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TURBO CODING FOR FFH-OCDMA
SYSTEM A SIMULATION STUDY
T N SUDHASHREE
(2009252041)
Project Guide
Mrs. G. GEETHAAssociate Professor
Department of Electronics andCommunication Engineering
Anna University, Chennai-25.
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Introduction
Optical Code Division Multiple Access(OCDMA)
The most promising multiple access
technique.
OCDMA offers several advantages:
Asynchronous access capability
User allocation flexibility
Security against unauthorized users
Anti-jamming capability
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Turbo codes
5
(a) PCCC and (b) SCCC
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Serial concatenated convolutional
code Encoder
input
SCCC
encoded
bits
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The MAP (Maximum A Posteriori)
algorithm
m)b(j ,j ,
1k
1
0j
m)b(j ,
1k
m
k
m)f(j,
1k
1
0j
mj ,
k
m
k
mi,
kk
i
kk
mi,
k vyux0.5exp
Forward state metric
Reverse state metric
Branch metric
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Graphical Representation for Calculating
and
m
k
m
k
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Log likelihood ratio
m
mf
k
m
k
k
m
m
mf
k
m
k
k
m
kdL
),0(
1
,0
),1(
1
,1
log)
(
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Decoder trellis an example
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Iterative decoding of SCCC
Inner MAP
Outer MAP
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Simulation Model
Communication System Model
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SCCC Encoder and MAP decoder
with trellis termination
without trellis termination
(equal probability initialization of beta)
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Serial Concatenated Convolutional
Coding With Trellis Termination
Serial Concatenated Convolutional
Code Encoder
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RSC ENCODER
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RSC Encoder
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SCCC iterative decoder
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Inner MAP decoder with trellis
termination
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Branch Metrics
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Inner MAP decoder with trellis
termination
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Outer MAP decoder with trellis
termination
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Serial Concatenated Convolutional
Coding Without Trellis Termination
Serial Concatenated Convolutional Code
Encoder
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Decision making device
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RSC Encoder
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SCCC iterative decoder
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Inner MAP decoder (without trellis
termination)
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Inner MAP decoder (without trellis
termination)
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Outer MAP decoder (without trellis
termination)
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Outer MAP decoder (without trellis
termination)
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Parameters Used For Serial Concatenated
Convolutional Coding
]
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SCCC with trellis termination
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SCCC without trellis termination
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Comparison
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Transmitted and received signal with
trellis termination
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Transmitted and received signal without
trellis termination
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Future work
Serial concatenated convolutional coding is to beincorporated into the existing FBG based FFH
OCDMA system.
The use of suitable serial concatenated
convolutional error correction codes to improve thesystem performance of FBG based FFH OCDMA
system is to be studied.
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References A.Stoke and E.H.Sargent, Role of Optical CDMA in access networks,
IEEE Communications Magazine, Vol.40, No.9, Sep 2002.
Isamu Saeki, Shouhei Nishi and Koso Murakami, All-Optical Code
Division Multiplexing Switching Network Based on Self-Routing
Principle, IEICE Trans,Commun., Vol E82-B, no.2.Feb 1999,pp 239-
245.
M.Meenashi and I.Andonovic, Effect of physical Layer Impairments onSUM and AND Detection Stratergies for 2D-Optical CDMA, IEEE
Photonics technology Letters, Vol.17, No.4, April 2005.
Henrik Lundqvist, Student Member, Ieee, And Gunnar Karlsson, Senior
Member, IEEE On Error-Correction Coding For Cdma Pon Journal Of
Lightwave Technology, Vol. 23, No. 8, August 2005.
M. Kulkarni, R. K. Sinha, and D. R. Bhaskar System Performance
Comparison of Turbo and Trellis Coded Optical CDMA Systems
International Journal of Signal Processing Summer 2007.
Jin Young Kim, Member, IEEE, and H. Vincent Poo, Fellow, Member,
IEEE, OSA Turbo-Coded Optical Direct-Detection Cdma System With
Ppm Modulation Journal Of Lightwave Technology, Vol. 19, No. 3,
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References G. D. Forney Jr., Concatenated Codes Cambridge, MA: MIT Press,
1966.
S. Benedetto, D. Divsalar, G. Montorsi, and F. Pollara Serial
Concatenation of Interleaved Codes: Performance Analysis, Design,
and Iterative Decoding TDA Progress Report 42-126, August 15, 1996.
Krishna R. Narayanan, Student Member, IEEE, and Gordon L. Stuber,
Senior Member, IEEE Selective Serial Concatenation of Turbo CodesIEEE Communications Letters, Vol. 1, No. 5, September 1997.
Horia Balta and Maria Kovaci A study on turbo decoding iterative
algorithms Transactions on Electronics and Communications Tom
49(63), a Fscicola 2, 2004.
E. Boutillon, C. Douillard, G. Montorsi Iterative Decoding ofConcatenated Convolutional Codes: Implementation Issues,
Proceedings of the IEEE. , No. 6, June 2007.
Bernard Sklar, Digital Communications-Fundamentals and
Applications, Second Edition S. Benedetto, D. Divsalar, G. Montorsi,
and F. Pollara Serial Concatenation of Interleaved Codes:
Performance Analysis, Design, and Iterative Decoding TDA Progress-
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THANK YOU