Turbo-synchronization. Friday, March 19 2004 Sébastien de la Kethulle de Ryhove –...
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Transcript of Turbo-synchronization. Friday, March 19 2004 Sébastien de la Kethulle de Ryhove –...
Turbo-synchronization
Friday, March 19 2004 Sébastien de la Kethulle de Ryhove – Turbo-synchronization
Introduction
• Communication systems based on the turbo principle
• Remarkable performances
• Ideal synchronization
Friday, March 19 2004 Sébastien de la Kethulle de Ryhove – Turbo-synchronization
Transmission System
Friday, March 19 2004 Sébastien de la Kethulle de Ryhove – Turbo-synchronization
The Turbo Principle
Compute soft information on the transmitted symbols using an
iterative receiver
Friday, March 19 2004 Sébastien de la Kethulle de Ryhove – Turbo-synchronization
Soft / Hard Information
• Hard approach
• Soft approach
Friday, March 19 2004 Sébastien de la Kethulle de Ryhove – Turbo-synchronization
The Turbo Principle
• Applicable to a wide variety of problems:
– Decoding: Turbo-decoding– Decoding + equalization: Turbo-equalization– Decoding + demodulation: Turbo-demodulation– …
• Turbo detection
Friday, March 19 2004 Sébastien de la Kethulle de Ryhove – Turbo-synchronization
Example: Turbo-demodulation
Transmitter
Friday, March 19 2004 Sébastien de la Kethulle de Ryhove – Turbo-synchronization
NSC Encoder
Friday, March 19 2004 Sébastien de la Kethulle de Ryhove – Turbo-synchronization
Grouping and Mapping
Friday, March 19 2004 Sébastien de la Kethulle de Ryhove – Turbo-synchronization
Example: Turbo-demodulation
Receiver – Exchange of soft information
Friday, March 19 2004 Sébastien de la Kethulle de Ryhove – Turbo-synchronization
Synchronization
• Find estimates for
– The carrier frequency
– The carrier phase
– The sampling time
Friday, March 19 2004 Sébastien de la Kethulle de Ryhove – Turbo-synchronization
Synchronization
Classical receiver
Friday, March 19 2004 Sébastien de la Kethulle de Ryhove – Turbo-synchronization
Turbo-synchronization
Soft receiver
Friday, March 19 2004 Sébastien de la Kethulle de Ryhove – Turbo-synchronization
Soft Synchronization – Example
• Traditional DD synchronization
• Soft DD synchronization
Friday, March 19 2004 Sébastien de la Kethulle de Ryhove – Turbo-synchronization
Algorithm: Soft Phase SynchronizationInitialize /* many possibilities */
do {
Correct the phase of the received sequence
Perform one soft det./dec. iteration on the corrected sequence
Find a new estimate for using the newly obtained soft information
} while ( changes a lot)
/* Continue with detection / decoding */
Friday, March 19 2004 Sébastien de la Kethulle de Ryhove – Turbo-synchronization
BER Performance
-150 -100 -50 0 50 100 15010
-5
10-4
10-3
10-2
10-1
100
Performances d'un système turbo codé en présence d'une erreur de phase
Erreur de phase (degrés)
Taux
d'e
rreu
r bi
naire
Eb/N
0 = 1 dB
Eb/N
0 = 2 dB
Eb/N
0 = 3 dB
Phase offset [degrees]
BE
R
BER Performance vs. Phase Offset for a Turbo Coded system
Friday, March 19 2004 Sébastien de la Kethulle de Ryhove – Turbo-synchronization
Mean Estimated Phase Offset
0 20 40 60 80 100 120 140 160 180-100
-50
0
50
100
150
200
Eb/N
0 = 1.0 dB
Erreur de phase (degrés)
Pha
se m
oyen
ne e
stim
ée (
degr
és)
Idéal Méthode traditionnelle (ML NDA)Méthode douce (Soft DD)
Phase offset [degrees]
Me
an
Est
ima
ted
Ph
ase
Off
set
[de
gre
es]
Friday, March 19 2004 Sébastien de la Kethulle de Ryhove – Turbo-synchronization
Estimator Variance
0 20 40 60 80 100 120 140 160 18010
0
101
102
103
104
105
Erreur de phase (degrés)
Var
ianc
e de
l'es
timat
eur
(deg
rés2 )
Eb/N
0 = 1.0 dB
Borne théorique Méthode traditionnelle (ML NDA)Méthode douce (Soft DD)
Phase offset [degrees]
Est
ima
tor
Va
rian
ce [
de
gre
es2
]
Friday, March 19 2004 Sébastien de la Kethulle de Ryhove – Turbo-synchronization
BER Performance
0 20 40 60 80 100 120 140 160 18010
-3
10-2
10-1
100
Eb/N
0 = 1.0 dB
Erreur de phase (degrés)
Taux
d'e
rreu
r bi
naire
Idéal Méthode traditionnelle (ML NDA)Méthode douce (Soft DD) Pas d'estimateur
Phase offset [degrees]
BE
R
Friday, March 19 2004 Sébastien de la Kethulle de Ryhove – Turbo-synchronization
Estimator Variance
0 0.5 1 1.5 2 2.510
0
101
102
Erreur de phase = 30 degrés
Eb/N
0 (dB)
Var
ianc
e de
l'es
timat
eur
(deg
rés2 )
Borne théorique Méthode traditionnelle (ML NDA)Méthode douce (Soft DD)
Phase offset = 30 degreesE
stim
ato
r V
aria
nce
[d
eg
ree
s2]
Eb / N0 [dB]
Friday, March 19 2004 Sébastien de la Kethulle de Ryhove – Turbo-synchronization
Performances – Acquisition
1 1.5 2 2.5 3 3.5 4 4.5 510
-5
10-4
10-3
10-2
10-1
100
Préambule: 7 symboles 16-QAM
Eb/N
0 (dB)
Taux
d'e
rreu
r bi
naire
Méthode Soft DD Méthode Hard DD Méthode DD TraditionnelleIdéal
BE
R
Preamble: 7 16-QAM symbols
Eb / N0 [dB]
Friday, March 19 2004 Sébastien de la Kethulle de Ryhove – Turbo-synchronization
Conclusions
• Performance enhancement– Synchronization algorithms– Overall system
• Encouraging results