# HG changeset patch
# User Tom Henderson <tomh@tomh.org>
# Date 1461358875 25200
#      Fri Apr 22 14:01:15 2016 -0700
# Node ID 8a21f6e3bf751cadfc7bc5b718c951cb36ae1cb4
# Parent  67a0fea6a7ccfcea50b885bc5632569768228633
wifi: (fixes #2385) Avoid invalid WifiTxVector in IdealWifiManager

diff -r 67a0fea6a7cc -r 8a21f6e3bf75 src/wifi/model/ideal-wifi-manager.cc
--- a/src/wifi/model/ideal-wifi-manager.cc	Fri Apr 22 02:27:25 2016 +0200
+++ b/src/wifi/model/ideal-wifi-manager.cc	Fri Apr 22 14:01:15 2016 -0700
@@ -37,7 +37,7 @@
 {
   double m_lastSnrObserved;  //!< SNR of most recently reported packet sent to the remote station
   double m_lastSnrCached;    //!< SNR most recently used to select a rate
-  double m_nss;          //!< SNR most recently used to select a rate
+  double m_nss;              //!< spatial stream recently used to remote station
   WifiMode m_lastMode;       //!< Mode most recently used to the remote station
 };
 
@@ -118,7 +118,7 @@
                     " short GI " << GetPhy ()->GetGuardInterval ());
       AddSnrThreshold (txVector, GetPhy ()->CalculateSnr (txVector, m_ber));
     }
-  // Add all Ht and Vht MCSes 
+  // Add all supported Ht and Vht MCSes 
   txVector.SetChannelWidth (GetPhy ()->GetChannelWidth ());
   if (HasVhtSupported () == true || HasHtSupported () == true )
     {
@@ -126,23 +126,36 @@
       for (uint32_t i = 0; i < nModes; i++)
         {
           mode = GetPhy ()->GetMcs (i);
-          if (mode.GetModulationClass () == WIFI_MOD_CLASS_HT)
+          txVector.SetMode (mode);
+          for (uint8_t j = 1; j <= GetPhy ()->GetSupportedTxSpatialStreams (); j++)
             {
-              //derive NSS from the Mcs index
-              nss = (mode.GetMcsValue () / 8) + 1;
+              if (mode.GetModulationClass () == WIFI_MOD_CLASS_HT)
+                {
+                  //derive NSS from the Mcs index
+                  nss = (mode.GetMcsValue () / 8) + 1;
+                  if (nss != j)
+                    {
+                      continue;
+                    }
+                }
+              else
+                {
+                  nss = j;
+                }
+              txVector.SetNss (nss);
+              if (IsSupportedTxVector (txVector) && WifiPhy::IsValidTxVector (txVector))
+                {
+                  NS_LOG_DEBUG ("Initialize, adding mode = " << mode.GetUniqueName () <<
+                                " channel width " << GetPhy ()->GetChannelWidth () <<
+                                " nss " << (uint16_t) nss << 
+                               " short GI " << GetPhy ()->GetGuardInterval ());
+                  AddSnrThreshold (txVector, GetPhy ()->CalculateSnr (txVector, m_ber));
+                }
+              else
+                {
+                  NS_LOG_DEBUG ("Skipping mode " << mode.GetUniqueName () << " as unsupported");
+                }
             }
-          else
-            {
-              nss = GetPhy ()->GetSupportedTxSpatialStreams ();
-            }
-          NS_LOG_DEBUG ("Initialize, adding mode = " << mode.GetUniqueName () <<
-                        " channel width " << GetPhy ()->GetChannelWidth () <<
-                        " nss " << (uint16_t) nss << 
-                        " short GI " << GetPhy ()->GetGuardInterval ());
-          NS_LOG_DEBUG ("In SetupPhy, adding mode = " << mode.GetUniqueName ());
-          txVector.SetNss (nss);
-          txVector.SetMode (mode);
-          AddSnrThreshold (txVector, GetPhy ()->CalculateSnr (txVector, m_ber));
         }
     }
 }
@@ -264,6 +277,7 @@
   //to ensure correct packet delivery.
   double maxThreshold = 0.0;
   WifiMode maxMode = GetDefaultMode ();
+  uint8_t maxNss = 1;
   std::vector<WifiTxVector> candidateTxVectors;
   WifiTxVector txVector;
   WifiMode mode;
@@ -275,7 +289,7 @@
       // SNR has not changed, so skip the search and use the last
       // mode selected
       maxMode = station->m_lastMode;      
-      nss = station->m_nss;
+      maxNss = station->m_nss;
       NS_LOG_DEBUG ("Using cached mode = " << maxMode.GetUniqueName () <<
                     " last snr observed " << station->m_lastSnrObserved <<
                     " cached " << station->m_lastSnrCached);
@@ -298,10 +312,10 @@
                   nss = GetPhy ()->GetSupportedTxSpatialStreams ();
                 }
               txVector.SetNss (nss);
-              if (WifiPhy::IsValidTxVector (txVector) == false)
+              if (WifiPhy::IsValidTxVector (txVector) == false || IsSupportedTxVector (txVector) == false)
                  {
                    NS_LOG_DEBUG ("Skipping mode " << mode.GetUniqueName () <<
-                                 " nss " << nss << " width " << 
+                                 " nss " << (uint16_t) nss << " width " << 
                                  txVector.GetChannelWidth());
                    continue;       
                  }
@@ -329,6 +343,7 @@
                                 station->m_lastSnrObserved);
                   maxThreshold = threshold;
                   maxMode = mode;
+                  maxNss = nss;
                 }
             }
         }
@@ -355,22 +370,23 @@
                                 station->m_lastSnrObserved);
                   maxThreshold = threshold;
                   maxMode = mode;
+                  maxNss = nss;
                 }
             }
         }
-      NS_LOG_DEBUG ("Updating cached values for station to " <<  maxMode.GetUniqueName () << " snr " << station->m_lastSnrObserved);
+      NS_LOG_DEBUG ("Updating cached values for station to " <<  maxMode.GetUniqueName () << " snr " << station->m_lastSnrObserved << " nss " << uint16_t (maxNss));
       station->m_lastSnrCached = station->m_lastSnrObserved;
       station->m_lastMode = maxMode;
-      station->m_nss = nss;
+      station->m_nss = maxNss;
     }
   uint32_t channelWidth = GetChannelWidth (station);
   NS_LOG_DEBUG ("Found maxMode: " << maxMode << " channelWidth: " << channelWidth);
-  if (m_currentRate != maxMode.GetDataRate (channelWidth, GetPhy ()->GetGuardInterval (), nss))
+  if (m_currentRate != maxMode.GetDataRate (channelWidth, GetPhy ()->GetGuardInterval (), maxNss))
     {
-      NS_LOG_DEBUG ("New datarate: " << maxMode.GetDataRate (channelWidth, GetPhy ()->GetGuardInterval (), nss));
-      m_currentRate = maxMode.GetDataRate (channelWidth, GetPhy ()->GetGuardInterval (), nss);
+      NS_LOG_DEBUG ("New datarate: " << maxMode.GetDataRate (channelWidth, GetPhy ()->GetGuardInterval (), maxNss));
+      m_currentRate = maxMode.GetDataRate (channelWidth, GetPhy ()->GetGuardInterval (), maxNss);
     }
-  return WifiTxVector (maxMode, GetDefaultTxPowerLevel (), GetLongRetryCount (station), false, nss, 0, channelWidth, GetAggregation (station), false);
+  return WifiTxVector (maxMode, GetDefaultTxPowerLevel (), GetLongRetryCount (station), false, maxNss, 0, channelWidth, GetAggregation (station), false);
 }
 
