docs: Update documentation and Doxygen documentation generation
diff --git a/helper/ndn-app-helper.h b/helper/ndn-app-helper.h
index 94d1046..e559260 100644
--- a/helper/ndn-app-helper.h
+++ b/helper/ndn-app-helper.h
@@ -31,6 +31,7 @@
 namespace ndn {
 
 /**
+ * @ingroup ndn-helpers
  * \brief A helper to make it easier to instantiate an ns3::NdnConsumer Application
  * on a set of nodes.
  */
diff --git a/helper/ndn-face-container.h b/helper/ndn-face-container.h
index 692daf6..e1566e6 100644
--- a/helper/ndn-face-container.h
+++ b/helper/ndn-face-container.h
@@ -32,7 +32,7 @@
 namespace ndn {
 
 /**
- * \ingroup ndn-helpers
+ * @ingroup ndn-helpers
  * \brief A pool for Ndn faces
  * 
  * Provides tools to perform basic manipulation on faces, such as
diff --git a/helper/ndn-global-routing-helper.h b/helper/ndn-global-routing-helper.h
index f233e89..53c7b15 100644
--- a/helper/ndn-global-routing-helper.h
+++ b/helper/ndn-global-routing-helper.h
@@ -32,7 +32,7 @@
 namespace ndn {
 
 /**
- * @ingroup ndn
+ * @ingroup ndn-helpers
  * @brief Helper for GlobalRouter interface
  */
 class GlobalRoutingHelper
diff --git a/helper/ndn-header-helper.h b/helper/ndn-header-helper.h
index 0e39c0c..1e3e086 100644
--- a/helper/ndn-header-helper.h
+++ b/helper/ndn-header-helper.h
@@ -34,7 +34,7 @@
 typedef Name NameComponents;
 
 /**
- * \ingroup ndn-helpers
+ * @ingroup ndn-helpers
  *
  * \brief Class implementing functionality to detect Ndn packet type and
  * create the corresponding object
@@ -94,13 +94,7 @@
 };
 
   /**
-   * \ingroup ndn
-   * \defgroup ndn-exceptions Exceptions
-   */
-  /**
-   * \ingroup ndn-exceptions
-   * \brief Exception thrown if Ndn stack receives unrecognized
-   * message type
+   * \brief Exception thrown if NDN stack receives unrecognized message type
    */
 class UnknownHeaderException {};
 
diff --git a/helper/ndn-link-control-helper.h b/helper/ndn-link-control-helper.h
index 619fb1c..1fb3251 100644
--- a/helper/ndn-link-control-helper.h
+++ b/helper/ndn-link-control-helper.h
@@ -29,8 +29,8 @@
 namespace ndn {
 
 /**
+ * @ingroup ndn-helpers
  * @brief Helper class to control the up or down statuss of an NDN link connecting two specific nodes
- * @ingroup Ndn
  */
 class LinkControlHelper
 {