The Arbitration Interframe Space (AIFS) is a fundamental component of the Enhanced Distributed Channel Access (EDCA) mechanism, which was introduced by the IEEE 802.11e amendment to provide Quality of Service (QoS) on Wi-Fi networks. Unlike the fixed Distributed Coordination Function Interframe Space (DIFS) used in legacy networks, AIFS is a variable time interval that a station must wait before contending for the medium. The duration of the AIFS depends on the Access Category (AC) of the data to be transmitted (e.g., Voice, Video, Best Effort, Background). Higher-priority traffic is assigned a shorter AIFS, giving it a statistical advantage in accessing the wireless medium over lower-priority traffic.

A: AIFS was introduced by 802.11e, not 802.11n, and is a widely implemented parameter within the EDCA access method as part of Wi-Fi Multimedia (WMM) certification.

C: AIFS is a MAC-layer timing parameter for medium contention, not a PHY-layer aggregation method. Aggregation is handled by mechanisms like A-MSDU and A-MPDU.

D: This describes power-saving functions. AIFS is related to medium access prioritization, not the duration a station can be in a low-power (sleep) state.

1. IEEE Std 802.11™-2020 (Revision of IEEE Std 802.11-2016), IEEE Standard for Information Technology—Telecommunications and Information Exchange between Systems Local and Metropolitan Area Networks—Specific Requirements - Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications.

Section 10.22.2.3 (EDCA timing): "A non-AP QSTA using the EDCA shall transmit a frame with a particular user priority (UP) when its carrier-sense mechanism determines that the medium is idle at the end of an AIFS period for that UP... The AIFS for a particular AC (AIFS[AC]) is defined by the following formula: AIFS[AC] = AIFSN[AC] × aSlotTime + aSIFSTime". This confirms AIFS is a variable interframe space dependent on the Access Category (AC).

2. Carnegie Mellon University, ECE Course 18-759: Wireless and Mobile Networking, Lecture 10: MAC Layer (Part 3).

Slide 15 ("EDCA (Enhanced Distributed Coordination Access)"): This slide explicitly states, "DIFS is replaced by AIFS (Arbitration Inter-Frame Spacing) whose value depends on the traffic class." It shows a diagram where higher priority classes (Voice, Video) have a shorter AIFS than lower priority classes (Best Effort, Background), illustrating how AIFS is used for prioritization.

3. Bianchi, G. (2000). Performance analysis of the IEEE 802.11 distributed coordination function. IEEE Journal on selected areas in communications, 18(3), 535-547. https://doi.org/10.1109/49.840210

While this paper predates 802.11e, it provides the foundational analysis of DCF and DIFS. Later works that analyze 802.11e, such as those by Mangold et al., build upon this to show how AIFS replaces DIFS to enable service differentiation, reinforcing that AIFS is an evolution of the interframe space concept for QoS. (Note: This reference provides context for the concept AIFS replaced).