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7/24/2019 Cours WiMax MIMO
1/58
Intro Norme
WiMax OFDM MIMO
Transmiss ions
relles
Traitement
du signal Concl .
1
Chane de transmission relleassocie un codage WiMax
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Intro Norme
WiMax OFDM MIMO
Transmiss ions
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Traitement
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Intro
volution des dbits en fonction de la vitessevolution des dbits en fonction de la vitesse
FixeIndoor> 20 Mbit/s
Vmax= 120km/hSuburbain outdoor
384 kbits/s
Vmax= 500km/hRural outdoor
144 kbits/s
Indoor/outdoor
jusqu 2Mbit/s Vmax= 10km/h
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Intro Norme
WiMax OFDM MIMO
Transmiss ions
relles
Traitement
du signal Concl .
3
Avantages de lassociation WiMaxAvantages de lassociation WiMax -- MIMOMIMO
Intro
Augmentation importante du dbit,
Augmentation de la robustesse,
Augmentation de la porte du signal, Taux derreur minimal,
Cot dinstallation raisonnable.
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Intro Norme
WiMax OFDM MIMO
Transmiss ions
relles
Traitement
du signal Concl .
4
Super
Mobile
Exemple dapplication viseExemple dapplication vise
Intro
Transmissions mobileshaut dbit de donnes
Audio / Vido.
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Intro Norme
WiMax OFDM MIMO
Transmiss ions
relles
Traitement
du signal Concl .
5
Schma gnral de la chane de transmissionSchma gnral de la chane de transmission
Intro
Data
OFDM
OFDM
DcodageWiMax
Data
DmodOFDM
Traitement
des donnes
DmodOFDM
Traitement
des donnes
DmodOFDM
Traitementdes donnes
DmodOFDM
Traitementdes donnes
Codage
WiMax
mission Rception
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Intro Norme
WiMax OFDM MIMO
Transmiss ions
relles
Traitement
du signal Concl .
6
Norme
WiMax
Norme WiMax IEEE 802.16Norme WiMax IEEE 802.16
Wimax : Worldwide Interoperability forMicrowave Access,
Norme technique base sur le standard detransmission radio 802.16, valid en 2001 parl'organisme international de normalisation IEEE.
Semblable au Wi-fi mais avec des performances
nettement suprieures en de nombreux points.
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Intro Norme
WiMax OFDM MIMO
Transmiss ions
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Traitement
du signal Concl .
7
Norme
WiMax
Norme WiMax IEEE 802.16Norme WiMax IEEE 802.16
Frquences radio de 2 11 GHz
Dbit maximum thorique de 70 mgabits par
seconde sur une porte de 50 km
En pratique, 12 mgabits par seconde sur uneporte de 20 km
Mobilit jusqu 60 km/h
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Intro Norme
WiMax OFDM MIMO
Transmiss ions
relles
Traitement
du signal Concl .
8
Norme
WiMax
Norme WiMax IEEE 802.16Norme WiMax IEEE 802.16
Utilisation de nombreuses techniques : Randomisation
Codes correcteurs derreurs
Perforation Entrelacement
Modulation QAM
Codes spatio-temporels (MIMO)
Forme donde OFDM
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Intro Norme
WiMax OFDM MIMO
Transmiss ions
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Traitement
du signal Concl .
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Norme
WiMax
Norme WiMax IEEE 802.16Norme WiMax IEEE 802.16
Codage
WiMax
Modulation
16QAM
Codage spatio-temporel
OFDM
OFDM
Data
PC
PC
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Intro Norme
WiMax OFDM MIMO
Transmiss ions
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Traitement
du signal Concl .
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Norme
WiMax
Norme WiMax IEEE 802.16Norme WiMax IEEE 802.16
Donnes binaires
Randomisation
Codage de Reed-Solomon
Code convolutif
Perforation
Entrelacement
Couche physique :
Randomisation
Codage de Reed-Solomon
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WiMax OFDM MIMO
Transmiss ions
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Norme
WiMax
Norme WiMax IEEE 802.16Norme WiMax IEEE 802.16
Randomisation :
Consiste viter les longues suites de 1 ou de 0qui sont lorigine de raies de forte nergie.
