mpdu-aggregator.cc

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/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
/*
 * Copyright (c) 2013
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation;
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 * Author: Ghada Badawy <gbadawy@gmail.com>
 *         Stefano Avallone <stavallo@unina.it>
 */
 
#include "ns3/log.h"
#include "ns3/packet.h"
#include "mpdu-aggregator.h"
#include "ampdu-subframe-header.h"
#include "wifi-phy.h"
#include "wifi-tx-vector.h"
#include "wifi-remote-station-manager.h"
#include "wifi-mac-queue-item.h"
#include "wifi-mac-queue.h"
#include "msdu-aggregator.h"
#include "wifi-net-device.h"
#include "ns3/ht-capabilities.h"
#include "ns3/vht-capabilities.h"
#include "ns3/he-capabilities.h"
#include "regular-wifi-mac.h"
#include "ctrl-headers.h"
#include "wifi-mac-trailer.h"
#include "wifi-tx-parameters.h"
 
NS_LOG_COMPONENT_DEFINE ("MpduAggregator");
 
namespace ns3 {
 
NS_OBJECT_ENSURE_REGISTERED (MpduAggregator);
 
TypeId
MpduAggregator::GetTypeId (void)
{
  static TypeId tid = TypeId ("ns3::MpduAggregator")
    .SetParent<Object> ()
    .SetGroupName ("Wifi")
    .AddConstructor<MpduAggregator> ()
  ;
  return tid;
}
 
MpduAggregator::MpduAggregator ()
{
}
 
MpduAggregator::~MpduAggregator ()
{
}
 
void
MpduAggregator::DoDispose ()
{
  m_mac = 0;
  Object::DoDispose ();
}
 
void
MpduAggregator::SetWifiMac (const Ptr<RegularWifiMac> mac)
{
  NS_LOG_FUNCTION (this << mac);
  m_mac = mac;
}
 
void
MpduAggregator::Aggregate (Ptr<const WifiMacQueueItem> mpdu, Ptr<Packet> ampdu, bool isSingle)
{
  NS_LOG_FUNCTION (mpdu << ampdu << isSingle);
  NS_ASSERT (ampdu);
  // if isSingle is true, then ampdu must be empty
  NS_ASSERT (!isSingle || ampdu->GetSize () == 0);
 
  // pad the previous A-MPDU subframe if the A-MPDU is not empty
  if (ampdu->GetSize () > 0)
    {
      uint8_t padding = CalculatePadding (ampdu->GetSize ());
 
      if (padding)
        {
          Ptr<Packet> pad = Create<Packet> (padding);
          ampdu->AddAtEnd (pad);
        }
    }
 
  // add MPDU header and trailer
  Ptr<Packet> tmp = mpdu->GetPacket ()->Copy ();
  tmp->AddHeader (mpdu->GetHeader ());
  AddWifiMacTrailer (tmp);
 
  // add A-MPDU subframe header and MPDU to the A-MPDU
  AmpduSubframeHeader hdr = GetAmpduSubframeHeader (static_cast<uint16_t> (tmp->GetSize ()), isSingle);
 
  tmp->AddHeader (hdr);
  ampdu->AddAtEnd (tmp);
}
 
uint32_t
MpduAggregator::GetSizeIfAggregated (uint32_t mpduSize, uint32_t ampduSize)
{
  NS_LOG_FUNCTION (mpduSize << ampduSize);
 
  return ampduSize + CalculatePadding (ampduSize) + 4 + mpduSize;
}
 
uint32_t
MpduAggregator::GetMaxAmpduSize (Mac48Address recipient, uint8_t tid,
                                 WifiModulationClass modulation) const
{
  NS_LOG_FUNCTION (this << recipient << +tid << modulation);
 
  AcIndex ac = QosUtilsMapTidToAc (tid);
 
  // Find the A-MPDU max size configured on this device
  uint32_t maxAmpduSize = m_mac->GetMaxAmpduSize (ac);
 
  if (maxAmpduSize == 0)
    {
      NS_LOG_DEBUG ("A-MPDU Aggregation is disabled on this station for AC " << ac);
      return 0;
    }
 
  Ptr<WifiRemoteStationManager> stationManager = m_mac->GetWifiRemoteStationManager ();
  NS_ASSERT (stationManager);
 
  // Retrieve the Capabilities elements advertised by the recipient
  Ptr<const HeCapabilities> heCapabilities = stationManager->GetStationHeCapabilities (recipient);
  Ptr<const VhtCapabilities> vhtCapabilities = stationManager->GetStationVhtCapabilities (recipient);
  Ptr<const HtCapabilities> htCapabilities = stationManager->GetStationHtCapabilities (recipient);
 
