The full form NAV in computer science is Network Allocation Vector.
It is a virtual aircraft carrier sensing system with wireless network protocols.
How does NAV work?
The wireless network protocols it uses are IEEE 802.11 and IEEE 802.16 that operates in the MAC ( Medium Access Control) layer. The necessity of physical career sensing is limited by the virtual career sensing at the air conjoin to save power.
The MAC layer frame headers that includes a duration field indicates the transferral time needed for the frame, when the channel will be busy. Before setting the NAV the station listens to the wireless medium and reads the duration field.
It is an instruction for a station, the amount of time it must wait from accessing the medium. When the data transmits, the value of the NAV is set to its maximum and gradually it decreases to zero at a same rate.
When the value is zero the virtual carrier sensing indicates that the medium is idle and other stations can contend for it.
But when it is not zero the indication shows busy which means no station contends for it.
How does energy conservation work through NAV?
The wireless stations are generally powered by battery. But if the NAV is inactive then the mobile stations need to check again and again if the channel is free. This task takes a way more considerable power.
Hence in order to save power the stations have power saving mode. However when NAV is used in the wireless network, no career sensing is needed to done by the devices. And thus energy conservation is performed.
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