diff --git a/src/wifi/helper/wifi-mac-helper.cc b/src/wifi/helper/wifi-mac-helper.cc
index b7c403ed7..261255fd5 100644
--- a/src/wifi/helper/wifi-mac-helper.cc
+++ b/src/wifi/helper/wifi-mac-helper.cc
@@ -65,10 +65,12 @@ WifiMacHelper::Create (Ptr<WifiNetDevice> device, WifiStandard standard) const
     {
       Ptr<WifiProtectionManager> protectionManager = m_protectionManager.Create<WifiProtectionManager> ();
       protectionManager->SetWifiMac (mac);
+      protectionManager->SetLinkId (SINGLE_LINK_OP_ID);
       fem->SetProtectionManager (protectionManager);
 
       Ptr<WifiAckManager> ackManager = m_ackManager.Create<WifiAckManager> ();
       ackManager->SetWifiMac (mac);
+      ackManager->SetLinkId (SINGLE_LINK_OP_ID);
       fem->SetAckManager (ackManager);
 
       // create and install the Multi User Scheduler if this is an HE AP
diff --git a/src/wifi/model/wifi-ack-manager.cc b/src/wifi/model/wifi-ack-manager.cc
index 5485bd494..d83b5a85b 100644
--- a/src/wifi/model/wifi-ack-manager.cc
+++ b/src/wifi/model/wifi-ack-manager.cc
@@ -40,6 +40,12 @@ WifiAckManager::GetTypeId (void)
   return tid;
 }
 
+WifiAckManager::WifiAckManager ()
+  : m_linkId (0)
+{
+  NS_LOG_FUNCTION (this);
+}
+
 WifiAckManager::~WifiAckManager ()
 {
   NS_LOG_FUNCTION_NOARGS ();
@@ -60,6 +66,13 @@ WifiAckManager::SetWifiMac (Ptr<WifiMac> mac)
   m_mac = mac;
 }
 
+void
+WifiAckManager::SetLinkId (uint8_t linkId)
+{
+  NS_LOG_FUNCTION (this << +linkId);
+  m_linkId = linkId;
+}
+
 void
 WifiAckManager::SetQosAckPolicy (Ptr<WifiMacQueueItem> item, const WifiAcknowledgment* acknowledgment)
 {
diff --git a/src/wifi/model/wifi-ack-manager.h b/src/wifi/model/wifi-ack-manager.h
index 1e97b1bbb..7b923ce8a 100644
--- a/src/wifi/model/wifi-ack-manager.h
+++ b/src/wifi/model/wifi-ack-manager.h
@@ -47,6 +47,7 @@ public:
    * \return the object TypeId
    */
   static TypeId GetTypeId (void);
+  WifiAckManager ();
   virtual ~WifiAckManager ();
 
   /**
@@ -55,6 +56,12 @@ public:
    * \param mac a pointer to the MAC
    */
   void SetWifiMac (Ptr<WifiMac> mac);
+  /**
+   * Set the ID of the link this Acknowledgment Manager is associated with.
+   *
+   * \param linkId the ID of the link this Acknowledgment Manager is associated with
+   */
+  void SetLinkId (uint8_t linkId);
 
   /**
    * Set the QoS Ack policy for the given MPDU, which must be a QoS data frame.
@@ -102,6 +109,7 @@ protected:
   void DoDispose (void) override;
 
   Ptr<WifiMac> m_mac; //!< MAC which is using this Acknowledgment Manager
+  uint8_t m_linkId;   //!< ID of the link this Acknowledgment Manager is operating on
 };
 
 
diff --git a/src/wifi/model/wifi-default-ack-manager.cc b/src/wifi/model/wifi-default-ack-manager.cc
index 2c8b973c8..af18fe42d 100644
--- a/src/wifi/model/wifi-default-ack-manager.cc
+++ b/src/wifi/model/wifi-default-ack-manager.cc
@@ -644,7 +644,7 @@ WifiDefaultAckManager::TryUlMuTransmission (Ptr<const WifiMacQueueItem> mpdu,
   Ptr<ApWifiMac> apMac = DynamicCast<ApWifiMac> (m_mac);
   NS_ABORT_MSG_IF (apMac == nullptr, "HE APs only can send Trigger Frames");
 
-  Ptr<HeFrameExchangeManager> heFem = DynamicCast<HeFrameExchangeManager> (m_mac->GetFrameExchangeManager ());
+  auto heFem = DynamicCast<HeFrameExchangeManager> (m_mac->GetFrameExchangeManager (m_linkId));
   NS_ABORT_MSG_IF (heFem == nullptr, "HE APs only can send Trigger Frames");
 
   CtrlTriggerHeader trigger;
diff --git a/src/wifi/model/wifi-protection-manager.cc b/src/wifi/model/wifi-protection-manager.cc
index f21563413..d2366a15b 100644
--- a/src/wifi/model/wifi-protection-manager.cc
+++ b/src/wifi/model/wifi-protection-manager.cc
@@ -39,6 +39,12 @@ WifiProtectionManager::GetTypeId (void)
   return tid;
 }
 
+WifiProtectionManager::WifiProtectionManager ()
+  : m_linkId (0)
+{
+  NS_LOG_FUNCTION (this);
+}
+
 WifiProtectionManager::~WifiProtectionManager ()
 {
   NS_LOG_FUNCTION_NOARGS ();
@@ -59,4 +65,11 @@ WifiProtectionManager::SetWifiMac (Ptr<WifiMac> mac)
   m_mac = mac;
 }
 
+void
+WifiProtectionManager::SetLinkId (uint8_t linkId)
+{
+  NS_LOG_FUNCTION (this << +linkId);
+  m_linkId = linkId;
+}
+
 } //namespace ns3
diff --git a/src/wifi/model/wifi-protection-manager.h b/src/wifi/model/wifi-protection-manager.h
index 7d00e9cb0..22e1ae6b4 100644
--- a/src/wifi/model/wifi-protection-manager.h
+++ b/src/wifi/model/wifi-protection-manager.h
@@ -46,6 +46,7 @@ public:
    * \return the object TypeId
    */
   static TypeId GetTypeId (void);
+  WifiProtectionManager ();
   virtual ~WifiProtectionManager ();
 
   /**
@@ -54,6 +55,12 @@ public:
    * \param mac a pointer to the MAC
    */
   void SetWifiMac (Ptr<WifiMac> mac);
+  /**
+   * Set the ID of the link this Protection Manager is associated with.
+   *
+   * \param linkId the ID of the link this Protection Manager is associated with
+   */
+  void SetLinkId (uint8_t linkId);
 
   /**
    * Determine the protection method to use if the given MPDU is added to the current
@@ -85,6 +92,7 @@ protected:
   virtual void DoDispose (void);
 
   Ptr<WifiMac> m_mac; //!< MAC which is using this Protection Manager
+  uint8_t m_linkId;   //!< ID of the link this Protection Manager is operating on
 };