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Part of this work is sponsored by France Télécom R&D and Region Nord Pas de Calais

University of Lille. Lab. TELICE. Communications on Indoor Power Lines. 1)Characterization of the noise ON the power lines 2)Noise modelling 3)Propagation channel model 4)Simulation of the link and optimization of the signal processing algorithms.

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Part of this work is sponsored by France Télécom R&D and Region Nord Pas de Calais

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  1. University of Lille. Lab. TELICE Communications on Indoor Power Lines 1)Characterization of the noise ON the power lines 2)Noise modelling 3)Propagation channel model 4)Simulation of the link and optimization of the signal processing algorithms Researchers: Virginie Degardin, Martine Liénard (Assistant professor) Pierre Degauque (Professor) 1 Ph. D. student Part of this work is sponsored by France Télécom R&D and Region Nord Pas de Calais COST 261

  2. Objectives Analysis of the Bit Error Rate of a Multicarrier-based transmission link in a low voltage power line channel  Optimisation of transmission parameters in presence of impulsive noise Outline • Impulsive Noise Classification • Transmission Technique • Performance of the transmission • Conclusion • Future work COST 261

  3. Power Spectrum Density, Narrow band noise measured on indoor power lines Indoor network connected to an overhead Outdoor power line Indoor network connected to a buried power line Broadcast transmitters Conclusion: Useful transmission bandwidth above 3 MHz COST 261

  4. I. Impulsive Noise Classification / Noise model Impulsive Noise : conducted emissions due to electrical devices connected to the network. Measurements carried out by France Telecom in a house during 40 h 2 classes of pulses (on 1644 pulses) : single transient and burst • Single transient: Damped sinusoid • Burst: Succession of heavy damped sinusoids COST 261

  5. I. Impulsive Noise Classification / Noise model (a) Single transient model • Parameters of single transient : • peakamplitude - pseudo frequency f0 =1/T0- damping factor- duration- Interarrival Time (b) Burst Model COST 261

  6. I. Impulsive Noise Classification / Noise characterization 1.Classification in time and frequency domain : Pb: Probability of occurence Bandwidth of PLT system 5 classes are introduced, depending on the pseudo frequency f0 COST 261

  7. I. Impulsive Noise Classification / Noise characterization 2. Statistical analysis:Noise Parameters are approximated by well-known analytical distributions to build a noise model Pseudo Frequency : Weibull distribution COST 261

  8. I. Impulsive Noise Classification / Noise characterization 2. Statistical analysis: Careful examination of long bursts  Pseudo-frequency of the elementary pulse varies with time(calculated with a running time window) The pseudo-frequency distribution around its mean value follows a normal distribution : • and s2 are the mean and the variance of x Agreement: m=1, s=0.17 COST 261

  9. I. Impulsive Noise Classification / Model validation Model validation : Comparison of the spectral densities of measured pulses and generated pulses : Good agreement between measurement and model ! Solution to cope with impulsive noise ? COST 261

  10. II. Transmission system / Principle Principle of multicarrier-based transmission : Transmission on N orthogonal subcarriers owing to an IFFT/FFT. Digital/analog Interface + Filter S/P IFFT P/S Prefix Add. ChannelCoding CHANNEL EMITTER TransferFunction (H) Noise RECEIVER P / S EQUALIZER FFT S / P Analog/digitalInterface Channel decoding Prefixe removal COST 261

  11. M=3 time III. Transmission performances / Noise processing 1. Impulsive Noise processingMatsuo process: (iterative) consists in first defining the number M of OFDM symbols which can be corrupted by noise and then removing it (iterative process) Demodulation Decision Remodulation Subtraction Critical point: choice of M and number of iteration COST 261

  12. Optimisation : threshold As time Matsuo process iterative (M, number i of iterations) Preprocessing Remove noise > threshold (As=3.4 V) {r} {X} Iteration n° 1 Iteration n° i > 1 III. Transmission performances / Noise processing Optimization :Since the amplitude of impulsive noise >> signal amplitudes Possibility of determine a threshold As COST 261

  13. III. Transmission performances / Noise processing • Example: Signal PSD of – 50 dBm/Hz, impulsive noise randomly generated by the model. Series of 1000 tests. For each one, an impulsive noise is introduced at a random time in the transmission chain. • At the end of each series of 1000 tests, determination of the number of erroneous bits One can deduce the average percentage of correction COST 261

  14. Reed-Solomoncode bytes word of K bytes code word of 255 bytes III. Transmission performances / Channel coding 2. Channel codingReed-Solomon code : RS(N,K) Word of K effective symbols Word of N symb. by adding redundancy (N-K symbols) ADSL normalization: Symbol: byte and N = 255 This code can correct up t = (N-K)/2 bytes. if K=239, t = 8 bytes. Interleaving:An interleaving matrix of 256 rows by D columns, D interleaving depth, varying from 2 to 64. Bytes introduced in lines and sent in columns COST 261

  15. III. Transmission performances/ Optimisation in presence of impulsive noise Contribution of channel coding and noise processing on the Bit Error Rate (BER), assuming that all pulses have a pseudo frequency f0 within the signal bandwidth and a PSD of -50 dBm/Hz Cumulative probability distribution of the mean BER for three different values of the interleaving depth D • Pb (BER<10-3) = 77% if D=16 • Pb (BER<10-3) = 96 % if D=64 Choice of D depends on acceptable BER BER COST 261

  16. IV. Conclusion • Study and optimization of a multi-carrier link in a channel modeling the powerline networkfor a bit rate of 10Mbit/s, and PSD (emission) = -50 dBm/Hz : • Statistical analysis of impulsive noise measured in a house during 40 h  stochastic noise model • Study of the transmission performances of two techniques to cope with noise : - the noise processing - the channel coding (Reed-Solomon code & interleaving) • Optimization of the transmission parameters COST 261

  17. IV. Conclusion, ctd • Other important points to optimize the transmission but not really within the scope of this COST action: • Determination of the channel transfer function. Equalization (Blind or Semi – blind) • Detection of a sudden change in the transfer function (When electrical devices are plugged or unplugged on the network) Sudden modification of the transfer function Optimization of pilot symbols COST 261

  18. Future research • Intensive measurement campaigns to characterize the impulsive noise on indoor power lines but in quite different environments: house, buildings, factories, railway or (and) subway stations • Generalization of the noise model for these types of environments • Simulation of the link, optimization of the transmission scheme • Comparison between the expected Bit Error Rate and the measured one for a transmission rate equal to or smaller than 2.5 Mbits/s • Measurement of the near field radiation of the indoor power line. Influence of the network architecture COST 261

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