wifi-default-protection-manager.cc

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/*
 * Copyright (c) 2020 Universita' degli Studi di Napoli Federico II
 *
 * 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: Stefano Avallone <stavallo@unina.it>
 */
 
#include "wifi-default-protection-manager.h"
 
#include "ap-wifi-mac.h"
#include "wifi-mpdu.h"
#include "wifi-tx-parameters.h"
 
#include "ns3/boolean.h"
#include "ns3/erp-ofdm-phy.h"
#include "ns3/log.h"
 
#include <type_traits>
 
namespace ns3
{
 
NS_LOG_COMPONENT_DEFINE("WifiDefaultProtectionManager");
 
NS_OBJECT_ENSURE_REGISTERED(WifiDefaultProtectionManager);
 
TypeId
WifiDefaultProtectionManager::GetTypeId()
{
    static TypeId tid =
        TypeId("ns3::WifiDefaultProtectionManager")
            .SetParent<WifiProtectionManager>()
            .SetGroupName("Wifi")
            .AddConstructor<WifiDefaultProtectionManager>()
            .AddAttribute("EnableMuRts",
                          "If enabled, always protect a DL/UL MU frame exchange with MU-RTS/CTS.",
                          BooleanValue(false),
                          MakeBooleanAccessor(&WifiDefaultProtectionManager::m_sendMuRts),
                          MakeBooleanChecker());
    return tid;
}
 
WifiDefaultProtectionManager::WifiDefaultProtectionManager()
{
    NS_LOG_FUNCTION(this);
}
 
WifiDefaultProtectionManager::~WifiDefaultProtectionManager()
{
    NS_LOG_FUNCTION_NOARGS();
}
 
std::unique_ptr<WifiProtection>
WifiDefaultProtectionManager::TryAddMpdu(Ptr<const WifiMpdu> mpdu, const WifiTxParameters& txParams)
{
    NS_LOG_FUNCTION(this << *mpdu << &txParams);
 
    // For a DL MU PPDU containing more than one PSDU, call a separate method.
    // A DL MU PPDU contains more than one PSDU if either the TX params' PSDU info map
    // contains more than one entry or it contains one entry but the MPDU being added is
    // addressed to a different receiver (hence generating a new entry if the MPDU is added)
    if (const auto& psduInfoMap = txParams.GetPsduInfoMap();
        txParams.m_txVector.IsDlMu() &&
        (psduInfoMap.size() > 1 ||
         (psduInfoMap.size() == 1 && psduInfoMap.begin()->first != mpdu->GetHeader().GetAddr1())))
    {
        return TryAddMpduToMuPpdu(mpdu, txParams);
    }
 
    // No protection for TB PPDUs (the soliciting Trigger Frame can be protected by an MU-RTS)
    if (txParams.m_txVector.IsUlMu())
    {
        if (txParams.m_protection)
        {
            NS_ASSERT(txParams.m_protection->method == WifiProtection::NONE);
            return nullptr;
        }
        return std::unique_ptr<WifiProtection>(new WifiNoProtection);
    }
 
    // if this is a Trigger Frame, call a separate method
    if (mpdu->GetHeader().IsTrigger())
    {
        return TryUlMuTransmission(mpdu, txParams);
    }
 
    // if the current protection method (if any) is already RTS/CTS or CTS-to-Self,
    // it will not change by adding an MPDU
    if (txParams.m_protection && (txParams.m_protection->method == WifiProtection::RTS_CTS ||
                                  txParams.m_protection->method == WifiProtection::CTS_TO_SELF))
    {
        return nullptr;
    }
 
    // if a protection method is set, it must be NONE
    NS_ASSERT(!txParams.m_protection || txParams.m_protection->method == WifiProtection::NONE);
 
    std::unique_ptr<WifiProtection> protection;
    protection =
        GetPsduProtection(mpdu->GetHeader(), txParams.GetSizeIfAddMpdu(mpdu), txParams.m_txVector);
 
    // return the newly computed method if none was set or it is not NONE
    if (!txParams.m_protection || protection->method != WifiProtection::NONE)
    {
        return protection;
    }
    // the protection method has not changed
    return nullptr;
}
 
std::unique_ptr<WifiProtection>
WifiDefaultProtectionManager::TryAggregateMsdu(Ptr<const WifiMpdu> msdu,
                                               const WifiTxParameters& txParams)
{
    NS_LOG_FUNCTION(this << *msdu << &txParams);
 
    // if the current protection method is already RTS/CTS, CTS-to-Self or MU-RTS/CTS,
    // it will not change by aggregating an MSDU
    NS_ASSERT(txParams.m_protection);
    if (txParams.m_protection->method == WifiProtection::RTS_CTS ||
        txParams.m_protection->method == WifiProtection::CTS_TO_SELF ||
        txParams.m_protection->method == WifiProtection::MU_RTS_CTS)
    {
        return nullptr;
    }
 
    NS_ASSERT(txParams.m_protection->method == WifiProtection::NONE);
 
