wifi: Do not double CW if CTS missing after ICF because of EMLSR clients starting UL TXOPs

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

@@ -85,6 +85,13 @@ class ApEmlsrManager : public Object
                                              const WifiTxVector& txVector,
                                              WifiPhyBand band) = 0;
 
+    /**
+     * \return whether the AP MLD shall double the CW upon CTS timeout after an MU-RTS in case
+     *         all the clients solicited by the MU-RTS are EMLSR clients that have sent (or
+     *         are sending) a frame to the AP
+     */
+    virtual bool UpdateCwAfterFailedIcf() = 0;
+
   protected:
     void DoDispose() override;
 

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

@@ -60,4 +60,10 @@ DefaultApEmlsrManager::GetDelayOnTxPsduNotForEmlsr(Ptr<const WifiPsdu> psdu,
     return WifiPhy::CalculateTxDuration(psdu, txVector, band);
 }
 
+bool
+DefaultApEmlsrManager::UpdateCwAfterFailedIcf()
+{
+    return true;
+}
+
 } // namespace ns3

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

@@ -45,6 +45,7 @@ class DefaultApEmlsrManager : public ApEmlsrManager
     Time GetDelayOnTxPsduNotForEmlsr(Ptr<const WifiPsdu> psdu,
                                      const WifiTxVector& txVector,
                                      WifiPhyBand band) override;
+    bool UpdateCwAfterFailedIcf() override;
 };
 
 } // namespace ns3

src/wifi/model/eht/eht-frame-exchange-manager.cc

@@ -33,6 +33,8 @@
 #include "ns3/wifi-net-device.h"
 #include "ns3/wifi-spectrum-phy-interface.h"
 
+#include <algorithm>
+
 #undef NS_LOG_APPEND_CONTEXT
 #define NS_LOG_APPEND_CONTEXT WIFI_FEM_NS_LOG_APPEND_CONTEXT
 
@@ -803,6 +805,10 @@ EhtFrameExchangeManager::CtsAfterMuRtsTimeout(Ptr<WifiMpdu> muRts, const WifiTxV
 {
     NS_LOG_FUNCTION(this << *muRts << txVector);
 
+    // check if all the clients solicited by the MU-RTS are EMLSR clients that have sent (or
+    // are sending) a frame to the AP
+    auto crossLinkCollision = true;
+
     // we blocked transmissions on the other EMLSR links for the EMLSR clients we sent the ICF to.
     // Given that no client responded, we can unblock transmissions for a client if there is no
     // ongoing UL TXOP held by that client
@@ -810,33 +816,61 @@ EhtFrameExchangeManager::CtsAfterMuRtsTimeout(Ptr<WifiMpdu> muRts, const WifiTxV
     {
         if (!GetWifiRemoteStationManager()->GetEmlsrEnabled(address))
         {
+            crossLinkCollision = false;
             continue;
         }
 
         auto mldAddress = GetWifiRemoteStationManager()->GetMldAddress(address);
         NS_ASSERT(mldAddress);
 
