Network Allocation Vector
Encyclopedia
The Network Allocation Vector (NAV) is virtual carrier sensing mechanism used with wireless network protocols such as IEEE 802.11
and IEEE 802.16
(WiMax). The virtual carrier sensing is a logical abstraction which limits the need for physical carrier sensing at the air interface in order to save power. The MAC layer
frame headers contain a Duration field that specifies the transmission time required for the frame, in which time the medium will be busy. The stations listening on the wireless medium read the Duration field and set their NAV, which is an indicator for a station on how long it must defer from accessing the medium.
The NAV may be thought of as a counter, which counts down to zero at a uniform rate. When the counter is zero, the virtual CS indication is that the medium is idle; when nonzero, the indication is busy. The medium shall be determined to be busy when the STA is transmitting.
Wireless stations
are often battery powered, so in order to conserve power the stations may enter a power-saving mode. A station decrements its NAV counter until it becomes zero, at which time it is awaken to sense the medium again.
The NAV virtual carrier sensing mechanism is a prominent part of the CSMA/CA
MAC
protocol used with IEEE 802.11
WLANs. NAV is used in DCF
, PCF
and HCF.
IEEE 802.11
IEEE 802.11 is a set of standards for implementing wireless local area network computer communication in the 2.4, 3.6 and 5 GHz frequency bands. They are created and maintained by the IEEE LAN/MAN Standards Committee . The base version of the standard IEEE 802.11-2007 has had subsequent...
and IEEE 802.16
IEEE 802.16
IEEE 802.16 is a series of Wireless Broadband standards authored by the Institute of Electrical and Electronics Engineers . The IEEE Standards Board in established a working group in 1999 to develop standards for broadband Wireless Metropolitan Area Networks...
(WiMax). The virtual carrier sensing is a logical abstraction which limits the need for physical carrier sensing at the air interface in order to save power. The MAC layer
Media Access Control
The media access control data communication protocol sub-layer, also known as the medium access control, is a sublayer of the data link layer specified in the seven-layer OSI model , and in the four-layer TCP/IP model...
frame headers contain a Duration field that specifies the transmission time required for the frame, in which time the medium will be busy. The stations listening on the wireless medium read the Duration field and set their NAV, which is an indicator for a station on how long it must defer from accessing the medium.
The NAV may be thought of as a counter, which counts down to zero at a uniform rate. When the counter is zero, the virtual CS indication is that the medium is idle; when nonzero, the indication is busy. The medium shall be determined to be busy when the STA is transmitting.
Wireless stations
Station (networking)
In IEEE 802.11 terminology, a station is a device that has the capability to use the 802.11 protocol. For example, a station may be a laptop, a desktop PC, PDA, access point or Wi-Fi phone. A STA may be fixed, mobile or portable...
are often battery powered, so in order to conserve power the stations may enter a power-saving mode. A station decrements its NAV counter until it becomes zero, at which time it is awaken to sense the medium again.
The NAV virtual carrier sensing mechanism is a prominent part of the CSMA/CA
Carrier sense multiple access with collision avoidance
Carrier sense multiple access with collision avoidance , in computer networking, is a wireless network multiple access method in which:*a carrier sensing scheme is used....
MAC
Media Access Control
The media access control data communication protocol sub-layer, also known as the medium access control, is a sublayer of the data link layer specified in the seven-layer OSI model , and in the four-layer TCP/IP model...
protocol used with IEEE 802.11
IEEE 802.11
IEEE 802.11 is a set of standards for implementing wireless local area network computer communication in the 2.4, 3.6 and 5 GHz frequency bands. They are created and maintained by the IEEE LAN/MAN Standards Committee . The base version of the standard IEEE 802.11-2007 has had subsequent...
WLANs. NAV is used in DCF
Distributed Coordination Function
Distributed coordination function is the fundamental MAC technique of the IEEE 802.11 based WLAN standard. DCF employs a CSMA/CA with binary exponential backoff algorithm....
, PCF
Point Coordination Function
Point coordination function is a Media Access Control technique used in IEEE 802.11 based WLANs. It resides in a point coordinator also known as Access Point , to coordinate the communication within the network. The AP waits for PIFS duration rather than DIFS duration to grasp the channel...
and HCF.