Cumulative Radiated Emissions From Metallic Broadband Data Distribution

Cumulative Radiated Emissions From Metallic Broadband Data Distribution Systems Dr I D Flintoft Dr A D Papatsoris Dr D Welsh Prof A C Marvin York EMC Services Ltd. University of York

Scope ionosphere Sky Wave 3 -30 MHz Space Wave 0. 1 -30 MHz Ground Wave 0. 1 -3 MHz London Near Field Rome suburban rural average UK ground 0 km 5 km 200 km 1500 km

Contents • • Overview of PLT and x. DSL 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 Technologies 30 k. Hz 300 k. Hz Low Frequency (LF) 3 MHz Medium Frequency (MF) 30 MHz High Frequency (HF) Ground Wave Sky Wave Space Wave ADSL (25 k. Hz-1. 1 MHz) VDSL (1. 1 -30 MHz) DPL (2. 9 & 5. 1 MHz)

Power Line Telecommunication (PLT) • • • Propriety systems Power. NET: 9 -95 k. Hz (EN 50065) 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 DPL Cell = Data Terminal Medium Voltage (MV) Network Low Voltage (LV) Network Secondary Substation Transformer Primary Substation To High Transformer Voltage (HV) Network 50 single phase services off each distributor 250 m

Physical Structure Of LV Network • • • Underground and overhead distribution Armoured cable Conditioning units (CU) may be used internal mains network CU substation data network Conditioning Unit (CU) LV network Network MV network Armoured Cable LV network CU data port

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 d. Bm/Hz = 1 m. W in 10 k. Hz bandwidth 10 k. Hz = typical HF AM radio bandwidth

Digital Subscriber Line (x. DSL) • • 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 overhead distribution overhead drop MDF underground distribution cross connect 1. 5 km exchange 4 km = Data Terminal cross connect 50 m footway junction box 300 m underground drop

x. DSL Varieties Technology Deployment Frequency POTS Splitter Cable ADSL FTTEx 25 k. Hz - 1. 1 MHz Yes single pair ADSL Lite FTTEx 25 k. Hz - 552 MHz No single pair VDSL FTTCab 0. 3 - 30 MHz Yes? single pair SDSL FTTEx DC – 784 k. Hz No multi pair HDSL FTTEx DC – 784 k. Hz No multi 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 k. Hz Cable balance – degrades with frequency Network balance – interfaces Splitters Three wire internal cabling Balance of UTP (New cable under controlled conditions)

Input Power For x. DSL ADSL VDSL (FTTCab) Downstream Upstream Frequency (MHz) 0. 138 - 1. 104 0. 138 - 0. 276 1. 104 - 10. 0 PSD (d. Bm/Hz) -36. 5 -34. 5 -60 Power in 10 k. Hz (m. W) 2. 2 3. 5 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 PLT House Main Ring Street Lamp 10 m 3 N m x. DSL 6 m Overhead Drop (Splitter) Overhead Drop (No Splitter) N Storey Building (N=1, 2, …, 10)

Antenna Patterns For x. DSL • • At low frequencies (ADSL) patterns are omni-directional Model using an effective short vertical monopole 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

Measured Balance Parameters Frequency (MHz) Measured Efficiency (d. B) Unbalanced Connection Balanced Connection 2. 2 -55 -79 3. 0 -46 4. 3 NEC Efficiency (d. B) Effective Balance For NEC Model (d. B) Unbalanced Connection Balanced Connection -19 36 60 -74 -17 29 57 -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, REC 533 We chose to use REC 533 model based on advice from RAL and the ITU Launch power and antenna pattern

Cumulative DPL Antenna Pattern

DPL Source Power For London • • Power in 10 k. Hz bandwidth: 1 m. W Area: 2500 km 2 Size of DPL cell: 0. 28 km 2 (diameter 600 m) Total number of cell: 2500/0. 28 8925 Total input power: 8925 1 m. W = 8. 9 W 40 d. Bm Antenna gain: – 15 d. B Total radiated power: 40 – 15 = 25 d. Bm

Coverage Of London At 5. 1 MHz 0 Subtract 15 d. B to read true d. Bm. V/m, . i. e. for 15 d. Bm. V/m read 0 d. Bm. V/m London cumulative antenna Isotropic antenna

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 d. B V/m Established ITU noise floor is 8 d. B V/m (rural area)

VDSL Source Power For London • • • Drop model without internal cables Average of 1000 homes per km 2 25 % technology penetration Antenna gain of – 25 d. B (corresponds to 20 d. B cable balance parameter) Terminal input power – 60 d. Bm/Hz or – 20 d. Bm/10 k. Hz Total radiated power 13 d. Bm (20 m. W)

Coverage Of London At 8 MHz Subtract 27 d. B to read true d. Bm. V/m, . i. e. for 15 d. Bm. V/m read -12 d. Bm. V/m

Cumulative VDSL Sky Wave From Many Urban Areas • • Sum powers from major UK cities and Ruhr area of Germany Cumulative field over UK at 8 MHz is – 6 d. B V/m in 10 k. Hz bandwidth Established ITU noise floor is 8 d. B V/m (rural area) 10 d. B lower than DPL

