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Powerline Communications: Channel Characterization and Modem Design Yangpo Gao Helsinki University of Technology [email protected] 2005-10-18 Thesis Contents Table of Contents Introduction PLC Technology Background Channel Measurement and Modeling Disturbance over PLC DMT Based PLC Modem Design Conclusion Reference This thesis is part of project “ PLC controlled LEDs for general lighting system”, which is sponsored by TEKES Powerline Communications: Channel Characterization and Modem Design 2 Yangpo Gao, 2005-10-18 Introduction History of PLC and Motivation of Thesis What is PLC PLC – Powerline Communications Using powerline as transmission medium for data communication History of PLC From high voltage (HV) low voltage (LV) Low data rate high data rate Control application multimedia data applications Motivation Cheap “the last mile” solution However, worse channel than other wired network Channel characterization reliable communications Powerline Communications: Channel Characterization and Modem Design 4 Yangpo Gao, 2005-10-18 PLC Technology Background PLC Technologies Three network levels High voltage (110–380 kV) Medium voltage (10–30 kV) Low voltage (230/400 V, in the USA 110 V) (my thesis range) Efficient coupling Inductive coupling Conductive coupling Modulation and error correction OFDM, DMT CDMA FEC Powerline Communications: Channel Characterization and Modem Design 6 Yangpo Gao, 2005-10-18 EMC Issues EMC --Electromagnetic compatibility The ability of a device or system to function satisfactorily in its electromagnetic environment without introducing intolerable electromagnetic disturbances in the form of interferences to any other system in that environment, even to itself. Electromagnetic compatibility (EMC) electromagnetic emission (EME) Conducted emission (CE) Radiated emission (RE) Electromagnetic susceptibility (EMS) Conducted susceptibility (CS) Radiated susceptibility (RS) Powerline Communications: Channel Characterization and Modem Design 7 Yangpo Gao, 2005-10-18 Standardizations PLC standardization bodies International IEC Committee TC 77 ITU ISO CISPR Aisa and Pacific organizations Product Committees CENELEC RA FCC RegTP National Regional Powerline Communications: Channel Characterization and Modem Design 8 Yangpo Gao, 2005-10-18 Channel Measurement and Modeling Transmission Line Theory A piece of mains cable can be modeled as following figure V ( z) V ( z) V ( z) V0 e z V0e z z Attenuation I ( z ) I ( z ) I ( z ) I 0 e constant I 0e z j (R jwL)(G jwC) phase constant i( z, t ) R z V0 R jwL R jwL Z0 I0 G jwC G jwC i ( z z , t ) Propagation constant Characteristic impedance L z C z G z v( z , t ) z z v( z z , t ) R : resistance . L : inductance. G : conductance C : capacitance z z Powerline Communications: Channel Characterization and Modem Design 10 Yangpo Gao, 2005-10-18 Channel Measurement Setup Transmit test head Coupler Network Analyzer (NA) Coupling Circuit Coupling circuit C1 Conductive coupling High pass filter Galvanic isolation Over Voltage protection NA PLC channel T1 D1 To powerline Coupler Equipment: Receive test head D2 D5 D3 D4 To measurement device C2 Powerline Communications: Channel Characterization and Modem Design 11 Yangpo Gao, 2005-10-18 PLC Cable Measurements 2 0 r -2 r R Attenuation (dB) R -4 (2) -6 Fluctuation at high frequency -8 (4) -10 -12 Cable transversal -14 -1 10 1. 2. 3. 4. 0.75mm2 Vulcanize rubber cable 1mm2 Vulcanize rubber cable 0.75mm2 PVC/PVC cable 0.5mm2 PVC/PVC cable 0 10 (1) (3) 1 10 2 10 Frequency (MHz) Cable Type Size (mm2) Vulcanize rubber cable (three-wire) 0.75 Vulcanize rubber cable (three-wire) 1 PVC/PVC cable (three-wire) 0.75 PVC/PVC cable (two-wire) 0.5 • Rapid fluctuation caused by impedance mismatch • Maximum of 4 dB attenuation difference @ 100 MHz Powerline Communications: Channel Characterization and Modem Design 12 Yangpo Gao, 2005-10-18 PLC Channel Measurements Scenario 1: Internet access and distribution Scenario 2: Home networking Central switch Path of scenario 1 Multipath 0 Amplitude Attenuation (dB) (4) 1. socket 1 2. socket 2 3. socket 3 4. 20 m cable -5 (1 ) Path of scenario 2 -10 Scenario 1: Network topology is known, or easy to estimate. Channel is simple, and -15 (2 ) -20 (3) -25 -30 0 has few multipath components Scenario 2: Network topology is unknown or it is hard to define. Channel acts as 20 40 60 Frequency (MHz) 80 100 black box. A lot of multipath components Powerline Communications: Channel Characterization and Modem Design 13 Yangpo Gao, 2005-10-18 -5 -10 -15 Frequency Domain -20 Channel attenuation (dB) Channel attenuation (dB) Channel Responses 0 -5 -10 -15 -20 -25 -30 0 20 40 60 80 100 0.02 -25 0 20 Frequency (MHz) 0.1 40 60 80 100 Frequency (MHz) 0.015 0.01 Amplitude Amplitude 0 0 Time Domain -0.1 -0.005 Scenario 1 -0.2 0 0.005 0.1 0.2 0.3 0.4 Time (us) 0.5 0.6 0.7 0.8 Scenario 2 -0.01 -0.015 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 Time (us) Powerline Communications: Channel Characterization and Modem Design 14 Yangpo Gao, 2005-10-18 PLC Channel Modeling According to PLC channel multipath phenomenon, channel can be modeled as: Lh Lh h(t ) g i (t i ) H ( f ) ri (t i ) r ( f , li ) ai e d ( f )li d ( f ) d R ( f ) dG ( f ) i 1 i 1 Input g 0 1 2 g 1 3 g 2 ... GZ 0 R v1 2Z 0 2 L h g ... 