  // Determine the constraint imposed by the recipient based on the PPDU
  // format used to transmit the A-MPDU
  if (modulation == WIFI_MOD_CLASS_HE)
    {
      NS_ABORT_MSG_IF (!heCapabilities, "HE Capabilities element not received");
 
      maxAmpduSize = std::min (maxAmpduSize, heCapabilities->GetMaxAmpduLength ());
    }
  else if (modulation == WIFI_MOD_CLASS_VHT)
    {
      NS_ABORT_MSG_IF (!vhtCapabilities, "VHT Capabilities element not received");
 
      maxAmpduSize = std::min (maxAmpduSize, vhtCapabilities->GetMaxAmpduLength ());
    }
  else if (modulation == WIFI_MOD_CLASS_HT)
    {
      NS_ABORT_MSG_IF (!htCapabilities, "HT Capabilities element not received");
 
      maxAmpduSize = std::min (maxAmpduSize, htCapabilities->GetMaxAmpduLength ());
    }
  else  // non-HT PPDU
    {
      NS_LOG_DEBUG ("A-MPDU aggregation is not available for non-HT PHYs");
 
      maxAmpduSize = 0;
    }
 
  return maxAmpduSize;
}
 
uint8_t
MpduAggregator::CalculatePadding (uint32_t ampduSize)
{
  return (4 - (ampduSize % 4 )) % 4;
}
 
AmpduSubframeHeader
MpduAggregator::GetAmpduSubframeHeader (uint16_t mpduSize, bool isSingle)
{
  AmpduSubframeHeader hdr;
  hdr.SetLength (mpduSize);
  if (isSingle)
    {
      hdr.SetEof (1);
    }
  return hdr;
}
 
std::vector<Ptr<WifiMacQueueItem>>
MpduAggregator::GetNextAmpdu (Ptr<WifiMacQueueItem> mpdu, WifiTxParameters& txParams,
                              Time availableTime, WifiMacQueueItem::ConstIterator queueIt) const
{
  NS_LOG_FUNCTION (this << *mpdu << &txParams << availableTime);
 
  std::vector<Ptr<WifiMacQueueItem>> mpduList;
 
  Mac48Address recipient = mpdu->GetHeader ().GetAddr1 ();
  NS_ASSERT (mpdu->GetHeader ().IsQosData () && !recipient.IsBroadcast ());
  uint8_t tid = mpdu->GetHeader ().GetQosTid ();
 
  Ptr<QosTxop> qosTxop = m_mac->GetQosTxop (tid);
  NS_ASSERT (qosTxop != 0);
 
  //Have to make sure that the block ack agreement is established and A-MPDU is enabled
  if (qosTxop->GetBaAgreementEstablished (recipient, tid)
      && GetMaxAmpduSize (recipient, tid, txParams.m_txVector.GetModulationClass ()) > 0)
    {
      /* here is performed MPDU aggregation */
      Ptr<WifiMacQueueItem> nextMpdu = mpdu;
 
      while (nextMpdu != 0)
        {
          // if we are here, nextMpdu can be aggregated to the A-MPDU.
          NS_LOG_DEBUG ("Adding packet with sequence number " << nextMpdu->GetHeader ().GetSequenceNumber ()
                        << " to A-MPDU, packet size = " << nextMpdu->GetSize ()
                        << ", A-MPDU size = " << txParams.GetSize (recipient));
 
          mpduList.push_back (nextMpdu);
 
          // If allowed by the BA agreement, get the next MPDU
          nextMpdu = 0;
 
          Ptr<const WifiMacQueueItem> peekedMpdu;
          peekedMpdu = qosTxop->PeekNextMpdu (queueIt, tid, recipient);
          if (peekedMpdu != 0)
            {
              // PeekNextMpdu() does not return an MPDU that is beyond the transmit window
              NS_ASSERT (IsInWindow (peekedMpdu->GetHeader ().GetSequenceNumber (),
                                     qosTxop->GetBaStartingSequence (recipient, tid),
                                     qosTxop->GetBaBufferSize (recipient, tid)));
 
              // get the next MPDU to aggregate, provided that the constraints on size
              // and duration limit are met. Note that the returned MPDU differs from
              // the peeked MPDU if A-MSDU aggregation is enabled.
              NS_LOG_DEBUG ("Trying to aggregate another MPDU");
              nextMpdu = qosTxop->GetNextMpdu (peekedMpdu, txParams, availableTime, false, queueIt);
            }
        }
 
      if (mpduList.size () == 1)
        {
          // return an empty vector if it was not possible to aggregate at least two MPDUs
          mpduList.clear ();
        }
    }
 
  return mpduList;
}
 
} //namespace ns3