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

Groundwave Propagation Theory (2) • • • The E-field formula applies to a linear short (h<< ) radiative element NEC used to determine the equivalent FM Pt of radiative structures associated with x. DSL 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 m 2 pi: percentage of building type associated with radiating source Di: density of installations per unit area Mpi: fraction of market penetration Li: fraction of installed lines used concurrently • • •

Calculation strategy of cumulative emissions (2) • • Step 1. Definition of radiating medium, A=25 km 2 The RSS summation, lends itself to an active spreadsheet implementation

Calculation strategy of cumulative emissions (3) • Step 2. Definition of makeup of city buildings

Calculation strategy of cumulative emissions (4) • Step 3. Specify reference radiating efficiencies, balance and attenuation at frequencies of interest for upstream and downstream transmission

Calculation strategy of cumulative emissions (5) • • Step 4. Define the appropriate transmission spectral mask, i. e. , for ADSL PSD=-34. 5 d. Bm/Hz (upstream 138 -276 k. Hz), PSD=-36. 5 d. Bm/Hz (downstream 138 -1104 k. Hz). Step 5. Calculate the unattenuated electric field for each radiative element, i. e. ,

Calculation strategy of cumulative emissions (6) • 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 x. DSL installations.

Test cases and results ADSL(1) • Case 1. A=25 km 2, bal=40 d. B, Mpi=20%, Lui=10%

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

Test cases and results ADSL(3) • • Balance – Radiation levels increase by a margin equal to the balance difference in d. B. – E(bal 2)=E(bal 1)+ bal, bal= bal 1 - bal 2 Market Penetration – E(M 2)=E(M 1)+ M, M=10 log(M 2/M 1) • Distance – -20 d. B/decade for f(100 k. Hz - 400 k. Hz) – -25 d. B/decade for f(600 k. Hz - 800 k. Hz) – -30 d. B/decade for f(1000 k. Hz)

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

Graph of current noise floor, ITU-R P. 372 • Median noise electric field at a receiver with bandwidth 10 k. Hz 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 d. B) model at d>1 km 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 5 d. B - 10 d. B at d<2 km – MDF field > cnf by 10 d. B - 20 d. B at d<3 km • For distances > 10 km, ADSL<cnf

Summary of results for VDSL • 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 d. B. )

VDSL and current noise floor • • No likely change to the median electric noise field for the well balanced small city (bal=30 d. B) model at d>1 km 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 10 d. B - 20 d. B at d<1. 5 km – LT-NT field > cnf by 5 d. B - 15 d. B at d<1. 5 km For distances > 5 km, 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 • 88 d. B V/m, 74 d. B V/m, 60 d. B V/m for typical city/industrial, city/residential and rural/residential areas, respectively. – AM transmitter serving designated metropolitan area enclosed by a 50 km radius in UK. • =15, =10 m. S/m, Pt=10 k. W • PR=30 d. B, thus interfering field 44 d. B V/m • x. DSL(d>1 km)< 44 d. B V/m, but Gaussian in nature – For rural locations near x. DSL fields important

Spectrum management issues • Digital MF broadcasting – DRM consortium preliminary specification • Narrow bandwidth (max 10 k. Hz), thus: – very efficient source coding scheme [MPEG-4 AAC] – multi-carrier modulation to overcome multipath, Doppler, [OFDM] – high state linecode modulation scheme, [QPSQ, 16 QAM, 64 QAM depending on service requirements] • Protection ratios: – AM interfered with by DM, [ f/k. Hz=0, PR=36 d. B] – DM interfered with by AM, [ f/k. Hz=0, PR=0 d. B] – DM interfered with by DM, [ f/k. Hz=0, PR=15 d. B]

Spectrum management issues • Digital MF broadcasting – DRM consortium preliminary specification • Carrier-to-noise ratios: • C/N of 24 d. B for BER=1 x 10 -5 is at least required.

Spectrum management issues • • • Power savings of 4 -8 d. B can be made by DM transmitters, for same daytime coverage. x. DSL(d<1 km)>C/N, near x. DSL ? assessment of x. DSL mux and mod techniques

Spectrum management issues • AM transmitters to be phased out by 2020 – Lower PR could be used, 10 -15 d. B less than the currently assumed for AM, thus: • reduced radiation of digital transmitter power • much quieter EM environment – If x. DSL>planned interference value: • DM power must increase (financial implications? ) • concerted actions of broadcasting authorities to restore the service • x. DSL near fields at remote locations?

x. DSL and aeronautical services • Services likely to be affected are: – Radiolocation & mobile communications • NEC simulations show a significant spacewave propagation component for f>1 MHz – most radiation is directed towards elevation angles ranging between 30 and 60 degrees • Space wave stronger than ground wave

x. DSL and government services • Services likely to be affected are: – Military mobile communications in HF • low data rate systems work even 8 d. B below ambient noise in a 3 k. Hz receiver bandwidth • 9. 6 kbps and above data rates at 3 k. Hz bandwidth are standardized requiring a minimum 33 d. B C/N ratio • 3 - 5 MHz, 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 • x. DSL(d<1 km) & selected areas • x. DSL 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 • x. DSL(d<1 km) & 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 x. DSL emissions should be contained at a maximum level of 20 d. B above the established radio noise floor near the effective radiation centres (d=1 km). (For the UK lower values than those in the ITU-R P. 372 can be used. )