-        if (m_ongoingTxopEnd.IsPending() && m_txopHolder &&
-            m_mac->GetMldAddress(*m_txopHolder) == mldAddress)
-        {
-            continue;
-        }
-
-        std::set<uint8_t> linkIds;
+        std::set<uint8_t> linkIds; // all EMLSR links of EMLSR client
         for (uint8_t linkId = 0; linkId < m_apMac->GetNLinks(); linkId++)
         {
-            if (linkId != m_linkId &&
-                m_mac->GetWifiRemoteStationManager(linkId)->GetEmlsrEnabled(*mldAddress))
+            if (m_mac->GetWifiRemoteStationManager(linkId)->GetEmlsrEnabled(*mldAddress))
             {
                 linkIds.insert(linkId);
             }
         }
+
+        if (std::any_of(linkIds.cbegin(),
+                        linkIds.cend(),
+                        /* lambda returning true if an UL TXOP is ongoing on the given link ID */
+                        [=, this](uint8_t id) {
+                            auto ehtFem = StaticCast<EhtFrameExchangeManager>(
+                                m_mac->GetFrameExchangeManager(id));
+                            return ehtFem->m_ongoingTxopEnd.IsPending() && ehtFem->m_txopHolder &&
+                                   m_mac->GetMldAddress(ehtFem->m_txopHolder.value()) == mldAddress;
+                        }))
+        {
+            // an UL TXOP is ongoing on one EMLSR link, do not unblock links
+            continue;
+        }
+
+        // no UL TXOP is ongoing on any EMLSR link; if the EMLSR client is not transmitting a
+        // frame to the AP on any EMLSR link, then the lack of response to the MU-RTS was not
+        // caused by a simultaneous UL transmission
+        if (std::none_of(linkIds.cbegin(),
+                         linkIds.cend(),
+                         /* lambda returning true if an MPDU from the EMLSR client is being received
+                            on the given link ID */
+                         [=, this](uint8_t id) {
+                             auto macHdr = m_mac->GetFrameExchangeManager(id)->GetReceivedMacHdr();
+                             return macHdr.has_value() &&
+                                    m_mac->GetMldAddress(macHdr->get().GetAddr2()) == mldAddress;
+                         }))
+        {
+            crossLinkCollision = false;
+        }
+
+        linkIds.erase(m_linkId);
         m_mac->UnblockUnicastTxOnLinks(WifiQueueBlockedReason::USING_OTHER_EMLSR_LINK,
                                        *mldAddress,
                                        linkIds);
     }
 
-    HeFrameExchangeManager::CtsAfterMuRtsTimeout(muRts, txVector);
+    auto updateFailedCw =
+        crossLinkCollision ? m_apMac->GetApEmlsrManager()->UpdateCwAfterFailedIcf() : true;
+    DoCtsAfterMuRtsTimeout(muRts, txVector, updateFailedCw);
 }
 
 void

src/wifi/model/he/he-frame-exchange-manager.cc

@@ -399,6 +399,15 @@ void
 HeFrameExchangeManager::CtsAfterMuRtsTimeout(Ptr<WifiMpdu> muRts, const WifiTxVector& txVector)
 {
     NS_LOG_FUNCTION(this << *muRts << txVector);
+    DoCtsAfterMuRtsTimeout(muRts, txVector, true);
+}
+
+void
+HeFrameExchangeManager::DoCtsAfterMuRtsTimeout(Ptr<WifiMpdu> muRts,
+                                               const WifiTxVector& txVector,
+                                               bool updateFailedCw)
+{
+    NS_LOG_FUNCTION(this << *muRts << txVector << updateFailedCw);
 
     if (m_psduMap.empty())
     {
@@ -446,7 +455,10 @@ HeFrameExchangeManager::CtsAfterMuRtsTimeout(Ptr<WifiMpdu> muRts, const WifiTxVe
     else
     {
         NS_LOG_DEBUG("Missed CTS, retransmit MPDUs");
-        m_edca->UpdateFailedCw(m_linkId);
+        if (updateFailedCw)
+        {
+            m_edca->UpdateFailedCw(m_linkId);
+        }
     }
     // Make the sequence numbers of the MPDUs available again if the MPDUs have never
     // been transmitted, both in case the MPDUs have been discarded and in case the

src/wifi/model/he/he-frame-exchange-manager.h

@@ -213,6 +213,17 @@ class HeFrameExchangeManager : public VhtFrameExchangeManager
      */
     virtual void CtsAfterMuRtsTimeout(Ptr<WifiMpdu> muRts, const WifiTxVector& txVector);
 
+    /**
+     * Called when no CTS frame is received after an MU-RTS.
+     *
+     * \param muRts the MU-RTS that solicited CTS responses
+     * \param txVector the TXVECTOR used to transmit the MU-RTS frame
+     * \param updateFailedCw whether to update CW in case of retransmission after TX failure
+     */
+    void DoCtsAfterMuRtsTimeout(Ptr<WifiMpdu> muRts,
+                                const WifiTxVector& txVector,
+                                bool updateFailedCw);
+
     /**
      * Send CTS after receiving an MU-RTS.
      *