diff -r 9677003feabc src/wifi/model/edca-txop-n.cc
--- a/src/wifi/model/edca-txop-n.cc	Sat Apr 30 16:51:45 2016 +0200
+++ b/src/wifi/model/edca-txop-n.cc	Sat Apr 30 18:11:38 2016 +0200
@@ -625,6 +625,49 @@
 void EdcaTxopN::NotifyInternalCollision (void)
 {
   NS_LOG_FUNCTION (this);
+  bool resetDcf = false;
+  bool needRts = m_stationManager->NeedRts (m_currentHdr.GetAddr1 (),
+                                            &m_currentHdr,
+                                            m_currentPacket,
+                                            m_low->GetDataTxVector (m_currentPacket, &m_currentHdr));
+  if (needRts)
+    {
+      if (!NeedRtsRetransmission ())
+      {
+        resetDcf = true;
+        m_stationManager->ReportFinalRtsFailed (m_currentHdr.GetAddr1 (), &m_currentHdr);
+      }
+      else
+      {
+        m_stationManager->ReportRtsFailed (m_currentHdr.GetAddr1 (), &m_currentHdr);
+      }
+    }
+  else
+    {
+      if (!NeedDataRetransmission ())
+      {
+        resetDcf = true;
+        m_stationManager->ReportFinalDataFailed (m_currentHdr.GetAddr1 (), &m_currentHdr);
+      }
+      else
+      {
+        m_stationManager->ReportDataFailed (m_currentHdr.GetAddr1 (), &m_currentHdr);
+      }
+    }
+  if (resetDcf)
+    {
+      if (!m_txFailedCallback.IsNull ())
+        {
+          m_txFailedCallback (m_currentHdr);
+        }
+      //to reset the dcf.
+      m_currentPacket = 0;
+      m_dcf->ResetCw ();
+    }
+  else
+    {
+      m_dcf->UpdateFailedCw ();
+    }
   NotifyCollision ();
 }
 
diff -r 9677003feabc src/wifi/model/mac-low.h
--- a/src/wifi/model/mac-low.h	Sat Apr 30 16:51:45 2016 +0200
+++ b/src/wifi/model/mac-low.h	Sat Apr 30 18:11:38 2016 +0200
@@ -823,7 +823,6 @@
    */
   void FlushAggregateQueue (void);
 
-protected:
   /**
    * Return a TXVECTOR for the DATA frame given the destination.
    * The function consults WifiRemoteStationManager, which controls the rate