1. 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)

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

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

4. 4 Current and Upcoming PLC Applications High Speed Indoor Applications: 12 …  70MHz - PLC for digital entertainment systems (>100 Mbits/s) 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.  PLC in automobiles  PLC for factory automation  PLC for advanced safety systems in the mining industry

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

6. 6 Typical Topology of European Power Distribution Networks in Residential Areas

7. 7 Some Details of “Last Mile” and “Last Meter” Environments medium voltage network local transformer station cross-bar system Z L1 Z L2 points of mismatch house connection forming a low impedance point - almost short circuit -

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

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

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

11. 11 Simplified Analysis of a Two-Wire System 650 100150200250300350400 350 400 450 500 550 600 D in mm ZL/ZL/ r =2mm r =4mm r =5mm open wires:  r =1 10 15202530 20 40 60 80 100 120 r =5mm r =7mm r =10mm D in mm ZL/ZL/ cable:  r =3.5 051015202530 -8 -6 -4 -2 0 f in MHz A(f)/dB l =5000m l =2000m l =1000m l =500m d=2r=5mm attenuation at open wires due to Skin effect D r characteristic impedance

12. 12 RF Properties of Typical Supply Cables Lossy Line Parameters (low losses) Attenuation Coefficient Characteristic Impedance N L1 r L3 L2 r a r i L1 rr L2 L3 PEN Access Cable Types L1 N L3 Model

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

14. 14 Some Ideas for Signal Coupling with Enhanced Symmetry Improving EMC typical RF coupling devices Transformer Station cross-bar system cable: Z LC   L  10µH BALUN MODEM RF-shorts impedance matching decoupling L > 10µH RF-shorts BALUN House Connection MODEM power meter impedance matching decoupling cable: Z LC    Ferrite material is required for these decoupling coils, which carry high currents!  Transformer: >150A  House connection: >30A

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

16. 16 Approaches Toward Deterministic Network Modeling bqribqri a b rara a b S 11 S 12 S 21 S 22 a2a2 b2b2 a1a1 b1b1 source line element sink a2a2 b2b2 a1a1 b1b1 a3a3 b3b3 branch example  high computational effort  requires detailed knowledge of network topology and device parameters  not applicable in practice

17. 17 impulse response transfer function skin-effect dielectric losses Attenuation Coefficient: The Echo-based Channel Model considering only echoes : k i =const low-pass behavior dependent on number, length and matching of branches generally complex s(t)   k1k1 r(t)   k2k2 k3k3 kNkN Fourier transform Result

18. 18 T R 200m   1 225m   2 FT 051015202530 -20 -15 -10 -5 0 f in MHz dB 051015202530 -40 -20 0 f in MHz dB path 2 path 1 attenuation H(f): single reflection, no losses 051015202530 -40 -20 f in MHz 0 dB single reflection, including losses 11.171.331.51.671.832 0 0.5 1 t in µs path 1 path 2 h(t): impulse response

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

20. 20 pathd i /mgigi 12000.64 2222.40.38 3244.8-0.15 4267.50.05 ZLZL G   30m 11m 170m 051015202530 -50 -40 -30 -20 -10 0 frequency in MHz dB |H(f)| 00.511.522.533.5 0 0.5 1 time in µs h(t)h(t) A First Realistic Example 0 510 1520 - 50 - 40 - 30 - 20 -10 0 f in MHz 012345 0 1 t in µs 0.5 calculation measurement

21. 21 A Second Example (more complex) pathd i /mgigi 1900.029 21020.043 31130.103 4143-0.058 5148-0.045 6200-0.040 72600.038 8322-0.038 94110.071 10490-0.035 115670.065 12740-0.055 139600.042 141130-0.059 1512500.049 051015202530 -80 -60 -40 -20 |H(f)| dB frequency in MHz 00.511.522.533.5 -0.5 0 0.5 1 h(t)h(t) time in µs 110m 15m

22. 22 2468 1012141618 80 70 60 50 40 30 20 10 0 Attenuation in dB Frequency in MHz Transmission Characteristics According to Length Classes 150 m 200 m 300 m 380 m

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

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

25. 25 FPGA 8 from ADC signal DAC FIFO channel emulation filters delay 5x7bit delay 5x5bit coeff. 32x8bit coeff. control 1420 FIR Notch FIR lowpass 32 P_DATA 26 8 14 8-bit-circular memory of length 500 periodic, synchronous, asynchronous impulsive noise & background noise narrow band noise control + P_ADDR 8x20bits load 500 x 8bits load control 14 8 interference DAC 20bit shift register 8 m-sequences of length 2 20 -1 control / load Ampli- tude Ampli- tude 14 D A D A Some Details Toward Emulator Realization

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

27. 27 FSK, GMSK f1f1 f2f2 f3f3 f fNfN not usable due to high attenuation restricted e.g. for protection of broadcast services OFDM sub-channel Channel Transfer Function Why OFDM for PLC?

28. 28 Conclusions and Further Work 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 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 Building advanced and user-friendly simulation and emulation environments is now an important issue