if (Simulator::Now () - m_lastRxStart <= m_sifs)

      //this may be caused only if PHY has started to receive a packet

        {

      //inside SIFS, so, we check that lastRxStart was maximum a SIFS ago

          //this may be caused if PHY has started to receive a packet

      NS_ASSERT (Simulator::Now () - m_lastRxStart <= m_sifs);

          //inside SIFS, so, we check that lastRxStart was within a SIFS ago

      m_lastRxEnd = Simulator::Now ();

          m_lastRxEnd = Simulator::Now ();

      m_lastRxDuration = m_lastRxEnd - m_lastRxStart;

          m_lastRxDuration = m_lastRxEnd - m_lastRxStart;

      m_lastRxReceivedOk = true;

          m_lastRxReceivedOk = true;

      m_rxing = false;

          m_rxing = false;

        }

      else

        {

          // Bug 2477:  It is possible for the DCF to fall out of 

          //            sync with the PHY state if there are problems

          //            receiving A-MPDUs.  PHY will cancel the reception

          //            and start to transmit

          NS_LOG_DEBUG ("Phy is transmitting despite DCF being in receive state");

          m_lastRxEnd = Simulator::Now ();

          m_lastRxDuration = m_lastRxEnd - m_lastRxStart;

          m_lastRxReceivedOk = false;

          m_rxing = false;

        }

  NS_LOG_DEBUG ("rx failed ");

  NS_LOG_DEBUG ("rx failed");

  NS_LOG_FUNCTION (this << (uint16_t) tid << originator << duration.As (Time::S) << blockAckReqTxVector << rxSnr);

  if (!m_phy->IsStateTx () && !m_phy->IsStateRx ())

  CtrlBAckResponseHeader blockAck;

    {

  uint16_t seqNumber = 0;

      NS_LOG_FUNCTION (this << (uint16_t) tid << originator << duration.As (Time::S) << blockAckReqTxVector << rxSnr);

  BlockAckCachesI i = m_bAckCaches.find (std::make_pair (originator, tid));

      CtrlBAckResponseHeader blockAck;

  NS_ASSERT (i != m_bAckCaches.end ());

      uint16_t seqNumber = 0;

  seqNumber = (*i).second.GetWinStart ();

      BlockAckCachesI i = m_bAckCaches.find (std::make_pair (originator, tid));

      NS_ASSERT (i != m_bAckCaches.end ());

      seqNumber = (*i).second.GetWinStart ();

  bool immediate = true;

      bool immediate = true;

  AgreementsI it = m_bAckAgreements.find (std::make_pair (originator, tid));

      AgreementsI it = m_bAckAgreements.find (std::make_pair (originator, tid));

  blockAck.SetStartingSequence (seqNumber);

      blockAck.SetStartingSequence (seqNumber);

  blockAck.SetTidInfo (tid);

      blockAck.SetTidInfo (tid);

  immediate = (*it).second.first.IsImmediateBlockAck ();

      immediate = (*it).second.first.IsImmediateBlockAck ();

  blockAck.SetType (COMPRESSED_BLOCK_ACK);

      blockAck.SetType (COMPRESSED_BLOCK_ACK);

  NS_LOG_DEBUG ("Got Implicit block Ack Req with seq " << seqNumber);

      NS_LOG_DEBUG ("Got Implicit block Ack Req with seq " << seqNumber);

  (*i).second.FillBlockAckBitmap (&blockAck);

      (*i).second.FillBlockAckBitmap (&blockAck);

  SendBlockAckResponse (&blockAck, originator, immediate, duration, blockAckReqTxVector.GetMode (), rxSnr);

      SendBlockAckResponse (&blockAck, originator, immediate, duration, blockAckReqTxVector.GetMode (), rxSnr);

    }

  else

    {

      NS_LOG_DEBUG ("Skip block ack response!");

    }