Arbitration inter-frame spacing (AIFS), in wireless LAN communications, is a method of prioritizing one Access Category (AC) over the other, such as giving voice or video priority over email.
AIFS functions by shortening or expanding the period a wireless node has to wait before it is allowed to transmit its next frame.
A shorter AIFS period means a message has a higher probability of being transmitted with low latency, which is particularly important for delay-critical data such as voice or streaming video.
AIFS is a time interval between frames being transmitted under the IEEE 802.11e EDCA MAC.
Short Interframe Space (SIFS) is the time between a DATA and ACK frame.