Arbitration inter-frame spacing
 | This article provides insufficient context for those unfamiliar with the subject. (April 2010) |
| This article may be too technical for most readers to understand. (April 2010) |
Arbitration Inter Frame Spacing (AIFS) is a time interval between frames being transmitted under the IEEE 802.11e EDCA MAC. It depends on the Access Class (AC) and generally depends on the AIFSN, or AIFS-number. The AIFS is a method of prioritizing one 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 period means a message has a high probability of being transmitted with low latency, which is particularly important for delay-critical data such as voice or streaming video.
AIFS is defined as: AIFSN[AC]*ST+SIFS, where the AIFSN depends on the Access Class. Slot time ST (also denoted with ) is physical layer-dependent. SIFS is the Short Inter Frame Spacing, the time between a DATA and ACK frame.
