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Published on November 27, 2007

Author: Willi

Source: authorstream.com

Cumulative Radiated Emissions From Metallic Broadband Data Distribution Systems:  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:  Scope Sky Wave Ground Wave Space Wave 200 km 1500 km 5 km 0 km ionosphere 3-30 MHz 0.1-3 MHz average UK ground London 0.1-30 MHz Rome suburban rural Near Field Contents:  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 Technologies:  Spectrum and Technologies 30 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):  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:  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:  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 LV network MV network data network Network Input Power For A DPL Cell:  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):  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 :  Telecommunications Network cross connect cross connect MDF exchange footway junction box underground drop overhead drop underground distribution overhead distribution 4 km 1.5 km 300 m 50 m = Data Terminal xDSL Varieties:  xDSL Varieties FTTEx = Fibre To The Exchange, FTTCab = Fibre To The Cabinet Physical Structure:  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) Input Power For xDSL:  Input Power For xDSL Modelling Methodology:  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:  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:  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:  Antenna Patterns For xDSL At low frequencies (ADSL) patterns are omni-directional Model using an effective short vertical monopole Normalised gains at 1 MHz Validation Measurements:  Validation Measurements Measurements on UTP aerial drop cable Balanced and unbalanced connections Results used to calibrate the NEC launch models Measured Balance Parameters:  Measured Balance Parameters Cumulative Radiated Power:  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:  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:  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:  Cumulative DPL Antenna Pattern DPL Source Power For London:  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:  Coverage Of London At 5.1 MHz London cumulative antenna Isotropic antenna 0 Subtract 15 dB to read true dBmV/m, .i.e. for 15 dBmV/m read 0 dBmV/m Cumulative DPL Sky Wave From Many Urban Areas:  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 dBV/m Established ITU noise floor is 8 dBmV/m (rural area) Slide27:  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:  Coverage Of London At 8 MHz Subtract 27 dB to read true dBmV/m, .i.e. for 15 dBmV/m read -12 dBmV/m Slide29:  Sum powers from major UK cities and Ruhr area of Germany Cumulative field over UK at 8 MHz is –6 dBmV/m in 10 kHz bandwidth Established ITU noise floor is 8 dBmV/m (rural area) 10 dB lower than DPL Cumulative VDSL Sky Wave From Many Urban Areas Groundwave Propagation Theory (1):  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):  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 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):  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 Calculation strategy of cumulative emissions (2):  Calculation strategy of cumulative emissions (2) Step 1. Definition of radiating medium, A=25km2 The RSS summation, lends itself to an active spreadsheet implementation Calculation strategy of cumulative emissions (3):  Calculation strategy of cumulative emissions (3) Step 2. Definition of makeup of city buildings Calculation strategy of cumulative emissions (4):  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):  Calculation strategy of cumulative emissions (5) 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., Calculation strategy of cumulative emissions (6):  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 xDSL installations. Test cases and results ADSL(1):  Test cases and results ADSL(1) Case 1. A=25 km2, bal=40dB, Mpi=20%, Lui=10% Test cases and results ADSL(2):  Test cases and results ADSL(2) Case 2. A=25 km2, bal=30dB, Mpi=50%, Lui=10% Test cases and results ADSL(3):  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 ADSL:  Summary of results for ADSL 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:  Graph of current noise floor, ITU-R P.372 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:  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 VDSL:  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 dB.) VDSL and current noise floor:  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:  Spectrum management issues AM broadcasting in band 6 (MF) For ‘good’ quality reception 88dBV/m, 74dBV/m, 60dBV/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 44dBV/m xDSL(d>1km)< 44dBV/m, but Gaussian in nature For rural locations near xDSL fields important Spectrum management issues:  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:  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. Spectrum management issues:  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:  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:  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:  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):  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):  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):  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.)

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