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Propagation Channel Characterization and Modeling

Propagation Channel Characterization and Modeling Outdoor Power Supply Grids as Communication Channels Prof. Dr.-Ing. habil. Klaus Dostert Institute of Industrial Information Systems UNIVERSITY OF KARLSRUHE (TH). Overview. Communication over outdoor electrical power supply lines.

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Propagation Channel Characterization and Modeling

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  1. Propagation Channel Characterization and Modeling Outdoor Power Supply Gridsas Communication Channels Prof. Dr.-Ing. habil. Klaus Dostert Institute of Industrial Information Systems UNIVERSITY OF KARLSRUHE (TH)

  2. Overview Communication over outdoor electrical power supply lines • Network structures and their basic properties • Access domain in Europe, ASIA, America • Analysis of line and cable properties • characteristic impedance • branching & matching • General aspects of channel modeling • transfer function, impulse response, channel parameterization • interference scenario • PLC channel simulation and emulation • channel adapted system development Conclusions and further work

  3. History: Carrier Frequency Transmission since 1920(on the high voltage level only) • no branching • optimal „wave guiding“ by network conditioning

  4. Low Speed (10…100 kbits/s) • - Office and home automation (intelligent appliances) • Energy information systems • Urban rail-based traffic systems Broadband Services: 1…30 MHz (1…2 Mbits/s - „Last Mile“ and „Last Meter“ high-speed internet access, voice over IP etc. High Speed Indoor Applications: 12 …  70MHz - PLC for digital entertainment systems (>100 Mbits/s) • PLC in automobiles • PLC for factory automation • PLC for advanced safety systems in the mining industry Current and Upcoming PLC Applications

  5. 3-phase supply details 400V 400V high voltage level: 110..380 kV 230V transformer station 400V medium voltage level 10...30kV 230V LV transformer stations low voltage distribution grid 3 Phases: 230V, 400V • supply cells • up to 350 households • cable length 100...400m The European Power Supply Network Structure

  6. Server Transformer Station 5 4 3 1 2 L2 L3 6 N L1 supply cable type NAYY150SE 9 8 7 cable length: max. 1 km 14 13 10 11 12 15 18 16 17 22 20 21 23 19 24 33 32 26 25 27 28 31 30 House connection cable NAYY50SE 29 Typical Topology of European Power DistributionNetworks in Residential Areas

  7. local transformer station medium voltage network cross-bar system ZL1 points of mismatch house connection forming a low impedance point - almost short circuit - Some Details of “Last Mile” and “Last Meter” Environments ZL2

  8. high voltage level: 110..380 kV single and split-phase transformer station 1st medium voltage level 10…30 kV 2ndmedium voltage distribution level 6 kV low voltage distribution grid single or split phase supply 125V, 250V 250V many LV transformers 125V 125V Power Supply Structures in Asia and America • small supply cells • few households per transformer • cable length  100m • grounding of 3rd wire • highly unsymmetrical

  9. compensation of exterior field compensation of exterior field X  The Ideal Two-Wire System

  10. 3-phase supply cable passive conductors X • “earth” in case of a three-wire supply passive conductors Symmetry in Multi-Wire Structures open wires • X

  11. Simplified Analysis of a Two-Wire System 650 characteristic impedance open wires: r=1 600 r =2mm ZL/ 550 r =2mm D r =4mm 500 r =5mm 450 r 400 350 attenuation at open wires due to Skin effect 100 150 200 250 300 350 400 0 120 l =500m cable: r=3.5 A(f)/dB 100 l =1000m -2 r =5mm 80 l =2000m r =7mm -4 60 ZL/ r =10mm 40 l =5000m -6 d=2r=5mm 20 -8 10 15 20 25 30 0 5 10 15 20 25 30 f in MHz D in mm D in mm

  12. Lossy Line Parameters (low losses) Model Access Cable Types J PEN J L3 L3 r i N L1 r L2 L3 a L1 L2 r er L1 N CharacteristicImpedance Attenuation Coefficient Characteristic Impedance Attenuation over 1km ZL/ 50 0 NAYY 150SE 10 40 House Connection NAYY50SE 20 30 30 NAYY50SE 40 Main Supply Cable 20 NAYY150SE 50 A(f) [dB] 10 60 0 70 5 20 1 2 5 10 20 1 2 10 f /MHz f /MHz RF Properties of Typical Supply Cables

  13. ZL ZL L >> ZL ZL R=ZL/3 ZL ZL/3 ZL/3 ZL ZL ZL ZL ZL ZL matched to ZL mismatch: ZL/2 The problem of Branching and Possible Solutions

  14. Transformer Station typical RF coupling devices cross-bar system decoupling L>10µH RF-shorts cable: ZLC » 25 W BALUN impedance matching House Connection MODEM L > 10µH decoupling cable: ZLC»35W BALUN power meter • Ferrite material is required for these decoupling coils, which carry high currents! • Transformer: >150A • House connection: >30A RF-shorts impedance matching MODEM Some Ideas for Signal Coupling with Enhanced SymmetryImproving EMC

