<s>
The	O
network	B-Protocol
allocation	I-Protocol
vector	I-Protocol
(	O
NAV	O
)	O
is	O
a	O
virtual	O
carrier-sensing	O
mechanism	O
used	O
with	O
wireless	O
network	O
protocols	O
such	O
as	O
IEEE	O
802.11	O
(	O
Wi-Fi	O
)	O
and	O
IEEE	O
802.16	O
(	O
WiMax	O
)	O
.	O
</s>
<s>
The	O
MAC	B-Protocol
layer	I-Protocol
frame	O
headers	O
contain	O
a	O
duration	O
field	O
that	O
specifies	O
the	O
transmission	O
time	O
required	O
for	O
the	O
frame	O
,	O
in	O
which	O
time	O
the	O
medium	O
will	O
be	O
busy	O
.	O
</s>
<s>
Wireless	B-Protocol
stations	I-Protocol
are	O
often	O
battery-powered	O
,	O
so	O
to	O
conserve	O
power	O
the	O
stations	O
may	O
enter	O
a	O
power-saving	O
mode	O
.	O
</s>
<s>
The	O
NAV	O
virtual	O
carrier	O
sensing	O
mechanism	O
is	O
a	O
prominent	O
part	O
of	O
the	O
CSMA/CA	O
MAC	B-Protocol
protocol	I-Protocol
used	O
with	O
IEEE	O
802.11	O
WLANs	O
.	O
</s>
