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wifi: Extend design documentation for multiple RF interfaces

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Sébastien Deronne
2023-04-16 13:59:36 +02:00
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src/wifi/doc/source/wifi-design.rst
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@@ -736,6 +736,35 @@ in the reception chain. After this point, valid Wi-Fi signals cause
``WifiPhy::StartReceivePreamble`` to be called, and the processing continues
as described above.
Furthermore, in order to support more flexible channel switching,
the ``SpectrumWifiPhy`` can hold multiple instances of ``WifiSpectrumPhyInterface``
(:ref:`fig-spectrum-wifi-phy-multiple-interfaces`).
Each of these instances handles a given frequency range of the spectrum, identified by
a start and a stop frequency expressed in MHz, and there can be no overlap in spectrum between them.
Only one of these ``WifiSpectrumPhyInterface`` instances corresponds to the active RF interface of the ``SpectrumWifiPhy``,
the other ones are referred to as inactive RF interfaces and might be disconnected from the spectrum channel.
.. _fig-spectrum-wifi-phy-multiple-interfaces:
.. figure:: figures/spectrum-wifi-phy-multiple-interfaces.*
:align: center
Multiple RF interfaces concept
If the ``SpectrumWifiPhy::TrackSignalsFromInactiveInterfaces`` attribute is set to true,
inactive RF interfaces are connected to their respective spectrum channels and the ``SpectrumWifiPhy``
forwards received signals from these inactive RF interfaces to the ``InterferenceHelper`` without processing them.
The benefit of the latter is that more accurate PHY-CCA.indication can be generated upon channel switching
if one or more signals started to be transmitted on the new channel before the switch occurs,
which would be ignored otherwise. This is illustrated in Figure :ref:`fig-cca-channel-switching-multiple-interfaces`, where the parts in red are only generated when ``SpectrumWifiPhy::TrackSignalsFromInactiveInterfaces`` is set to true.
.. _fig-cca-channel-switching-multiple-interfaces:
.. figure:: figures/cca-channel-switching-multiple-interfaces.*
:align: center
Illustration of signals tracking upon channel switching
The MAC model
=============