Permet de rpartir lnergie du signal surlensemble du canal de transmission.
Occupation spectrale du signal quivalente celle dun bruit alatoire.
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WiMax OFDM MIMO
Transmiss ions
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Norme
WiMax
Norme WiMax IEEE 802.16Norme WiMax IEEE 802.16
Randomisation :Dispositif form de 15 registres dcalage et d'un OU exclusif :
( )iSeqSeqiIniOut )15()14()()( =
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Intro Norme
WiMax OFDM MIMO
Transmiss ions
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Traitement
du signal Concl .
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Norme
WiMax
Norme WiMax IEEE 802.16Norme WiMax IEEE 802.16
Codes correcteurs derreur :
Les Codes en BlocsLes Codes en BlocsLes Codes en TreillisLes Codes en Treillis
Modulations Codesen Treillis
Modulations Codesen Treillis
Les Codes Non RcursifsLes Codes Non RcursifsLes Codes RcursifsLes Codes Rcursifs Les Codes Non CycliqueLes Codes Non Cyclique
Modulations Codesen Blocs
Modulations Codesen Blocs
Les Codes CorrlsLes Codes Corrls
Les Codes ConvolutifsLes Codes Convolutifs
Les Codes CycliquesLes Codes Cycliques
Les Codes LinairesLes Codes Linaires
Les Codes Non LinairesLes Codes Non Linaires
Les Codes CorrecteursdErreurs
Les Codes CorrecteursdErreurs
Les Codes en BlocsLes Codes en BlocsLes Codes en TreillisLes Codes en Treillis
Modulations Codesen Treillis
Modulations Codesen Treillis
Les Codes Non RcursifsLes Codes Non RcursifsLes Codes RcursifsLes Codes Rcursifs Les Codes Non CycliqueLes Codes Non Cyclique
Modulations Codesen Blocs
Modulations Codesen Blocs
Les Codes CorrlsLes Codes Corrls
Les Codes ConvolutifsLes Codes Convolutifs
Les Codes CycliquesLes Codes Cycliques
Les Codes LinairesLes Codes Linaires
Les Codes Non LinairesLes Codes Non Linaires
Les Codes CorrecteursdErreurs
Les Codes CorrecteursdErreurs
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Intro Norme
WiMax OFDM MIMO
Transmiss ions
relles
Traitement
du signal Concl .
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Norme
WiMax
Norme WiMax IEEE 802.16Norme WiMax IEEE 802.16
Codes correcteurs derreur :
Codes de Reed-SolomonCode en bloc qui consiste ajouter des octets de redondance la fin de
chaque paquet de donnes.
Codes convolutifsRenforce les mesures de protection des donnes transmettre.
Lie un bit un ou plusieurs bits prcdents afin de pouvoir retrouver sa valeur en cas derreur.
Code dit "en treillis", permet de retrouver la valeur la plus probable d'un bit en observant les
bits prcdemment reus.
Dcodeur de Viterbi
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WiMax OFDM MIMO
Transmiss ions
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Norme
WiMax
Norme WiMax IEEE 802.16Norme WiMax IEEE 802.16
Perforation :
=11
01P
Le rendement du codeur convolutif est de . Pour 1 bit d'entre, 2 bits de sortie.
La perforation (ou poinonnage) consiste amliorer ce rendement en ne transmettant pas
certains bits sortant du codeur.
Rendement = 3 / 4
Gnre des erreurs compenses par le code
convolutif de Viterbi
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Intro Norme
WiMax OFDM MIMO
Transmiss ions
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Traitement
du signal Concl .
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Norme
WiMax
Norme WiMax IEEE 802.16Norme WiMax IEEE 802.16
Entrelacement :Consiste mlanger les paquets entre eux.
Permet de palier les problmes lis de longues suites de bits ou d'octets conscutifs
errons.
