802.11n MAC Timings
=======================


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        **What are MAC timings in IEEE 802.11n?**

        MAC timings define intervals and durations for frame transmission, acknowledgments, and backoff to control medium access.

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

        SIFS is the shortest waiting time between frames, used for acknowledgments and high priority transmissions.

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        **How does Distributed Interframe Space (DIFS) work?**

        DIFS is a waiting period before a station can contend for medium access after the channel is idle.

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        **What is Arbitration Interframe Space (AIFS)?**

        AIFS varies per traffic category in QoS to provide prioritized medium access in 802.11n.

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        **How does the backoff timer function in 802.11n MAC?**

        Stations pick a random backoff period within a contention window to reduce collisions before transmission.

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        **What are contention windows (CWmin and CWmax)?**

        CWmin and CWmax define the minimum and maximum range for random backoff intervals during channel contention.

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        **How is the contention window adjusted?**

        It doubles upon collisions (exponential backoff) until CWmax, then resets after successful transmissions.

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        **What timing governs acknowledgement (ACK) frames?**

        ACK frames are sent after a SIFS interval following successful frame reception.

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        **What is the role of Extended Interframe Space (EIFS)?**

        EIFS is a longer wait period after detecting erroneous frames, to avoid collisions during recovery.

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        **How does MAC timing support frame aggregation in 802.11n?**

        Timings are adjusted to accommodate longer aggregated frames and reduce overhead between them.

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        **What is the timing for Block Acknowledgment (BA)?**

        BAs are sent after a SIFS interval to acknowledge multiple frames in one response.

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        **How does MAC timing affect QoS in 802.11n?**

        Different traffic classes use varied AIFS and contention windows to prioritize access.

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        **What is slot time in 802.11n?**

        Slot time is the basic unit of backoff and timing, typically 9 microseconds for 802.11n in 5 GHz.

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        **Why is timing synchronization important in MAC?**

        It ensures coordinated transmissions, prevents collisions, and maintains fairness in medium access.

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        **How are MAC timings affected by different PHY rates?**

        Higher PHY rates may reduce frame durations but MAC timing intervals like SIFS remain constant.

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        **What timing mechanisms prevent hidden node collisions?**

        RTS/CTS handshake timings help reserve the medium and avoid collisions from hidden nodes.

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        **How do MAC timings interact with power save modes?**

        Stations use timing parameters to wake up and listen for buffered frames signaled in beacon intervals.

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        **What happens if timing intervals are not respected?**

        Violations can cause collisions, reduced throughput, and increased retransmissions.

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        **How does the MAC timing adapt in dense networks?**

        Contention windows may increase to reduce collisions, and QoS timings help prioritize critical traffic.


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        Topics in this section,

                * :ref:`Reference links <mac_timings_n_step17>`


.. _mac_timings_n_step17:

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    .. tab-item:: Reference links
     
       * Reference links