wifi: EMLSR Manager relies on CAM for resetting backoffs when no PHY on link

src/wifi/model/eht/advanced-emlsr-manager.cc

@@ -364,7 +364,7 @@ AdvancedEmlsrManager::DoNotifyTxopEnd(uint8_t linkId)
             !m_switchAuxPhy || m_mainPhySwitchInfo.end >= Simulator::Now(),
             "Aux PHY next link ID should have a value when interrupting a main PHY switch");
         uint8_t nextLinkId = m_switchAuxPhy ? m_mainPhySwitchInfo.from : GetMainPhyId();
-        SwitchMainPhy(nextLinkId, false, DONT_RESET_BACKOFF, REQUEST_ACCESS, std::move(*traceInfo));
+        SwitchMainPhy(nextLinkId, false, REQUEST_ACCESS, std::move(*traceInfo));
     }
     else
     {
@@ -381,11 +381,7 @@ AdvancedEmlsrManager::DoNotifyTxopEnd(uint8_t linkId)
             // no TXOP started on another link (which will require the main PHY to switch link)
             if (!GetEhtFem(linkId)->UsingOtherEmlsrLink())
             {
-                SwitchMainPhy(GetMainPhyId(),
-                              false,
-                              DONT_RESET_BACKOFF,
-                              REQUEST_ACCESS,
-                              std::move(*traceInfo));
+                SwitchMainPhy(GetMainPhyId(), false, REQUEST_ACCESS, std::move(*traceInfo));
             }
         });
     }
@@ -760,7 +756,6 @@ AdvancedEmlsrManager::SwitchMainPhyIfTxopGainedByAuxPhy(uint8_t linkId, AcIndex
 
         SwitchMainPhy(linkId,
                       false,
-                      RESET_BACKOFF,
                       DONT_REQUEST_ACCESS,
                       EmlsrUlTxopAuxPhyNotTxCapableTrace(aci, Time{0}, remNav));
 
@@ -917,7 +912,6 @@ AdvancedEmlsrManager::SwitchMainPhyIfTxopToBeGainedByAuxPhy(uint8_t linkId,
 
     SwitchMainPhy(linkId,
                   false,
-                  RESET_BACKOFF,
                   DONT_REQUEST_ACCESS,
                   EmlsrUlTxopAuxPhyNotTxCapableTrace(aci, delay, remNav));
 

src/wifi/model/eht/default-emlsr-manager.cc

@@ -263,7 +263,6 @@ DefaultEmlsrManager::SwitchMainPhyBackToPreferredLink(uint8_t linkId,
     {
         SwitchMainPhy(GetMainPhyId(),
                       false,
-                      DONT_RESET_BACKOFF,
                       REQUEST_ACCESS,
                       std::forward<EmlsrMainPhySwitchTrace>(traceInfo));
     }
@@ -275,11 +274,7 @@ DefaultEmlsrManager::SwitchMainPhyBackToPreferredLink(uint8_t linkId,
             // require the main PHY to switch link)
             if (!GetEhtFem(linkId)->UsingOtherEmlsrLink())
             {
-                SwitchMainPhy(GetMainPhyId(),
-                              false,
-                              DONT_RESET_BACKOFF,
-                              REQUEST_ACCESS,
-                              std::move(*info));
+                SwitchMainPhy(GetMainPhyId(), false, REQUEST_ACCESS, std::move(*info));
             }
         });
     }
@@ -395,11 +390,7 @@ DefaultEmlsrManager::NotifyRtsSent(uint8_t linkId,
 
     NS_LOG_DEBUG("Schedule main Phy switch in " << delay.As(Time::US));
     m_ulMainPhySwitch[linkId] = Simulator::Schedule(delay, [=, this]() {
-        SwitchMainPhy(linkId,
-                      false,
-                      RESET_BACKOFF,
-                      DONT_REQUEST_ACCESS,
-                      EmlsrUlTxopRtsSentByAuxPhyTrace{});
+        SwitchMainPhy(linkId, false, DONT_REQUEST_ACCESS, EmlsrUlTxopRtsSentByAuxPhyTrace{});
     });
 }
 

