List of PPDUs Supported in 802.11n
========================================


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        **What is a PPDU in IEEE 802.11n?**

        A PPDU is the Physical Protocol Data Unit, the format used to transmit data at the physical layer in 802.11n.

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        **What are the main components of an 802.11n PPDU?**

        It consists of a preamble, SIGNAL field, and data payload fields.

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        **How does 802.11n PPDU differ from earlier 802.11 standards?**

        802.11n introduces HT (High Throughput) PPDUs with enhanced preambles and multiple spatial streams.

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        **What is the purpose of the preamble in 802.11n PPDU?**

        The preamble synchronizes transmitter and receiver and allows channel estimation.

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        **What types of PPDUs are defined in 802.11n?**

        Legacy PPDU, HT Mixed PPDU, and HT Greenfield PPDU.

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        **What is the HT Mixed PPDU?**

        A PPDU type compatible with legacy 802.11a/b/g devices, containing a legacy preamble plus HT fields.

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        **What is the HT Greenfield PPDU?**

        A PPDU type optimized for 802.11n-only networks with no legacy preamble, improving efficiency.

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        **How does MIMO affect the PPDU structure in 802.11n?**

        Multiple spatial streams are transmitted simultaneously, increasing the data payload in the PPDU.

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        **What modulation schemes are used in 802.11n PPDU?**

        OFDM modulation with BPSK, QPSK, 16-QAM, or 64-QAM depending on the data rate.

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        **What is the SIGNAL field in the 802.11n PPDU?**

        It carries information about the modulation, coding rate, length, and MCS index.

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        **How long is the preamble in 802.11n PPDUs?**

        It varies depending on the PPDU type, ranging from 16 to 40 microseconds.

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        **What is the purpose of the HT-SIG field?**

        The HT-SIG field provides signaling specific to the HT (High Throughput) mode like MCS and spatial stream count.

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        **Does the 802.11n PPDU support channel bonding?**

        Yes, PPDUs can use 40 MHz channels by bonding two adjacent 20 MHz channels.

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        **How does channel bonding impact the PPDU?**

        It increases the data payload capacity and throughput by using wider channels.

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        **Are PPDUs encrypted in 802.11n?**

        Encryption is applied at higher layers; PPDU itself carries encoded but not encrypted data.

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        **How is error detection handled in the PPDU?**

        Error detection uses CRC in the MAC layer, and channel coding at the PHY layer protects the PPDU.

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        **What is the maximum data rate achievable with 802.11n PPDUs?**

        Up to 600 Mbps using 4 spatial streams and 40 MHz channels.

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        **How does 802.11n ensure backward compatibility via PPDUs?**

        By including legacy preambles in HT Mixed PPDUs so older devices can detect transmissions.

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        **What is the difference between PPDU and MPDU?**

        PPDU is the physical layer data unit including preamble and payload, MPDU is the MAC Protocol Data Unit inside the payload.



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        Topics in this section,

                * :ref:`Reference links <ppdu_n_step17>`

.. _ppdu_n_step17:

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