spectrum-wifi-phy.cc

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/*
 * Copyright (c) 2005,2006 INRIA
 *
 * SPDX-License-Identifier: GPL-2.0-only
 *
 * Authors: Mathieu Lacage <mathieu.lacage@sophia.inria.fr>
 *          Ghada Badawy <gbadawy@gmail.com>
 *          Sébastien Deronne <sebastien.deronne@gmail.com>
 *
 * Ported from yans-wifi-phy.cc by several contributors starting
 * with Nicola Baldo and Dean Armstrong
 */
 
#include "spectrum-wifi-phy.h"
 
#include "interference-helper.h"
#include "wifi-net-device.h"
#include "wifi-psdu.h"
#include "wifi-spectrum-phy-interface.h"
#include "wifi-spectrum-signal-parameters.h"
#include "wifi-utils.h"
 
#include "ns3/boolean.h"
#include "ns3/double.h"
#include "ns3/he-phy.h"
#include "ns3/log.h"
#include "ns3/node.h"
#include "ns3/simulator.h"
#include "ns3/spectrum-channel.h"
 
#include <algorithm>
#include <numeric>
 
#undef NS_LOG_APPEND_CONTEXT
#define NS_LOG_APPEND_CONTEXT WIFI_PHY_NS_LOG_APPEND_CONTEXT(Ptr(this, false))
 
namespace ns3
{
 
NS_LOG_COMPONENT_DEFINE("SpectrumWifiPhy");
 
NS_OBJECT_ENSURE_REGISTERED(SpectrumWifiPhy);
 
TypeId
SpectrumWifiPhy::GetTypeId()
{
    static TypeId tid =
        TypeId("ns3::SpectrumWifiPhy")
            .SetParent<WifiPhy>()
            .SetGroupName("Wifi")
            .AddConstructor<SpectrumWifiPhy>()
            .AddAttribute("DisableWifiReception",
                          "Prevent Wi-Fi frame sync from ever happening",
                          BooleanValue(false),
                          MakeBooleanAccessor(&SpectrumWifiPhy::m_disableWifiReception),
                          MakeBooleanChecker())
            .AddAttribute(
                "TrackSignalsFromInactiveInterfaces",
                "Enable or disable tracking signals coming from inactive spectrum PHY interfaces",
                BooleanValue(true),
                MakeBooleanAccessor(&SpectrumWifiPhy::m_trackSignalsInactiveInterfaces),
                MakeBooleanChecker())
            .AddAttribute(
                "TxMaskInnerBandMinimumRejection",
                "Minimum rejection (dBr) for the inner band of the transmit spectrum mask",
                DoubleValue(-20.0),
                MakeDoubleAccessor(&SpectrumWifiPhy::m_txMaskInnerBandMinimumRejection),
                MakeDoubleChecker<dBr_u>())
            .AddAttribute(
                "TxMaskOuterBandMinimumRejection",
                "Minimum rejection (dBr) for the outer band of the transmit spectrum mask",
                DoubleValue(-28.0),
                MakeDoubleAccessor(&SpectrumWifiPhy::m_txMaskOuterBandMinimumRejection),
                MakeDoubleChecker<dBr_u>())
            .AddAttribute(
                "TxMaskOuterBandMaximumRejection",
                "Maximum rejection (dBr) for the outer band of the transmit spectrum mask",
                DoubleValue(-40.0),
                MakeDoubleAccessor(&SpectrumWifiPhy::m_txMaskOuterBandMaximumRejection),
                MakeDoubleChecker<dBr_u>())
            .AddTraceSource(
                "SignalArrival",
                "Trace start of all signal arrivals, including weak and foreign signals",
                MakeTraceSourceAccessor(&SpectrumWifiPhy::m_signalCb),
                "ns3::SpectrumWifiPhy::SignalArrivalCallback");
    return tid;
}
 
SpectrumWifiPhy::SpectrumWifiPhy()
    : m_spectrumPhyInterfaces{},
      m_currentSpectrumPhyInterface{nullptr},
      m_frequenciesBeforeSwitch{},
      m_widthsBeforeSwitch{}
{
    NS_LOG_FUNCTION(this);
}
 
SpectrumWifiPhy::~SpectrumWifiPhy()
{
    NS_LOG_FUNCTION(this);
}
 
void
SpectrumWifiPhy::DoDispose()
{
    NS_LOG_FUNCTION(this);
    m_spectrumPhyInterfaces.clear();
    m_currentSpectrumPhyInterface = nullptr;
    m_antenna = nullptr;
    m_channelSwitchedCallback.Nullify();
    WifiPhy::DoDispose();
}
 
void
SpectrumWifiPhy::DoInitialize()
{
    NS_LOG_FUNCTION(this);
    WifiPhy::DoInitialize();
}
 
