cumulative radiated emissions from metallic broadband data distribution systems dr i d flintoft dr a...

Cumulative Radiated Emissions From Metallic Broadband Data

Distribution SystemsDr I D Flintoft

Dr A D PapatsorisDr D Welsh

Prof A C Marvin

York EMC Services Ltd.University of York

Scope

Sky Wave

Ground Wave

Space Wave

200 km 1500 km5 km0 km

ionosphere

3-30 MHz

0.1-3 MHz

average UK ground

London

0.1-30 MHz

Romesuburban rural

Near Field

Contents

• Overview of PLT and xDSL technologies

• Modelling methodology

• RF launch models and measurements

• Sky wave propagation of PLT & VDSL

• Ground wave propagation of ADSL &VDSL

• Spectrum management

• Conclusions

Spectrum and Technologies30 kHz 300 kHz 3 MHz 30 MHz

Low Frequency (LF) High Frequency (HF)Medium Frequency (MF)

Ground Wave

Sky Wave

ADSL (25 kHz-1.1 MHz) VDSL (1.1-30 MHz)

DPL (2.9 & 5.1 MHz)

Space Wave

Power Line Telecommunication (PLT)

• Propriety systems

• PowerNET: 9-95 kHz (EN50065)

• Digital Power Line (DPL)

• Frequencies: 2.2-3.5 & 4.2-5.8 MHz

• 2 Mbit/s channels demonstrated

• Uses low voltage (LV) network

Mains Network Topology

Secondary Substation

Transformer

250 m

Primary Substation

Transformer

50 single phase services off each distributor

Medium Voltage (MV)

Network

To High Voltage

(HV) Network

Low Voltage (LV) Network

= Data Terminal

DPL Cell

Physical Structure Of LV Network

• Underground and overhead distribution

• Armoured cable• Conditioning units (CU)

may be used

data port

LV network

internal mains

network

Conditioning Unit (CU)

Armoured Cable

CU

substation

CU

LV network

MV network

data network

Network

Input Power For A DPL Cell

• DPL cell – coherently excited segment of network

• Physical channel shared by all users in cell• Multi-user access scheme: TDMA• Power spectral density from terminal

= –40 dBm/Hz = 1 mW in 10 kHz bandwidth

• 10 kHz = typical HF AM radio bandwidth

Digital Subscriber Line (xDSL)

• Overlay technology enabling broadband services on telephony metallic local loop

• Symmetric and asymmetric upstream/downstream data rates

• Data rates up to 50 Mbit/s (VDSL)• CAP, QAM, DMT modulation techniques

Telecommunications Network

cross connect

cross connect

MDF

exchangefootway

junction box

underground drop

overhead drop

underground distribution

overhead distribution

4 km

1.5 km

300 m

50 m

= Data Terminal

xDSL VarietiesTechnology Deployment Frequency POTS

Splitter

Cable

ADSL FTTEx 25 kHz - 1.1MHz Yes single pair

ADSL Lite FTTEx 25 kHz - 552 MHz No single pair

VDSL FTTCab 0.3 - 30 MHz Yes? single pair

SDSL FTTEx DC – 784 kHz No multi pair

HDSL FTTEx DC – 784 kHz Nomulti pair & single pair

FTTEx = Fibre To The Exchange, FTTCab = Fibre To The Cabinet

Physical Structure• Bundles of unshielded twisted pair

(UTP)• Designed for POTS – up to a

few kHz• Cable balance – degrades with

frequency• Network balance – interfaces• Splitters• Three wire internal cabling

Balance of UTP

(New cable under controlled conditions)

0 2 4 6 1 0F req u en cy (M H z)

8 0

6 0

4 0

2 0

0B

alan

ce (

dB)

Input Power For xDSL

ADSL VDSL (FTTCab)

Downstream Upstream Downstream Upstream

Frequency

(MHz)0.138 - 1.104 0.138 - 0.276 1.104 - 10.0 1.104 - 10.0

PSD (dBm/Hz)

-36.5 -34.5 -60 -60

Power in 10 kHz (mW)

