<s>
Serial	B-Error_Name
concatenated	I-Error_Name
convolutional	I-Error_Name
codes	I-Error_Name
(	O
SCCC	O
)	O
are	O
a	O
class	O
of	O
forward	B-Error_Name
error	I-Error_Name
correction	I-Error_Name
(	O
FEC	O
)	O
codes	O
highly	O
suitable	O
for	O
turbo	B-Error_Name
(	O
iterative	O
)	O
decoding	O
.	O
</s>
<s>
A	O
distinguishing	O
feature	O
of	O
SCCCs	O
is	O
the	O
use	O
of	O
a	O
recursive	B-Error_Name
convolutional	I-Error_Name
code	I-Error_Name
as	O
the	O
inner	O
code	O
.	O
</s>
<s>
The	O
analysis	O
of	O
SCCCs	O
was	O
spawned	O
in	O
part	O
by	O
the	O
earlier	O
discovery	O
of	O
turbo	B-Error_Name
codes	I-Error_Name
in	O
1993	O
.	O
</s>
<s>
The	O
research	O
offered	O
SCCC	O
's	O
as	O
a	O
form	O
of	O
turbo-like	O
serial	O
concatenated	O
codes	O
that	O
1	O
)	O
were	O
iteratively	O
( 	O
 '	O
turbo	B-Error_Name
 '	O
)	O
decodable	O
with	O
reasonable	O
complexity	O
,	O
and	O
2	O
)	O
gave	O
error	O
correction	O
performance	O
comparable	O
with	O
the	O
turbo	B-Error_Name
codes	I-Error_Name
.	O
</s>
<s>
Additionally	O
,	O
the	O
constituent	O
codes	O
used	O
in	O
prior	O
forms	O
of	O
serial	O
concatenated	O
codes	O
were	O
generally	O
too	O
complex	O
for	O
reasonable	O
soft-in-soft-out	O
(	O
SISO	B-Error_Name
)	O
decoding	O
.	O
</s>
<s>
SISO	B-Error_Name
decoding	O
is	O
considered	O
essential	O
for	O
turbo	B-Error_Name
decoding	O
.	O
</s>
<s>
Serial	B-Error_Name
concatenated	I-Error_Name
convolutional	I-Error_Name
codes	I-Error_Name
have	O
not	O
found	O
widespread	O
commercial	O
use	O
,	O
although	O
they	O
were	O
proposed	O
for	O
communications	O
standards	O
such	O
as	O
DVB-S2	O
.	O
</s>
<s>
Nonetheless	O
,	O
the	O
analysis	O
of	O
SCCCs	O
has	O
provided	O
insight	O
into	O
the	O
performance	O
and	O
bounds	O
of	O
all	O
types	O
of	O
iterative	O
decodable	O
codes	O
including	O
turbo	B-Error_Name
codes	I-Error_Name
and	O
LDPC	B-Error_Name
codes	I-Error_Name
.	O
</s>
<s>
Serial	B-Error_Name
concatenated	I-Error_Name
convolutional	I-Error_Name
codes	I-Error_Name
were	O
first	O
analyzed	O
with	O
a	O
view	O
toward	O
turbo	B-Error_Name
decoding	O
in	O
"	O
Serial	O
Concatenation	O
of	O
Interleaved	O
Codes	O
:	O
Performance	O
Analysis	O
,	O
Design	O
,	O
and	O
Iterative	O
Decoding	O
"	O
by	O
S	O
.	O
Benedetto	O
,	O
D	O
.	O
Divsalar	O
,	O
G	O
.	O
Montorsi	O
and	O
F	O
.	O
Pollara	O
.	O
</s>
<s>
This	O
analysis	O
yielded	O
a	O
set	O
of	O
observations	O
for	O
designing	O
high	O
performance	O
,	O
turbo	B-Error_Name
decodable	O
serial	O
concatenated	O
codes	O
that	O
resembled	O
turbo	B-Error_Name
codes	I-Error_Name
