diff --git a/src/node/mobility-model.h b/src/node/mobility-model.h
index f483378ad..4c4cf9000 100644
--- a/src/node/mobility-model.h
+++ b/src/node/mobility-model.h
@@ -43,16 +43,19 @@ public:
 
   /**
    * \returns the current position
-   * Unit is meters
    */
   Position Get (void) const;
+  /**
+   * \param position the position to set.
+   */
   void Set (const Position &position);
+  /**
+   * \returns the current position.
+   */
   Speed GetSpeed (void) const;
   /**
-   * \param position a reference to another position object instance
-   * \returns the distance between the two objects.
-   *
-   * Unit is meters
+   * \param position a reference to another mobility model
+   * \returns the distance between the two objects. Unit is meters.
    */
   double GetDistanceFrom (const MobilityModel &position) const;
 protected:
@@ -63,17 +66,25 @@ protected:
   void NotifyCourseChange (void) const;
 private:
   /**
-   * \param x reference to floating-point variable for x coordinate.
-   * \param y reference to floating-point variable for y coordinate.
-   * \param z reference to floating-point variable for z coordinate.
+   * \returns the current position.
    *
-   * Store in the x, y, and z variables the current coordinates
-   * managed by this position object. Concrete subclasses of this 
-   * base class must implement this method.
-   * Unit is meters
+   * Concrete subclasses of this base class must 
+   * implement this method.
    */
   virtual Position DoGet (void) const = 0;
+  /**
+   * \param position the position to set.
+   *
+   * Concrete subclasses of this base class must 
+   * implement this method.
+   */
   virtual void DoSet (const Position &position) = 0;
+  /**
+   * \returns the current speed.
+   *
+   * Concrete subclasses of this base class must 
+   * implement this method.
+   */
   virtual Speed DoGetSpeed (void) const = 0;
 };
 
diff --git a/src/node/random-walk-2d-mobility-model.cc b/src/node/random-walk-2d-mobility-model.cc
index b8530ce4f..158a32244 100644
--- a/src/node/random-walk-2d-mobility-model.cc
+++ b/src/node/random-walk-2d-mobility-model.cc
@@ -84,6 +84,36 @@ RandomWalk2dMobilityModelParameters::~RandomWalk2dMobilityModelParameters ()
   m_direction = 0;
 }
 
+void 
+RandomWalk2dMobilityModelParameters::SetSpeed (const RandomVariable &speed)
+{
+  delete m_speed;
+  m_speed = speed.Copy ();
+}
+void 
+RandomWalk2dMobilityModelParameters::SetDirection (const RandomVariable &direction)
+{
+  delete m_direction;
+  m_direction = direction.Copy ();
+}
+void 
+RandomWalk2dMobilityModelParameters::SetModeDistance (double distance)
+{
+  m_mode = RandomWalk2dMobilityModelParameters::MODE_DISTANCE;
+  m_modeDistance = distance;
+}
+void 
+RandomWalk2dMobilityModelParameters::SetModeTime (Time time)
+{
+  m_mode = RandomWalk2dMobilityModelParameters::MODE_TIME;
+  m_modeTime = time;
+}
+void 
+RandomWalk2dMobilityModelParameters::SetBounds (const Rectangle &bounds)
+{
+  m_bounds = bounds;
+}
+
 Ptr<RandomWalk2dMobilityModelParameters> 
 RandomWalk2dMobilityModelParameters::GetCurrent (void)
 {
diff --git a/src/node/random-walk-2d-mobility-model.h b/src/node/random-walk-2d-mobility-model.h
index d1cbd9aef..2e921216b 100644
--- a/src/node/random-walk-2d-mobility-model.h
+++ b/src/node/random-walk-2d-mobility-model.h
@@ -34,7 +34,10 @@ namespace ns3 {
 class RandomVariable;
 
 /**
- * \brief parameters to control a random walk model
+ * \brief parameters to control a random walk 2d model
+ *
+ * A single parameter object can be shared by multiple random
+ * walk models.
  */
 class RandomWalk2dMobilityModelParameters : public Object
 {
@@ -46,21 +49,37 @@ class RandomWalk2dMobilityModelParameters : public Object
   RandomWalk2dMobilityModelParameters ();
   virtual ~RandomWalk2dMobilityModelParameters ();
   /**
+   * \param speed the random variable used to pick a new
+   *        speed when the direction is changed.
+   *
    */
   void SetSpeed (const RandomVariable &speed);
+  /**
+   * \param direction the random variable used to pick a new
+   *        direction.
+   */
   void SetDirection (const RandomVariable &direction);
   /**
    * \param distance the distance before a direction change
    *
-   * Unit is meters
+   * Unit is meters.
+   * "time" mode is incompatible with "distance" mode.
    */
   void SetModeDistance (double distance);
   /**
    * \param time the delay before a direction change.
+   *
+   * "time" mode is incompatible with "distance" mode.
    */
   void SetModeTime (Time time);
 
+  /**
+   * \param bounds the bounds of the random walk
+   */
+  void SetBounds (const Rectangle &bounds);
 
+
+  // needed public for internal default value code.
   enum Mode  {
     MODE_DISTANCE,
     MODE_TIME
@@ -81,13 +100,13 @@ class RandomWalk2dMobilityModelParameters : public Object
  * \brief a 2D random walk position model
  *
  * Each instance moves with a speed and direction choosen at random
- * in the intervals [minspeed,maxspeed] and [0,2pi] until
+ * with the user-provided random variables until
  * either a fixed distance has been walked or until a fixed amount
  * of time.
  *
  * The parameters of the model can be specified either with the ns3::Bind
- * function and the variables "RandomWalk2dMinSpeed", "RandomWalk2dMaxSpeed",
- * "RandomWalk2dMode", "RandomWalk2dModeDistance", and, "RandomWalk2dModeTime" or
+ * function and the variables "RandomWalk2dSpeed", "RandomWalk2dMode", 
+ * "RandomWalk2dDistance", "RandomWalk2dTime", and, "RandomWalk2dBounds" or
  * with an instance of the RandomWalk2dMobilityModelParameters class which
  * must be fed to the RandomWalk2dMobilityModel constructors.
  */
@@ -100,7 +119,11 @@ class RandomWalk2dMobilityModel : public MobilityModel
    */
   RandomWalk2dMobilityModel ();
   /**
-   * Create a new position object located at position (0,0,0)
+   * \param parameters the parameters to use to control
+   * the movement of this mobile object.
+   *
+   * Create a new position object located at position (0,0,0) with
+   * the specified parameters.
    */
   RandomWalk2dMobilityModel (Ptr<RandomWalk2dMobilityModelParameters> parameters);