Adding simple highway mobility model
diff --git a/utils/highway-position-allocator.h b/utils/highway-position-allocator.h
new file mode 100644
index 0000000..4028b4a
--- /dev/null
+++ b/utils/highway-position-allocator.h
@@ -0,0 +1,53 @@
+/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
+/*
+ * Copyright (c) 2007 INRIA
+ *
+ * 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: Lucas Wang <lucas@cs.ucla.edu>
+ */
+#ifndef HIGHWAY_POSITION_ALLOCATOR_H
+#define HIGHWAY_POSITION_ALLOCATOR_H
+
+#include "ns3/position-allocator.h"
+
+namespace ns3 {
+  
+/**
+ * This position allocator is used to generate positions for cars 
+ * on a highway.
+ */
+
+class HighwayPositionAllocator : public PositionAllocator
+{
+public:
+  static TypeId GetTypeId (void);
+  HighwayPositionAllocator ();
+  virtual Vector GetNext (void) const;
+  void SetStartPosition(Vector start);
+  Vector GetStartPosition(void) const;
+  void SetDirection(double direction); // the angle in terms of radian degrees
+  double GetDirection(void) const ;
+  void SetLength(double length);
+  double GetLength(void) const ;
+
+private:
+  mutable Vector m_previous_position; // previously generated vehicle position
+  Vector m_start; // highway starting point
+  double m_direction; //highway direction
+  double m_length; // highway length
+};
+}
+
+#endif