Transmission on indoor power lines: from a stochastic channel … · 2015. 7. 29. · Transmission on indoor power lines: from a stochastic channel model to ... Conclusion : software

COST 286 - 25/03/2004 - TELICE 1

Transmission on indoor power lines: from a stochastic channel model to the optimization and performances evaluation of multicarrier system

By V. Dégardin, M. Liénard, P. DegauqueUniversity of Lille, IEMN / DHS

TELICE GroupTélécommunications, Interférences et

Compatibilité Electromagnétique

COST 286 - 25/03/2004 - TELICE 2

Objective

Analysis of the Bit Error Ratein the presence of narrow band noise &in time varying selective channelin the presence of impulsive noise

Influence of channel estimation methods⇒ Optimization of semi-blind techniquesOptimization of noise processing and channel coding

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Outline

I. Indoor Powerline channel : Measurements & modelII. System optimization in the presence of narrow band noise & in time varying selective channel

Transmission processSemi-blind channel estimationSimulation results

III. System optimization in the presence of impulsive noiseNoise processing and channel codingSimulation results

Conclusion : software and demonstrator

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I. Indoor powerline channel model

Two classes of NoiseThe stationary Noise : colored and narrow band noiseThe impulsive noise

The transfer function with 2 main characteristicsMultipath environment : frequency selective channelTime varying channel

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The stationary noise [0-30] MHz

⇒ Modelled by filtered gaussian noise and sinusoids characterized by their frequency, amplitude and phase (randomly distributed)

Transmission Band

I. Indoor powerline channel model

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I. Indoor powerline channel modelIdea : mobile platform for measuring impulsive noiseDifficulties :* Programming (Measurement of interarrival time and data acquisition in real time)* System protection against over voltages (attenuators et couplers ) ⇒ frequency response must be flat in the band

Noise acquisition

acquisitionTIA

coupler

resetBattery 12V

PC

CH AExt trigger

Port //Trig out

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⇒ Damped sinusoid

⇒ Succession of damped sinusoids :higher pseudo-frequency higher amplitude

⇒ Bursts may degrade PLT systems

I. Indoor powerline channel model

Impulsive noise :Measurements have been performed in a house during 40 hours. Two types of impulses are given : Single transient & Burst impulse

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Characteristic parameters of single transient :

- peak amplitude - pseudo-frequency- damped coefficient - duration- interarrival time

(b) Model of burst impulse

(a) Model of single transient

I. Indoor powerline channel model

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Class 5 (18 %)Class 4 (11 %)Class 3 (3 % )Burst pulses Class 2 (20 %)Class 1 (48 %)Single transient

fo>3 MHz0.5 MHz < fo < 3MHzfo

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I. Indoor powerline channel modelModel validation : Comparison of mean spectral density of measured and generated pulses

Good agreement Measurement/Model ⇒ Validation of stochastic model of impulsive noise

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I. Indoor powerline channel model

The measured transfer function :intensive measurements were carried out on a specific installation comprising a line, 30 m long, with wall plugs

⇒ Fading in each frequency band⇒ Sudden channel variations : succession of stationary states⇒ Modeled by a tap delay line filter, the amplitude being determined by a Rayleigh distribution and phase angle being uniformly distributed.

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II. System optimization in the presence of narrow band noise & in time varying selective channel

The OFDM process & semi-blind (SB) channel estimation⇒ Simulation resultsThe DMT process & extension of SB channel estimation⇒ Simulation comparison

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II. The OFDM process

Bits stream

S/P

IFFT

PrefixAdd.

P/S

S/P

Removeprefix

FFT

P/S

EqualizerQAM

demapper

ReceivedBits

streamQAM

Mapper

Parameters :256 subcarriers modulated in 4-QAM, prefix = 32 samplesBit rate = 10 Mbit/s, Bandwidth = 5.5 MHzSynchronization assumed to be ideal

Channel responseand noise

ZF criteria :inverse of the channel estimation

kk HC ˆ

1=

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New algorithm based on a semi-blind (SB) estimationPerformances comparison of different estimation methods

Canal 2Canal 1

Eb/No = 14 dB

⇒ efficient results for SB estimation & detection

⇒ extension to the DMT ?

II. Simulation results of OFDM processes :Influence of the channel estimation

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II. DMT process & extension of SB estimation

The DMT principle :OFDM link + Algorithm which optimizes the number of bits/symbol (size of constellation) versus the SNR in each subband

Extension of SB estimation not straightforward !⇒ SB estimation not accurate when M

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III. System optimization in the presence of impulsive noise

Noise processingChannel codingSimulation results

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Preprocessing :Remove noise>

threshold(As=3.4 V)

{r}Matsuo iterative process

(M, number i of iterations){X}

Iteration n° 1 Iteration n° i > 1

time

M=3 largest amplitudes Optimization : threshold As

III. Noise processingMatsuo iterative process: consist in determining at reception the largest amplitudes of bruit and subtract them

Optimization: amplitude (noise) >> amplitude (signal )⇒ Possibility of determining a threshold As

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Informative word of K bytes

Reed-Solomoncode

Code word of 255 bytes

bytes

III. Channel codingThe Reed-Solomon code:This code adds (255-K) parity bytes and correct up to t = (N-K)/2 bytes. (N=255, K=239, t = 8 bytes)

The interleaving:

1 2 3 255

256257258 510

511 765

766

Bytes are read on 255 columns

Bytes are written on D rows

2 ≤ D ≤ 64

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⇒ P (BER

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Conclusion of the study

Simulation toolDemonstrator

Perspectives

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Software based on MATLAB (The Mathworks)

Conclusion : Simulation Tool

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Characteristics :256 subcarriersP=-50 dBm/HzBit rate: 2,5 Mb/s

Adaptative aspects of the system :Transmission bandwidth [10-30] MHzInjection PowerNumber of subcarriersvariable rate (following phase)

The difficulties of the OFDM process:Synchronization of the received symbolsSynchronization of the OFDM framesOL synchronization Peak power of the received signal

Conclusion : Demonstrator realization

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emission cardCPLD (e/s)DSP (IFFT)

ModulationDemodulation

TimeSynchro

Horlogecard

Conclusion : Demonstrator realization

Impulsive noise generator

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Perspectives

Transmission on powerline in subway stationsProblem : low SNR, long lines (few hundred meters) ⇒ channel measurement and modeling

PLC in cars (high bit rate)

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Transmission on indoor power lines: from a stochastic channel model to the optimization and performances evaluation of multicarrier system

By V. Dégardin, M. Liénard, P. DegauqueUniversity of Lille, IEMN / DHS

TELICE GroupTélécommunications, Interférences et

Compatibilité Electromagnétique