diff --git a/src/devices/wifi/dcf-manager-test.cc b/src/devices/wifi/dcf-manager-test.cc
index 2c2acf34e..d1ec00317 100644
--- a/src/devices/wifi/dcf-manager-test.cc
+++ b/src/devices/wifi/dcf-manager-test.cc
@@ -6,15 +6,6 @@
 #include "dcf-manager.h"
 #include "mac-parameters.h"
 
-#define TEST_ASSERT_EQUAL(got, expected)			\
-  if ((got) != (expected))					\
-      {								\
-	std::clog << __FILE__ << ":" <<__LINE__			\
-		  << ": expected " << (expected)		\
-		  << ", got " << (got) << std::endl;		\
-      }
-
-
 namespace ns3 {
 
 class DcfManagerTest;
@@ -90,11 +81,15 @@ DcfStateTest::NotifyAccessGranted (void)
 void
 DcfStateTest::NotifyInternalCollision (void)
 {
+  UpdateFailedCw ();
+  StartBackoffNow (0);
   m_test->NotifyInternalCollision (m_i);
 }
 void 
 DcfStateTest::NotifyCollision (void)
 {
+  UpdateFailedCw ();
+  StartBackoffNow (0);
   m_test->NotifyCollision (m_i);
 }
 
@@ -265,7 +260,7 @@ DcfManagerTest::RunTests (void)
   m_result = true;
 
   StartTest ();
-  AddDcfState (2, 5, 1);
+  AddDcfState (8, 64, 1);
   AddAccessRequest (10, 0);
   ExpectAccessGranted (10, 0);
   EndTest ();
diff --git a/src/devices/wifi/dcf-manager.cc b/src/devices/wifi/dcf-manager.cc
index 815f209a7..cd4a74833 100644
--- a/src/devices/wifi/dcf-manager.cc
+++ b/src/devices/wifi/dcf-manager.cc
@@ -190,6 +190,7 @@ DcfManager::RequestAccess (DcfState *state)
   if (state->GetBackoffSlots () == 0 && 
       IsBusy ())
     {
+      NS_LOG_DEBUG ("medium is busy: collision");
       /* someone else has accessed the medium.
        * generate a backoff.
        */
@@ -203,7 +204,8 @@ DcfManager::RequestAccess (DcfState *state)
 void
 DcfManager::DoGrantAccess (void)
 {
-  for (States::const_iterator i = m_states.begin (); i != m_states.end (); )
+  uint32_t k = 0;
+  for (States::const_iterator i = m_states.begin (); i != m_states.end (); k++)
     {
       DcfState *state = *i;
       if (state->GetBackoffSlots () == 0 && state->NeedsAccess ())
@@ -212,13 +214,16 @@ DcfManager::DoGrantAccess (void)
            * This is the first dcf we find with an expired backoff and which
            * needs access to the medium. i.e., it has data to send.
            */
+          NS_LOG_DEBUG ("dcf " << k << " needs access. backoff expired. access granted.");
           state->NotifyAccessGranted ();
           i++; // go to the next item in the list.
-          for (States::const_iterator j = i; j != m_states.end (); j++)
+          k++;
+          for (States::const_iterator j = i; j != m_states.end (); j++, k++)
             {
               DcfState *state = *j;
               if (state->GetBackoffSlots () == 0 && state->NeedsAccess ())
                 {
+                  NS_LOG_DEBUG ("dcf " << k << " needs access. backoff expired. internal collision.");
                   /**
                    * all other dcfs with a lower priority whose backoff
                    * has expired and which needed access to the medium
@@ -271,7 +276,8 @@ DcfManager::GetAccessGrantStart (void) const
 void
 DcfManager::UpdateBackoff (void)
 {
-  for (States::const_iterator i = m_states.begin (); i != m_states.end (); i++)
+  uint32_t k = 0;
+  for (States::const_iterator i = m_states.begin (); i != m_states.end (); i++, k++)
     {
       DcfState *state = *i;
 
@@ -289,6 +295,7 @@ DcfManager::UpdateBackoff (void)
            */
           if (nIntSlots > state->GetAifsn ())
             {
+              NS_LOG_DEBUG ("dcf " << k << " dec backoff slots=" << nIntSlots - state->GetAifsn ());
               state->UpdateBackoffSlotsNow (nIntSlots - state->GetAifsn ());
             }
         }
@@ -321,6 +328,7 @@ DcfManager::DoRestartAccessTimeoutIfNeeded (void)
        * backoff is expected to end.
        */
       Time expectedBackoffEnd = GetAccessGrantStart () + Scalar (minNSlots) * m_parameters->GetSlotTime ();
+      NS_LOG_DEBUG ("min n slots=" << minNSlots << ", expected backoff end="<<expectedBackoffEnd);
       /**
        * It is not possible that the backoff was expected to end before now
        * because if it were possible, this would mean that we have missed