wifi: Let EmlsrManager explicitly indicate whether UL TXOP can be sta…

…rted ...instead of relying on whether the delay to request channel access is zero
nsnam · Sep 23, 2024 · a46abc4 · a46abc4
1 parent bf1524f
commit a46abc4
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Showing 7 changed files with 51 additions and 50 deletions.
diff --git a/src/wifi/model/eht/advanced-emlsr-manager.cc b/src/wifi/model/eht/advanced-emlsr-manager.cc
@@ -107,7 +107,7 @@ AdvancedEmlsrManager::DoSetWifiMac(Ptr<StaWifiMac> mac)
     }
 }
 
-Time
+std::pair<bool, Time>
 AdvancedEmlsrManager::DoGetDelayUntilAccessRequest(uint8_t linkId)
 {
     NS_LOG_FUNCTION(this << linkId);
@@ -131,7 +131,7 @@ AdvancedEmlsrManager::DoGetDelayUntilAccessRequest(uint8_t linkId)
                     hdr.IsTrigger() &&
                     (hdr.GetAddr1().IsBroadcast() || hdr.GetAddr1() == GetEhtFem(id)->GetAddress()))
                 {
-                    return phy->GetDelayUntilIdle();
+                    return {false, phy->GetDelayUntilIdle()};
                 }
                 continue;
             }
@@ -143,7 +143,7 @@ AdvancedEmlsrManager::DoGetDelayUntilAccessRequest(uint8_t linkId)
                 if (!m_allowUlTxopInRx)
                 {
                     // retry channel access after the end of the current PHY header field
-                    return phy->GetDelayUntilIdle();
+                    return {false, phy->GetDelayUntilIdle()};
                 }
                 continue;
             }
@@ -157,7 +157,7 @@ AdvancedEmlsrManager::DoGetDelayUntilAccessRequest(uint8_t linkId)
                     if (!m_useNotifiedMacHdr)
                     {
                         // restart channel access at the end of PSDU reception
-                        return phy->GetDelayUntilIdle();
+                        return {false, phy->GetDelayUntilIdle()};
                     }
 
                     // retry channel access after the expected end of the MAC header reception
@@ -192,14 +192,14 @@ AdvancedEmlsrManager::DoGetDelayUntilAccessRequest(uint8_t linkId)
                                               .CalculateBytesTxTime(macHdrSize);
                     const auto timeSinceRxStart =
                         Simulator::Now() - phy->GetState()->GetLastTime({WifiPhyState::CCA_BUSY});
-                    return Max(macHdrDuration - timeSinceRxStart, Time{0});
+                    return {false, Max(macHdrDuration - timeSinceRxStart, Time{0})};
                 }
                 continue;
             }
         }
     }
 
-    return Time{0};
+    return {true, Time{0}};
 }
 
 void
@@ -290,7 +290,7 @@ AdvancedEmlsrManager::DoNotifyTxopEnd(uint8_t linkId)
     }
 }
 
-Time
+std::pair<bool, Time>
 AdvancedEmlsrManager::GetDelayUnlessMainPhyTakesOverUlTxop(uint8_t linkId)
 {
     NS_LOG_FUNCTION(this << linkId);
@@ -316,7 +316,7 @@ AdvancedEmlsrManager::GetDelayUnlessMainPhyTakesOverUlTxop(uint8_t linkId)
         NS_LOG_DEBUG("Not enough time for main PHY to switch link (main PHY state: "
                      << mainPhy->GetState()->GetState() << ")");
         // retry channel access when the CTS was expected to be received
-        return timeToCtsEnd;
+        return {false, timeToCtsEnd};
     }
 
     // TXOP can be started, schedule main PHY switch. Main PHY shall terminate the channel switch
@@ -333,7 +333,7 @@ AdvancedEmlsrManager::GetDelayUnlessMainPhyTakesOverUlTxop(uint8_t linkId)
                                                     RESET_BACKOFF,
                                                     DONT_REQUEST_ACCESS);
 
-    return Time{0};
+    return {true, Time{0}};
 }
 
 void

diff --git a/src/wifi/model/eht/advanced-emlsr-manager.h b/src/wifi/model/eht/advanced-emlsr-manager.h
@@ -34,8 +34,8 @@ class AdvancedEmlsrManager : public DefaultEmlsrManager
   protected:
     void DoDispose() override;
     void DoSetWifiMac(Ptr<StaWifiMac> mac) override;
-    Time DoGetDelayUntilAccessRequest(uint8_t linkId) override;
-    Time GetDelayUnlessMainPhyTakesOverUlTxop(uint8_t linkId) override;
+    std::pair<bool, Time> DoGetDelayUntilAccessRequest(uint8_t linkId) override;
+    std::pair<bool, Time> GetDelayUnlessMainPhyTakesOverUlTxop(uint8_t linkId) override;
     void SwitchMainPhyIfTxopGainedByAuxPhy(uint8_t linkId, AcIndex aci) override;
 
