satellite-fwd-link-scheduler-time-slicing.cc

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/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
/*
 * Copyright (c) 2013 Magister Solutions Ltd
 *
 * 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: Bastien Tauran <bastien.tauran@viveris.fr>
 */
 
#include "satellite-fwd-link-scheduler-time-slicing.h"
 
#include "satellite-utils.h"
 
NS_LOG_COMPONENT_DEFINE("SatFwdLinkSchedulerTimeSlicing");
 
namespace ns3
{
 
NS_OBJECT_ENSURE_REGISTERED(SatFwdLinkSchedulerTimeSlicing);
 
TypeId
SatFwdLinkSchedulerTimeSlicing::GetTypeId(void)
{
    static TypeId tid =
        TypeId("ns3::SatFwdLinkSchedulerTimeSlicing")
            .SetParent<SatFwdLinkScheduler>()
            .AddConstructor<SatFwdLinkSchedulerTimeSlicing>()
            .AddAttribute("NumberOfSlices",
                          "Number of slices used.",
                          UintegerValue(1),
                          MakeUintegerAccessor(&SatFwdLinkSchedulerTimeSlicing::m_numberOfSlices),
                          MakeUintegerChecker<uint8_t>(1, 255));
    return tid;
}
 
TypeId
SatFwdLinkSchedulerTimeSlicing::GetInstanceTypeId() const
{
    return GetTypeId();
}
 
SatFwdLinkSchedulerTimeSlicing::SatFwdLinkSchedulerTimeSlicing()
    : SatFwdLinkScheduler()
{
    NS_LOG_FUNCTION(this);
    NS_FATAL_ERROR("Default constructor for SatFwdLinkSchedulerTimeSlicing not supported");
}
 
SatFwdLinkSchedulerTimeSlicing::SatFwdLinkSchedulerTimeSlicing(Ptr<SatBbFrameConf> conf,
                                                               Mac48Address address,
                                                               double carrierBandwidthInHz)
    : SatFwdLinkScheduler(conf, address, carrierBandwidthInHz),
      m_lastSliceAssigned(1),
      m_lastSliceDequeued(1)
{
    NS_LOG_FUNCTION(this);
 
    ObjectBase::ConstructSelf(AttributeConstructionList());
 
    std::vector<SatEnums::SatModcod_t> modCods = conf->GetModCodsUsed();
 
    // Create control and broadcast container
    m_bbFrameContainers.insert(std::pair<uint8_t, Ptr<SatBbFrameContainer>>(
        0,
        CreateObject<SatBbFrameContainer>(modCods, m_bbFrameConf)));
    m_bbFrameContainers.at(0)->SetMaxSymbolRate(m_carrierBandwidthInHz);
 
    // Initialize containers
    for (uint8_t i = 0; i < m_numberOfSlices; i++)
    {
        Ptr<SatBbFrameContainer> container =
            CreateObject<SatBbFrameContainer>(modCods, m_bbFrameConf);
        container->SetMaxSymbolRate(m_carrierBandwidthInHz / m_numberOfSlices);
        m_bbFrameContainers.insert(std::pair<uint8_t, Ptr<SatBbFrameContainer>>(i + 1, container));
    }
 
    // Initialize number of symbols sent per slice
    for (uint8_t i = 0; i <= m_numberOfSlices; i++)
    {
        m_symbolsSent.insert(std::pair<uint8_t, uint32_t>(i, 0));
    }
 
    // Check if all symbol rates are high enough
    for (std::map<uint8_t, Ptr<SatBbFrameContainer>>::iterator it = m_bbFrameContainers.begin();
         it != m_bbFrameContainers.end();
         it++)
    {
        uint32_t maxSymbolPerCycle =
            it->second->GetMaxSymbolRate() * m_periodicInterval.GetSeconds();
        uint32_t symbolsMostRobustModcod;
        if (m_bbFrameConf->GetMostRobustModcod(SatEnums::NORMAL_FRAME) !=
            SatEnums::SAT_NONVALID_MODCOD)
        {
            symbolsMostRobustModcod = it->second->GetFrameSymbols(
                m_bbFrameConf->GetMostRobustModcod(SatEnums::NORMAL_FRAME));
        }
        else
        {
            // We are using only short Frames, as new ModCod exists for normal Frames.
            symbolsMostRobustModcod = it->second->GetFrameSymbols(
                m_bbFrameConf->GetMostRobustModcod(SatEnums::SHORT_FRAME));
        }
        if (symbolsMostRobustModcod > maxSymbolPerCycle)
        {
            NS_FATAL_ERROR("Symbol rate of slice " + std::to_string(it->first) + " (" +
                           std::to_string(it->second->GetMaxSymbolRate()) +
                           " Baud) is too low to allow at least one BBFrame of the most robust "
                           "ModCod. Must be at least " +
                           std::to_string((uint32_t)(symbolsMostRobustModcod /
                                                     m_periodicInterval.GetSeconds())) +
                           " Baud");
        }
    }
 
