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wifi: Clarify behavioral change due to preamble detection model

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This commit is contained in:
Tom Henderson
2019-06-25 16:15:31 -07:00
parent 8490704c65
commit 6c87dff0ea
3 changed files with 11 additions and 1 deletions
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3
CHANGES.html
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@@ -106,7 +106,8 @@ us a note on ns-developers mailing list.</p>
<h2>Changed behavior:</h2>
<ul>
<li>The wifi ADDBA handshake process is now protected with the use of two timeouts who makes sure we do not end up in a blocked situation. If the handshake process is not established, packets that are in the queue are sent as normal MPDUs. Once handshake is successfully established, A-MPDUs can be transmitted.</li>
<li> The default value of the <b>Margin</b> attribute in SimpleFrameCaptureModel was changed from 10 to 5.</li>
<li> In the wifi module, the default value of the <b>Margin</b> attribute in SimpleFrameCaptureModel was changed from 10 to 5.</li>
<li> A ThresholdPreambleDetectionModel is added by default to the WifiPhy. Using default values, this model will discard frames that fall below either -82 dBm RSSI or below 4 dB SNR. Users may notice that weak wifi signals that were successfully received based on the error model alone (in previous ns-3 releases) are no longer received. Previous behavior can be obtained by lowering both threshold values or by removing the preamble detection model (via WifiPhyHelper::DisablePreambleDetectionModel()).</li>
<li>LTE/EPC model has been enhanced with the new features. These new features allow the simulation user to test more realistic simulations related to the core network. These features are:</li>
<ul>
<li>SGW, PGW and MME are full nodes.</li>

8
src/wifi/doc/source/wifi-design.rst
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@@ -322,6 +322,14 @@ and the PHY is put into the RX state. Currently, there is only a
simple threshold-based preamble detection model in ns-3,
called ``ThresholdPreambleDetectionModel``. If there is no preamble detection
model, the preamble is assumed to have been detected.
It is important to note that, starting with the ns-3.30 release, the default
in the WifiPhyHelper is to add the ``ThresholdPreambleDetectionModel`` with
a threshold RSSI of -82 dBm, and a threshold SNR of 4 dB. Both the RSSI
and SNR must be above these respective values for the preamble to be
successfully detected. The default sensitivity has been reduced in ns-3.30
compared with that of previous releases, so some packet receptions that were
previously successful will now fail on this check. More details on the
modeling behind this change are provided in [lanante2019]_.
In a real system, the ``EndReceive ()`` time would
not be determined until later when the PHY headers are successfully decoded,

1
src/wifi/doc/source/wifi-references.rst
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@@ -45,3 +45,4 @@ References
.. [baldo2010] \ N. Baldo et al., "Validation of the ns-3 IEEE 802.11 model using the EXTREME testbed", Proceedings of SIMUTools Conference, March 2010.
.. [lanante2019] \ L. Lanante Jr. et al., "Improved Abstraction for Clear Channel Assessment in ns-3 802.11 WLAN Model", Proceedings of the 2019 Workshop on ns-3, June 2019.