     /**

diff --git a/src/wifi/model/eht/default-emlsr-manager.cc b/src/wifi/model/eht/default-emlsr-manager.cc
@@ -171,11 +171,11 @@ DefaultEmlsrManager::NotifyMainPhySwitch(std::optional<uint8_t> currLinkId,
     }
 }
 
-Time
+std::pair<bool, Time>
 DefaultEmlsrManager::DoGetDelayUntilAccessRequest(uint8_t linkId)
 {
     NS_LOG_FUNCTION(this << linkId);
-    return Time{0}; // start the TXOP
+    return {true, Time{0}}; // start the TXOP
 }
 
 void
@@ -271,7 +271,7 @@ DefaultEmlsrManager::GetTimeToCtsEnd(uint8_t linkId) const
     return rtsTxTime + phy->GetSifs() + ctsTxTime + MicroSeconds(2 * MAX_PROPAGATION_DELAY_USEC);
 }
 
-Time
+std::pair<bool, Time>
 DefaultEmlsrManager::GetDelayUnlessMainPhyTakesOverUlTxop(uint8_t linkId)
 {
     NS_LOG_FUNCTION(this << linkId);
@@ -296,7 +296,7 @@ DefaultEmlsrManager::GetDelayUnlessMainPhyTakesOverUlTxop(uint8_t linkId)
             NS_LOG_DEBUG("Not enough time for main PHY to switch link (main PHY state: "
                          << mainPhy->GetState()->GetState() << ")");
             // retry channel access when the CTS was expected to be received
-            return timeToCtsEnd;
+            return {false, timeToCtsEnd};
         }
         break;
     default:
@@ -317,7 +317,7 @@ DefaultEmlsrManager::GetDelayUnlessMainPhyTakesOverUlTxop(uint8_t linkId)
                                                     RESET_BACKOFF,
                                                     DONT_REQUEST_ACCESS);
 
-    return Time{0};
+    return {true, Time{0}};
 }
 
 } // namespace ns3
diff --git a/src/wifi/model/eht/default-emlsr-manager.h b/src/wifi/model/eht/default-emlsr-manager.h
@@ -36,9 +36,9 @@ class DefaultEmlsrManager : public EmlsrManager
   protected:
     uint8_t GetLinkToSendEmlOmn() override;
     std::optional<uint8_t> ResendNotification(Ptr<const WifiMpdu> mpdu) override;
-    Time DoGetDelayUntilAccessRequest(uint8_t linkId) override;
+    std::pair<bool, Time> DoGetDelayUntilAccessRequest(uint8_t linkId) override;
     void SwitchMainPhyIfTxopGainedByAuxPhy(uint8_t linkId, AcIndex aci) override;
-    Time GetDelayUnlessMainPhyTakesOverUlTxop(uint8_t linkId) override;
+    std::pair<bool, Time> GetDelayUnlessMainPhyTakesOverUlTxop(uint8_t linkId) override;
 
     /**
      * This function is intended to be called when an aux PHY is about to transmit an RTS on

diff --git a/src/wifi/model/eht/eht-frame-exchange-manager.cc b/src/wifi/model/eht/eht-frame-exchange-manager.cc
@@ -276,28 +276,24 @@ EhtFrameExchangeManager::StartTransmission(Ptr<Txop> edca, MHz_u allowedWidth)
         }
 
         // let EMLSR manager decide whether to prevent or allow this UL TXOP
-        if (auto delay = emlsrManager->GetDelayUntilAccessRequest(
+        if (const auto [startTxop, delay] = emlsrManager->GetDelayUntilAccessRequest(
                 m_linkId,
                 DynamicCast<QosTxop>(edca)->GetAccessCategory());
-            delay.IsStrictlyPositive())
-        {
-            NotifyChannelReleased(edca);
-            Simulator::Schedule(delay,
-                                &Txop::StartAccessAfterEvent,
-                                edca,
-                                m_linkId,
-                                Txop::DIDNT_HAVE_FRAMES_TO_TRANSMIT, // queued frames cannot be
-                                                                     // transmitted until RX ends
-                                Txop::CHECK_MEDIUM_BUSY); // generate backoff if medium busy
-            return false;
-        }
+            !startTxop)
 
-        // in case of aux PHY that is not TX capable, the main PHY can transmit if the medium is
-        // sensed idle for a PIFS after the end of channel switch (assuming main PHY is switching)
-        if (auto mainPhy = m_staMac->GetDevice()->GetPhy(emlsrManager->GetMainPhyId());
-            m_phy != mainPhy && !emlsrManager->GetAuxPhyTxCapable())
         {
-            NS_LOG_DEBUG("Aux PHY is not capable of transmitting a PPDU");
+            if (delay.IsStrictlyPositive())
+            {
+                NotifyChannelReleased(edca);
+                Simulator::Schedule(
+                    delay,
+                    &Txop::StartAccessAfterEvent,
+                    edca,
+                    m_linkId,
+                    Txop::DIDNT_HAVE_FRAMES_TO_TRANSMIT, // queued frames cannot be
+                                                         // transmitted until RX ends
+                    Txop::CHECK_MEDIUM_BUSY);            // generate backoff if medium busy
+            }
             return false;
         }
     }

diff --git a/src/wifi/model/eht/emlsr-manager.cc b/src/wifi/model/eht/emlsr-manager.cc
@@ -404,7 +404,7 @@ EmlsrManager::NotifyIcfReceived(uint8_t linkId)
     DoNotifyIcfReceived(linkId);
 }
 
