diff --git a/SConstruct b/SConstruct
index b89015f4c..db7883eff 100644
--- a/SConstruct
+++ b/SConstruct
@@ -256,6 +256,7 @@ node.add_sources ([
     'random-rectangle-topology.cc',
     'random-walk-mobility-model.cc',
     'random-direction-mobility-model.cc',
+    'hierarchical-mobility-model.cc',
     ])
 node.add_inst_headers ([
     'node.h',
@@ -281,6 +282,7 @@ node.add_inst_headers ([
     'random-rectangle-topology.h',
     'random-walk-mobility-model.h',
     'random-direction-mobility-model.h',
+    'hierarchical-mobility-model.h',
     ])
 
 applications = build.Ns3Module ('applications', 'src/applications')
diff --git a/src/node/hierarchical-mobility-model.cc b/src/node/hierarchical-mobility-model.cc
new file mode 100644
index 000000000..2c2e84f21
--- /dev/null
+++ b/src/node/hierarchical-mobility-model.cc
@@ -0,0 +1,95 @@
+/* -*-  Mode: C++; c-file-style: "gnu"; indent-tabs-mode:nil; -*- */
+/*
+ * Copyright (c) 2007 INRIA
+ * All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation;
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ *
+ * Author: Mathieu Lacage <mathieu.lacage@sophia.inria.fr>
+ */
+#include "hierarchical-mobility-model.h"
+#include "mobility-model-notifier.h"
+
+namespace ns3 {
+
+HierarchicalMobilityModel::HierarchicalMobilityModel (Ptr<MobilityModel> child, Ptr<MobilityModel> parent)
+  : m_child (child),
+    m_parent (parent)
+{
+  Ptr<MobilityModelNotifier> childNotifier = 
+    m_child->QueryInterface<MobilityModelNotifier> (MobilityModelNotifier::iid);
+  Ptr<MobilityModelNotifier> parentNotifier = 
+    m_parent->QueryInterface<MobilityModelNotifier> (MobilityModelNotifier::iid);
+  if (childNotifier == 0)
+    {
+      childNotifier = Create<MobilityModelNotifier> ();
+      child->AddInterface (childNotifier);
+    }
+  if (parentNotifier == 0)
+    {
+      parentNotifier = Create<MobilityModelNotifier> ();
+      parent->AddInterface (parentNotifier);
+    }
+  childNotifier->RegisterListener (MakeCallback (&HierarchicalMobilityModel::ChildChanged, this));
+  parentNotifier->RegisterListener (MakeCallback (&HierarchicalMobilityModel::ParentChanged, this));
+}
+
+Ptr<MobilityModel> 
+HierarchicalMobilityModel::GetChild (void) const
+{
+  return m_child;
+}
+
+Ptr<MobilityModel> 
+HierarchicalMobilityModel::GetParent (void) const
+{
+  return m_parent;
+}
+
+Position 
+HierarchicalMobilityModel::DoGet (void) const
+{
+  Position parentPosition = m_parent->Get ();
+  Position childPosition = m_child->Get ();
+  return Position (parentPosition.x + childPosition.x,
+		   parentPosition.y + childPosition.y,
+		   parentPosition.z + childPosition.z);
+}
+void 
+HierarchicalMobilityModel::DoSet (const Position &position)
+{
+  // This implementation of DoSet is really an arbitraty choice.
+  // anything else would have been ok.
+  Position parentPosition = m_parent->Get ();
+  Position childPosition (position.x - parentPosition.x,
+			  position.y - parentPosition.y,
+			  position.z - parentPosition.z);
+  m_child->Set (childPosition);
+}
+
+void 
+HierarchicalMobilityModel::ParentChanged (Ptr<const MobilityModel> model)
+{
+  MobilityModel::NotifyCourseChange ();
+}
+
+void 
+HierarchicalMobilityModel::ChildChanged (Ptr<const MobilityModel> model)
+{
+  MobilityModel::NotifyCourseChange ();
+}
+
+
+
+} // namespace ns3
diff --git a/src/node/hierarchical-mobility-model.h b/src/node/hierarchical-mobility-model.h
new file mode 100644
index 000000000..a1bb61713
--- /dev/null
+++ b/src/node/hierarchical-mobility-model.h
@@ -0,0 +1,52 @@
+/* -*-  Mode: C++; c-file-style: "gnu"; indent-tabs-mode:nil; -*- */
+/*
+ * Copyright (c) 2007 INRIA
+ * All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation;
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ *
+ * Author: Mathieu Lacage <mathieu.lacage@sophia.inria.fr>
+ */
+#ifndef HIERARCHICAL_MOBILITY_MODEL_H
+#define HIERARCHICAL_MOBILITY_MODEL_H
+
+#include "mobility-model.h"
+
+namespace ns3 {
+
+class HierarchicalMobilityModel : public MobilityModel
+{
+public:
+  static const InterfaceId iid;
+
+  HierarchicalMobilityModel (Ptr<MobilityModel> child, Ptr<MobilityModel> parent);
+
+  Ptr<MobilityModel> GetChild (void) const;
+  Ptr<MobilityModel> GetParent (void) const;
+  
+private:
+  virtual Position DoGet (void) const;
+  virtual void DoSet (const Position &position);
+
+  void ParentChanged (Ptr<const MobilityModel> model);
+  void ChildChanged (Ptr<const MobilityModel> model);
+
+  Ptr<MobilityModel> m_child;
+  Ptr<MobilityModel> m_parent;
+};
+
+
+} // namespace ns3
+
+#endif /* HIERARCHICAL_MOBILITY_MODEL_H */