<s>
A	O
space	B-Protocol
–	I-Protocol
time	I-Protocol
code	I-Protocol
(	O
STC	O
)	O
is	O
a	O
method	O
employed	O
to	O
improve	O
the	O
reliability	O
of	O
data	O
transmission	O
in	O
wireless	O
communication	O
systems	O
using	O
multiple	O
transmit	O
antennas	O
.	O
</s>
<s>
STCs	O
rely	O
on	O
transmitting	O
multiple	O
,	O
redundant	B-General_Concept
copies	O
of	O
a	O
data	O
stream	O
to	O
the	O
receiver	O
in	O
the	O
hope	O
that	O
at	O
least	O
some	O
of	O
them	O
may	O
survive	O
the	O
physical	O
path	O
between	O
transmission	O
and	O
reception	O
in	O
a	O
good	O
enough	O
state	O
to	O
allow	O
reliable	O
decoding	O
.	O
</s>
<s>
Space	B-Protocol
time	I-Protocol
codes	I-Protocol
may	O
be	O
split	O
into	O
two	O
main	O
types	O
:	O
</s>
<s>
Space	O
–	O
time	O
trellis	O
codes	O
(	O
STTCs	O
)	O
distribute	O
a	O
trellis	B-Error_Name
code	I-Error_Name
over	O
multiple	O
antennas	O
and	O
multiple	O
time-slots	O
and	O
provide	O
both	O
coding	O
gain	O
and	O
diversity	B-Protocol
gain	I-Protocol
.	O
</s>
<s>
Space	O
–	O
time	O
block	O
codes	O
(	O
STBCs	O
)	O
act	O
on	O
a	O
block	O
of	O
data	O
at	O
once	O
(	O
similarly	O
to	O
block	O
codes	O
)	O
and	O
also	O
provide	O
diversity	B-Protocol
gain	I-Protocol
but	O
does	O
n't	O
provide	O
coding	O
gain	O
.	O
</s>
<s>
The	O
STLC	O
scheme	O
provides	O
full	O
diversity	B-Protocol
gain	I-Protocol
even	O
when	O
there	O
is	O
no	O
full	O
channel	O
state	O
information	O
(	O
CSI	O
)	O
at	O
the	O
receiver	O
.	O
</s>
<s>
In	O
differential	O
space	B-Protocol
–	I-Protocol
time	I-Protocol
codes	I-Protocol
neither	O
the	O
channel	O
nor	O
the	O
statistics	O
of	O
the	O
channel	O
are	O
available	O
.	O
</s>