-Time
+std::pair<bool, Time>
 EmlsrManager::GetDelayUntilAccessRequest(uint8_t linkId, AcIndex aci)
 {
     auto phy = m_staMac->GetWifiPhy(linkId);
@@ -413,15 +413,15 @@ EmlsrManager::GetDelayUntilAccessRequest(uint8_t linkId, AcIndex aci)
     auto mainPhy = m_staMac->GetDevice()->GetPhy(m_mainPhyId);
 
     // check possible reasons to give up the TXOP that apply to both main PHY and aux PHYs
-    if (auto delay = DoGetDelayUntilAccessRequest(linkId); delay.IsStrictlyPositive())
+    if (const auto [startTxop, delay] = DoGetDelayUntilAccessRequest(linkId); !startTxop)
     {
-        return delay;
+        return {false, delay};
     }
 
     if (phy == mainPhy)
     {
         // no more constraints to check if medium was gained by main PHY
-        return Time{0};
+        return {true, Time{0}};
     }
 
     // an aux PHY is operating on the given link; call the appropriate method depending on
@@ -433,7 +433,8 @@ EmlsrManager::GetDelayUntilAccessRequest(uint8_t linkId, AcIndex aci)
         // PHY switches link, the UL TXOP will be started; if the main PHY does not switch, it is
         // because it is going to start an UL TXOP on another link and this link will be restarted
         // at the end of that UL TXOP when this link will be unblocked
-        return Time{0};
+        NS_LOG_DEBUG("Aux PHY is not capable of transmitting a PPDU");
+        return {false, Time{0}};
     }
 
     return GetDelayUnlessMainPhyTakesOverUlTxop(linkId);

diff --git a/src/wifi/model/eht/emlsr-manager.h b/src/wifi/model/eht/emlsr-manager.h
@@ -18,6 +18,7 @@
 #include <map>
 #include <optional>
 #include <set>
+#include <utility>
 
 class EmlsrCcaBusyTest;
 
@@ -147,10 +148,11 @@ class EmlsrManager : public Object
      *
      * \param linkId the ID of the given link
      * \param aci the index of the given AC
-     * \return zero, if the UL TXOP can be started, or the delay after which the EMLSR client
-     *         restarts channel access, otherwise
+     * \return a pair consisting of a boolean value indicating whether the UL TXOP can be started
+     *         and a Time value indicating the delay after which the EMLSR client must restart
+     *         channel access (if needed) in case the UL TXOP is not started
      */
-    Time GetDelayUntilAccessRequest(uint8_t linkId, AcIndex aci);
+    std::pair<bool, Time> GetDelayUntilAccessRequest(uint8_t linkId, AcIndex aci);
 
     /**
      * Set the member variable indicating whether Aux PHYs are capable of transmitting PPDUs.
@@ -357,10 +359,11 @@ class EmlsrManager : public Object
      * check possible reasons to give up the TXOP that apply to both main PHY and aux PHYs.
      *
      * \param linkId the ID of the given link
-     * \return zero, if the UL TXOP can be started, or the delay after which the EMLSR client
-     *         restarts channel access, otherwise
+     * \return a pair consisting of a boolean value indicating whether the UL TXOP can be started
+     *         and a Time value indicating the delay after which the EMLSR client must restart
+     *         channel access (if needed) in case the UL TXOP is not started
      */
-    virtual Time DoGetDelayUntilAccessRequest(uint8_t linkId) = 0;
+    virtual std::pair<bool, Time> DoGetDelayUntilAccessRequest(uint8_t linkId) = 0;
 
     /**
      * Subclasses have to provide an implementation for this method, that is called by the base
@@ -381,10 +384,11 @@ class EmlsrManager : public Object
      * EMLSR client restarts channel access on the given link, otherwise.
      *
      * \param linkId the ID of the given link
-     * \return zero, if the UL TXOP can be started, or the delay after which the EMLSR client
-     *         restarts channel access, otherwise
+     * \return a pair consisting of a boolean value indicating whether the UL TXOP can be started
+     *         and a Time value indicating the delay after which the EMLSR client must restart
+     *         channel access (if needed) in case the UL TXOP is not started
      */
-    virtual Time GetDelayUnlessMainPhyTakesOverUlTxop(uint8_t linkId) = 0;
+    virtual std::pair<bool, Time> GetDelayUnlessMainPhyTakesOverUlTxop(uint8_t linkId) = 0;
 
     Time m_emlsrPaddingDelay;    //!< EMLSR Padding delay
     Time m_emlsrTransitionDelay; //!< EMLSR Transition delay