2.2 3.5 0.01 0.01

Modelling Methodology• Identify coherently excited network

elements• Determine the radiative characteristics of

these network elements• Construct an effective single source for

cumulative emissions – pattern & power• Use these effective sources in propagation

calculations

RF Launch Models

• Numerical Electromagnetics Code

• Sommerfeld-Norton lossy ground model

• Common-mode current model

• Predict antenna gain and radiation efficiency of the network elements

• Underground cables not considered these will be conservative estimates

Network Elements

xDSL

PLT

Overhead Drop (Splitter)

Overhead Drop (No Splitter)

N Storey Building (N=1,2,…, 10)

House Main Ring Street Lamp

3N m

6 m

10 m

Antenna Patterns For xDSL

• At low frequencies (ADSL) patterns are omni-directional

• Model using an effective short vertical monopole -1.5

-1.3

-1.1

-0.9

-0.7

-0.5

-0.3

-0.1

0 60 120 180 240 300 360

Azimuth (Degrees)

Fie

ld S

tre

ng

th (

dB

uV

/m)

Drop 1

Drop 2

Storey 2

Storey 5

Storey 10

Normalised gains at 1 MHz

Validation Measurements

• Measurements on UTP aerial drop cable

• Balanced and unbalanced connections

• Results used to calibrate the NEC launch models

Receiver

Coaxial cable feed

Balun

6 m

Plastic pole 100 load

POTS UTP

130 m

Measured Balance Parameters

Frequency

(MHz)

Measured Efficiency

(dB)

NEC Efficiency

(dB)

Effective Balance For NEC Model (dB)

Unbalanced Connection

Balanced Connection

Unbalanced Connection

Balanced Connection

2.2 -55 -79 -19 36 60

3.0 -46 -74 -17 29 57

4.3 -47 -87 -14 33 73

5.9 -40 -79 -11 29 68

7.0 -30 - -10 20 -

Cumulative Radiated Power

• Digital data transmission is a random process which can be modelled as a noise source

• Cumulative field from incoherently excited network elements calculated by noise power addition (REC. ITU-R PI.372-6)

• Phase effects ignored

Sky Wave Propagation

• Time of day

• Time of year

• Transmitter antenna power

• Transmitter antenna pattern

• Transmitter antenna position

• We have considered transmission on a February evening

ITS (Institute For Telecommunication Sciences)

HF Propagation Software• Package caters for area coverage or point to

point predictions

• Allows choice of several propagation models: ICEPAC, VOACAP, REC533

• We chose to use REC533 model based on advice from RAL and the ITU

• Launch power and antenna pattern

Cumulative DPL Antenna Pattern

enclosing hemisphere

Source patterns shown as hemispheres

DPL Source Power For London

• Power in 10 kHz bandwidth: 1 mW

• Area: 2500 km2

• Size of DPL cell: 0.28 km2 (diameter 600 m)

• Total number of cell: 2500/0.28 8925

• Total input power: 8925 1 mW = 8.9 W 40 dBm

• Antenna gain: –15 dB

• Total radiated power: 40 – 15 = 25 dBm

Coverage Of London At 5.1 MHz

London cumulative antenna Isotropic antenna

0

Subtract 15 dB to read true

dBV/m, .i.e. for 15 dBV/m read 0 dBV/m

Cumulative DPL Sky Wave From Many Urban Areas

• Since the coverage from each urban area is Europe wide we need to sum the field from many urban areas

• Major sources over UK would be the Ruhr area of Germany, London, Birmingham and Manchester

• Total field over UK due to these major sources plus other major UK cities is predicted to be between 5 and 11 dBV/m

• Established ITU noise floor is 8 dBV/m (rural area)

• Drop model without internal cables• Average of 1000 homes per km2

• 25 % technology penetration• Antenna gain of –25 dB (corresponds to

20 dB cable balance parameter)• Terminal input power –60 dBm/Hz or

–20 dBm/10kHz• Total radiated power 13 dBm (20 mW)

VDSL Source Power For London

Coverage Of London At 8 MHz

Subtract 27 dB to read true

dBV/m, .i.e. for 15 dBV/m

read -12 dBV/m

• Sum powers from major UK cities and Ruhr area of Germany

• Cumulative field over UK at 8 MHz is –6 dBV/m in 10 kHz bandwidth

• Established ITU noise floor is 8 dBV/m (rural area)

• 10 dB lower than DPL

Cumulative VDSL Sky Wave From Many Urban Areas

Groundwave Propagation Theory (1)

