From b699ad9ae12705ea9ec15165f7fe80ac66574032 Mon Sep 17 00:00:00 2001
From: Mathieu Lacage <mathieu.lacage@sophia.inria.fr>
Date: Mon, 19 Nov 2007 16:20:30 +0100
Subject: [PATCH] use a simple request/grant scheme for dcf accesses

---
 src/devices/wifi/dcf-manager-test.cc | 18 +++++--------
 src/devices/wifi/dcf-manager.cc      | 38 +++++++++++++++++++++++++---
 src/devices/wifi/dcf-manager.h       | 15 +++++++----
 3 files changed, 50 insertions(+), 21 deletions(-)

diff --git a/src/devices/wifi/dcf-manager-test.cc b/src/devices/wifi/dcf-manager-test.cc
index cceeb7677..cb1b15c1f 100644
--- a/src/devices/wifi/dcf-manager-test.cc
+++ b/src/devices/wifi/dcf-manager-test.cc
@@ -18,10 +18,9 @@ public:
   void QueueTx (uint64_t txTime, uint64_t expectedGrantTime);
 private:
   friend class DcfManagerTest;
-  virtual bool NeedsAccess (void) const;
-  virtual void NotifyAccessGranted (void);
-  virtual void NotifyInternalCollision (void);
-  virtual void NotifyCollision (void);
+  virtual void DoNotifyAccessGranted (void);
+  virtual void DoNotifyInternalCollision (void);
+  virtual void DoNotifyCollision (void);
 
   typedef std::pair<uint64_t,uint64_t> ExpectedGrant;
   typedef std::list<ExpectedGrant> ExpectedGrants;
@@ -83,23 +82,18 @@ DcfStateTest::QueueTx (uint64_t txTime, uint64_t expectedGrantTime)
 {
   m_expectedGrants.push_back (std::make_pair (txTime, expectedGrantTime));
 }
-bool 
-DcfStateTest::NeedsAccess (void) const
-{
-  return !m_expectedGrants.empty ();
-}
 void 
-DcfStateTest::NotifyAccessGranted (void)
+DcfStateTest::DoNotifyAccessGranted (void)
 {
   m_test->NotifyAccessGranted (m_i);
 }
 void
-DcfStateTest::NotifyInternalCollision (void)
+DcfStateTest::DoNotifyInternalCollision (void)
 {
   m_test->NotifyInternalCollision (m_i);
 }
 void 
-DcfStateTest::NotifyCollision (void)
+DcfStateTest::DoNotifyCollision (void)
 {
   m_test->NotifyCollision (m_i);
 }
diff --git a/src/devices/wifi/dcf-manager.cc b/src/devices/wifi/dcf-manager.cc
index ddac2671e..f1f12b11c 100644
--- a/src/devices/wifi/dcf-manager.cc
+++ b/src/devices/wifi/dcf-manager.cc
@@ -21,7 +21,8 @@ namespace ns3 {
 
 DcfState::DcfState ()
   : m_backoffSlots (0),
-    m_backoffStart (Seconds (0.0))
+    m_backoffStart (Seconds (0.0)),
+    m_accessRequested (false)
 {}
 
 DcfState::~DcfState ()
@@ -91,6 +92,33 @@ DcfState::GetBackoffStart (void) const
 {
   return m_backoffStart;
 }
+bool 
+DcfState::IsAccessRequested (void) const
+{
+  return m_accessRequested;
+}
+void 
+DcfState::NotifyAccessRequested (void)
+{
+  m_accessRequested = true;
+}
+void 
+DcfState::NotifyAccessGranted (void)
+{
+  NS_ASSERT (m_accessRequested);
+  m_accessRequested = false;
+  DoNotifyAccessGranted ();
+}
+void 
+DcfState::NotifyCollision (void)
+{
+  DoNotifyCollision ();
+}
+void 
+DcfState::NotifyInternalCollision (void)
+{
+  DoNotifyInternalCollision ();
+}
 
 
 /****************************************************************
@@ -185,6 +213,8 @@ void
 DcfManager::RequestAccess (DcfState *state)
 {
   UpdateBackoff ();
+  NS_ASSERT (!state->IsAccessRequested ());
+  state->NotifyAccessRequested ();
   /**
    * If there is a collision, generate a backoff
    * by notifying the collision to the user.
@@ -211,7 +241,7 @@ DcfManager::DoGrantAccess (void)
   for (States::const_iterator i = m_states.begin (); i != m_states.end (); k++)
     {
       DcfState *state = *i;
-      if (state->NeedsAccess () &&
+      if (state->IsAccessRequested () && 
           GetBackoffEndFor (state) <= Simulator::Now ())
         {
           /**
@@ -225,7 +255,7 @@ DcfManager::DoGrantAccess (void)
           for (States::const_iterator j = i; j != m_states.end (); j++, k++)
             {
               DcfState *otherState = *j;
-              if (otherState->NeedsAccess () &&
+              if (otherState->IsAccessRequested () &&
                   GetBackoffEndFor (otherState) <= Simulator::Now ())
                 {
                   MY_DEBUG ("dcf " << k << " needs access. backoff expired. internal collision. slots=" << 
@@ -346,7 +376,7 @@ DcfManager::DoRestartAccessTimeoutIfNeeded (void)
   for (States::const_iterator i = m_states.begin (); i != m_states.end (); i++)
     {
       DcfState *state = *i;
-      if (state->NeedsAccess ())
+      if (state->IsAccessRequested ())
         {
           Time tmp = GetBackoffEndFor (state);
           if (tmp > Simulator::Now ())
diff --git a/src/devices/wifi/dcf-manager.h b/src/devices/wifi/dcf-manager.h
index 44414620c..001abb759 100644
--- a/src/devices/wifi/dcf-manager.h
+++ b/src/devices/wifi/dcf-manager.h
@@ -21,6 +21,7 @@ public:
   void UpdateFailedCw (void);
   void StartBackoffNow (uint32_t nSlots);
   uint32_t GetCw (void) const;
+  bool IsAccessRequested (void) const;
 
 private:
   friend class DcfManager;
@@ -28,13 +29,16 @@ private:
   uint32_t GetAifsn (void) const;
   uint32_t GetBackoffSlots (void) const;
   Time GetBackoffStart (void) const;
-
   void UpdateBackoffSlotsNow (uint32_t nSlots, Time backoffUpdateBound);
+  void NotifyAccessRequested (void);
+  void NotifyAccessGranted (void);
+  void NotifyCollision (void);
+  void NotifyInternalCollision (void);
 
-  virtual bool NeedsAccess (void) const = 0;
-  virtual void NotifyAccessGranted (void) = 0;
-  virtual void NotifyInternalCollision (void) = 0;
-  virtual void NotifyCollision (void) = 0;
+
+  virtual void DoNotifyAccessGranted (void) = 0;
+  virtual void DoNotifyInternalCollision (void) = 0;
+  virtual void DoNotifyCollision (void) = 0;
 
   uint32_t m_aifsn;
   uint32_t m_backoffSlots;
@@ -45,6 +49,7 @@ private:
   uint32_t m_cwMin;
   uint32_t m_cwMax;
   uint32_t m_cw;
+  bool m_accessRequested;
 };
 
 class DcfManager