WifiSpectrumBands
SpectrumWifiPhy::ComputeBands(Ptr<WifiSpectrumPhyInterface> spectrumPhyInterface)
{
    NS_LOG_FUNCTION(this << spectrumPhyInterface);
    WifiSpectrumBands bands{};
    const auto channelWidth = spectrumPhyInterface->GetChannelWidth();
    if (channelWidth < MHz_u{20})
    {
        bands.push_back(GetBandForInterface(spectrumPhyInterface, channelWidth));
    }
    else
    {
        for (MHz_u bw = channelWidth; bw >= MHz_u{20}; bw = bw / 2)
        {
            for (uint16_t i = 0; i < (channelWidth / bw); ++i)
            {
                bands.push_back(GetBandForInterface(spectrumPhyInterface, bw, i));
            }
        }
    }
    return bands;
}
 
RuBands
SpectrumWifiPhy::GetRuBands(Ptr<WifiSpectrumPhyInterface> spectrumPhyInterface,
                            MHz_u guardBandwidth)
{
    RuBands ruBands{};
    const auto channelWidth = spectrumPhyInterface->GetChannelWidth();
    const auto p20Index = GetOperatingChannel().GetPrimaryChannelIndex(MHz_u{20});
    std::vector<WifiModulationClass> modClasses{WIFI_MOD_CLASS_HE};
    if (GetStandard() >= WIFI_STANDARD_80211be)
    {
        modClasses.push_back(WIFI_MOD_CLASS_EHT);
    }
    for (const auto modClass : modClasses)
    {
        for (MHz_u bw = channelWidth; bw >= MHz_u{20}; bw = bw / 2)
        {
            if (bw > GetMaximumChannelWidth(modClass))
            {
                continue;
            }
            for (uint8_t i = 0; i < (channelWidth / bw); ++i)
            {
                for (uint32_t type = 0;
                     type <= static_cast<uint32_t>(WifiRu::GetMaxRuType(modClass));
                     ++type)
                {
                    const auto ruType = static_cast<RuType>(type);
                    const auto nRus = WifiRu::GetNRus(bw, ruType, modClass);
                    std::size_t undefRus{0};
                    for (std::size_t phyIndex = 1; phyIndex <= nRus + undefRus; ++phyIndex)
                    {
                        const auto group =
                            WifiRu::GetSubcarrierGroup(bw, ruType, phyIndex, modClass);
                        if (group.empty())
                        {
                            ++undefRus;
                            continue;
                        }
                        const auto subcarrierRange =
                            std::make_pair(group.front().first, group.back().second);
                        const auto bandIndices = HePhy::ConvertRuSubcarriers(
                            {bw,
                             guardBandwidth,
                             spectrumPhyInterface->GetCenterFrequencies(),
                             spectrumPhyInterface->GetChannelWidth(),
                             GetSubcarrierSpacing(),
                             modClass,
                             subcarrierRange,
                             i});
 
                        WifiSpectrumBandInfo band{};
                        for (const auto& indicesPerSegment : bandIndices)
                        {
                            band.indices.emplace_back(indicesPerSegment);
                            band.frequencies.emplace_back(
                                ConvertIndicesToFrequenciesForInterface(spectrumPhyInterface,
                                                                        indicesPerSegment));
                        }
                        WifiRu::RuSpec ru;
                        if (modClass == WIFI_MOD_CLASS_HE)
                        {
                            const auto index = HeRu::GetIndexIn80MHzSegment(bw, ruType, phyIndex);
                            const auto primary80 =
                                HeRu::GetPrimary80MHzFlag(bw, ruType, phyIndex, p20Index);
                            ru = HeRu::RuSpec{ruType, index, primary80};
                        }
                        else
                        {
                            const auto index = EhtRu::GetIndexIn80MHzSegment(bw, ruType, phyIndex);
                            const auto& [primary160, primary80OrLow80] =
                                EhtRu::GetPrimaryFlags(bw, ruType, phyIndex, p20Index);
                            ru = EhtRu::RuSpec{ruType, index, primary160, primary80OrLow80};
                        }
                        NS_ABORT_IF(WifiRu::GetPhyIndex(ru, bw, p20Index) != phyIndex);
                        ruBands.insert({band, ru});
                    }
                }
            }
        }
    }
    return ruBands;
}
 
