802.11ac MAC Timings

What are MAC timing parameters in 802.11ac?

MAC timings refer to the specific time intervals used for coordinating frame transmission and medium access in 802.11ac.

What is the Slot Time in 802.11ac?

Slot Time is the basic time unit (usually 9 microseconds in 802.11ac) used for backoff and interframe spacing calculations.

What is the SIFS (Short Interframe Space) in 802.11ac?

SIFS is the shortest waiting time (typically 16 microseconds) between frames, used for ACKs, CTS, and data fragments.

What is the DIFS (DCF Interframe Space)?

DIFS is the time a device waits after the medium becomes idle before starting a new transmission; it is longer than SIFS.

How is the Backoff Time calculated?

Backoff Time is a random multiple of Slot Time used to avoid collisions in CSMA/CA before transmission.

What is the EIFS (Extended Interframe Space)?

EIFS is a longer wait time used after detecting erroneous frames, allowing time for acknowledgments or recovery.

How do MAC timings impact throughput in 802.11ac?

Efficient timing reduces idle time and collision, enhancing throughput and latency performance.

Are MAC timing parameters fixed in 802.11ac?

Many timing values like Slot Time and SIFS are standardized but can vary slightly depending on PHY layer specifics.

How does MAC timing relate to frame aggregation?

Aggregation affects timing because multiple frames are sent together, changing interframe spacing and acknowledgment timing.

What timing is used for Block ACK in 802.11ac?

Block ACK follows SIFS timing after a data aggregation burst for efficient acknowledgment of multiple frames.

What is the impact of RTS/CTS timing on MAC?

RTS/CTS frames use SIFS and DIFS timings to reserve the medium and avoid collisions before data transmission.

How does MAC timing support QoS in 802.11ac?

Different interframe spaces and contention windows enable traffic prioritization under EDCA.

Are MAC timing parameters the same as in 802.11n?

Mostly similar, but 802.11ac uses timings optimized for the 5 GHz band and enhanced features.

What timing constraints exist for power save modes?

Power save requires synchronization with beacon intervals and defined listen intervals to manage sleep cycles.

How is NAV timing used in MAC?

NAV indicates how long the medium will be busy, preventing other stations from transmitting prematurely.

What role does timing play in roaming?

Timing affects reassociation and handoff delays to ensure seamless transitions between APs.

Where are MAC timing parameters defined for 802.11ac?

Defined within the IEEE 802.11ac amendment to the 802.11 standard, aligned with PHY specifications.

How do MAC timings affect latency-sensitive applications?

Precise and reduced interframe spacing improves responsiveness for voice, video, and gaming.

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