--- a/src/devices/wifi/dca-txop.cc	Thu Feb 25 22:45:40 2010 +0300
+++ b/src/devices/wifi/dca-txop.cc	Fri Feb 26 12:11:11 2010 +0300
@@ -268,6 +268,13 @@
                                     packet);
 }
 
+void
+DcaTxop::DoStart ()
+{
+  m_dcf->ResetCw ();
+  m_dcf->StartBackoffNow (m_rng->GetNext (0, m_dcf->GetCw ()));
+  ns3::Dcf::DoStart ();
+}
 bool
 DcaTxop::NeedRtsRetransmission (void)
 {