void
SpectrumWifiPhy::UpdateInterferenceHelperBands(Ptr<WifiSpectrumPhyInterface> spectrumPhyInterface)
{
    NS_LOG_FUNCTION(this << spectrumPhyInterface);
    auto&& bands = ComputeBands(spectrumPhyInterface);
    WifiSpectrumBands allBands{bands};
    if (GetStandard() >= WIFI_STANDARD_80211ax)
    {
        const auto channelWidth = spectrumPhyInterface->GetChannelWidth();
        auto&& ruBands = GetRuBands(spectrumPhyInterface, GetGuardBandwidth(channelWidth));
        for (const auto& bandRuPair : ruBands)
        {
            allBands.push_back(bandRuPair.first);
        }
        spectrumPhyInterface->SetRuBands(std::move(ruBands));
    }
 
    spectrumPhyInterface->SetBands(std::move(bands));
 
    if (m_interference->HasBands())
    {
        m_interference->UpdateBands(allBands, spectrumPhyInterface->GetFrequencyRange());
    }
    else
    {
        for (const auto& band : allBands)
        {
            m_interference->AddBand(band);
        }
    }
}
 
Ptr<Channel>
SpectrumWifiPhy::GetChannel() const
{
    NS_ABORT_IF(!m_currentSpectrumPhyInterface);
    return m_currentSpectrumPhyInterface->GetChannel();
}
 
void
SpectrumWifiPhy::AddChannel(const Ptr<SpectrumChannel> channel, const FrequencyRange& freqRange)
{
    NS_LOG_FUNCTION(this << channel << freqRange);
 
    const auto foundOverlappingChannel =
        std::any_of(m_spectrumPhyInterfaces.cbegin(),
                    m_spectrumPhyInterfaces.cend(),
                    [freqRange, channel](const auto& item) {
                        const auto spectrumRange = item.first;
                        const auto noOverlap =
                            ((freqRange.minFrequency >= spectrumRange.maxFrequency) ||
                             (freqRange.maxFrequency <= spectrumRange.minFrequency));
                        return (!noOverlap);
                    });
    NS_ABORT_MSG_IF(foundOverlappingChannel,
                    "Added a wifi spectrum channel that overlaps with another existing wifi "
                    "spectrum channel");
 
    auto wifiSpectrumPhyInterface = CreateObject<WifiSpectrumPhyInterface>(freqRange);
    wifiSpectrumPhyInterface->SetSpectrumWifiPhy(this);
    wifiSpectrumPhyInterface->SetChannel(channel);
    if (GetDevice())
    {
        wifiSpectrumPhyInterface->SetDevice(GetDevice());
    }
    m_spectrumPhyInterfaces.emplace(freqRange, wifiSpectrumPhyInterface);
}
 
void
SpectrumWifiPhy::ResetSpectrumModel(Ptr<WifiSpectrumPhyInterface> spectrumPhyInterface,
                                    const std::vector<MHz_u>& centerFrequencies,
                                    MHz_u channelWidth)
{
    std::stringstream ss;
    for (const auto& centerFrequency : centerFrequencies)
    {
        ss << centerFrequency << " ";
    }
    NS_LOG_FUNCTION(this << spectrumPhyInterface << ss.str() << channelWidth);
 
    // We have to reset the spectrum model because we changed RF channel. Consequently,
    // we also have to add the spectrum interface to the spectrum channel again because
    // MultiModelSpectrumChannel keeps spectrum interfaces in a map indexed by the RX
    // spectrum model UID (which has changed after channel switching).
    // Both SingleModelSpectrumChannel and MultiModelSpectrumChannel ensure not to keep
    // duplicated spectrum interfaces (the latter removes the spectrum interface and adds
    // it again in the entry associated with the new RX spectrum model UID)
 
    // Replace existing spectrum model with new one
    spectrumPhyInterface->SetRxSpectrumModel(centerFrequencies,
                                             channelWidth,
                                             GetSubcarrierSpacing(),
                                             GetGuardBandwidth(channelWidth));
 
    spectrumPhyInterface->GetChannel()->AddRx(spectrumPhyInterface);
 
    UpdateInterferenceHelperBands(spectrumPhyInterface);
}
 
void
SpectrumWifiPhy::DoChannelSwitch()
{
    NS_LOG_FUNCTION(this);
    m_frequenciesBeforeSwitch = GetOperatingChannel().IsSet()
                                    ? GetOperatingChannel().GetFrequencies()
                                    : std::vector<MHz_u>{};
    m_widthsBeforeSwitch =
        GetOperatingChannel().IsSet() ? GetOperatingChannel().GetWidths() : std::vector<MHz_u>{};
    WifiPhy::DoChannelSwitch();
}
 
void
SpectrumWifiPhy::FinalizeChannelSwitch()
{
    NS_LOG_FUNCTION(this);
    const auto frequenciesAfter = GetOperatingChannel().GetFrequencies();
    const auto widthsAfter = GetOperatingChannel().GetWidths();
    if ((m_frequenciesBeforeSwitch == frequenciesAfter) && (m_widthsBeforeSwitch == widthsAfter))
    {
        NS_LOG_DEBUG("Same RF channel as before, do nothing");
        if (IsInitialized())
        {
            SwitchMaybeToCcaBusy(nullptr);
        }
        return;
    }
 