src/wifi/model/eht/emlsr-manager.cc

@@ -507,7 +507,6 @@ EmlsrManager::NotifyIcfReceived(uint8_t linkId)
     {
         SwitchMainPhy(linkId,
                       true, // channel switch should occur instantaneously
-                      RESET_BACKOFF,
                       DONT_REQUEST_ACCESS,
                       EmlsrDlTxopIcfReceivedByAuxPhyTrace{});
     }
@@ -873,12 +872,10 @@ EmlsrManager::SetCcaEdThresholdOnLinkSwitch(Ptr<WifiPhy> phy, uint8_t linkId)
 void
 EmlsrManager::SwitchMainPhy(uint8_t linkId,
                             bool noSwitchDelay,
-                            bool resetBackoff,
                             bool requestAccess,
                             EmlsrMainPhySwitchTrace&& traceInfo)
 {
-    NS_LOG_FUNCTION(this << linkId << noSwitchDelay << resetBackoff << requestAccess
-                         << traceInfo.GetName());
+    NS_LOG_FUNCTION(this << linkId << noSwitchDelay << requestAccess << traceInfo.GetName());
 
     auto mainPhy = m_staMac->GetDevice()->GetPhy(m_mainPhyId);
 
@@ -947,12 +944,6 @@ EmlsrManager::SwitchMainPhy(uint8_t linkId,
         m_staMac->NotifySwitchingEmlsrLink(mainPhy, linkId, timeToSwitchEnd);
     }
 
-    if (resetBackoff && currMainPhyLinkId.has_value())
-    {
-        // reset the backoffs on the link left by the main PHY
-        m_staMac->GetChannelAccessManager(*currMainPhyLinkId)->ResetAllBackoffs();
-    }
-
     if (requestAccess)
     {
         // schedule channel access request on the new link when switch is completed
@@ -1346,20 +1337,6 @@ EmlsrManager::ApplyMaxChannelWidthAndModClassOnAuxPhys()
         auxPhy->SetAttribute("ChannelSwitchDelay", TimeValue(Time{0}));
         auxPhy->SetOperatingChannel(channel);
         auxPhy->SetAttribute("ChannelSwitchDelay", TimeValue(delay));
-
-        // the way the ChannelAccessManager handles EMLSR link switch implies that a PHY listener
-        // is removed when the channel switch starts and another one is attached when the channel
-        // switch ends. In the meantime, no PHY is connected to the ChannelAccessManager. Thus,
-        // reset all backoffs (so that access timeout is also cancelled) when the channel switch
-        // starts and request channel access (if needed) when the channel switch ends.
-        cam->ResetAllBackoffs();
-        for (const auto& [acIndex, ac] : wifiAcList)
-        {
-            m_staMac->GetQosTxop(acIndex)->StartAccessAfterEvent(
-                linkId,
-                Txop::DIDNT_HAVE_FRAMES_TO_TRANSMIT,
-                Txop::CHECK_MEDIUM_BUSY);
-        }
     }
 }
 

src/wifi/model/eht/emlsr-manager.h

@@ -408,8 +408,6 @@ class EmlsrManager : public Object
      *
      * @param linkId the ID of the link on which the main PHY has to operate
      * @param noSwitchDelay whether switching delay should be zero
-     * @param resetBackoff whether backoff should be reset on the link on which the main PHY
-     *                     is operating
      * @param requestAccess whether channel access should be requested on the link on which the
      *                      main PHY is moving onto
      * @param traceInfo information to pass to the main PHY switch traced callback (the fromLinkId
@@ -417,12 +415,9 @@ class EmlsrManager : public Object
      */
     void SwitchMainPhy(uint8_t linkId,
                        bool noSwitchDelay,
-                       bool resetBackoff,
                        bool requestAccess,
                        EmlsrMainPhySwitchTrace&& traceInfo);
 
-    static constexpr bool RESET_BACKOFF = true;       //!< reset backoff on main PHY switch
-    static constexpr bool DONT_RESET_BACKOFF = false; //!< do not reset backoff on main PHY switch
     static constexpr bool REQUEST_ACCESS = true; //!< request channel access when PHY switch ends
     static constexpr bool DONT_REQUEST_ACCESS =
         false; //!< do not request channel access when PHY switch ends

src/wifi/test/wifi-emlsr-test.cc

@@ -4923,7 +4923,6 @@ EmlsrCcaBusyTest::StartTraffic()
     m_staMacs[0]->GetEmlsrManager()->SwitchMainPhy(
         m_nextMainPhyLinkId,
         false,
-        EmlsrManager::DONT_RESET_BACKOFF,
         EmlsrManager::DONT_REQUEST_ACCESS,
         EmlsrDlTxopIcfReceivedByAuxPhyTrace{}); // trace info not used