Network Allocation Vector

The power allocation vector ( network allocation vector, NAV) is a tool for virtual carrier sense in the industry standard IEEE 802.11 Wireless Local Area Networks ( WLAN).

In a WLAN, all networked computers to share a single communication medium. Would simultaneously transmit data on the medium a plurality of computers, it would lead to data collisions, and thus to delay or even loss of information. The aim of the virtual carrier sense is to prevent simultaneous transmission attempts. These are each sender before sending its data known how long he will occupy the medium. The computers of the network manage this additional information in the network occupancy vector and can thus estimate when the medium is available again at the earliest.

Each computer of the network internally managed its own power allocation vector. Receives a computer information of the form " the medium is busy for the next x seconds ", the expected occupancy time interval is entered in the network occupancy vector. This value is regularly counted down the time until it reaches zero. The calculator takes no transmission attempts, as long as the network allocation vector is not zero.

In WLANs, the time specification is not seconds or any other time unit, but in the expected number of data frames. Contrary to the name is a network allocation vector is not a vector in the mathematical sense, but a pure counter variable. Power allocation vectors have also been adopted in other network protocols after the introduction in the 802.11 standard, for example, sensor media access control.

• Wi-Fi