    Ptr<WifiSpectrumPhyInterface> newSpectrumPhyInterface;
    const auto numSegments = GetOperatingChannel().GetNSegments();
    NS_ASSERT(numSegments == frequenciesAfter.size() && numSegments == widthsAfter.size());
    for (std::size_t i = 0; i < numSegments; ++i)
    {
        auto interfaceCoveringBand =
            GetInterfaceCoveringChannelBand(frequenciesAfter.at(i), widthsAfter.at(i));
        NS_ABORT_MSG_IF(!interfaceCoveringBand,
                        "No spectrum channel covers frequency range ["
                            << frequenciesAfter.at(i) - (widthsAfter.at(i) / 2) << " MHz - "
                            << frequenciesAfter.at(i) + (widthsAfter.at(i) / 2) << " MHz]");
        if (!newSpectrumPhyInterface)
        {
            newSpectrumPhyInterface = interfaceCoveringBand;
        }
        else
        {
            NS_ABORT_MSG_IF(interfaceCoveringBand != newSpectrumPhyInterface,
                            "All segments are not covered by the same spectrum channel");
        }
    }
    const auto interfaceChanged = (newSpectrumPhyInterface != m_currentSpectrumPhyInterface);
 
    if (interfaceChanged)
    {
        std::stringstream ss;
        for (std::size_t i = 0; i < frequenciesAfter.size(); ++i)
        {
            ss << "(" << frequenciesAfter.at(i) << ", " << widthsAfter.at(i) << ") ";
        }
        NS_LOG_DEBUG("Switch to existing RF interface with frequency/width "
                     << (numSegments > 1 ? "pair" : "pairs") << " of " << ss.str());
        if (m_currentSpectrumPhyInterface && !m_trackSignalsInactiveInterfaces)
        {
            m_currentSpectrumPhyInterface->GetChannel()->RemoveRx(m_currentSpectrumPhyInterface);
        }
    }
 
    m_currentSpectrumPhyInterface = newSpectrumPhyInterface;
 
    auto reset = true;
    if (m_currentSpectrumPhyInterface->GetCenterFrequencies() == frequenciesAfter)
    {
        // Center frequencies have not changed for that interface, hence we do not need to
        // reset the spectrum model nor update any band stored in the interference helper
        if (!m_trackSignalsInactiveInterfaces)
        {
            // If we are not tracking signals from inactive interface,
            // this means the spectrum interface has been disconnected
            // from the spectrum channel and has to be connected back
            m_currentSpectrumPhyInterface->GetChannel()->AddRx(m_currentSpectrumPhyInterface);
        }
        reset = false;
    }
 
    if (reset)
    {
        ResetSpectrumModel(m_currentSpectrumPhyInterface,
                           frequenciesAfter,
                           GetOperatingChannel().GetTotalWidth());
    }
 
    if (IsInitialized())
    {
        NotifyChannelSwitched();
    }
    else
    {
        Simulator::ScheduleNow(&SpectrumWifiPhy::NotifyChannelSwitched, this);
    }
}
 
void
SpectrumWifiPhy::NotifyChannelSwitched()
{
    if (!m_channelSwitchedCallback.IsNull())
    {
        m_channelSwitchedCallback();
    }
}
 
void
SpectrumWifiPhy::ConfigureInterface(const std::vector<MHz_u>& frequencies, MHz_u width)
{
    std::stringstream ss;
    for (const auto& centerFrequency : frequencies)
    {
        ss << centerFrequency << " ";
    }
    NS_LOG_FUNCTION(this << ss.str() << width);
 
    if (!m_trackSignalsInactiveInterfaces)
    {
        NS_LOG_DEBUG("Tracking of signals on inactive interfaces is not enabled");
        return;
    }
 
