--- 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)

--- a/src/wifi/model/wifi-tx-vector.h	Fri Dec 19 16:22:49 2014 -0800
+++ b/src/wifi/model/wifi-tx-vector.h	Fri Dec 19 18:28:40 2014 -0800
@@ -35,6 +35,20 @@
  * and also 15.4.4.2 "PMD_SAP peer-to-peer service primitive
  * parameters".
  *
+ * If this class is constructed with the constructor that takes no
+ * arguments, then the client must explicitly set the mode and 
+ * transmit power level parameters before using them.  Default
+ * member initializers are provided for the other parameters, to
+ * conform to a non-MIMO/long guard configuration, although these
+ * may also be explicitly set after object construction.
+ *
+ * When used in a infrastructure context, WifiTxVector values should be 
+ * drawn from WifiRemoteStationManager parameters since rate adaptation 
+ * is responsible for picking the mode, number of streams, etc., but in 
+ * the case in which there is no such manager (e.g. mesh), the client 
+ * still needs to initialize at least the mode and transmit power level 
+ * appropriately.
+ *
  * \note the above reference is valid for the DSSS PHY only (clause
  * 15). TXVECTOR is defined also for the other PHYs, however they
  * don't include the TXPWRLVL explicitly in the TXVECTOR. This is
@@ -144,10 +158,13 @@
                            to PMD_TXPWRLVL.request */ 
   uint8_t  m_retries;      /**< The DATA_RETRIES/RTS_RETRIES parameter
                            for Click radiotap information */
-  bool     m_shortGuardInterval; //true if short GI is going to be used
-  uint8_t  m_nss; //number of streams
-  uint8_t  m_ness; //number of streams in beamforming
-  bool     m_stbc; //STBC used or not
+  bool     m_shortGuardInterval; /**< true if short GI is going to be used */
+  uint8_t  m_nss; /**< number of streams */
+  uint8_t  m_ness; /**< number of streams in beamforming */
+  bool     m_stbc; /**< STBC used or not */
+
+  bool     m_modeInitialized; //*< Internal initialization flag */
+  bool     m_txPowerLevelInitialized; //*< Internal initialization flag */
 
 };