3 ... f v2 f d ( f ) (c0 c1 f ) g Lh Output ... Powerline Communications: Channel Characterization and Modem Design 15 Yangpo Gao, 2005-10-18 Disturbance over PLC PLC Noise Noise Classification: Colored background noise Narrowband noise Periodic impulsive noise, asynchronous to the main frequency Periodic impulsive noise, noise, synchronous to the main frequency Asynchronous impulsive noise Our concentration Colored background noise Asynchronous impulsive noise Powerline Communications: Channel Characterization and Modem Design 17 Yangpo Gao, 2005-10-18 Noise Measurement setup Equipment: Oscilloscope Spectrum Analyzer Coupler Coupler PLC channel Spectrum analyzer (frequency domain) Oscilloscope (time domain) Powerline Communications: Channel Characterization and Modem Design 18 Yangpo Gao, 2005-10-18 Colored Background Noise -30 1. Maximum background noise PSD 2. Average background noise PSD 3. Minimum background noise PSD Curve fitting -40 Background Noise PSD (dBm) Quasi-Static behavior Statistic information is extracted in table Can be modeled as: s b f c N ( f ) 10 (W/Hz) -50 -60 (1) (2) -70 -80 -90 -100 (3) -110 -120 -130 0 20 40 60 80 100 Frequency (MHz) s b c Max -94 -80 -0.4 Min -124 -100 -0.6 Average -105 -90 -0.5 Powerline Communications: Channel Characterization and Modem Design 19 Yangpo Gao, 2005-10-18 Random Impulsive Noise Caused by frequency bursts generated by electrical devices connected to the powerline. Statistic information is extracted 0.6 0.5 Impulsive noise amplitude (V) Impulsive noise amplitude (v) 0.4 0.3 0.2 0.1 0 -0.1 -0.2 -0.3 0.4 0.2 0 -0.2 -0.4 -0.6 -0.4 -0.5 0 2 4 6 8 10 12 Time (ms) 14 16 18 20 -0.8 0 200 400 600 800 1000 1200 1400 1600 1800 2000 Time (us) Powerline Communications: Channel Characterization and Modem Design 20 Yangpo Gao, 2005-10-18 Other Disturbance NEXT (Near End crosstalk) FEXT (Far End crosstalk). Transmit NEXT Receive ELFEXT FEXT Cable Attenuation NEXT Formation 20 (2) FEXT Attenuation (dB) 0 Transmit -20 -40 FEXT (4) (1) Receive -60 -80 1. PLC FEXT 2. Cable Attenuation 3. PLC ELFEXT 4. xDSL FEXT -100 -120 0 20 40 FEXT Formation (3) 60 80 100 Frequency (MHz) Powerline Communications: Channel Characterization and Modem Design 21 Yangpo Gao, 2005-10-18 DMT Based PLC Modem Design DMT Technology Discrete Multi-tone Modulation (DMT) Advantages: Multicarrier technology – combat frequency selective fading Dynamic bit loading based on SNR – efficient spectrum utilization High channel capacity Encoder Constellation mapping and Tone shuffle IFFT Cyclic prefix P/S Transmitter filter Noise Decoder Constellation de-mapping and Tone shuffle FFT Cyclic prefix remove S/P PLC Channel Receiver filter Powerline Communications: Channel Characterization and Modem Design 23 Yangpo Gao, 2005-10-18 DMT Based PLC Modem Design -5 Simulation environment: Simulated channel Measured channel -10 Attenuation (dB) MATLAB SimuLink MATLAB DSP Blockset Simulated channel response -15 -20 -25 Expected result Bit Error Rate (BER) -30 0 20 40 Noise Generator Bit Source Adaptive Loading Algorithm DMT Modulator PLC Channel Spectrum Observation 60 80 100 Frequency (MHz) DMT Demodulator BER Comparison Spectrum Observation Powerline Communications: Channel Characterization and Modem Design 24 Yangpo Gao, 2005-10-18 Simulation and Performance 15 10 10 BER 0 Number of bits per chanel 10 10 10 10 Optimized bit loading algorithm -1 10 -2 -3 5 Modem performance PLC vs AWGN -4 -5 0 0 64 32 128 96 192 160 224 256 Channel Number 10 10 -6 -7 0 DMT over AWGN channel DMT over PLC channel Signal spectrum after PLC channel 10 20 30 Signal spectrum before PLC channel 40 50 SNR (dB) Powerline Communications: Channel Characterization and Modem Design 25 Yangpo Gao, 2005-10-18 Publications Related to My Thesis Publications More information can be found in my publications: “Channel modeling and modem design for broadband power line communications”, Proceeding of ISPLC 2004, April, Spain “Broadband characterization of indoor powerline channel”, Proceeding of ISPLC 2004, April, Spain “Broadband Characterization of Indoor Powerline Channel and Its Capacity Consideration”, Proceeding of ICC 2005, May, Korea Powerline Communications: Channel Characterization and Modem Design 27 Yangpo Gao, 2005-10-18 Any Questions? Thank You!