( )1616 )16mod(
kfloorkN
m cbps +
=
( ))mod(
16
scbps
cbps NkfloorNk
skfloorsj
++=
Ralis en deux tapes par les quations suivantes :
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WiMax OFDM MIMO
Transmiss ions
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Norme
WiMax
Norme WiMax IEEE 802.16Norme WiMax IEEE 802.16
Modulation numrique M-QAM :M-QAM = Quadrature Amplitude Modulation sur M tats.
Technique qui emploie une combinaison de modulation de phase et damplitude.
Largement employe par les modems.
Permet doffrir des dbits binaires levs
Autres types de modulation possibles :
En frquence - FSK (Frequency Shift Keying)
En phase - PSK (Phase Shift Keying)
En amplitude ou ASK (Amplitude Shift Keying)
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Intro Norme
WiMax OFDM MIMO
Transmiss ions
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Norme
WiMax
Norme WiMax IEEE 802.16Norme WiMax IEEE 802.16
Modulation numrique M-QAM :Pour une modulation 16-QAM :
4 bits donnent un symbole (complexe)
3 niveaux d'amplitude
12 niveaux de phases
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WiMax OFDM MIMO
Transmiss ions
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Norme
WiMax
Norme WiMax IEEE 802.16Norme WiMax IEEE 802.16
Modulation numrique M-QAM :
802.16a standard
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WiMax OFDM MIMO
Transmiss ions
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Norme
WiMax
Norme WiMax IEEE 802.16Norme WiMax IEEE 802.16
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Modulations OFDMModulations OFDM
OFDM
OFDM = Orthogonal Frequency DivisionMultiplexing
Idale pour les canaux multi-trajets (cas du
canyon urbain)
Utilisation optimale la bande de frquencealloue par othogonalisation des porteuses
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Modulations OFDMModulations OFDM
OFDM
Rpartition des symboles gnrs sur une bande defrquence donne avec un nombre de porteusesdonn.
Estimation priodique de la rponse du
canal
Mise en place par une simple FFT
Amlioration du taux d'erreur par un
codage et un entrelacement adapts
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Applications
q Rseaux sans fils (Wi Fi, Hiperlan).
q Internet et vido pour la tlphonie mobile
Tlvision numrique terrestre (DVB-T).
Permet de transmettre des donnes avec un dbit trslev sur un canal slectif en frquence avec le tauxderreur le plus faible possible
Robustesse vis vis des canaux slectifs en frquence
OFDM
Modulations OFDMModulations OFDM
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S/P
Donnes lmission
P/S
IFFT
Ajouter le Prfixe cyclique
P/SFFT
Supprimer le Prfixe cyclique
S/P
Donnes la rception
OFDM
Modulations OFDMModulations OFDM
Principe de la modulation OFDM
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s y m b o l iCP Symbole i+1 CP CP Symbole i CP
copiecopie
s y m b o l iCP Symbole i+1 CP CP Symbole i CP
copiecopie
La dure du prfixe cyclique doit tre suprieur ltalement des retardsLa dure des donnes plus grande suffisamment que la dure du prfixe cycliqueLa dure des donnes doit tre courte suffisamment que le canal ne change paspendant la dure dun block
OFDM
Modulations OFDMModulations OFDM
Prfixe cyclique
Permet dviter les interfrences entre symboles dues au canal de propagation
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La convolution circulaire
En prsence des interfrences introduit par le canal
{ } { } { }NNN ksFFTkhFFTkskhFFT )(.)()(*)(
Le prfixe cyclique permet dobtenir une convolution circulaire
{ } { }NNN ksFFTkhFFTkskhFFT )(.)()(*)( =
Cette proprit permet lutilisation dune galisation simple
la rception
)().()( nynHny =
OFDM
Modulations OFDMModulations OFDM
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Construction des signaux OFDM
Nb de sous porteuses
La largeur de bande
Lorthogonalit des sous-porteuse Les porteuses pilotes
OFDM
Modulations OFDMModulations OFDM