    Simulator::Schedule(m_periodicInterval,
                        &SatFwdLinkSchedulerTimeSlicing::PeriodicTimerExpired,
                        this);
}
 
SatFwdLinkSchedulerTimeSlicing::~SatFwdLinkSchedulerTimeSlicing()
{
    NS_LOG_FUNCTION(this);
}
 
void
SatFwdLinkSchedulerTimeSlicing::DoDispose()
{
    NS_LOG_FUNCTION(this);
    SatFwdLinkScheduler::DoDispose();
    m_bbFrameContainers.clear();
}
 
std::pair<Ptr<SatBbFrame>, const Time>
SatFwdLinkSchedulerTimeSlicing::GetNextFrame()
{
    NS_LOG_FUNCTION(this);
 
    Ptr<SatBbFrame> frame;
    Time frameDuration;
 
    // Send slice control messages first if there is any.
    if (!m_bbFrameContainers.at(0)->IsEmpty(0, m_bbFrameConf->GetDefaultModCod()))
    {
        frame = m_bbFrameContainers.at(0)->GetNextFrame();
        if (frame != NULL)
        {
            frame->SetSliceId(0);
            frameDuration = frame->GetDuration();
            m_symbolsSent.at(0) += ceil(frame->GetDuration().GetSeconds() * m_carrierBandwidthInHz);
        }
        else
        {
            frameDuration = m_bbFrameConf->GetDummyBbFrameDuration();
        }
    }
    else
    {
        uint8_t firstDeque = m_lastSliceDequeued;
        do
        {
            uint32_t symbols = m_symbolsSent.at(m_lastSliceDequeued) + m_symbolsSent.at(0);
            double maxSymbolRate = m_bbFrameContainers.at(m_lastSliceDequeued)->GetMaxSymbolRate();
 
            frame = m_bbFrameContainers.at(m_lastSliceDequeued)->GetNextFrame();
            if (frame != NULL)
            {
                m_symbolsSent.at(m_lastSliceDequeued) +=
                    ceil(frame->GetDuration().GetSeconds() * m_carrierBandwidthInHz);
                symbols += ceil(frame->GetDuration().GetSeconds() * m_carrierBandwidthInHz);
                frame->SetSliceId(m_lastSliceDequeued);
                frameDuration = frame->GetDuration();
 
                if (symbols / m_periodicInterval.GetSeconds() > maxSymbolRate)
                {
                    NS_LOG_WARN("Symbol rate not respected for slice " +
                                std::to_string(m_lastSliceDequeued) + ". Got " +
                                std::to_string(symbols / m_periodicInterval.GetSeconds()) + "Baud" +
                                " while max is " + std::to_string(maxSymbolRate) + " Baud");
                }
            }
            if (m_lastSliceDequeued == m_numberOfSlices)
            {
                m_lastSliceDequeued = -1;
            }
            m_lastSliceDequeued++;
        } while (frame == NULL && m_lastSliceDequeued != firstDeque);
    }
 
    // create dummy frame
    if (m_dummyFrameSendingEnabled && frame == NULL)
    {
        frame = Create<SatBbFrame>(m_bbFrameConf->GetDefaultModCod(),
                                   SatEnums::DUMMY_FRAME,
                                   m_bbFrameConf);
 
        // create dummy packet
        Ptr<Packet> dummyPacket = Create<Packet>(1);
 
        // Add MAC tag
        SatMacTag mTag;
        mTag.SetDestAddress(Mac48Address::GetBroadcast());
        mTag.SetSourceAddress(m_macAddress);
        dummyPacket->AddPacketTag(mTag);
 
        // Add E2E address tag
        SatAddressE2ETag addressE2ETag;
        addressE2ETag.SetE2EDestAddress(Mac48Address::GetBroadcast());
        addressE2ETag.SetE2ESourceAddress(m_macAddress);
        dummyPacket->AddPacketTag(addressE2ETag);
 
        // Add dummy packet to dummy frame
        frame->AddPayload(dummyPacket);
        frame->SetSliceId(0);
        frameDuration = frame->GetDuration();
    }
    // If no bb frame available and dummy frames disabled
    else if (frame == NULL)
    {
        frameDuration = m_bbFrameConf->GetDummyBbFrameDuration();
    }
 
    return std::make_pair(frame, frameDuration);
}
 
void
SatFwdLinkSchedulerTimeSlicing::PeriodicTimerExpired()
{
    NS_LOG_FUNCTION(this);
 