• Sommerfeld (1909), Norton (1936, 1937)

• (V) fields >> (H) fields

• A(d,f,,) for (V) polarised fields

• Attenuation factor calculated according to ITU-R P.368, originally developed by GEC

),,,,( onpolarisatifdAd

PFME r

t

Groundwave Propagation Theory (2)

• The E-field formula applies to a linear short (h<<) radiative element

• NEC used to determine the equivalent FMPt of radiative structures associated with xDSL

• Calculations done for upstream and downstream mode of transmission

• Radiation patterns omnidirectional for ADSL

• Balance, attenuation of UTPs

Calculation strategy of cumulative emissions (1)

• Electric fields Ei from uncorrelated individual sources add incoherently, i.e.,

• A: area enclosing all radiating sources in m2

• pi: percentage of building type associated with ith radiating source

• Di: density of installations per unit area

• Mpi: fraction of market penetration

• Li: fraction of installed lines used concurrently

m

iiipiii ELMDpAE

1

2


• Step 1. Definition of radiating medium, A=25km2

• The RSS summation, lends itself to an active spreadsheet implementation

m

iiipiii ELMDpAE

1

2


• Step 2. Definition of makeup of city buildings

Di Mpi i Lui

pi density max line market radiative subscriber concurrent concurrent

[%] lines/ m2 number penetration element lines usage % line use

5,00% 0,005 6250 20,00% drop1 1250 10,00% 125

31,00% 0,008 62000 20,00% drop1 12400 10,00% 1240

41,00% 0,006 61500 20,00% drop1 12300 10,00% 1230

17,00% 0,003 12750 20,00% drop2 2550 10,00% 255

1,70% 0,002 850 20,00% storey1 170 10,00% 17

2,50% 0,002 1250 20,00% storey2 250 10,00% 25

1,00% 0,003 750 20,00% storey3 150 10,00% 15

0,50% 0,004 500 20,00% storey4 100 10,00% 10

0,20% 0,005 250 20,00% storey5 50 10,00% 5

0,10% 0,010 250 20,00% storey10 50 10,00% 5

146350 29270 2927

Percentage of 2 storey buildings



Percentage of bungalow houses

Percentage of semi-det. houses

Percentage of detached houses


Percentage of terraced houses

Makeup of radiating area




• Step 3. Specify reference radiating efficiencies, balance and attenuation at frequencies of interest for upstream and downstream transmission

1,0

Rad CF Att PSD Frequency BalancedB [dB] [dBm/ Hz] [MHz] [dB] drop1e drop2e storey1e storey2e storey3e storey4e storey5e storey10e0 10 -36,5 0,1 50 0,006391 0,00586 0,001769 0,006632 0,012668 0,020294 0,029506 0,099175

0 12 -36,5 0,2 50 0,024381 0,022364 0,006746 0,025278 0,048256 0,077249 0,112219 0,37559

0 14 -36,5 0,4 50 0,091679 0,084213 0,025357 0,094806 0,180598 0,28848 0,418136 1,384081

0 16 -36,5 0,6 50 0,197467 0,181758 0,054553 0,203306 0,386215 0,615251 0,889444 2,904588

0 18 -36,5 0,8 50 0,339397 0,313297 0,093527 0,347179 0,65749 1,044215 1,505028 4,834889

0 20 -36,5 1,0 50 0,516229 0,47834 0,141679 0,523571 0,988036 1,563975 2,246684 7,08051

Pt/ Pin, [%]

ATU-C customer end Cable length


• Step 4. Define the appropriate transmission spectral mask, i.e., for ADSL PSD=-34.5dBm/Hz (upstream 138-276 kHz), PSD=-36.5dBm/Hz (downstream 138-1104 kHz).

• Step 5. Calculate the unattenuated electric field for each radiative element, i.e.,

attbalancePP

PP ref

xDSLinref

in

trad

)()/(1 kWPFMmmVE rad


• Step 6. Calculate the appropriate electric field correction factor for each radiative element.

• Step 7. Evaluate the total electric field by performing the RSS summation over all xDSL installations.