 WifiTxVector
@@ -411,4 +427,14 @@
   return true;
 }
 
+bool 
+IdealWifiManager::IsSupportedTxVector (const WifiTxVector txVector) const
+{
+  if (txVector.GetNss () > GetPhy ()->GetSupportedTxSpatialStreams ())
+    {
+      return false;
+    } 
+  return true;
+}
+
 } //namespace ns3
diff -r 67a0fea6a7cc -r 8a21f6e3bf75 src/wifi/model/ideal-wifi-manager.h
--- a/src/wifi/model/ideal-wifi-manager.h	Fri Apr 22 02:27:25 2016 +0200
+++ b/src/wifi/model/ideal-wifi-manager.h	Fri Apr 22 14:01:15 2016 -0700
@@ -74,6 +74,21 @@
   virtual bool IsLowLatency (void) const;
 
   /**
+   * Return true or false depending on whether the txVector is supported 
+   * for transmitting.  The list of supported modes stored in the 
+   * WifiPhy may be larger than the list of usable modes for sending data 
+   * because the number of transmit antennas and receive antennas may 
+   * be unequal.
+   *
+   * Note that WifiPhy has a similar IsValidTxVector() that may be used
+   * to check whether the standard allows the combination of channel width,
+   * NSS, and MCS.
+   *
+   * \param txVector the txVector to check
+   * \return true if the station can transmit using this txVector
+   */
+  bool IsSupportedTxVector (const WifiTxVector txVector) const;
+  /**
    * Return the minimum SNR needed to successfully transmit
    * data with this WifiTxVector at the specified BER.
    *