    SendAndClearSymbolsSentStat();
    ScheduleBbFrames();
 
    Simulator::Schedule(m_periodicInterval,
                        &SatFwdLinkSchedulerTimeSlicing::PeriodicTimerExpired,
                        this);
}
 
void
SatFwdLinkSchedulerTimeSlicing::SendAndClearSymbolsSentStat()
{
    NS_LOG_FUNCTION(this);
 
    for (std::map<uint8_t, uint32_t>::iterator it = m_symbolsSent.begin();
         it != m_symbolsSent.end();
         it++)
    {
        m_schedulingSymbolRateTrace(it->first, it->second / Seconds(1).GetSeconds());
    }
 
    m_symbolsSent.clear();
 
    for (uint8_t i = 0; i <= m_numberOfSlices; i++)
    {
        m_symbolsSent.insert(std::pair<uint8_t, uint32_t>(i, 0));
    }
}
 
void
SatFwdLinkSchedulerTimeSlicing::ScheduleBbFrames()
{
    NS_LOG_FUNCTION(this);
 
    // Get scheduling objects from LLC
    std::vector<Ptr<SatSchedulingObject>> so;
    GetSchedulingObjects(so);
 
    for (std::vector<Ptr<SatSchedulingObject>>::const_iterator it = so.begin();
         (it != so.end()) && (GetTotalDuration() < m_periodicInterval);
         it++)
    {
        uint32_t currentObBytes = (*it)->GetBufferedBytes();
        uint32_t currentObMinReqBytes = (*it)->GetMinTxOpportunityInBytes();
        uint8_t flowId = (*it)->GetFlowId();
        Mac48Address address = (*it)->GetMacAddress();
 
        if ((m_slicesMapping.find(address) == m_slicesMapping.end()) &&
            (address != Mac48Address::GetBroadcast()))
        {
            m_slicesMapping.insert(std::pair<Mac48Address, uint8_t>(address, m_lastSliceAssigned));
            if (m_lastSliceAssigned == m_numberOfSlices)
            {
                m_lastSliceAssigned = 0;
            }
            m_lastSliceAssigned++;
 
            SendTimeSliceSubscription(address, std::vector<uint8_t>{m_slicesMapping.at(address)});
 
            // Begin again scheduling to insert slice subscription control packet.
            Simulator::Schedule(Seconds(0),
                                &SatFwdLinkSchedulerTimeSlicing::ScheduleBbFrames,
                                this);
            return;
        }
        uint8_t slice = (address == Mac48Address::GetBroadcast()) ? 0 : m_slicesMapping.at(address);
        SatEnums::SatModcod_t modcod =
            m_bbFrameContainers.at(slice)->GetModcod(flowId, GetSchedulingObjectCno(*it));
 
        uint32_t frameBytes =
            m_bbFrameContainers.at(slice)->GetBytesLeftInTailFrame(flowId, modcod);
 
        if ((m_bbFrameContainers.at(slice)->IsEmpty(flowId, modcod)) && (currentObBytes > 0) &&
            !CanOpenBbFrame(address, flowId, modcod))
        {
            continue;
        }
 
        while ((GetTotalDuration() < m_periodicInterval) && (currentObBytes > 0))
        {
            if (frameBytes < currentObMinReqBytes)
            {
                frameBytes =
                    m_bbFrameContainers.at(slice)->GetMaxFramePayloadInBytes(flowId, modcod) -
                    m_bbFrameConf->GetBbFrameHeaderSizeInBytes();
 
                if (!CanOpenBbFrame(address, flowId, modcod))
                {
                    break;
                }
 
                // if frame bytes still too small, we must have too long control message, so let's
                // crash
                if (frameBytes < currentObMinReqBytes)
                {
                    NS_FATAL_ERROR("Control package probably too long!!!");
                }
            }
 
