Arbitration inter-frame spacing
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.
Source: Wikipedia — Arbitration inter-frame spacing (CC BY-SA 4.0)