diff -r c9b19f516c5f src/wifi/model/dca-txop.cc
--- a/src/wifi/model/dca-txop.cc	Wed Oct 31 23:17:27 2012 -0700
+++ b/src/wifi/model/dca-txop.cc	Fri Nov 02 10:13:29 2012 -0400
@@ -103,6 +103,10 @@
   {
     m_txop->Cancel ();
   }
+  virtual void EndTxNoAck (void)
+  {
+    m_txop->EndTxNoAck ();
+  }
 
 private:
   DcaTxop *m_txop;
@@ -407,10 +411,6 @@
                                  &m_currentHdr,
                                  params,
                                  m_transmissionListener);
-      m_currentPacket = 0;
-      m_dcf->ResetCw ();
-      m_dcf->StartBackoffNow (m_rng->GetNext (0, m_dcf->GetCw ()));
-      StartAccessIfNeeded ();
       NS_LOG_DEBUG ("tx broadcast");
     }
   else
@@ -621,4 +621,15 @@
    */
 }
 
+void
+DcaTxop::EndTxNoAck (void)
+{
+  NS_LOG_FUNCTION (this);
+  NS_LOG_DEBUG ("a transmission that did not require an ACK just finished");
+  m_currentPacket = 0;
+  m_dcf->ResetCw ();
+  m_dcf->StartBackoffNow (m_rng->GetNext (0, m_dcf->GetCw ()));
+  StartAccessIfNeeded ();
+}
+
 } // namespace ns3
diff -r c9b19f516c5f src/wifi/model/dca-txop.h
--- a/src/wifi/model/dca-txop.h	Wed Oct 31 23:17:27 2012 -0700
+++ b/src/wifi/model/dca-txop.h	Fri Nov 02 10:13:29 2012 -0400
@@ -147,6 +147,7 @@
   void MissedAck (void);
   void StartNext (void);
   void Cancel (void);
+  void EndTxNoAck (void);
 
   void RestartAccessIfNeeded (void);
   void StartAccessIfNeeded (void);
diff -r c9b19f516c5f src/wifi/model/edca-txop-n.cc
--- a/src/wifi/model/edca-txop-n.cc	Wed Oct 31 23:17:27 2012 -0700
+++ b/src/wifi/model/edca-txop-n.cc	Fri Nov 02 10:13:29 2012 -0400
@@ -111,6 +111,10 @@
   {
     m_txop->Cancel ();
   }
+  virtual void EndTxNoAck (void)
+  {
+    m_txop->EndTxNoAck ();
+  }
 
 private:
   EdcaTxopN *m_txop;
@@ -384,10 +388,6 @@
                                 params,
                                 m_transmissionListener);
 
-      m_currentPacket = 0;
-      m_dcf->ResetCw ();
-      m_dcf->StartBackoffNow (m_rng->GetNext (0, m_dcf->GetCw ()));
-      StartAccessIfNeeded ();
       NS_LOG_DEBUG ("tx broadcast");
     }
   else if (m_currentHdr.GetType () == WIFI_MAC_CTL_BACKREQ)
@@ -730,6 +730,17 @@
   NS_LOG_DEBUG ("transmission cancelled");
 }
 
+void
+EdcaTxopN::EndTxNoAck (void)
+{
+  NS_LOG_FUNCTION (this);
+  NS_LOG_DEBUG ("a transmission that did not require an ACK just finished");
+  m_currentPacket = 0;
+  m_dcf->ResetCw ();
+  m_dcf->StartBackoffNow (m_rng->GetNext (0, m_dcf->GetCw ()));
+  StartAccessIfNeeded ();
+}
+
 bool
 EdcaTxopN::NeedFragmentation (void) const
 {
diff -r c9b19f516c5f src/wifi/model/edca-txop-n.h
--- a/src/wifi/model/edca-txop-n.h	Wed Oct 31 23:17:27 2012 -0700
+++ b/src/wifi/model/edca-txop-n.h	Fri Nov 02 10:13:29 2012 -0400
@@ -126,6 +126,7 @@
   void MissedAck (void);
   void StartNext (void);
   void Cancel (void);
+  void EndTxNoAck (void);
 
   void RestartAccessIfNeeded (void);
   void StartAccessIfNeeded (void);
diff -r c9b19f516c5f src/wifi/model/mac-low.cc
--- a/src/wifi/model/mac-low.cc	Wed Oct 31 23:17:27 2012 -0700
+++ b/src/wifi/model/mac-low.cc	Fri Nov 02 10:13:29 2012 -0400
@@ -360,6 +360,7 @@
     m_sendAckEvent (),
     m_sendDataEvent (),
     m_waitSifsEvent (),
+    m_endTxNoAckEvent (),
     m_currentPacket (0),
     m_listener (0)
 {
@@ -396,6 +397,7 @@
   m_sendAckEvent.Cancel ();
   m_sendDataEvent.Cancel ();
   m_waitSifsEvent.Cancel ();
+  m_endTxNoAckEvent.Cancel ();
   m_phy = 0;
   m_stationManager = 0;
   delete m_phyMacLowListener;
@@ -457,6 +459,11 @@
       m_waitSifsEvent.Cancel ();
       oneRunning = true;
     }
+  if (m_endTxNoAckEvent.IsRunning ()) 
+    {
+      m_endTxNoAckEvent.Cancel ();
+      oneRunning = true;
+    }
   if (oneRunning && m_listener != 0)
     {
       m_listener->Cancel ();
@@ -1352,7 +1359,7 @@
   else
     {
       // since we do not expect any timer to be triggered.
-      m_listener = 0;
+      Simulator::Schedule(txDuration, &MacLow::EndTxNoAck, this);
     }
 }
 
@@ -1490,6 +1497,14 @@
   m_listener->StartNext ();
 }
 
+void 
+MacLow::EndTxNoAck (void)
+{
+  MacLowTransmissionListener *listener = m_listener;
+  m_listener = 0;
+  listener->EndTxNoAck ();
+}
+
 void
 MacLow::FastAckFailedTimeout (void)
 {
diff -r c9b19f516c5f src/wifi/model/mac-low.h
--- a/src/wifi/model/mac-low.h	Wed Oct 31 23:17:27 2012 -0700
+++ b/src/wifi/model/mac-low.h	Fri Nov 02 10:13:29 2012 -0400
@@ -123,7 +123,15 @@
    * you can assume that the packet has not been passed
    * down the stack to the PHY.
    */
-  virtual void Cancel (void) = 0;
+  virtual void Cancel (void) = 0;	
+
+  /** 
+   * Invoked upon the end of the transmission of a frame that does not
+   * require an ACK (e.g., broadcast and multicast frames).
+   * 
+   */
+  virtual void EndTxNoAck (void) = 0;
+
 };
 
 
@@ -541,6 +549,7 @@
   void SendAckAfterData (Mac48Address source, Time duration, WifiMode txMode, double rtsSnr);
   void SendDataAfterCts (Mac48Address source, Time duration, WifiMode txMode);
   void WaitSifsAfterEndTx (void);
+  void EndTxNoAck (void);
 
   void SendRtsForPacket (void);
   void SendDataPacket (void);
@@ -614,6 +623,7 @@
   EventId m_sendAckEvent;
   EventId m_sendDataEvent;
   EventId m_waitSifsEvent;
+  EventId m_endTxNoAckEvent;
   EventId m_navCounterResetCtsMissed;
 
   Ptr<Packet> m_currentPacket;