wifi: (fixes #2320) Add method to check whether a WifiTxVector contains a valid combination of WifiMode, number of spatial streams and channel width

RELEASE_NOTES

@@ -122,6 +122,7 @@ Bugs fixed
 - Bug 2316 - MacLow shall use a single TXVECTOR for all MPDUs belonging to a same A-MPDU
 - Bug 2318 - MPDU Aggregation fails with TCP
 - Bug 2319 - BlockAckTimeout value is too low for 802.11n operating at 2.4 GHz
+- Bug 2320 - Add method to check whether a WifiTxVector contains a valid combination of WifiMode, number of spatial streams and channel width
 - Bug 2321 - Wifi rate managers should not be triggered for each MPDU when A-MPDU is used
 - Bug 2327 - CWmin value selection for 802.11g is not compliant with the standard rules
 

src/wifi/model/wifi-phy.cc

@@ -1559,6 +1559,42 @@ WifiPhy::GetVhtMcs9 ()
   return mcs;
 }
 
+bool
+WifiPhy::IsValidTxVector (WifiTxVector txVector)
+{
+  uint32_t chWidth = txVector.GetChannelWidth();
+  uint8_t nss = txVector.GetNss();
+  std::string modeName = txVector.GetMode().GetUniqueName();
+
+  if (chWidth == 20)
+    {
+      if (nss != 3 && nss != 6)
+        {
+          return (modeName != "VhtMcs9");
+        }
+    }
+  else if (chWidth == 80)
+    {
+      if (nss == 3 || nss == 7)
+        {
+          return (modeName != "VhtMcs6");
+        }
+      else if (nss == 6)
+        {
+          return (modeName != "VhtMcs9");
+        }
+    }
+  else if (chWidth == 160)
+    {
+      if (nss == 3)
+        {
+          return (modeName != "VhtMcs9");
+        }
+    }
+
+  return true;
+}
+
 std::ostream& operator<< (std::ostream& os, enum WifiPhy::State state)
 {
   switch (state)

src/wifi/model/wifi-phy.h

@@ -1056,6 +1056,15 @@ public:
    * \return MCS 9 from VHT MCS values
    */
   static WifiMode GetVhtMcs9 ();
+  /**
+   * The standard disallows certain combinations of WifiMode, number of
+   * spatial streams, and channel widths.  This method can be used to
+   * check whether this WifiTxVector contains an invalid combination.
+   *
+   * \param txVector the WifiTxVector to inspect
+   * \return true if the WifiTxVector parameters are allowed by the standard
+   */
+  static bool IsValidTxVector (WifiTxVector txVector);
 
   /**
    * Public method used to fire a PhyTxBegin trace.