    // No protection for TB PPDUs and DL MU PPDUs containing more than one PSDU
    if (txParams.m_txVector.IsUlMu() ||
        (txParams.m_txVector.IsDlMu() && txParams.GetPsduInfoMap().size() > 1))
    {
        return nullptr;
    }
 
    std::unique_ptr<WifiProtection> protection;
    protection = GetPsduProtection(msdu->GetHeader(),
                                   txParams.GetSizeIfAggregateMsdu(msdu).second,
                                   txParams.m_txVector);
 
    // the protection method may still be none
    if (protection->method == WifiProtection::NONE)
    {
        return nullptr;
    }
 
    // the protection method has changed
    return protection;
}
 
std::unique_ptr<WifiProtection>
WifiDefaultProtectionManager::GetPsduProtection(const WifiMacHeader& hdr,
                                                uint32_t size,
                                                const WifiTxVector& txVector) const
{
    NS_LOG_FUNCTION(this << hdr << size << txVector);
 
    // a non-initial fragment does not need to be protected, unless it is being retransmitted
    if (hdr.GetFragmentNumber() > 0 && !hdr.IsRetry())
    {
        return std::unique_ptr<WifiProtection>(new WifiNoProtection());
    }
 
    // check if RTS/CTS is needed
    if (GetWifiRemoteStationManager()->NeedRts(hdr, size))
    {
        WifiRtsCtsProtection* protection = new WifiRtsCtsProtection;
        protection->rtsTxVector = GetWifiRemoteStationManager()->GetRtsTxVector(hdr.GetAddr1());
        protection->ctsTxVector =
            GetWifiRemoteStationManager()->GetCtsTxVector(hdr.GetAddr1(),
                                                          protection->rtsTxVector.GetMode());
        return std::unique_ptr<WifiProtection>(protection);
    }
 
    // check if CTS-to-Self is needed
    if (GetWifiRemoteStationManager()->GetUseNonErpProtection() &&
        GetWifiRemoteStationManager()->NeedCtsToSelf(txVector))
    {
        WifiCtsToSelfProtection* protection = new WifiCtsToSelfProtection;
        protection->ctsTxVector = GetWifiRemoteStationManager()->GetCtsToSelfTxVector();
        return std::unique_ptr<WifiProtection>(protection);
    }
 
    return std::unique_ptr<WifiProtection>(new WifiNoProtection());
}
 
std::unique_ptr<WifiProtection>
WifiDefaultProtectionManager::TryAddMpduToMuPpdu(Ptr<const WifiMpdu> mpdu,
                                                 const WifiTxParameters& txParams)
{
    NS_LOG_FUNCTION(this << *mpdu << &txParams);
    NS_ASSERT(txParams.m_txVector.IsDlMu());
 
    if (!m_sendMuRts)
    {
        // No protection because sending MU-RTS is disabled
        if (txParams.m_protection && txParams.m_protection->method == WifiProtection::NONE)
        {
            return nullptr;
        }
        return std::unique_ptr<WifiProtection>(new WifiNoProtection());
    }
 
    WifiMuRtsCtsProtection* protection = nullptr;
    if (txParams.m_protection && txParams.m_protection->method == WifiProtection::MU_RTS_CTS)
    {
        protection = static_cast<WifiMuRtsCtsProtection*>(txParams.m_protection.get());
    }
 
    auto receiver = mpdu->GetHeader().GetAddr1();
 
    if (txParams.GetPsduInfo(receiver) == nullptr)
    {
        // we get here if this is the first MPDU for this receiver.
        NS_ABORT_MSG_IF(m_mac->GetTypeOfStation() != AP, "HE APs only can send DL MU PPDUs");
        auto apMac = StaticCast<ApWifiMac>(m_mac);
        auto txWidth = txParams.m_txVector.GetChannelWidth();
 
        if (protection != nullptr)
        {
            // txParams.m_protection points to an existing WifiMuRtsCtsProtection object.
            // We have to return a copy of this object including the needed changes
            protection = new WifiMuRtsCtsProtection(*protection);
        }
        else
        {
            // we have to create a new WifiMuRtsCtsProtection object
            protection = new WifiMuRtsCtsProtection;
 
            // initialize the MU-RTS Trigger Frame
            // The UL Length, GI And HE-LTF Type, MU-MIMO HE-LTF Mode, Number Of HE-LTF Symbols,
            // UL STBC, LDPC Extra Symbol Segment, AP TX Power, Pre-FEC Padding Factor,
            // PE Disambiguity, UL Spatial Reuse, Doppler and UL HE-SIG-A2 Reserved subfields in
            // the Common Info field are reserved. (Sec. 9.3.1.22.5 of 802.11ax)
            protection->muRts.SetType(TriggerFrameType::MU_RTS_TRIGGER);
            protection->muRts.SetUlBandwidth(txWidth);
 
            NS_ASSERT_MSG(txParams.GetPsduInfoMap().size() == 1,
                          "There should be one PSDU in the DL MU PPDU when creating a new "
                          "WifiMuRtsCtsProtection object");
 
