wifi: Add check on channel width compatibility with the candidate AP

src/wifi/doc/source/wifi-user.rst

@@ -579,6 +579,28 @@ The wifi standard can be configured only once, i.e., it is not possible to
 change standard during a simulation. It is instead possible to change the
 channel settings at any time.
 
+Advertisement of the channel width
+++++++++++++++++++++++++++++++++++
+
+STAs are advertizing their channel width in capabilities and operations (for APs) information elements
+contained in management frames.
+
+The channel width that is being advertised is the value that is returned by WifiPhy::ChannelWidth, which corresponds to
+the value that is set in the ChannelSettings attribute (or the total width in case of non-contiguous channel operation).
+
+Not all the channel widths can be advertised for non-AP STAs, depending on the standard and the band.
+This is not a problem as long as the AP the non-AP STA is associated with is operating on the same channel width
+or on a narrower one. Otherwise, the AP might select a larger channel width for the transmission of downlink PPDUs,
+which would then be dropped by the PHY of the non-AP STA.
+
+For example, since VHT Capabilities Information Elements only allow the advertisement of 80 and 160 MHz channel widths,
+a VHT non-AP STA with its ChannelSettings set to use a 40 MHz channel width won't be able to receive any downlink PPDUs
+if the VHT AP has its ChannelSettings set to operate on an 80 MHz channel width.
+
+It is possible to configure the behavior of the association manager to either abort the simulation when such
+a problematic situation is detected (default) or to allow the association anyway, depending on the configured value
+for the ``ns3::WifiMac::AllowAssociationWithDifferentChannelWidth`` attribute.
+
 
 SpectrumWifiPhyHelper
 =====================

src/wifi/model/wifi-assoc-manager.cc

@@ -10,8 +10,10 @@
 #include "wifi-assoc-manager.h"
 
 #include "sta-wifi-mac.h"
+#include "wifi-phy.h"
 
 #include "ns3/attribute-container.h"
+#include "ns3/boolean.h"
 #include "ns3/eht-configuration.h"
 #include "ns3/enum.h"
 #include "ns3/log.h"
@@ -67,7 +69,15 @@ WifiAssocManager::GetTypeId()
                 "set are processed. An empty set is equivalent to the set of all links.",
                 AttributeContainerValue<UintegerValue>(),
                 MakeAttributeContainerAccessor<UintegerValue>(&WifiAssocManager::m_allowedLinks),
-                MakeAttributeContainerChecker<UintegerValue>(MakeUintegerChecker<uint8_t>()));
+                MakeAttributeContainerChecker<UintegerValue>(MakeUintegerChecker<uint8_t>()))
+            .AddAttribute("AllowAssocAllChannelWidths",
+                          "If set to true, it bypasses the check on channel width compatibility "
+                          "with the candidate AP. A channel width is compatible if the STA can "
+                          "advertise it to the AP, or AP operates on a channel width that is equal "
+                          "or lower than that channel width.",
+                          BooleanValue(false),
+                          MakeBooleanAccessor(&WifiAssocManager::m_allowAssocAllChannelWidths),
+                          MakeBooleanChecker());
     return tid;
 }
 
@@ -236,6 +246,10 @@ WifiAssocManager::ScanningTimeout()
         m_apListIt.erase(bestAp.m_bssid);
     } while (!CanBeReturned(bestAp));
 
+    NS_ABORT_MSG_IF(!m_allowAssocAllChannelWidths && !IsChannelWidthCompatible(bestAp),
+                    "Channel width of STA is not part of the channel width set that can be "
+                    "advertised to the AP");
+
     m_mac->ScanningTimeout(std::move(bestAp));
 }
 
@@ -361,4 +375,14 @@ WifiAssocManager::GetAllAffiliatedAps(const ReducedNeighborReport& rnr)
     return apList;
 }
 
+bool
+WifiAssocManager::IsChannelWidthCompatible(const StaWifiMac::ApInfo& apInfo) const
+{
+    auto phy = m_mac->GetWifiPhy(apInfo.m_linkId);
+    return GetSupportedChannelWidthSet(phy->GetStandard(), apInfo.m_channel.band)
+               .contains(phy->GetChannelWidth()) ||
+           (phy->GetChannelWidth() >= m_mac->GetWifiRemoteStationManager(apInfo.m_linkId)
+                                          ->GetChannelWidthSupported(apInfo.m_bssid));
+}
+
 } // namespace ns3

src/wifi/model/wifi-assoc-manager.h

@@ -199,6 +199,16 @@ class WifiAssocManager : public Object
      */
     virtual bool CanBeReturned(const StaWifiMac::ApInfo& apInfo) const = 0;
 
+    /**
+     * Check whether the channel width of the STA is compatible with the channel width of the
+     * operating channel of a given AP. A channel width is compatible if the STA can advertise it to
+     * the AP, or AP operates on a channel width that is equal or lower than that channel width
+     *
+     * @param apInfo the given AP information
+     * @return true if the channel width of the STA is compatible, false otherwise
+     */
+    bool IsChannelWidthCompatible(const StaWifiMac::ApInfo& apInfo) const;
+
     /**
      * Extract the best AP to associate with from the sorted list and return
      * it, if any, to the STA wifi MAC along with the notification that scanning
@@ -226,6 +236,9 @@ class WifiAssocManager : public Object
     std::set<uint8_t> m_allowedLinks; /**< "Only Beacon and Probe Response frames received on a
                                             link belonging to the this set are processed */
 
+    bool m_allowAssocAllChannelWidths; ///< flag whether the check on channel width compatibility
+                                       ///< with the candidate AP should be skipped
+
   private:
     /**
      * Start a scanning procedure. This method needs to schedule a call to