wifi: Get most recent RSSI received on other links if none is available on the current link

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

@@ -121,4 +121,37 @@ EhtFrameExchangeManager::ForwardPsduDown(Ptr<const WifiPsdu> psdu, WifiTxVector&
     HeFrameExchangeManager::ForwardPsduDown(psdu, txVector);
 }
 
+std::optional<double>
+EhtFrameExchangeManager::GetMostRecentRssi(const Mac48Address& address) const
+{
+    auto optRssi = HeFrameExchangeManager::GetMostRecentRssi(address);
+
+    if (optRssi)
+    {
+        return optRssi;
+    }
+
+    auto mldAddress = GetWifiRemoteStationManager()->GetMldAddress(address);
+
+    if (!mldAddress)
+    {
+        // not an MLD, nothing else can be done
+        return std::nullopt;
+    }
+
+    for (uint8_t linkId = 0; linkId < m_mac->GetNLinks(); linkId++)
+    {
+        std::optional<Mac48Address> linkAddress;
+        if (linkId != m_linkId &&
+            (linkAddress = m_mac->GetWifiRemoteStationManager(linkId)->GetAffiliatedStaAddress(
+                 *mldAddress)) &&
+            (optRssi = m_mac->GetWifiRemoteStationManager(linkId)->GetMostRecentRssi(*linkAddress)))
+        {
+            return optRssi;
+        }
+    }
+
+    return std::nullopt;
+}
+
 } // namespace ns3

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

@@ -45,6 +45,17 @@ class EhtFrameExchangeManager : public HeFrameExchangeManager
     void SetLinkId(uint8_t linkId) override;
     Ptr<WifiMpdu> CreateAliasIfNeeded(Ptr<WifiMpdu> mpdu) const override;
 
+    /**
+     * Get the RSSI (in dBm) of the most recent packet received from the station having
+     * the given address. If there is no such information for the given station and the
+     * station is affiliated with an MLD, return the RSSI (in dBm) of the most recent
+     * packet received from another station of the same MLD.
+     *
+     * \param address of the remote station
+     * \return the RSSI (in dBm) of the most recent packet received from the remote station
+     */
+    std::optional<double> GetMostRecentRssi(const Mac48Address& address) const override;
+
   protected:
     void ForwardPsduDown(Ptr<const WifiPsdu> psdu, WifiTxVector& txVector) override;
 };

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

@@ -1195,10 +1195,12 @@ HeFrameExchangeManager::GetHeTbTxVector(CtrlTriggerHeader trigger, Mac48Address
      *
      * Refer to section 27.3.14.2 (Power pre-correction) of 802.11ax Draft 4.0 for more details.
      */
+    auto optRssi = GetMostRecentRssi(triggerSender);
+    NS_ASSERT(optRssi);
     int8_t pathLossDb =
         trigger.GetApTxPower() -
-        static_cast<int8_t>(GetWifiRemoteStationManager()->GetMostRecentRssi(
-            triggerSender)); // cast RSSI to be on equal footing with AP Tx power information
+        static_cast<int8_t>(
+            *optRssi); // cast RSSI to be on equal footing with AP Tx power information
     double reqTxPowerDbm = static_cast<double>(userInfoIt->GetUlTargetRssi() + pathLossDb);
 
     // Convert the transmit power to a power level
@@ -1231,6 +1233,12 @@ HeFrameExchangeManager::GetHeTbTxVector(CtrlTriggerHeader trigger, Mac48Address
     return v;
 }
 
+std::optional<double>
+HeFrameExchangeManager::GetMostRecentRssi(const Mac48Address& address) const
+{
+    return GetWifiRemoteStationManager()->GetMostRecentRssi(address);
+}
+
 void
 HeFrameExchangeManager::SetTargetRssi(CtrlTriggerHeader& trigger) const
 {
@@ -1244,8 +1252,9 @@ HeFrameExchangeManager::SetTargetRssi(CtrlTriggerHeader& trigger) const
         const auto staList = m_apMac->GetStaList(m_linkId);
         auto itAidAddr = staList.find(userInfo.GetAid12());
         NS_ASSERT(itAidAddr != staList.end());
-        int8_t rssi = static_cast<int8_t>(
-            GetWifiRemoteStationManager()->GetMostRecentRssi(itAidAddr->second));
+        auto optRssi = GetMostRecentRssi(itAidAddr->second);
+        NS_ASSERT(optRssi);
+        int8_t rssi = static_cast<int8_t>(*optRssi);
         rssi = (rssi >= -20)
                    ? -20
                    : ((rssi <= -110) ? -110 : rssi); // cap so as to keep within [-110; -20] dBm

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

@@ -93,6 +93,15 @@ class HeFrameExchangeManager : public VhtFrameExchangeManager
      */
     virtual void SetTargetRssi(CtrlTriggerHeader& trigger) const;
 
+    /**
+     * Get the RSSI (in dBm) of the most recent packet received from the station having
+     * the given address.
+     *
+     * \param address of the remote station
+     * \return the RSSI (in dBm) of the most recent packet received from the remote station
+     */
+    virtual std::optional<double> GetMostRecentRssi(const Mac48Address& address) const;
+
   protected:
     void DoDispose() override;
 

src/wifi/model/wifi-remote-station-manager.cc

@@ -1338,7 +1338,7 @@ WifiRemoteStationManager::GetInfo(Mac48Address address)
     return LookupState(address)->m_info;
 }
 
-double
+std::optional<double>
 WifiRemoteStationManager::GetMostRecentRssi(Mac48Address address) const
 {
     auto stationIt = m_stations.find(address);
@@ -1346,8 +1346,11 @@ WifiRemoteStationManager::GetMostRecentRssi(Mac48Address address) const
     auto station = stationIt->second;
     auto rssi = station->m_rssiAndUpdateTimePair.first;
     auto ts = station->m_rssiAndUpdateTimePair.second;
-    NS_ASSERT_MSG(ts.IsStrictlyPositive(), "address: " << address << " ts:" << ts);
-    return rssi;
+    if (ts.IsStrictlyPositive())
+    {
+        return rssi;
+    }
+    return std::nullopt;
 }
 
 std::shared_ptr<WifiRemoteStationState>

src/wifi/model/wifi-remote-station-manager.h

@@ -973,7 +973,7 @@ class WifiRemoteStationManager : public Object
      * to estimate the target UL RSSI info to put in the
      * Trigger frame to send to the remote station.
      */
-    double GetMostRecentRssi(Mac48Address address) const;
+    std::optional<double> GetMostRecentRssi(Mac48Address address) const;
     /**
      * Set the default transmission power level
      *