arbitrated interframe space (AIFS)

In a WLAN, when the transmission medium is free for a certain time corresponding to a new interframe space( IFS), an independent backoff algorithm is triggered for each traffic category( TC).

The new interframe space is called arbitrated interframe space (AIFS). It represents a minimum waiting time after which the transmission medium can be accessed. The AIFS depends on the traffic class and is smaller the higher the priority. It therefore becomes very small for real-time applications such as voice transmissions and can correspond to the backoff as a minimum.

Prioritization in WLANs using Interframe Spaces (IFS)

The AIFS interval can be used to define the quality of service( QoS) by means of priority control. To prevent stations with the same priority from interfering with each other, the various IFS intervals are extended by backoff times of different lengths.

The smallest AIFS interval has a duration of about 30 µs for 802.11a and 802.11e and corresponds to the Point Interframe Space( PIFS).