mpdu-aggregator.cc

Go to the documentation of this file.

/*
 * 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 "mpdu-aggregator.h"
 
#include "ampdu-subframe-header.h"
#include "ctrl-headers.h"
#include "msdu-aggregator.h"
#include "qos-txop.h"
#include "wifi-mac-trailer.h"
#include "wifi-mac.h"
#include "wifi-mpdu.h"
#include "wifi-net-device.h"
#include "wifi-phy.h"
#include "wifi-remote-station-manager.h"
#include "wifi-tx-parameters.h"
#include "wifi-tx-vector.h"
 
#include "ns3/he-capabilities.h"
#include "ns3/ht-capabilities.h"
#include "ns3/log.h"
#include "ns3/packet.h"
#include "ns3/vht-capabilities.h"
 
NS_LOG_COMPONENT_DEFINE("MpduAggregator");
 
namespace ns3
{
 
NS_OBJECT_ENSURE_REGISTERED(MpduAggregator);
 
TypeId
MpduAggregator::GetTypeId()
{
    static TypeId tid = TypeId("ns3::MpduAggregator")
                            .SetParent<Object>()
                            .SetGroupName("Wifi")
                            .AddConstructor<MpduAggregator>();
    return tid;
}
 
MpduAggregator::MpduAggregator()
{
}
 
MpduAggregator::~MpduAggregator()
{
}
 
void
MpduAggregator::DoDispose()
{
    m_mac = nullptr;
    Object::DoDispose();
}
 
void
MpduAggregator::SetWifiMac(const Ptr<WifiMac> mac)
{
    NS_LOG_FUNCTION(this << mac);
    m_mac = mac;
}
 
void
MpduAggregator::Aggregate(Ptr<const WifiMpdu> 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<WifiMpdu>>
MpduAggregator::GetNextAmpdu(Ptr<WifiMpdu> mpdu,
                             WifiTxParameters& txParams,
                             Time availableTime) const
{
    NS_LOG_FUNCTION(this << *mpdu << &txParams << availableTime);
 
    std::vector<Ptr<WifiMpdu>> 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);
 
    // 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<WifiMpdu> nextMpdu = mpdu;
 
        while (nextMpdu)
        {
            // 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
            auto peekedMpdu = qosTxop->PeekNextMpdu(SINGLE_LINK_OP_ID, tid, recipient, nextMpdu);
            nextMpdu = nullptr;
 
            if (peekedMpdu)
            {
                // 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(SINGLE_LINK_OP_ID,
                                                peekedMpdu,
                                                txParams,
                                                availableTime,
                                                false);
            }
        }
 
        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