            // this is the first MPDU for the second receiver added to the DL MU PPDU.
            // Add a User Info field for the first receiver
            AddUserInfoToMuRts(protection->muRts,
                               txWidth,
                               txParams.GetPsduInfoMap().cbegin()->first);
 
            // compute the TXVECTOR to use to send the MU-RTS Trigger Frame
            protection->muRtsTxVector = GetWifiRemoteStationManager()->GetRtsTxVector(receiver);
            // The transmitter of an MU-RTS Trigger frame shall not request a non-AP STA to send
            // a CTS frame response in a 20 MHz channel that is not occupied by the PPDU that
            // contains the MU-RTS Trigger frame. (Sec. 26.2.6.2 of 802.11ax)
            protection->muRtsTxVector.SetChannelWidth(txWidth);
        }
 
        // Add a User Info field for the new receiver
        // The UL HE-MCS, UL FEC Coding Type, UL DCM, SS Allocation and UL Target RSSI fields
        // in the User Info field are reserved (Sec. 9.3.1.22.5 of 802.11ax)
        AddUserInfoToMuRts(protection->muRts, txWidth, receiver);
 
        return std::unique_ptr<WifiMuRtsCtsProtection>(protection);
    }
 
    // an MPDU addressed to the same receiver has been already added
    NS_ASSERT(protection != nullptr);
 
    // no change is needed
    return nullptr;
}
 
std::unique_ptr<WifiProtection>
WifiDefaultProtectionManager::TryUlMuTransmission(Ptr<const WifiMpdu> mpdu,
                                                  const WifiTxParameters& txParams)
{
    NS_LOG_FUNCTION(this << *mpdu << &txParams);
    NS_ASSERT(mpdu->GetHeader().IsTrigger());
 
    if (!m_sendMuRts)
    {
        // No protection because sending MU-RTS is disabled
        return std::unique_ptr<WifiProtection>(new WifiNoProtection());
    }
 
    CtrlTriggerHeader trigger;
    mpdu->GetPacket()->PeekHeader(trigger);
    NS_ASSERT(trigger.GetNUserInfoFields() > 0);
    auto txWidth = trigger.GetUlBandwidth();
 
    WifiMuRtsCtsProtection* protection = new WifiMuRtsCtsProtection;
    // initialize the MU-RTS Trigger Frame
    // The UL Length, GI And HE-LTF Type, MU-MIMO HE-LTF Mode, Number Of HE-LTF Symbols,
    // UL STBC, LDPC Extra Symbol Segment, AP TX Power, Pre-FEC Padding Factor,
    // PE Disambiguity, UL Spatial Reuse, Doppler and UL HE-SIG-A2 Reserved subfields in
    // the Common Info field are reserved. (Sec. 9.3.1.22.5 of 802.11ax)
    protection->muRts.SetType(TriggerFrameType::MU_RTS_TRIGGER);
    protection->muRts.SetUlBandwidth(txWidth);
 
    NS_ABORT_MSG_IF(m_mac->GetTypeOfStation() != AP, "HE APs only can send DL MU PPDUs");
    const auto& staList = StaticCast<ApWifiMac>(m_mac)->GetStaList(m_linkId);
    std::remove_reference_t<decltype(staList)>::const_iterator staIt;
 
    for (const auto& userInfo : trigger)
    {
        // Add a User Info field to the MU-RTS for this solicited station
        // The UL HE-MCS, UL FEC Coding Type, UL DCM, SS Allocation and UL Target RSSI fields
        // in the User Info field are reserved (Sec. 9.3.1.22.5 of 802.11ax)
        staIt = staList.find(userInfo.GetAid12());
        NS_ASSERT(staIt != staList.cend());
        AddUserInfoToMuRts(protection->muRts, txWidth, staIt->second);
    }
 
    // compute the TXVECTOR to use to send the MU-RTS Trigger Frame
    protection->muRtsTxVector =
        GetWifiRemoteStationManager()->GetRtsTxVector(mpdu->GetHeader().GetAddr1());
    // The transmitter of an MU-RTS Trigger frame shall not request a non-AP STA to send
    // a CTS frame response in a 20 MHz channel that is not occupied by the PPDU that
    // contains the MU-RTS Trigger frame. (Sec. 26.2.6.2 of 802.11ax)
    protection->muRtsTxVector.SetChannelWidth(txWidth);
    // OFDM is needed to transmit the PPDU over a bandwidth that is a multiple of 20 MHz
    const auto modulation = protection->muRtsTxVector.GetModulationClass();
    if (modulation == WIFI_MOD_CLASS_DSSS || modulation == WIFI_MOD_CLASS_HR_DSSS)
    {
        protection->muRtsTxVector.SetMode(ErpOfdmPhy::GetErpOfdmRate6Mbps());
    }
 
    return std::unique_ptr<WifiMuRtsCtsProtection>(protection);
}
 
} // namespace ns3