            Ptr<Packet> p = m_txOpportunityCallback(frameBytes,
                                                    address,
                                                    flowId,
                                                    currentObBytes,
                                                    currentObMinReqBytes);
 
            if (p)
            {
                if ((flowId == 0) || (address == Mac48Address::GetBroadcast()))
                {
                    m_bbFrameContainers.at(0)->AddData(flowId, modcod, p);
                }
                else
                {
                    m_bbFrameContainers.at(slice)->AddData(flowId, modcod, p);
                    frameBytes =
                        m_bbFrameContainers.at(slice)->GetBytesLeftInTailFrame(flowId, modcod);
                }
            }
            else if (m_bbFrameContainers.at(slice)->GetMaxFramePayloadInBytes(flowId, modcod) !=
                     m_bbFrameContainers.at(slice)->GetBytesLeftInTailFrame(flowId, modcod))
            {
                frameBytes =
                    m_bbFrameContainers.at(slice)->GetMaxFramePayloadInBytes(flowId, modcod);
 
                if (!CanOpenBbFrame(address, flowId, modcod))
                {
                    break;
                }
            }
            else
            {
                NS_FATAL_ERROR("Packet does not fit in empty BB Frame. Control package too long or "
                               "fragmentation problem in user package!!!");
            }
        }
 
        m_bbFrameContainers.at(slice)->MergeBbFrames(m_carrierBandwidthInHz);
    }
}
 
void
SatFwdLinkSchedulerTimeSlicing::GetSchedulingObjects(std::vector<Ptr<SatSchedulingObject>>& output)
{
    NS_LOG_FUNCTION(this);
 
    if (GetTotalDuration() < m_periodicInterval)
    {
        // Get scheduling objects from LLC
        m_schedContextCallback(output);
 
        SortSchedulingObjects(output);
    }
}
 
Time
SatFwdLinkSchedulerTimeSlicing::GetTotalDuration()
{
    NS_LOG_FUNCTION(this);
 
    Time duration = Time(0);
    for (std::map<uint8_t, Ptr<SatBbFrameContainer>>::iterator it = m_bbFrameContainers.begin();
         it != m_bbFrameContainers.end();
         it++)
    {
        duration += it->second->GetTotalDuration();
    }
 
    return duration;
}
 
void
SatFwdLinkSchedulerTimeSlicing::SendTimeSliceSubscription(Mac48Address address,
                                                          std::vector<uint8_t> slices)
{
    NS_LOG_FUNCTION(this);
 
    for (std::vector<uint8_t>::iterator it = slices.begin(); it != slices.end(); ++it)
    {
        Ptr<SatSliceSubscriptionMessage> sliceSubscription =
            CreateObject<SatSliceSubscriptionMessage>();
        sliceSubscription->SetSliceId(*it);
        sliceSubscription->SetAddress(address);
 
        m_sendControlMsgCallback(sliceSubscription, Mac48Address::GetBroadcast());
    }
}
 
bool
SatFwdLinkSchedulerTimeSlicing::CanOpenBbFrame(Mac48Address address,
                                               uint32_t priorityClass,
                                               SatEnums::SatModcod_t modcod)
{
    NS_LOG_FUNCTION(this);
 
    if (priorityClass == 0)
    {
        // Always allow control messages to be send
        // TODO add a margin to take this into account ?
        return true;
    }
 
    uint8_t sliceId = (address == Mac48Address::GetBroadcast()) ? 0 : m_slicesMapping.at(address);
    double maxSymbolRate = m_bbFrameContainers.at(sliceId)->GetMaxSymbolRate();
 
    if (sliceId == 0)
    {
        // This is broadcast -> need to test all slices >= 1
        uint32_t symbols = GetSymbols(0, modcod);
        for (std::map<uint8_t, Ptr<SatBbFrameContainer>>::iterator it = m_bbFrameContainers.begin();
             it != m_bbFrameContainers.end();
             it++)
        {
            if (it->first == 0)
            {
                continue;
            }
            double symbolRate = (symbols + GetSymbols(it->first, SatEnums::SAT_NONVALID_MODCOD)) /
                                m_periodicInterval.GetSeconds();
            if (symbolRate > maxSymbolRate)
            {
                // One slice will not respect constraints
                return false;
            }
        }
        // Constraints are respected for all slices
        return true;
    }
    else
    {
        uint32_t symbols =
            GetSymbols(sliceId, modcod) + GetSymbols(0, SatEnums::SAT_NONVALID_MODCOD);
        double symbolRate = symbols / m_periodicInterval.GetSeconds();
        return symbolRate < maxSymbolRate;
    }
}
 
uint32_t
SatFwdLinkSchedulerTimeSlicing::GetSymbols(uint8_t sliceId, SatEnums::SatModcod_t modcod)
{
    NS_LOG_FUNCTION(this);
 
    uint32_t symbols =
        m_bbFrameContainers.at(sliceId)->GetTotalDuration().GetSeconds() * m_carrierBandwidthInHz;
 
    if (modcod != SatEnums::SAT_NONVALID_MODCOD)
    {
        symbols += m_bbFrameContainers.at(sliceId)->GetFrameSymbols(modcod);
    }
 
    return symbols;
}
 
} // namespace ns3