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286 -4 -2 2 4 6-2
- 5
-
-5
5
5
2
OFDM
Modulations OFDMModulations OFDM
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OFDM
Modulations OFDMModulations OFDM
Sous-porteuses pilotes
Introduction dans le spectre de sous-porteuses connues
Permettent de synchroniser les donnes la rception
Corrigent les dcalages de phase
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Sf
St
Donnesutiles
DonnesPilotes
(a): Trames pilotes (b): Porteuses pilotes (c): Porteuses parpilles
Temps
Frquenc
e
Sf
St
Donnesutiles
DonnesPilotes
(a): Trames pilotes (b): Porteuses pilotes (c): Porteuses parpilles
Temps
Frquenc
e
OFDM
Modulations OFDMModulations OFDM
Sous-porteuses pilotes
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Les avantages et les inconvnients
Une grande efficacitspectraleRobuste contre laslectivit frquentiellegalisation plus simple
Une parfaite synchronisation
grande est exigeLe facteur de crte PAPRVulnrabilit au dcalagefrquentiel
=> Perte dorthogonalitentre les porteuses=> Les interfrences entre
porteuses
OFDM
Modulations OFDMModulations OFDM
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CodeurConvolutif
CodeurConvolutif
EntrelaceurCodeurReed
Solomon
CodeurReed
SolomonDonnes
lmissionDonnes
lmissionM-QAMM-QAM
ModulationOFDM
ModulationOFDM
Dcodeurde ViterbiDcodeurde Viterbi
Donnes la rceptionDonnes la rception
DcodeurReed
Solomon
DcodeurReed
SolomonDsentrelaceur
DmodulationOFDMDmodulationOFDM
Estimationdu canal
Estimationdu canal
Synchronisationdes signaux &
des trames
Synchronisationdes signaux &
des trames
M-QAMM-QAM
galisation &correctionde phase
galisation &correctionde phase
OFDM
Schma global de la chane SISOSchma global de la chane SISO
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mission MIMOmission MIMO
MIMO
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mission MIMOmission MIMO
MIMO
EMETTEUR
x1
R
ECEPTEUR
x2
y1
y2
y3
h11
h12
h21
h22
h31h32
Nt antennes Nrantennes
datadata
signal reu signal mis
y1(n)
y2(n)
y3(n)y4(n)
h11 h12h21 h22
h31 h32h41 h42
x1
x2= x +
n1n2
n3n4
Matrice de
canal
Matrice
de bruit
Modlisation dune
transmission
MIMO (2,4) :
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Codages spatioCodages spatio--temporelstemporels
MIMO
TraitementMIMO
lmission
Multiplexagespatial (MS)
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Transmiss ions
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Codages spatioCodages spatio--temporelstemporels
MIMO
*
4
*
3
*
2
*
14321 S-S-S-SS-S-S-S
*
3
*
4
*
1
*
23412 S-SSSS-SSS
*
2
*
1
*
4
*
32143 SSS-SSSS-S
*
1
*
2
*
3
*
41234 SS-SSSS-SS
4321 SSSS
TraitementMIMO
lmission
Codage spatio-temporel en bloc
1/2 (STBC)
Dbit utile 2
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WiMax OFDM MIMO
Transmiss ions
relles
Traitement
du signal Concl .
37
Codages spatioCodages spatio--temporelstemporels
MIMO
[ ]1210 ... = nssssE
=
*
01
*
10
2
1
ss
ssC
=
*
21
*
12
*
23
*
32
*
01
*
10 ...2
1
nn
nn
ss
ss
ss
ss
ss
ssS
Signal dentre :
Codage modlis par :
Expression de la matrice de sortie :
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WiMax OFDM MIMO
Transmiss ions
relles
Traitement
du signal Concl .
38
Direction
de
propagation
MIMO
Transmissions simultanes sur 2 antennes
Codages spatioCodages spatio--temporelstemporels
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WiMax OFDM MIMO
Transmiss ions
relles
Traitement
du signal Concl .
39
PrambulesPrambules
MIMO
Symboles OFDM connus pour :
Synchroniser les donnes la rception, Estimer le canal de propagation.
Deux prambules sont utiliss pour 24 symboles OFDM utiles
2 Prambules 24 symboles OFDM Trame OFDM avec prambules
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WiMax OFDM MIMO
Transmiss ions
relles
Traitement
du signal Concl .
40
Rsum de lmissionRsum de lmission
MIMO
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WiMax OFDM MIMO
Transmiss ions
relles
Traitement
du signal Concl .
