--- a/src/wifi/model/wifi-tx-vector.cc	Fri Dec 19 16:22:49 2014 -0800
+++ b/src/wifi/model/wifi-tx-vector.cc	Fri Dec 19 18:28:40 2014 -0800
@@ -20,10 +20,18 @@
  */
 
 #include "ns3/wifi-tx-vector.h"
+#include "ns3/fatal-error.h"
 
 namespace ns3 {
 
 WifiTxVector::WifiTxVector ()
+  : m_retries (0),
+    m_shortGuardInterval (false),
+    m_nss (1),
+    m_ness (0),
+    m_stbc (false),
+    m_modeInitialized (false),
+    m_txPowerLevelInitialized (false)
 {
 }
 
@@ -35,18 +43,28 @@
     m_shortGuardInterval(shortGuardInterval),
     m_nss(nss),
     m_ness(ness),
-    m_stbc(stbc)
+    m_stbc(stbc),
+    m_modeInitialized (true),
+    m_txPowerLevelInitialized (true)
 {
 }
 
 WifiMode
 WifiTxVector::GetMode (void) const
 {
+  if (!m_modeInitialized)
+    {
+      NS_FATAL_ERROR ("WifiTxVector mode must be set before using");
+    }
   return m_mode;
 }
 uint8_t 
 WifiTxVector::GetTxPowerLevel (void) const
 {
+  if (!m_txPowerLevelInitialized)
+    {
+      NS_FATAL_ERROR ("WifiTxVector txPowerLevel must be set before using");
+    }
   return m_txPowerLevel;
 }
 uint8_t 
@@ -79,11 +97,13 @@
 WifiTxVector::SetMode (WifiMode mode)
 {
   m_mode=mode;
+  m_modeInitialized = true;
 }
 void 
 WifiTxVector::SetTxPowerLevel (uint8_t powerlevel)
 {
   m_txPowerLevel=powerlevel;
+  m_txPowerLevelInitialized = true;
 }
 void 
 WifiTxVector::SetRetries (uint8_t retries)