<s>
A-VSB	B-Device
or	O
Advanced	O
VSB	O
is	O
a	O
modification	O
of	O
the	O
8VSB	B-Device
modulation	B-Application
system	O
used	O
for	O
transmission	O
of	O
digital	B-Application
television	I-Application
using	O
the	O
ATSC	B-Device
system	I-Device
.	O
</s>
<s>
One	O
of	O
the	O
constraints	O
of	O
conventional	O
ATSC	B-Device
transmission	O
is	O
that	O
reliable	O
reception	O
is	O
difficult	O
or	O
impossible	O
when	O
the	O
receiver	B-Application
is	O
moving	O
at	O
speeds	O
associated	O
with	O
normal	O
vehicular	O
traffic	O
.	O
</s>
<s>
The	O
technology	O
was	O
jointly	O
developed	O
by	O
Samsung	B-Application
and	O
Rohde	O
&	O
Schwarz	O
.	O
</s>
<s>
A-VSB	B-Device
builds	O
on	O
the	O
existing	O
ATSC	B-Device
transmission	O
standard	O
to	O
enhance	O
DTV	B-Application
receivers’	O
ability	O
to	O
receive	O
the	O
main	O
MPEG	O
transport	O
stream	O
in	O
dynamic	O
environments	O
.	O
</s>
<s>
The	O
system	O
enables	O
broadcasters	O
to	O
include	O
multiple	O
streams	O
with	O
additional	O
error	B-Error_Name
correction	I-Error_Name
and	O
time	B-Protocol
diversity	I-Protocol
encoding	O
for	O
enhanced	O
reception	O
.	O
</s>
<s>
In	O
addition	O
,	O
A-VSB	B-Device
facilitates	O
synchronization	O
of	O
multiple	O
transmission	O
towers	O
,	O
which	O
should	O
improve	O
coverage	O
with	O
higher	O
uniform	O
signal	O
strength	O
throughout	O
a	O
service	O
area	O
,	O
even	O
in	O
locations	O
that	O
normally	O
would	O
be	O
shielded	O
by	O
obstacles	O
such	O
as	O
hills	O
or	O
buildings	O
.	O
</s>
<s>
A-VSB	B-Device
incorporates	O
three	O
new	O
elements	O
:	O
a	O
Supplementary	O
Reference	O
Signal	O
(	O
SRS	O
)	O
,	O
a	O
Scalable	O
Turbo	B-Application
Stream	O
(	O
STS	O
)	O
,	O
and	O
support	O
for	O
Single	O
Frequency	O
Networks	O
(	O
SFN	O
)	O
.	O
</s>
<s>
A-VSB	B-Device
receivers	O
utilize	O
the	O
SRS	O
in	O
order	O
to	O
remain	O
synchronized	O
with	O
the	O
transmission	O
.	O
</s>
<s>
This	O
helps	O
maintain	O
reception	O
of	O
the	O
main	O
stream	O
and	O
any	O
turbo	B-Application
streams	O
even	O
with	O
rapidly	O
changing	O
multipath	O
interference	O
,	O
such	O
as	O
when	O
the	O
signal	O
is	O
reflected	O
from	O
moving	O
objects	O
near	O
the	O
receiver	B-Application
or	O
when	O
the	O
receiver	B-Application
itself	O
is	O
moving	O
.	O
</s>
<s>
The	O
SRS	O
adds	O
an	O
additional	O
equalizer	B-Algorithm
training	O
sequence	O
to	O
the	O
Transport	O
Stream	O
Adaptation	O
Field	O
,	O
which	O
should	O
be	O
ignored	O
by	O
existing	O
transport	O
decoders	O
.	O
</s>
<s>
The	O
added	O
signal	O
shortens	O
the	O
existing	O
24ms	O
equalizer	B-Algorithm
update	O
time	O
by	O
a	O
selectable	O
factor	O
,	O
from	O
120x	O
to	O
312x	O
.	O
</s>
<s>
A	O
receiver	B-Application
equipped	O
with	O
this	O
new	O
equalizer	B-Algorithm
can	O
track	O
rapid	O
multipath	O
fading	O
,	O
and	O
thus	O
supports	O
mobile	O
reception	O
.	O
</s>
<s>
The	O
addition	O
of	O
a	O
new	O
turbo-coded	O
stream	O
enables	O
broadcasters	O
to	O
increase	O
the	O
error-correction	B-Error_Name
capability	O
of	O
a	O
secondary	O
stream	O
transmission	O
.	O
</s>
<s>
Two	O
options	O
are	O
proposed	O
for	O
the	O
turbo	B-Application
stream	O
:	O
½	O
and	O
¼	O
rate	O
codes	O
,	O
i.e.	O
,	O
the	O
new	O
video	O
stream	O
requires	O
2x	O
or	O
4x	O
the	O
video	O
rate	O
in	O
final	O
transport	O
payload	O
.	O
</s>
<s>
Conventional	O
8VSB	B-Device
has	O
a	O
TOV	O
SNR	O
of	O
15.1	O
dB	O
.	O
</s>
<s>
The	O
turbo	B-Application
codec	O
uses	O
single-input	O
single-output	O
(	O
SISO	O
)	O
iterative	O
decoding	O
and	O
time	O
interleaving	O
.	O
</s>