41
Rsum de lmissionRsum de lmission
MIMO
Porteuse Pilote Data
64 Porteuses
40 Porteuses de donnes
6 Porteuses pilotes
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WiMax OFDM MIMO
Transmiss ions
relles
Traitement
du signal Concl .
42
Rsum de lmissionRsum de lmission
MIMO
0 200 400 600 800 1000 1200 1400 1600 1800 2000-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
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WiMax OFDM MIMO
Transmiss ions
relles
Traitement
du signal Concl .
43
Transmiss ions
relles
Transmissions rellesTransmissions relles
Lors de transmissions relles, le signal subit desperturbations :
Attnuations lies au canal de propagation,
Dcalages de phase,
Effet Doppler,
Multi-trajets
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WiMax OFDM MIMO
Transmiss ions
relles
Traitement
du signal Concl .
44
Transmiss ions
relles
Transmissions rellesTransmissions relles
diffusiondiffusion
diffractionsdiffractions
rflexion
Le signal la rception est la somme de tous les signauxissus des diffrents trajets
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WiMax OFDM MIMO
Transmiss ions
relles
Traitement
du signal Concl .
45
Traitement
du signal
Traitement du signalTraitement du signal
Filtrage
Synchronisation des signaux
Estimation du canal
galisation
Correction de phase
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WiMax OFDM MIMO
Transmiss ions
relles
Traitement
du signal Concl .
46
Traitement
du signal
Traitement du signalTraitement du signal
Filtrage Porte sinc
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WiMax OFDM MIMO
Transmiss ions
relles
Traitement
du signal Concl .
47
Traitement
du signal
Traitement du signalTraitement du signal
Synchronisation des signaux
Fonction de corrlation
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WiMax OFDM MIMO
Transmiss ions
relles
Traitement
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Traitement
du signal
Traitement du signalTraitement du signal
2 4 6 8 10 12 14
x 104
0
0.51
1.5
2
2.5
3
3.5
4
4.5
5
x 105
Dbuts des signaux
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WiMax OFDM MIMO
Transmiss ions
relles
Traitement
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49
Traitement
du signal
Traitement du signalTraitement du signal
1.5 2 2.5 3 3.5 4 4.5
x 104
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5x 105
Dbuts des trames
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WiMax OFDM MIMO
Transmiss ions
relles
Traitement
du signal Concl .
50
Traitement
du signal
Traitement du signalTraitement du signal
Estimation du canal de propagationRcepteur Turbo MAP (Maximum posteriori)
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WiMax OFDM MIMO
Transmiss ions
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Traitement
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Traitement
du signal
Traitement du signalTraitement du signal
Estimation du canal de propagationRcepteur Turbo MMSE (Minimum Mean Square
Error)
MMSE
JD
Mapp
ing
De
Mapping
LD(c)
P(a|y,G,)E(a)
Cov(a,a)
y
LC(c)
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Transmiss ions
relles
Traitement
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52
Traitement
du signal
Traitement du signalTraitement du signal
galisationfY
fX )(
)( =
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Transmiss ions
relles
Traitement
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Correction de phase : Utilisation des sous-porteuses pilote
Traitement du signalTraitement du signal
Traitement
du signal
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Transmiss ions
relles
Traitement
du signal Concl .
54
Correction de phase : Utilisation des sous-porteuses pilote
Traitement du signalTraitement du signal
Traitement
du signal
N T i i T i
T i
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WiMax OFDM MIMO
Transmiss ions
relles
Traitement
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Traitement du signalTraitement du signal
Traitement
du signal
N T i i T it t
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WiMax OFDM MIMO
Transmiss ions
relles
Traitement
du signal Concl .
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Concl .
SNR= 8dBBER= 0 SNR= 7dBBER= 9.10-3
H263 video stream
N T i i T it t
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WiMax OFDM MIMO
Transmiss ions
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Traitement
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57
Quelques antennes fi l i formes
N T i i T it t
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WiMax OFDM MIMO
Transmiss ions
relles
Traitement
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Quelques antennes f i l i formes
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