    Ptr<WifiSpectrumPhyInterface> spectrumPhyInterface;
    const auto numSegments = frequencies.size();
    const auto segmentWidth = width / numSegments;
    for (std::size_t i = 0; i < numSegments; ++i)
    {
        auto interfaceCoveringBand =
            GetInterfaceCoveringChannelBand(frequencies.at(i), segmentWidth);
        NS_ABORT_MSG_IF(!interfaceCoveringBand,
                        "No spectrum channel covers frequency range ["
                            << frequencies.at(i) - (segmentWidth / 2) << " MHz - "
                            << frequencies.at(i) + (segmentWidth / 2) << " MHz]");
        if (!spectrumPhyInterface)
        {
            spectrumPhyInterface = interfaceCoveringBand;
        }
        else
        {
            NS_ABORT_MSG_IF(interfaceCoveringBand != spectrumPhyInterface,
                            "All segments are not covered by the same spectrum channel");
        }
    }
 
    NS_ABORT_MSG_IF(spectrumPhyInterface == m_currentSpectrumPhyInterface,
                    "This method should not be called for the current interface");
 
    if ((frequencies == spectrumPhyInterface->GetCenterFrequencies()) &&
        (width == spectrumPhyInterface->GetChannelWidth()))
    {
        NS_LOG_DEBUG("Same RF channel as before on that interface, do nothing");
        return;
    }
 
    ResetSpectrumModel(spectrumPhyInterface, frequencies, width);
}
 
bool
SpectrumWifiPhy::CanStartRx(Ptr<const WifiPpdu> ppdu) const
{
    return GetLatestPhyEntity()->CanStartRx(ppdu);
}
 
void
SpectrumWifiPhy::StartRx(Ptr<SpectrumSignalParameters> rxParams,
                         Ptr<const WifiSpectrumPhyInterface> interface)
{
    NS_LOG_FUNCTION(this << rxParams << interface);
    Time rxDuration = rxParams->duration;
    Ptr<SpectrumValue> receivedSignalPsd = rxParams->psd;
    if (interface)
    {
        NS_ASSERT_MSG(receivedSignalPsd->GetValuesN() ==
                          interface->GetRxSpectrumModel()->GetNumBands(),
                      "Incorrect spectrum conversion or multi model spectrum channel is not used!");
    }
    NS_LOG_DEBUG("Received signal with PSD " << *receivedSignalPsd << " and duration "
                                             << rxDuration.As(Time::NS));
    uint32_t senderNodeId = 0;
    if (rxParams->txPhy)
    {
        senderNodeId = rxParams->txPhy->GetDevice()->GetNode()->GetId();
    }
    NS_LOG_DEBUG("Received signal from " << senderNodeId << " with unfiltered power "
                                         << WToDbm(Integral(*receivedSignalPsd)) << " dBm");
 
    // Integrate over our receive bandwidth (i.e., all that the receive
    // spectral mask representing our filtering allows) to find the
    // total energy apparent to the "demodulator".
    // This is done per 20 MHz channel band.
    const auto channelWidth = interface ? interface->GetChannelWidth() : GetChannelWidth();
    const auto& bands =
        interface ? interface->GetBands() : m_currentSpectrumPhyInterface->GetBands();
    Watt_u totalRxPower{0.0};
    RxPowerWattPerChannelBand rxPowers;
 
    const auto rxGainRatio = DbToRatio(GetRxGain());
 
    std::size_t index = 0;
    MHz_u prevBw{0};
    for (const auto& band : bands)
    {
        const auto bw =
            std::accumulate(band.frequencies.cbegin(),
                            band.frequencies.cend(),
                            MHz_u{0},
                            [](MHz_u sum, const auto& startStopFreqs) {
                                return sum + HzToMHz(startStopFreqs.second - startStopFreqs.first);
                            });
        NS_ASSERT(bw <= channelWidth);
        index = ((bw != prevBw) ? 0 : (index + 1));
        auto rxPowerPerBand =
            WifiSpectrumValueHelper::GetBandPowerW(receivedSignalPsd, band.indices);
        NS_LOG_DEBUG("Signal power received (watts) before antenna gain for "
                     << bw << " MHz channel band " << index << ": " << band);
        rxPowerPerBand *= rxGainRatio;
        rxPowers.insert({band, rxPowerPerBand});
        NS_LOG_DEBUG("Signal power received after antenna gain for "
                     << bw << " MHz channel band " << index << ": " << rxPowerPerBand << " W"
                     << (rxPowerPerBand > Watt_u{0.0}
                             ? " (" + std::to_string(WToDbm(rxPowerPerBand)) + " dBm)"
                             : ""));
        if (bw <= MHz_u{20})
        {
            totalRxPower += rxPowerPerBand;
        }
        prevBw = bw;
    }
 
    if (GetStandard() >= WIFI_STANDARD_80211ax)
    {
        const auto& ruBands =
            interface ? interface->GetRuBands() : m_currentSpectrumPhyInterface->GetRuBands();
        NS_ASSERT(!ruBands.empty());
        for (const auto& [band, ru] : ruBands)
        {
            auto rxPowerPerBand =
                WifiSpectrumValueHelper::GetBandPowerW(receivedSignalPsd, band.indices);
            rxPowerPerBand *= rxGainRatio;
            rxPowers.insert({band, rxPowerPerBand});
        }
    }
 
