<s>
Statistical	B-Algorithm
multiplexing	I-Algorithm
is	O
a	O
type	O
of	O
communication	O
link	O
sharing	O
,	O
very	O
similar	O
to	O
dynamic	B-Protocol
bandwidth	I-Protocol
allocation	I-Protocol
(	O
DBA	O
)	O
.	O
</s>
<s>
In	O
statistical	B-Algorithm
multiplexing	I-Algorithm
,	O
a	O
communication	O
channel	O
is	O
divided	O
into	O
an	O
arbitrary	O
number	O
of	O
variable	O
bitrate	O
digital	O
channels	O
or	O
data	O
streams	O
.	O
</s>
<s>
This	O
is	O
an	O
alternative	O
to	O
creating	O
a	O
fixed	O
sharing	O
of	O
a	O
link	O
,	O
such	O
as	O
in	O
general	O
time	B-Protocol
division	I-Protocol
multiplexing	I-Protocol
(	O
TDM	B-Protocol
)	O
and	O
frequency	O
division	O
multiplexing	O
(	O
FDM	O
)	O
.	O
</s>
<s>
When	O
performed	O
correctly	O
,	O
statistical	B-Algorithm
multiplexing	I-Algorithm
can	O
provide	O
a	O
link	O
utilization	O
improvement	O
,	O
called	O
the	O
statistical	B-Algorithm
multiplexing	I-Algorithm
gain	O
.	O
</s>
<s>
Statistical	B-Algorithm
multiplexing	I-Algorithm
is	O
facilitated	O
through	O
packet	B-Algorithm
mode	I-Algorithm
or	O
packet-oriented	B-Protocol
communication	O
,	O
which	O
among	O
others	O
is	O
utilized	O
in	O
packet	B-Protocol
switched	I-Protocol
computer	O
networks	O
.	O
</s>
<s>
Each	O
stream	O
is	O
divided	O
into	O
packets	B-Protocol
that	O
normally	O
are	O
delivered	O
asynchronously	O
in	O
a	O
first-come	O
first-served	O
fashion	O
.	O
</s>
<s>
In	O
alternative	O
fashion	O
,	O
the	O
packets	B-Protocol
may	O
be	O
delivered	O
according	O
to	O
some	O
scheduling	O
discipline	O
for	O
fair	O
queuing	O
or	O
differentiated	O
and/or	O
guaranteed	O
quality	O
of	O
service	O
.	O
</s>
<s>
Statistical	B-Algorithm
multiplexing	I-Algorithm
of	O
an	O
analog	O
channel	O
,	O
for	O
example	O
a	O
wireless	O
channel	O
,	O
is	O
also	O
facilitated	O
through	O
the	O
following	O
schemes	O
:	O
</s>
<s>
Statistical	B-Algorithm
multiplexing	I-Algorithm
normally	O
implies	O
"	O
on-demand	O
"	O
service	O
rather	O
than	O
one	O
that	O
preallocates	O
resources	O
for	O
each	O
data	O
stream	O
.	O
</s>
<s>
Statistical	B-Algorithm
multiplexing	I-Algorithm
schemes	O
do	O
not	O
control	O
user	O
data	O
transmissions	O
.	O
</s>
<s>
Time	O
domain	O
statistical	B-Algorithm
multiplexing	I-Algorithm
(	O
packet	B-Protocol
mode	I-Protocol
communication	I-Protocol
)	O
is	O
similar	O
to	O
time-division	B-Protocol
multiplexing	I-Protocol
(	O
TDM	B-Protocol
)	O
,	O
except	O
that	O
,	O
rather	O
than	O
assigning	O
a	O
data	O
stream	O
to	O
the	O
same	O
recurrent	O
time	O
slot	O
in	O
every	O
TDM	B-Protocol
,	O
each	O
data	O
stream	O
is	O
assigned	O
time	O
slots	O
(	O
of	O
fixed	O
length	O
)	O
or	O
data	B-Protocol
frames	I-Protocol
(	O
of	O
variable	O
lengths	O
)	O
that	O
often	O
appear	O
to	O
be	O
scheduled	O
in	O
a	O
randomized	O
order	O
,	O
and	O
experience	O
varying	O
delay	O
(	O
while	O
the	O
delay	O
is	O
fixed	O
in	O
TDM	B-Protocol
)	O
.	O
</s>
<s>
Statistical	B-Algorithm
multiplexing	I-Algorithm