.	O
</s>
<s>
Additional	O
analysis	O
of	O
SCCCs	O
was	O
done	O
in	O
"	O
Coding	O
Theorems	O
for	O
'	O
Turbo-Like	O
'	O
Codes	O
"	O
by	O
D	O
.	O
Divsalar	O
,	O
Hui	O
Jin	O
,	O
and	O
Robert	O
J	O
.	O
McEliece	O
.	O
</s>
<s>
This	O
paper	O
analyzed	O
repeat-accumulate	O
(	O
RA	O
)	O
codes	O
which	O
are	O
the	O
serial	O
concatenation	O
of	O
an	O
inner	O
two-state	O
recursive	B-Error_Name
convolutional	I-Error_Name
code	I-Error_Name
(	O
also	O
called	O
an	O
'	O
accumulator	O
 '	O
or	O
parity-check	O
code	O
)	O
with	O
a	O
simple	O
repeat	O
code	O
as	O
the	O
outer	O
code	O
,	O
with	O
both	O
codes	O
linked	O
by	O
an	O
interleaver	O
.	O
</s>
<s>
SCCC	O
codes	O
were	O
further	O
analyzed	O
in	O
"	O
Serial	O
Turbo	B-Error_Name
Trellis	O
Coded	O
Modulation	O
with	O
Rate-1	O
Inner	O
Code	O
"	O
.	O
</s>
<s>
Excellent	O
performing	O
codes	O
with	O
inner	O
and	O
outer	O
constituent	O
convolutional	B-Error_Name
codes	I-Error_Name
of	O
only	O
two	O
or	O
four	O
states	O
were	O
presented	O
.	O
</s>
<s>
The	O
example	O
encoder	O
is	O
composed	O
of	O
a	O
16-state	O
outer	O
convolutional	B-Error_Name
code	I-Error_Name
and	O
a	O
2-state	O
inner	O
convolutional	B-Error_Name
code	I-Error_Name
linked	O
by	O
an	O
interleaver	O
.	O
</s>
<s>
For	O
example	O
,	O
an	O
overall	O
code	O
rate	O
of	O
1/2	O
may	O
be	O
achieved	O
by	O
puncturing	O
the	O
outer	O
convolutional	B-Error_Name
code	I-Error_Name
to	O
rate	O
3/4	O
and	O
the	O
inner	O
convolutional	B-Error_Name
code	I-Error_Name
to	O
rate	O
2/3	O
.	O
</s>
<s>
A	O
recursive	O
inner	O
convolutional	B-Error_Name
code	I-Error_Name
is	O
preferable	O
for	O
turbo	B-Error_Name
decoding	O
of	O
the	O
SCCC	O
.	O
</s>
<s>
The	O
SCCC	O
decoder	O
includes	O
two	O
soft-in-soft-out	O
(	O
SISO	B-Error_Name
)	O
decoders	O
and	O
an	O
interleaver	O
.	O
</s>
<s>
While	O
shown	O
as	O
separate	O
units	O
,	O
the	O
two	O
SISO	B-Error_Name
decoders	O
may	O
share	O
all	O
or	O
part	O
of	O
their	O
circuitry	O
.	O
</s>
<s>
The	O
SISO	B-Error_Name
decoding	O
may	O
be	O
done	O
is	O
serial	O
or	O
parallel	O
fashion	O
,	O
or	O
some	O
combination	O
thereof	O
.	O
</s>
<s>
The	O
SISO	B-Error_Name
decoding	O
is	O
typically	O
done	O
using	O
Maximum	B-General_Concept
a	I-General_Concept
posteriori	I-General_Concept
(	O
MAP	O
)	O
decoders	O
using	O
the	O
BCJR	B-Error_Name
algorithm	I-Error_Name
.	O
</s>
<s>
SCCCs	O
provide	O
performance	O
comparable	O
to	O
other	O
iteratively	O
decodable	O
codes	O
including	O
turbo	B-Error_Name
codes	I-Error_Name
and	O
LDPC	B-Error_Name
codes	I-Error_Name
.	O
</s>