).300/)/(log(20)( 1 mmVEdBCF

Test cases and results ADSL(1)• Case 1. A=25 km2, bal=40dB, Mpi=20%, Lui=10%

-50

-40

-30

-20

-10

0

10

20

1 10 25 50 75 100 200 300 400 500

Distance, [km]

AT

U-R

ele

ctri

c fi

eld

, [d

Bu

V/m

]

100 kHz 200 kHz

-80

-70

-60

-50

-40

-30

-20

-10

0

10

20

1 10 25 50 75 100 200 300 400 500

Distance, [km]

MD

F e

lect

ric

fie

ld, [

dB

uV

/m]

400 kHz 600 kHz 800 kHz 1 M Hz

Test cases and results ADSL(2)• Case 2. A=25 km2, bal=30dB, Mpi=50%, Lui=10%

-40

-30

-20

-10

0

10

20

30

40

1 10 25 50 75 100 200 300 400 500

Distance, [km]

AT

U-R

ele

ctri

c fi

eld

, [d

Bu

V/m

]

100 kHz 200 kHz

-80

-60

-40

-20

0

20

40

1 10 25 50 75 100 200 300 400 500

Distance, [km]

MD

F e

lect

ric

fie

ld, [

dB

uV

/m]

400 kHz 600 kHz 800 kHz 1 M Hz

Test cases and results ADSL(3)

• Balance– Radiation levels

increase by a margin equal to the balance difference in dB.

– E(bal2)=E(bal1)+bal, bal= bal1 - bal2

• Market Penetration– E(M2)=E(M1)+M,

M=10log(M2/M1)

• Distance– -20 dB/decade for

f(100kHz - 400kHz)

– -25 dB/decade for f(600kHz - 800kHz)

– -30 dB/decade for f(1000kHz)

Summary of results for ADSLSmall city

(York)Large city

(Leeds)Freq.

[MHz]Typ. Opt. Typ. Opt.

0.1 27.67 7.67 35.45 15.45

0.2 26.91 6.91 34.69 14.69

Small city(York)

Large city(Leeds)

Freq.[MHz]

Typ. Opt. Typ. Opt.

0.4 28.44 8.44 36.22 16.22

0.6 24.86 4.86 32.64 12.64

0.8 21.20 1.20 28.98 8.98

1.0 17.94 -2.06 25.72 5.72

• Emission electric fields resulting from cumulative ATU-R upstream and MDF downstream transmissions at distance 1km away from the effective emission centre.(M=20%, L=10%, Typical bal=30 dB)

Graph of current noise floor, ITU-R P.372

0,00

10,00

20,00

30,00

40,00

50,00

60,00

0,03 0,30 3,00 30,00

Frequency, [MHz]

No

ise

ele

ctri

c fi

eld

, [d

Bu

V/m

]

Winter Summer Spring Autumn

• Median noise electric field at a receiver with bandwidth 10kHz at 12 noon in a residential location in the central UK.

ADSL and current noise floor

• No likely change to the established median electric noise field for the well balanced city (bal=50 dB) model at d>1km away from the MDF centre.

• For the typically balanced city model ADSL fields are predicted above the current noise floor (cnf)– ATU-R field > cnf by 5dB - 10dB at d<2km

– MDF field > cnf by 10dB - 20dB at d<3km

• For distances > 10km, ADSL<cnf

Summary of results for VDSLSmall city

(York)Large city

(Leeds)Freq.

[MHz]Typ. Opt. Typ. Opt.

1 21.43 11.43 27.46 17.46

2 20.67 10.67 26.70 16.70

4 17.97 7.97 24.00 14.00

6 14.39 4.39 20.42 10.42

8 10.73 0.73 16.76 6.76

10 7.07 -2.53 13.50 3.50

Small city(York)

Large city(Leeds)

Freq.[MHz]

Typ. Opt. Typ. Opt.

1 17.94 7.94 23.96 13.96

2 17.18 7.18 23.2 13.20

4 11.52 1.52 20.50 10.50

6 10.90 0.90 16.92 6.92

8 7.24 -2.76 13.26 3.26

10 3.98 -6.02 10.0 0.0

• Emission electric fields resulting from cumulative NT-LT upstream and LT-NT downstream transmissions at distance 1 km away from the effective emission centre. (M=20%, L=20%, Typical bal=20 dB.)

VDSL and current noise floor• No likely change to the median electric noise field

for the well balanced small city (bal=30 dB) model at d>1km away from the emission centre.