    NS_ASSERT_MSG(totalRxPower >= Watt_u{0.0}, "Negative RX power");
    NS_LOG_DEBUG("Total signal power received after antenna gain: "
                 << totalRxPower << " W"
                 << (totalRxPower > Watt_u{0.0}
                         ? " (" + std::to_string(WToDbm(totalRxPower)) + " dBm)"
                         : ""));
 
    Ptr<WifiSpectrumSignalParameters> wifiRxParams =
        DynamicCast<WifiSpectrumSignalParameters>(rxParams);
 
    // Log the signal arrival to the trace source
    if (totalRxPower > Watt_u{0.0})
    {
        m_signalCb(rxParams, senderNodeId, WToDbm(totalRxPower), rxDuration);
    }
 
    if (m_trackSignalsInactiveInterfaces && interface &&
        (interface != m_currentSpectrumPhyInterface))
    {
        NS_LOG_INFO("Received Wi-Fi signal from a non-active PHY interface "
                    << interface->GetFrequencyRange());
        m_interference->AddForeignSignal(rxDuration, rxPowers, interface->GetFrequencyRange());
        return;
    }
 
    if (!wifiRxParams)
    {
        NS_LOG_INFO("Received non Wi-Fi signal");
        m_interference->AddForeignSignal(rxDuration,
                                         rxPowers,
                                         interface ? interface->GetFrequencyRange()
                                                   : GetCurrentFrequencyRange());
        SwitchMaybeToCcaBusy(nullptr);
        return;
    }
 
    if (wifiRxParams && m_disableWifiReception)
    {
        NS_LOG_INFO("Received Wi-Fi signal but blocked from syncing");
        NS_ASSERT(interface);
        m_interference->AddForeignSignal(rxDuration, rxPowers, interface->GetFrequencyRange());
        SwitchMaybeToCcaBusy(nullptr);
        return;
    }
 
    // Do no further processing if signal is too weak
    // Current implementation assumes constant RX power over the PPDU duration
    // Compare received TX power per MHz to normalized RX sensitivity
    const auto ppdu = GetRxPpduFromTxPpdu(wifiRxParams->ppdu);
    if (totalRxPower < DbmToW(GetRxSensitivity()) * (ppdu->GetTxChannelWidth() / MHz_u{20}))
    {
        NS_LOG_INFO("Received signal too weak to process: "
                    << totalRxPower << " W"
                    << (totalRxPower > Watt_u{0.0}
                            ? " (" + std::to_string(WToDbm(totalRxPower)) + " dBm)"
                            : ""));
        m_interference->Add(ppdu, rxDuration, rxPowers, GetCurrentFrequencyRange());
        SwitchMaybeToCcaBusy(nullptr);
        return;
    }
 
    if (wifiRxParams->txPhy)
    {
        if (!CanStartRx(ppdu))
        {
            NS_LOG_INFO("Cannot start reception of the PPDU, consider it as interference");
            m_interference->Add(ppdu, rxDuration, rxPowers, GetCurrentFrequencyRange());
            SwitchMaybeToCcaBusy(ppdu);
            return;
        }
    }
 
    NS_LOG_INFO("Received Wi-Fi signal");
    StartReceivePreamble(ppdu, rxPowers, rxDuration);
}
 
Ptr<const WifiPpdu>
SpectrumWifiPhy::GetRxPpduFromTxPpdu(Ptr<const WifiPpdu> ppdu)
{
    return GetPhyEntityForPpdu(ppdu)->GetRxPpduFromTxPpdu(ppdu);
}
 
