<s>
Dynamic	B-Protocol
Single	I-Protocol
Frequency	I-Protocol
Networks	I-Protocol
(	O
DSFN	B-Protocol
)	O
is	O
a	O
transmitter	O
macrodiversity	B-Protocol
technique	O
for	O
OFDM	B-Protocol
based	O
cellular	O
networks	O
.	O
</s>
<s>
DSFN	B-Protocol
is	O
based	O
on	O
the	O
idea	O
of	O
single	B-Device
frequency	I-Device
networks	I-Device
(	O
SFN	O
)	O
,	O
which	O
is	O
a	O
group	O
of	O
radio	O
transmitters	O
that	O
send	O
the	O
same	O
signal	O
simultaneously	O
over	O
the	O
same	O
frequency	O
.	O
</s>
<s>
Digital	O
wireless	O
communication	O
systems	O
based	O
on	O
the	O
OFDM	B-Protocol
modulation	B-Application
scheme	O
are	O
well-suited	O
to	O
SFN	O
operation	O
,	O
since	O
OFDM	B-Protocol
in	O
combination	O
with	O
some	O
forward	O
error	B-Error_Name
correction	I-Error_Name
scheme	O
can	O
eliminate	O
intersymbol	O
interference	O
and	O
fading	O
caused	O
by	O
multipath	O
propagation	O
without	O
the	O
use	O
of	O
complex	O
equalization	B-Algorithm
.	O
</s>
<s>
The	O
concept	O
of	O
DSFN	B-Protocol
implies	O
the	O
SFN	O
grouping	O
is	O
changed	O
dynamically	O
over	O
time	O
,	O
from	O
timeslot	O
to	O
timeslot	O
.	O
</s>
<s>
The	O
aim	O
is	O
to	O
achieve	O
efficient	O
spectrum	O
utilization	O
for	O
downlink	O
unicast	B-Protocol
or	O
multicast	O
communication	O
services	O
in	O
centrally	O
controlled	O
cellular	O
systems	O
based	O
on	O
for	O
example	O
the	O
OFDM	B-Protocol
modulation	B-Application
scheme	O
.	O
</s>
<s>
DSFN	B-Protocol
can	O
be	O
considered	O
as	O
a	O
combination	O
of	O
packet	O
scheduling	O
,	O
macro-diversity	B-Protocol
and	O
dynamic	B-Protocol
channel	I-Protocol
allocation	I-Protocol
(	O
DCA	O
)	O
.	O
</s>
<s>
The	O
scheduling	O
algorithm	O
can	O
be	O
further	O
extended	O
to	O
dynamically	O
assign	O
other	O
radio	B-Protocol
resource	I-Protocol
management	I-Protocol
parameters	O
to	O
each	O
timeslot	O
and	O
transmitter	O
,	O
such	O
as	O
modulation	B-Application
scheme	O
and	O
error	B-Error_Name
correction	I-Error_Name
scheme	O
,	O
in	O
view	O
to	O
optimize	O
the	O
efficiency	O
.	O
</s>
<s>
DSFN	B-Protocol
makes	O
it	O
possible	O
to	O
increase	O
the	O
received	O
signal	O
strength	O
to	O
a	O
mobile	O
terminal	O
in	O
between	O
several	O
base	O
station	O
transmitters	O
in	O
comparison	O
to	O
non-macrodiversity	O
communication	O
schemes	O
.	O
</s>
<s>
Thus	O
,	O
DSFN	B-Protocol
can	O
improve	O
the	O
coverage	O
area	O
and	O
lessen	O
the	O
outage	O
probability	O
.	O
</s>
<s>
Alternatively	O
,	O
DSFN	B-Protocol
may	O
allow	O
the	O
same	O
outage	O
probability	O
with	O
a	O
less	O
robust	O
but	O
more	O
efficient	O
modulation	B-Application
and	O
error	B-Error_Name
coding	I-Error_Name
scheme	O
,	O
and	O
thus	O
improve	O
the	O
spectral	B-Protocol
efficiency	I-Protocol
in	O
bit/s/Hz/base	O
station	O
transmitter	O
in	O
comparison	O
to	O
a	O
non-macrodiversity	O
communication	O
scheme	O
.	O
</s>
<s>
DSFN	B-Protocol
resembles	O
the	O
CDMA	B-Protocol
downlink	O
soft	B-Protocol
handover	I-Protocol
.	O
</s>
<s>
A	O
difference	O
is	O
that	O
in	O
the	O
CDMA	B-Protocol
case	O
,	O
co-channel	O
interference	O
from	O
transmissions	O
to	O
other	O
users	O
are	O
more	O
efficiently	O
avoided	O
by	O
giving	O
the	O
other	O
users	O
other	O
spreading	O
codes	O
.	O
</s>
<s>
A	O
special	O
form	O
of	O
DSFN	B-Protocol
is	O
Continuous	O
Transmission	O
DSFN	B-Protocol
,	O
where	O
all	O
base	O
station	O
transmitters	O
always	O
transmit	O
at	O
full	O
power	O
,	O
without	O
blocking	O
of	O
non-utilized	O
transmitters	O
,	O
and	O
without	O
power	O
control	O
.	O
</s>
<s>
This	O
concept	O
is	O
very	O
similar	O
to	O
so	O
called	O
Virtual	O
cellular	O
networks	O
(	O
VCNs	O
)	O
,	O
where	O
a	O
virtual	O
cell	O
is	O
a	O
group	O
of	O
base	O
stations	O
sending	O
using	O
the	O
same	O
spreading	O
code	O
,	O
or	O
a	O
group	O
of	O
OFDM	B-Protocol
transmitters	O
form	O
a	O
Single	B-Device
Frequency	I-Device
Network	I-Device
.	O
</s>
<s>
DSFN	B-Protocol
schemes	O
can	O
be	O
described	O
as	O
a	O
form	O
of	O
"	O
virtual	O
"	O
power	O
control	O
.	O
</s>