• For the typically balanced city model VDSL fields are predicted above the current noise floor (cnf):– NT-LT field > cnf by 10dB - 20dB at d<1.5km– LT-NT field > cnf by 5dB - 15dB at d<1.5km

• For distances > 5km, VDSL<cnf.• Radiation diagrams of radiative elements give rise

to significant space wave component.

Spectrum management issues• AM broadcasting in band 6 (MF)

– For ‘good’ quality reception• 88dBV/m, 74dBV/m, 60dBV/m for typical

city/industrial, city/residential and rural/residential areas, respectively.

– AM transmitter serving designated metropolitan area enclosed by a 50km radius in UK.=15, =10mS/m, Pt=10kW • PR=30dB, thus interfering field 44dBV/m• xDSL(d>1km)< 44dBV/m, but Gaussian in nature

– For rural locations near xDSL fields important

Spectrum management issues• Digital MF broadcasting

– DRM consortium preliminary specification• Narrow bandwidth (max 10kHz), thus:

– very efficient source coding scheme [MPEG-4 AAC]

– multi-carrier modulation to overcome multipath, Doppler, [OFDM]

– high state linecode modulation scheme, [QPSQ, 16QAM, 64QAM depending on service requirements]

• Protection ratios:– AM interfered with by DM, [f/kHz=0, PR=36dB]

– DM interfered with by AM, [f/kHz=0, PR=0dB]

– DM interfered with by DM, [f/kHz=0, PR=15dB]

Spectrum management issues• Digital MF broadcasting

– DRM consortium preliminary specification• Carrier-to-noise ratios:

• C/N of 24dB for BER=1x10-5 is at least required.

CHANNELMODEL

CHANNELTYPE

PROPAGATIONMODE

C/N FORBER=1X10-4

Channel 1 AWGN Ground Wave,LF, MF

14.9

Channel 2 Ricean withdelay

Ground Wave,MF

16.0

Channel 3 USConsortium

Sky Wave, HF 22.7

Channel 4 CCIR poor Sky Wave, HF 21.7

Spectrum management issues

• Power savings of 4-8dB can be made by DM transmitters, for same daytime coverage.

• xDSL(d<1km)>C/N, near xDSL ?

• assessment of xDSL mux and mod techniques

Spectrum management issues• AM transmitters to be phased out by 2020

– Lower PR could be used, 10-15 dB less than the currently assumed for AM, thus:

• reduced radiation of digital transmitter power

• much quieter EM environment

– If xDSL>planned interference value:• DM power must increase (financial implications?)

• concerted actions of broadcasting authorities to restore the service

• xDSL near fields at remote locations?

xDSL and aeronautical services

• Services likely to be affected are:– Radiolocation & mobile communications

• NEC simulations show a significant space-wave propagation component for f>1MHz– most radiation is directed towards elevation

angles ranging between 30 and 60 degrees

• Space wave stronger than ground wave

xDSL and government services• Services likely to be affected are:

– Military mobile communications in HF• low data rate systems work even 8 dB below

ambient noise in a 3 kHz receiver bandwidth• 9.6 kbps and above data rates at 3 kHz bandwidth

are standardized requiring a minimum 33 dB C/N ratio

• 3 - 5MHz, critically important for short/medium length communications paths at night when other HF frequencies do not work

Conclusions (1)

• Active spreadsheet tool for RA• Preliminary calculations suggest:

– AM and DM broadcasting may be unfavourably affected

• xDSL(d<1km) & selected areas• xDSL near fields need to be assessed• lower PR for DM mean very low power Tx resulting

to a much quieter EM environment, fossil fuel savings and reduction in greenhouse gases

Conclusions (2)• Preliminary calculations suggest:

– Aeronautical services may be unfavourably affected

• xDSL(d<1km) & selected areas• Further study is needed

– cumulative space wave emissions– technical and operational characteristics of aeronautical

NDBs, current and future mobile communications

– Government services may be unfavourably affected

• Mobile communications• Further study is needed

Conclusions (3)• It is therefore provisionally suggested that

xDSL emissions should be contained at a maximum level of 20dB above the established radio noise floor near the effective radiation centres (d=1km). (For the UK lower values than those in the ITU-R P.372 can be used.)

cumulative radiated emissions from metallic broadband data distribution systems dr i d flintoft dr a...

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