1139   WifiMode ackTxMode = GetAckTxModeForData (source, dataTxMode);

  1139   WifiMode ackTxMode = GetAckTxModeForData (source, dataTxMode);

  1140   WifiMacHeader ack;

  1140   WifiMacHeader ack;

  1141   ack.SetType (WIFI_MAC_CTL_ACK);

  1141   ack.SetType (WIFI_MAC_CTL_ACK);

  1142   ack.SetDsNotFrom ();

  1142   ack.SetDsNotFrom ();

  1143   ack.SetDsNotTo ();

  1143   ack.SetDsNotTo ();

  1144   ack.SetNoMoreFragments ();

  1145   ack.SetNoMoreFragments ();

  1145   ack.SetAddr1 (source);

  1146   ack.SetAddr1 (source);

  1146   duration -= GetAckDuration (source, dataTxMode);

  1147   duration -= GetAckDuration (source, dataTxMode);

  1147   duration -= GetSifs ();

  1148   duration -= GetSifs ();

  1148   NS_ASSERT (duration >= MicroSeconds (0));

  1149   NS_ASSERT (duration >= MicroSeconds (0));