802.11r PHYs
==============


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        **What is the PHY layer used in IEEE 802.11r?**

        IEEE 802.11r does not define a new PHY; it uses the PHY layers defined in other 802.11 standards such as 802.11a, 802.11g, 802.11n, or 802.11ac.

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        **Does 802.11r modify the physical layer (PHY) transmissions?**

        No, 802.11r focuses on fast roaming at the MAC layer and key management but does not change PHY transmission methods.

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        **Can 802.11r be used with OFDM PHY?**

        Yes, 802.11r is compatible with OFDM PHYs such as those in 802.11a, 802.11n, and 802.11ac.

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        **Does 802.11r support PHY layer enhancements like MIMO?**

        802.11r works over PHYs that may have MIMO (like 802.11n/ac), but it itself does not add or modify MIMO features.

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        **How does 802.11r impact PHY layer channel switching?**

        802.11r supports fast roaming, which may require quick channel switching at the PHY layer as clients move between APs on different channels.

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        **Is 802.11r PHY-dependent?**

        No, 802.11r is designed to be PHY-independent and works on any standard-compliant PHY layer.

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        **Does 802.11r require PHY layer support for fast roaming?**

        The PHY layer itself does not require changes, but rapid re-association must be supported by the radio hardware for seamless transition.

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        **Can 802.11r be used with DSSS or FHSS PHYs?**

        While theoretically possible, 802.11r is primarily used with OFDM-based PHYs common in modern Wi-Fi (like 802.11a/n/ac).

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        **What is the typical channel bandwidth with 802.11r?**

        802.11r supports standard channel bandwidths used by the underlying PHY such as 20 MHz, 40 MHz, and 80 MHz channels.

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        **Does 802.11r affect modulation schemes at PHY?**

        No, modulation and coding schemes are determined by the PHY and channel conditions, independent of 802.11r.

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        **How does 802.11r support low latency at the PHY layer?**

        802.11r reduces upper-layer handoff delay but depends on PHY-layer speed and efficiency to deliver low-latency transmissions.

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        **Is there a specific PHY preamble for 802.11r?**

        No, 802.11r uses the standard PHY preamble of the underlying 802.11 standard in use.

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        **How does 802.11r interact with PHY power control?**

        802.11r relies on PHY power control mechanisms but does not alter them; power control helps maintain link quality during fast roaming.

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        **What PHY features enhance 802.11r roaming performance?**

        Features like MIMO, beamforming, and wider channels improve overall throughput and link robustness, complementing fast roaming.

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        **Does 802.11r influence PHY symbol timing?**

        No, symbol timing is controlled by the PHY standard; 802.11r operates above that layer.

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        **Is PHY layer synchronization affected by 802.11r?**

        No, synchronization (timing, frequency) is managed at the PHY and MAC layers independently from 802.11r functions.

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        **Can 802.11r improve PHY layer error rates?**

        Indirectly, by enabling faster roaming and reducing retransmissions due to better signal quality on the new AP.

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        **Are there PHY layer limitations for implementing 802.11r?**

        Hardware and driver support for rapid channel changes and fast re-association is essential, but no new PHY layer protocols are required.

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        **What PHY bands are typically used with 802.11r?**

        Both 2.4 GHz and 5 GHz bands are supported, as long as the underlying PHY and APs support 802.11r features.

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        Topics in this section,

                * :ref:`Reference links <phy_80211r_step17>`


.. _phy_80211r_step17:

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    .. tab-item:: Reference links

       * Reference links