Ptr<AntennaModel>
SpectrumWifiPhy::GetAntenna() const
{
    return m_antenna;
}
 
void
SpectrumWifiPhy::SetAntenna(const Ptr<AntennaModel> a)
{
    NS_LOG_FUNCTION(this << a);
    m_antenna = a;
}
 
void
SpectrumWifiPhy::SetDevice(const Ptr<WifiNetDevice> device)
{
    NS_LOG_FUNCTION(this << device);
    WifiPhy::SetDevice(device);
    for (auto& spectrumPhyInterface : m_spectrumPhyInterfaces)
    {
        spectrumPhyInterface.second->SetDevice(device);
    }
}
 
void
SpectrumWifiPhy::StartTx(Ptr<const WifiPpdu> ppdu)
{
    NS_LOG_FUNCTION(this << ppdu);
    m_signalTransmissionCb(ppdu, ppdu->GetTxVector());
    GetPhyEntity(ppdu->GetModulation())->StartTx(ppdu);
}
 
void
SpectrumWifiPhy::Transmit(Ptr<WifiSpectrumSignalParameters> txParams)
{
    NS_LOG_FUNCTION(this << txParams);
    NS_ABORT_IF(!m_currentSpectrumPhyInterface);
    m_currentSpectrumPhyInterface->StartTx(txParams);
}
 
MHz_u
SpectrumWifiPhy::GetGuardBandwidth(MHz_u currentChannelWidth) const
{
    MHz_u guardBandwidth{0};
    if (currentChannelWidth == MHz_u{22})
    {
        // handle case of DSSS transmission
        guardBandwidth = MHz_u{10};
    }
    else
    {
        // In order to properly model out of band transmissions for OFDM, the guard
        // band has been configured so as to expand the modeled spectrum up to the
        // outermost referenced point in "Transmit spectrum mask" sections' PSDs of
        // each PHY specification of 802.11-2016 standard. It thus ultimately corresponds
        // to the currently considered channel bandwidth (which can be different from
        // supported channel width).
        guardBandwidth = currentChannelWidth;
    }
    return guardBandwidth;
}
 
uint32_t
SpectrumWifiPhy::GetNumBandsBetweenSegments(const std::vector<MHz_u>& centerFrequencies,
                                            MHz_u totalWidth,
                                            Hz_u subcarrierSpacing)
{
    const auto numSegments = centerFrequencies.size();
    NS_ABORT_MSG_IF(numSegments > 2, "Only 2 non-contiguous frequency segments are supported");
    if (numSegments < 2)
    {
        return 0;
    }
    const auto lowFrequency = *centerFrequencies.cbegin();
    const auto highFrequency = *centerFrequencies.crbegin();
    NS_ASSERT(lowFrequency != highFrequency);
    // all segments have the same width
    const auto segmentsWidth = totalWidth / numSegments;
    const auto widthBetweenSegments = highFrequency - lowFrequency - segmentsWidth;
    return MHzToHz(widthBetweenSegments) / subcarrierSpacing;
}
 
WifiSpectrumBandInfo
SpectrumWifiPhy::GetBandForInterface(Ptr<WifiSpectrumPhyInterface> spectrumPhyInterface,
                                     MHz_u bandWidth,
                                     uint8_t bandIndex /* = 0 */)
{
    const auto channelWidth = spectrumPhyInterface->GetChannelWidth();
    NS_ASSERT_MSG(bandWidth <= channelWidth,
                  "Bandwidth (" << bandWidth << ") cannot exceed total operating channel width ("
                                << channelWidth << ")");
    const auto subcarrierSpacing = GetSubcarrierSpacing();
    WifiSpectrumBandInfo bandInfo;
    std::size_t numSegments = 1;
    if (const auto segmentWidth =
            (channelWidth / spectrumPhyInterface->GetCenterFrequencies().size());
        bandWidth > segmentWidth)
    {
        NS_ASSERT(bandIndex == 0);
        numSegments = spectrumPhyInterface->GetCenterFrequencies().size();
        bandWidth /= spectrumPhyInterface->GetCenterFrequencies().size();
    }
    const auto numBandsInBand = static_cast<size_t>(MHzToHz(bandWidth) / subcarrierSpacing);
    auto numBandsInChannel = static_cast<size_t>(MHzToHz(channelWidth) / subcarrierSpacing);
    const auto numBands = channelWidth / bandWidth;
    if (numBandsInBand % 2 == 0)
    {
        numBandsInChannel += 1; // symmetry around center frequency
    }
    auto rxSpectrumModel = spectrumPhyInterface->GetRxSpectrumModel();
    size_t totalNumBands = rxSpectrumModel->GetNumBands();
    NS_ASSERT_MSG((numBandsInChannel % 2 == 1) && (totalNumBands % 2 == 1),
                  "Should have odd number of bands");
    for (std::size_t segmentIndex = 0; segmentIndex < numSegments; ++segmentIndex)
    {
        NS_ASSERT_MSG(bandIndex < numBands, "Band index is out of bound");
        NS_ASSERT(totalNumBands >= numBandsInChannel);
        const auto numBandsBetweenSegments =
            GetNumBandsBetweenSegments(spectrumPhyInterface->GetCenterFrequencies(),
                                       channelWidth,
                                       GetSubcarrierSpacing());
        auto startIndex = ((totalNumBands - numBandsInChannel - numBandsBetweenSegments) / 2) +
                          (bandIndex * numBandsInBand);
        if (bandIndex >= (numBands / 2))
        {
            startIndex += numBandsBetweenSegments;
        }
        auto stopIndex = startIndex + numBandsInBand - 1;
        auto frequencies =
            ConvertIndicesToFrequenciesForInterface(spectrumPhyInterface, {startIndex, stopIndex});
        auto freqRange = spectrumPhyInterface->GetFrequencyRange();
        NS_ASSERT(frequencies.first >= MHzToHz(freqRange.minFrequency));
        NS_ASSERT(frequencies.second <= MHzToHz(freqRange.maxFrequency));
        NS_ASSERT((frequencies.second - frequencies.first) == MHzToHz(bandWidth));
        if (startIndex >= totalNumBands / 2)
        {
            // step past DC
            startIndex += 1;
        }
        bandInfo.indices.emplace_back(startIndex, stopIndex);
        bandInfo.frequencies.emplace_back(frequencies);
        ++bandIndex;
    }
    return bandInfo;
}
 