  15. wireless channel as example T direct path echo path R delay:  =2-1 simplified analysis of a line with 1 unmatched branch Tbit  in practice: multiple echoes direct echo result 2 R T 1 impulse response strong inter-symbol interference:   Tbit t 1 2 Reflections Causing Echoes and Inter-Symbol Interference

  16. a a2 a ra b b2 b a2 a1 S11S12 S21S22 branch example b2 b1 a1 b1 b3 a3 Approaches Toward Deterministic Network Modeling source sink line element bq ri • high computational effort • requires detailed knowledge of network topology and device parameters • not applicable in practice

  17. s(t) t1 t2 tN impulse response k1 k2 k3 kN Fourier transform transfer function r(t) S Result low-pass behavior Attenuation Coefficient: dependent on number, lengthand matching of branches generally complex skin-effectdielectric losses The Echo-based Channel Model considering only echoes : ki=const

  18. h(t): impulse response 1 path 1 dB FT 0 path 2 -5 0.5 -10 -15 0 1 1.17 1.33 1.5 1.67 1.83 2 -20 225m  2 0 5 10 15 20 25 30 R T attenuation 200m  1 single reflection, including losses 0 0 dB dB -20 -20 path 1 path 2 -40 -40 0 5 10 15 20 25 30 0 5 10 15 20 25 30 f in MHz t in µs f in MHz f in MHz H(f): single reflection, no losses

  19. Two-Path Channel without Losses but Varying Path Weights Path 1 0.52 0.26 0.173 0.46 0.71 0.793 Path 2 0.627 0.347 0.208 0.149 0.76 0.817

  20. 0 |H(f)| dB -10 ¥ 11m -20 170m 30m » G ZL -30 -40 -50 1 0 0 5 10 15 20 25 30 -10 calculation 1 measurement 0.5 - 20 h(t) - 30 0 - 40 0.5 - 50 0 1 2 3 4 5 0 15 20 5 10 t in µs f in MHz 0 frequency in MHz 0 0.5 1 1.5 2 2.5 3 3.5 time in µs A First Realistic Example

  21. |H(f)| -20 dB 110m 15m -40 -60 -80 0 5 10 15 20 25 30 1 h(t) 0.5 0 frequency in MHz -0.5 0 0.5 1 1.5 2 2.5 3 3.5 time in µs A Second Example (more complex)

  22. Transmission Characteristics According to Length Classes 0 10 Attenuation in dB 20 30 150 m 40 200 m 50 60 300 m 70 380 m 80 10 12 14 16 18 2 4 6 8 Frequency in MHz

  23. A General Powerline Interference Model narrowband- interference periodic impulsive noise synchronous with the mains periodic impulsive noise asynchronous with the mains background noise aperiodic asynchronous impulsive noise + Channel as a Linear Filter Interference h(t) H(f) tB threat of burst errors Amplitude A tA time tIAT A, tB and tA are random variables with exponential distributions

  24. PLC Modem PLC Modem Host-PC Configuration Interface + + A A FIR Filter PGA LPF LPF D D PGA A A D D Noise Generator PGA LPF PGA A Noise Generator LPF D A FIR Filter LPF LPF D Idea of a Universal PLC-Channel Emulator

  25. FPGA channel emulation filters delay 14 from ADC D 8 signal DAC 20 14 FIR Notch FIR lowpass FIFO A control 5x7bit delay 5x5bit coeff. 32x8bit coeff. periodic, synchronous, asynchronous impulsive noise & background noise interference DAC 8 m-sequences of length 220-1 8 14 14 + Ampli- tude 14 control D 20bit shift register A 8x20bits load Ampli- tude narrow band noise 8 14 8-bit-circular memory of length 500 500 x 8bits load control 26 P_ADDR control / load 32 P_DATA Some Details Toward Emulator Realization

  26. A First Powerline Channel Emulator Prototype modified filter structure reference channel coeff. filter 1 coeff. filter 2 |H| in dB simulations, implementation |H| in dB hardware f in MHz verification measurements f in MHz

  27. FSK, GMSK not usable due to high attenuation OFDM sub-channel Why OFDM for PLC? Channel Transfer Function restricted e.g. for protection of broadcast services f fN f3 f1 f2

  28. PLC or BPL offers a variety of valuable applications • data rates exceeding many Mbits/s will enable numerous new services • Mature channel models are covering any channel of interest • successful development of a new generation of ”channel adapted” PLC systems is possible • no more pitfalls: sophisticated simulation and emulation Building advanced and user-friendly simulation and emulation environments is now an important issue • Further development and standardization of PLC or BPL goes on • ETSI, CENELEC, CISPR • EU Project OPERA (Open PLC European Research Alliance) • HomePlug Alliance (USA) • IEEE PHY/MAC Working Group Conclusions and Further Work

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