802.11ah PHYs
==============


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        **What frequency band does the 802.11ah PHY operate in?**

        The 802.11ah PHY operates primarily in the sub-1 GHz unlicensed bands (around 900 MHz).

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        **What modulation schemes does 802.11ah PHY support?**

        It supports various modulation schemes including BPSK, QPSK, 16-QAM, and 64-QAM.

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        **What channel bandwidths are defined for 802.11ah PHY?**

        Channel bandwidths include 1 MHz, 2 MHz, 4 MHz, 8 MHz, and 16 MHz.

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        **How does 802.11ah PHY achieve long-range communication?**

        By operating at lower frequencies with narrow channel bandwidths and using robust modulation and coding schemes.

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        **What type of OFDM does 802.11ah PHY use?**

        It uses OFDM tailored for narrowband channels with longer symbol durations to improve resilience.

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        **What is the maximum data rate supported by 802.11ah PHY?**

        The maximum theoretical data rate is approximately 347 Mbps under ideal conditions.

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        **How does 802.11ah PHY handle multipath fading?**

        It employs convolutional coding, interleaving, and robust OFDM subcarrier modulation to mitigate multipath effects.

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        **What is the OFDM symbol duration in 802.11ah PHY?**

        Symbol duration varies by channel bandwidth, generally longer than traditional Wi-Fi to support longer range.

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        **Does 802.11ah PHY support MIMO?**

        No, 802.11ah primarily uses single-antenna (SISO) PHY for power efficiency and simplicity.

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        **How does 802.11ah PHY differ from 802.11ac PHY?**

        802.11ah targets sub-1 GHz bands with narrow channels and low power for IoT, while 802.11ac operates at 5 GHz with wider channels and MIMO.

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        **What coding schemes does 802.11ah PHY use?**

        It uses convolutional coding with different rates to balance throughput and reliability.

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        **How is synchronization achieved in 802.11ah PHY?**

        Via preambles designed for coarse and fine timing and frequency synchronization.

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        **What is the role of the SIGNAL field in 802.11ah PHY?**

        It carries information about data rate, length, and coding used for proper frame decoding.

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        **How does 802.11ah PHY manage power consumption?**

        By using narrow bandwidths, low-order modulations, and efficient coding, it reduces power needs.

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        **Is 802.11ah PHY backward compatible with other 802.11 standards?**

        No, it is designed specifically for sub-1 GHz and differs significantly in PHY layer.

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        **What type of channel coding interleaving is used in 802.11ah PHY?**

        Bit interleaving is used to spread errors and improve error correction performance.

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        **Does 802.11ah PHY support adaptive modulation and coding?**

        Yes, it dynamically adjusts modulation and coding based on channel quality.

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        **What applications benefit from 802.11ah PHY?**

        IoT sensor networks, smart agriculture, smart cities, and long-range low power wireless communications.


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        Topics in this section,

                * :ref:`Reference links <phy_ah_step17>`


.. _phy_ah_step17:

.. tab-set::

    .. tab-item:: Reference links

       * Reference links