WifiSpectrumBandInfo
SpectrumWifiPhy::GetBand(MHz_u bandWidth, uint8_t bandIndex /* = 0 */)
{
    NS_ABORT_IF(!m_currentSpectrumPhyInterface);
    return GetBandForInterface(m_currentSpectrumPhyInterface, bandWidth, bandIndex);
}
 
WifiSpectrumBandFrequencies
SpectrumWifiPhy::ConvertIndicesToFrequencies(const WifiSpectrumBandIndices& indices) const
{
    NS_ABORT_IF(!m_currentSpectrumPhyInterface);
    return ConvertIndicesToFrequenciesForInterface(m_currentSpectrumPhyInterface, indices);
}
 
WifiSpectrumBandFrequencies
SpectrumWifiPhy::ConvertIndicesToFrequenciesForInterface(
    Ptr<WifiSpectrumPhyInterface> spectrumPhyInterface,
    const WifiSpectrumBandIndices& indices) const
{
    NS_ABORT_IF(!spectrumPhyInterface);
    auto rxSpectrumModel = spectrumPhyInterface->GetRxSpectrumModel();
    auto startGuardBand = rxSpectrumModel->Begin();
    auto startChannel = std::next(startGuardBand, indices.first);
    auto endChannel = std::next(startGuardBand, indices.second + 1);
    return {Hz_u{startChannel->fc}, Hz_u{endChannel->fc}};
}
 
std::tuple<dBr_u, dBr_u, dBr_u>
SpectrumWifiPhy::GetTxMaskRejectionParams() const
{
    return std::make_tuple(m_txMaskInnerBandMinimumRejection,
                           m_txMaskOuterBandMinimumRejection,
                           m_txMaskOuterBandMaximumRejection);
}
 
FrequencyRange
SpectrumWifiPhy::GetCurrentFrequencyRange() const
{
    NS_ABORT_IF(!m_currentSpectrumPhyInterface);
    return m_currentSpectrumPhyInterface->GetFrequencyRange();
}
 
const std::map<FrequencyRange, Ptr<WifiSpectrumPhyInterface>>&
SpectrumWifiPhy::GetSpectrumPhyInterfaces() const
{
    return m_spectrumPhyInterfaces;
}
 
Ptr<WifiSpectrumPhyInterface>
SpectrumWifiPhy::GetInterfaceCoveringChannelBand(MHz_u frequency, MHz_u width) const
{
    const auto lowFreq = frequency - (width / 2);
    const auto highFreq = frequency + (width / 2);
    const auto it = std::find_if(m_spectrumPhyInterfaces.cbegin(),
                                 m_spectrumPhyInterfaces.cend(),
                                 [lowFreq, highFreq](const auto& item) {
                                     return ((lowFreq >= item.first.minFrequency) &&
                                             (highFreq <= item.first.maxFrequency));
                                 });
    if (it == std::end(m_spectrumPhyInterfaces))
    {
        return nullptr;
    }
    return it->second;
}
 
Ptr<WifiSpectrumPhyInterface>
SpectrumWifiPhy::GetCurrentInterface() const
{
    return m_currentSpectrumPhyInterface;
}
 
void
SpectrumWifiPhy::SetChannelSwitchedCallback(Callback<void> callback)
{
    m_channelSwitchedCallback = callback;
}
 
} // namespace ns3