SOME CIRCUITS WILL ALWAYS BE DIFFICULT!!

14-2 14-2-214-2-2

12-314-3

14-212-2

12-2 (FEED)14-2

Epilogue…


Back-Up Slides…


World Trends in PLCs



Coexistence Issues

• There is no demarcation between access and in-home power line cables it is a bus running from sub-station transformer to every plug in the home

• Access signals and in-home signals must co-exist

From Mike Stelts (CEPCA), UPLC Conference, Sep. 2005


• Power line cables are a shared medium, like coax cable and unlike DSL

• Signals in your home become interference for your neighbor, and viceversa

• Not only complicated MAC problem, but also security issues

Coexistence Issues

From Mike Stelts (CEPCA), UPLC Conference, Sep. 2005


high voltage level: 110..380 kV

medium voltage level10...30kV

low voltage distribution grid3 Phases: 230V, 400V

LV transformerstations

supply cells up to 350 households cable length 100...400m

transformerstation

European Power Supply Network Structure

From Klaus Dostert, Keynote Talk, ISPLC 2005


Single phaseSingle phase: hot/neutral connectors (sometimes separate “earth” wire)

– typical for residences 240V (UK) or 220V (rest of EU), but harmonization process towards 230 V (±10%)

Three phase:Three phase: three hot wires and one return – 230V/400V (typical for homes in Germany, Sweden and

Finland), but sometimes 127/220V (Finland and Belgium), and 230V and no neutral in the supply - outlets are wired between two phases (Scandinavia)

European power distribution details

Typical access network in Europe is composed of LV lines (underground cables)


high voltage level: 110..380 kV

1st medium voltage level10…30 kV

low voltage distribution gridsingle or split phase supply125V, 250V many LV transformers

transformerstation

2nd medium voltage distribution level 6 kV

small supply cells few households per transformer cable length 100m grounding of 3rd wire

American Power Supply Network Structure

From Klaus Dostert, Keynote Talk, ISPLC 2005


Single phaseSingle phase: hot and neutral connectors

– 120V AC, sometimes separate ground wire

Two phaseTwo phase: two hot conductors (opposite polarity) with one neutral.

– Typical 120V AC (120/240V AC split phase), but sometimes two legs of 120/208 wye (apartment complexes)

Three phase:Three phase: three hot wires and one return

– 120/208 V, but rare for homes

American power distribution details

Typical access network in the US is composed of both MV and LV lines (overhead cables)


The Noise Environment

narrowband-interference

backgroundnoise

+

periodic impulsive noiseasynchronouswith the mains

periodic impulsive noise synchronous with the mains

aperiodicasynchronous

impulsive noise

• Colored background noise, significantly higher at low frequencies

• Narrow-band interference consisting of modulated sinusoids, e.g. broadcast radio stations

• Periodic synchronous Impulse Noise (IN), by rectifiers within DC power supplies and appliances.

• Periodic asynchronous IN, by switching of power supplies of appliances

• Aperiodic asynchronous IN caused by switching transients, which occur all over a power supply network at irregular intervals



Colored background noise• Characterized by a fairly low power spectral density,

which, however, significantly increases toward lower frequencies.

• It is caused, for example, by common household appliances like computers, dimmers, or hair dryers, which can cause disturbances in the frequency range of up to 30 MHz.

Narrowband interference• Normally consists of modulated sinusoids, the origin of

which are broadcast radio stations in the frequency range of 1–22 MHz (typical). Figure 2 includes an example of a measurement showing colored background noise together with typical narrowband interference.



From M. Götz et al., IEEE Comm. Mag., April 2004



Periodic Impulsive Noise

• Periodic impulsive noise is further divided into interference synchronous or asynchronous to the mains frequency.

• The synchronous portions are mainly caused by rectifiers within DC power supplies and appliances such as thyristor- or triac-based light dimmers. Generally, repetition rates of multiples of the mains frequency are observed.

• The asynchronous portion exhibits considerably higher repetition rates of 50–200 kHz. Such interference is mainly caused by extended use of switching power supplies found in various household appliances today.



Aperiodic Asynchronous Impulsive Noise

• Mainly caused by switching transients, which occur all over a power supply network at irregular intervals.

• This type of noise contains a broadband portion significantly exceeding the background noise, and a narrowband portion appearing only in certain frequency ranges.

• Impulses containing frequencies up to 20 MHz are not unusual. The broadband portion results from sharp rising edges, whereas the narrowband portions arise from oscillations.

• For the majority of impulses, it was found that amplitudes were around 1 V, impulse widths were in the range of 100 us, and interarrival times were of the order of 100 ms.



From M. Götz et al., IEEE Comm. Mag., April 2004


B

open

B

B

B

(X) (Y)Isolation of Resonant Modes


Isolation of resonant modes

• Ground bonding shunt creates dips at 3.3, 9.9, 16.7, 23.3 MHz; • First bridged tap (R2 = ) creates a dip at 11.4 MHz• Second bridged tap creates dips at 7.0 and 21 MHz• The mains feed (shorted bridged tap, R4=0) creates dips at 4.8,

9.8, 14.9, 19.8 and 24.8 MHz.

When the PL channel transfer function changes because of a change in the boundary conditions,

some features do not change correlation


Isolation of resonant modes

• Although some appliances in the home may be switched on or off several times during the day, some appliances are usually always on and their input impedance varies slowly during the day.

• Some other features of the network can be considered constant during the day: the presence of the mains feed, the bonding, some unused plugs in certain rooms, etc.

• Therefore, it is not unreasonable to assume that the transfer function between two PL modems located at two home network nodes may always exhibit notches at certain frequencies.

• This suggests the possibility that PL modems could effectively try to map particular features of the entire PL home network. This mapping could be accomplished adaptively by continuously transmitting training sequences or by embedding into the modems some a priori information on the topology.

• Over time, it is likely that all the states of the channel are encountered so that the PL modem can infer and, therefore, exploit, the actual state of the network on the basis of the estimated channel transfer function, e.g. with a look-up table.

modeling of the transfer function of the indoor power line channel stefano galli telcordia...

Documents

power lines

power delivery

better power utilization

communications theory

communications system

channel models available

auto plcs

control network