allows	O
the	O
bandwidth	O
to	O
be	O
divided	O
arbitrarily	O
among	O
a	O
variable	O
number	O
of	O
channels	O
(	O
while	O
the	O
number	O
of	O
channels	O
and	O
the	O
channel	O
data	O
rate	O
are	O
fixed	O
in	O
TDM	B-Protocol
)	O
.	O
</s>
<s>
Statistical	B-Algorithm
multiplexing	I-Algorithm
ensures	O
that	O
slots	O
will	O
not	O
be	O
wasted	O
(	O
whereas	O
TDM	B-Protocol
can	O
waste	O
slots	O
)	O
.	O
</s>
<s>
The	O
transmission	O
capacity	O
of	O
the	O
link	O
will	O
be	O
shared	O
by	O
only	O
those	O
users	O
who	O
have	O
packets	B-Protocol
.	O
</s>
<s>
Static	O
TDM	B-Protocol
and	O
other	O
circuit	O
switching	O
is	O
carried	O
out	O
at	O
the	O
physical	B-Application
layer	I-Application
in	O
the	O
OSI	O
model	O
and	O
TCP/IP	B-Protocol
model	I-Protocol
,	O
while	O
statistical	B-Algorithm
multiplexing	I-Algorithm
is	O
carried	O
out	O
at	O
the	O
data	B-Protocol
link	I-Protocol
layer	I-Protocol
and	O
above	O
.	O
</s>
<s>
In	O
statistical	B-Algorithm
multiplexing	I-Algorithm
,	O
each	O
packet	B-Protocol
or	O
frame	O
contains	O
a	O
channel/data	O
stream	O
identification	O
number	O
,	O
or	O
(	O
in	O
the	O
case	O
of	O
datagram	B-Protocol
communication	O
)	O
complete	O
destination	O
address	O
information	O
.	O
</s>
<s>
Examples	O
of	O
statistical	B-Algorithm
multiplexing	I-Algorithm
are	O
:	O
</s>
<s>
The	O
MPEG	O
transport	O
stream	O
for	O
digital	B-Application
TV	I-Application
transmission	O
.	O
</s>
<s>
Statistical	B-Algorithm
multiplexing	I-Algorithm
is	O
used	O
to	O
allow	O
several	O
video	O
,	O
audio	O
and	O
data	O
streams	O
of	O
different	O
data	O
rates	O
to	O
be	O
transmitted	O
over	O
a	O
bandwidth-limited	O
channel	O
(	O
see	O
Statistical	O
multiplexer	O
)	O
.	O
</s>
<s>
The	O
packets	B-Protocol
have	O
constant	O
lengths	O
.	O
</s>
<s>
The	O
UDP	B-Protocol
and	O
TCP	B-Protocol
protocols	I-Protocol
,	O
where	O
data	O
streams	O
from	O
several	O
application	O
processes	O
are	O
multiplexed	O
together	O
.	O
</s>
<s>
The	O
packets	B-Protocol
may	O
have	O
varying	O
lengths	O
.	O
</s>
<s>
The	O
port	B-Protocol
numbers	I-Protocol
constitute	O
channel	O
identification	O
numbers	O
(	O
and	O
also	O
address	O
information	O
)	O
.	O
</s>
<s>
The	O
X.25	B-Protocol
and	O
Frame	B-Protocol
Relay	I-Protocol
packet-switching	B-Protocol
protocols	O
,	O
where	O
the	O
packets	B-Protocol
have	O
varying	O
lengths	O
,	O
and	O
the	O
channel	O
number	O
is	O
denoted	O
virtual	O
connection	O
identifier	O
(	O
VCI	O
)	O
.	O
</s>
<s>
The	O
international	O
collection	O
of	O
X.25	B-Protocol
providers	O
,	O
using	O
the	O
X.25	B-Protocol
protocol	I-Protocol
suite	I-Protocol
was	O
colloquially	O
known	O
as	O
"	O
the	O
Packet	B-Protocol
switched	I-Protocol
network	I-Protocol
"	O
in	O
the	O
1980s	O
and	O
into	O
the	O
beginning	O
of	O
the	O
1990s	O
.	O
</s>
<s>
The	O
Asynchronous	O
Transfer	O
Mode	O
packet-switched	B-Protocol
protocol	O
,	O
where	O
the	O
packets	B-Protocol
have	O
fixed	O
length	O
.	O
</s>
