wifi: CAM detects if a PHY switched channel to operate on another EMLSR link

src/wifi/model/channel-access-manager.cc

@@ -19,11 +19,11 @@
 
 #include "channel-access-manager.h"
 
-#include "frame-exchange-manager.h"
 #include "txop.h"
 #include "wifi-phy-listener.h"
 #include "wifi-phy.h"
 
+#include "ns3/eht-frame-exchange-manager.h"
 #include "ns3/log.h"
 #include "ns3/simulator.h"
 
@@ -122,7 +122,7 @@ class PhyListener : public ns3::WifiPhyListener
 
     void NotifySwitchingStart(Time duration) override
     {
-        m_cam->NotifySwitchingStartNow(duration);
+        m_cam->NotifySwitchingStartNow(this, duration);
     }
 
     void NotifySleep() override
@@ -245,6 +245,12 @@ ChannelAccessManager::SetupPhyListener(Ptr<WifiPhy> phy)
     }
     m_phy = phy; // this is the new active PHY
     InitLastBusyStructs();
+    if (phy->IsStateSwitching())
+    {
+        auto duration = phy->GetDelayUntilIdle();
+        NS_LOG_DEBUG("switching start for " << duration);
+        m_lastSwitchingEnd = Simulator::Now() + duration;
+    }
 }
 
 void
@@ -277,6 +283,17 @@ ChannelAccessManager::DeactivatePhyListener(Ptr<WifiPhy> phy)
     }
 }
 
+void
+ChannelAccessManager::NotifySwitchingEmlsrLink(Ptr<WifiPhy> phy,
+                                               const WifiPhyOperatingChannel& channel,
+                                               uint8_t linkId)
+{
+    NS_LOG_FUNCTION(this << phy << channel << linkId);
+    NS_ASSERT_MSG(m_switchingEmlsrLinks.count(phy) == 0,
+                  "The given PHY is already expected to switch channel");
+    m_switchingEmlsrLinks.emplace(phy, EmlsrLinkSwitchInfo{channel, linkId});
+}
+
 void
 ChannelAccessManager::SetLinkId(uint8_t linkId)
 {
@@ -845,13 +862,40 @@ ChannelAccessManager::NotifyCcaBusyStartNow(Time duration,
 }
 
 void
-ChannelAccessManager::NotifySwitchingStartNow(Time duration)
+ChannelAccessManager::NotifySwitchingStartNow(PhyListener* phyListener, Time duration)
 {
-    NS_LOG_FUNCTION(this << duration);
+    NS_LOG_FUNCTION(this << phyListener << duration);
+
     Time now = Simulator::Now();
     NS_ASSERT(m_lastTxEnd <= now);
     NS_ASSERT(m_lastSwitchingEnd <= now);
 
+    if (phyListener) // to make tests happy
+    {
+        // check if the PHY switched channel to operate on another EMLSR link
+        decltype(m_switchingEmlsrLinks)::const_iterator emlsrInfoIt;
+
+        for (const auto& [phyRef, listener] : m_phyListeners)
+        {
+            Ptr<WifiPhy> phy = phyRef;
+            if (listener.get() == phyListener &&
+                (emlsrInfoIt = m_switchingEmlsrLinks.find(phy)) != m_switchingEmlsrLinks.cend() &&
+                phy->GetOperatingChannel() == emlsrInfoIt->second.channel)
+            {
+                // the PHY associated with the given PHY listener switched channel to
+                // operate on another EMLSR link as expected. We don't need this listener
+                // anymore. The MAC will connect a new listener to the ChannelAccessManager
+                // instance associated with the link the PHY is now operating on
+                RemovePhyListener(phy);
+                auto ehtFem = DynamicCast<EhtFrameExchangeManager>(m_feManager);
+                NS_ASSERT(ehtFem);
+                ehtFem->NotifySwitchingEmlsrLink(phy, emlsrInfoIt->second.linkId, duration);
+                m_switchingEmlsrLinks.erase(emlsrInfoIt);
+                return;
+            }
+        }
+    }
+
     ResetState();
 
     // Notify the FEM, which will in turn notify the MAC

src/wifi/model/channel-access-manager.h

@@ -21,6 +21,7 @@
 #define CHANNEL_ACCESS_MANAGER_H
 
 #include "wifi-phy-common.h"
+#include "wifi-phy-operating-channel.h"
 
 #include "ns3/event-id.h"
 #include "ns3/nstime.h"
@@ -206,13 +207,14 @@ class ChannelAccessManager : public Object
                                WifiChannelListType channelType,
                                const std::vector<Time>& per20MhzDurations);
     /**
+     * \param phyListener the PHY listener that sent this notification
      * \param duration expected duration of channel switching period
      *
      * Notify the Txop that a channel switching period has just started.
      * During switching state, new packets can be enqueued in Txop/QosTxop
      * but they won't access to the medium until the end of the channel switching.
      */
-    void NotifySwitchingStartNow(Time duration);
+    void NotifySwitchingStartNow(PhyListener* phyListener, Time duration);
     /**
      * Notify the Txop that the device has been put in sleep mode.
      */
@@ -276,6 +278,19 @@ class ChannelAccessManager : public Object
      */
     void ResetState();
 
+    /**
+     * Notify that the given PHY is about to switch to the given operating channel, which is
+     * used by the given link. This notification is sent by the EMLSR Manager when a PHY object
+     * switches operating channel to operate on another link.
+     *
+     * \param phy the PHY object that is going to switch channel
+     * \param channel the new operating channel of the given PHY
+     * \param linkId the ID of the link on which the given PHY is going to operate
+     */
+    void NotifySwitchingEmlsrLink(Ptr<WifiPhy> phy,
+                                  const WifiPhyOperatingChannel& channel,
+                                  uint8_t linkId);
+
   protected:
     void DoInitialize() override;
     void DoDispose() override;
@@ -390,6 +405,16 @@ class ChannelAccessManager : public Object
     Time m_eifsNoDifs;       //!< EIFS no DIFS time
     EventId m_accessTimeout; //!< the access timeout ID
 
+    /// Information associated with each PHY that is going to operate on another EMLSR link
+    struct EmlsrLinkSwitchInfo
+    {
+        WifiPhyOperatingChannel channel; //!< new operating channel
+        uint8_t linkId; //!< ID of the EMLSR link on which the PHY is going to operate
+    };
+
+    /// Store information about the PHY objects that are going to operate on another EMLSR link
+    std::unordered_map<Ptr<WifiPhy>, EmlsrLinkSwitchInfo> m_switchingEmlsrLinks;
+
     /// Maps each PHY listener to the associated PHY
     using PhyListenerMap = std::unordered_map<Ptr<WifiPhy>, std::unique_ptr<PhyListener>>;
 

src/wifi/test/channel-access-manager-test.cc

@@ -836,6 +836,7 @@ ChannelAccessManagerTest<TxopType>::AddSwitchingEvt(uint64_t at, uint64_t durati
     Simulator::Schedule(MicroSeconds(at) - Now(),
                         &ChannelAccessManager::NotifySwitchingStartNow,
                         m_ChannelAccessManager,
+                        nullptr,
                         MicroSeconds(duration));
 }