lr-wpan-csmaca.cc

Go to the documentation of this file.

/*
 * Copyright (c) 2011 The Boeing Company
 *
 * 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:
 *  kwong yin <kwong-sang.yin@boeing.com>
 *  Sascha Alexander Jopen <jopen@cs.uni-bonn.de>
 *  Alberto Gallegos Ramonet <ramonet@fc.ritsumei.ac.jp>
 */
 
#include "lr-wpan-csmaca.h"
 
#include "lr-wpan-constants.h"
 
#include <ns3/log.h>
#include <ns3/random-variable-stream.h>
#include <ns3/simulator.h>
 
#include <algorithm>
 
#undef NS_LOG_APPEND_CONTEXT
#define NS_LOG_APPEND_CONTEXT std::clog << "[address " << m_mac->GetShortAddress() << "] ";
 
namespace ns3
{
 
NS_LOG_COMPONENT_DEFINE("LrWpanCsmaCa");
 
NS_OBJECT_ENSURE_REGISTERED(LrWpanCsmaCa);
 
TypeId
LrWpanCsmaCa::GetTypeId()
{
    static TypeId tid = TypeId("ns3::LrWpanCsmaCa")
                            .SetParent<Object>()
                            .SetGroupName("LrWpan")
                            .AddConstructor<LrWpanCsmaCa>();
    return tid;
}
 
LrWpanCsmaCa::LrWpanCsmaCa()
{
    // TODO-- make these into ns-3 attributes
 
    m_isSlotted = false;
    m_NB = 0;
    m_CW = 2;
    m_macBattLifeExt = false;
    m_macMinBE = 3;
    m_macMaxBE = 5;
    m_macMaxCSMABackoffs = 4;
    m_random = CreateObject<UniformRandomVariable>();
    m_BE = m_macMinBE;
    m_ccaRequestRunning = false;
    m_randomBackoffPeriodsLeft = 0;
    m_coorDest = false;
}
 
LrWpanCsmaCa::~LrWpanCsmaCa()
{
    m_mac = nullptr;
}
 
void
LrWpanCsmaCa::DoDispose()
{
    m_lrWpanMacStateCallback = MakeNullCallback<void, LrWpanMacState>();
    m_lrWpanMacTransCostCallback = MakeNullCallback<void, uint32_t>();
 
    Cancel();
    m_mac = nullptr;
}
 
void
LrWpanCsmaCa::SetMac(Ptr<LrWpanMac> mac)
{
    m_mac = mac;
}
 
Ptr<LrWpanMac>
LrWpanCsmaCa::GetMac() const
{
    return m_mac;
}
 
void
LrWpanCsmaCa::SetSlottedCsmaCa()
{
    NS_LOG_FUNCTION(this);
    m_isSlotted = true;
}
 
void
LrWpanCsmaCa::SetUnSlottedCsmaCa()
{
    NS_LOG_FUNCTION(this);
    m_isSlotted = false;
}
 
bool
LrWpanCsmaCa::IsSlottedCsmaCa() const
{
    NS_LOG_FUNCTION(this);
    return (m_isSlotted);
}
 
bool
LrWpanCsmaCa::IsUnSlottedCsmaCa() const
{
    NS_LOG_FUNCTION(this);
    return (!m_isSlotted);
}
 
void
LrWpanCsmaCa::SetMacMinBE(uint8_t macMinBE)
{
    NS_LOG_FUNCTION(this << macMinBE);
    NS_ASSERT_MSG(macMinBE <= m_macMaxBE,
                  "MacMinBE (" << macMinBE << ") should be <= MacMaxBE (" << m_macMaxBE << ")");
    m_macMinBE = macMinBE;
}
 
uint8_t
LrWpanCsmaCa::GetMacMinBE() const
{
    NS_LOG_FUNCTION(this);
    return m_macMinBE;
}
 
void
LrWpanCsmaCa::SetMacMaxBE(uint8_t macMaxBE)
{
    NS_LOG_FUNCTION(this << macMaxBE);
    NS_ASSERT_MSG(macMaxBE >= 3 && macMaxBE <= 8,
                  "MacMaxBE (" << macMaxBE << ") should be >= 3 and <= 8");
    m_macMaxBE = macMaxBE;
}
 
uint8_t
LrWpanCsmaCa::GetMacMaxBE() const
{
    NS_LOG_FUNCTION(this);
    return m_macMaxBE;
}
 
void
LrWpanCsmaCa::SetMacMaxCSMABackoffs(uint8_t macMaxCSMABackoffs)
{
    NS_LOG_FUNCTION(this << macMaxCSMABackoffs);
    NS_ASSERT_MSG(macMaxCSMABackoffs <= 5, "MacMaxCSMABackoffs should be <= 5");
    m_macMaxCSMABackoffs = macMaxCSMABackoffs;
}
 
uint8_t
LrWpanCsmaCa::GetMacMaxCSMABackoffs() const
{
    NS_LOG_FUNCTION(this);
    return m_macMaxCSMABackoffs;
}
 
Time
LrWpanCsmaCa::GetTimeToNextSlot() const
{
    NS_LOG_FUNCTION(this);
 
    // The reference for the beginning of the SUPERFRAME (the active period) changes depending
    // on the data packet being sent from the Coordinator/outgoing frame (Tx beacon time reference)
    // or other device/incoming frame (Rx beacon time reference ).
 
    Time elapsedSuperframe; // (i.e  The beacon + the elapsed CAP)
    Time currentTime = Simulator::Now();
    double symbolsToBoundary;
    Time nextBoundary;
    uint64_t elapsedSuperframeSymbols;
    uint64_t symbolRate =
        (uint64_t)m_mac->GetPhy()->GetDataOrSymbolRate(false); // symbols per second
    Time timeAtBoundary;
 
    if (m_coorDest)
    {
        // Take the Incoming Frame Reference
        elapsedSuperframe = currentTime - m_mac->m_macBeaconRxTime;
 
        Time beaconTime [[maybe_unused]] = Seconds((double)m_mac->m_rxBeaconSymbols / symbolRate);
        Time elapsedCap [[maybe_unused]] = elapsedSuperframe - beaconTime;
        NS_LOG_DEBUG("Elapsed incoming CAP symbols: " << (elapsedCap.GetSeconds() * symbolRate)
                                                      << " (" << elapsedCap.As(Time::S) << ")");
    }
    else
    {
        // Take the Outgoing Frame Reference
        elapsedSuperframe = currentTime - m_mac->m_macBeaconTxTime;
    }
 
    // get a close value to the the boundary in symbols
    elapsedSuperframeSymbols = elapsedSuperframe.GetSeconds() * symbolRate;
    symbolsToBoundary = lrwpan::aUnitBackoffPeriod -
                        std::fmod((double)elapsedSuperframeSymbols, lrwpan::aUnitBackoffPeriod);
 
    timeAtBoundary = Seconds((double)(elapsedSuperframeSymbols + symbolsToBoundary) / symbolRate);
 
    // get the exact time boundary
    nextBoundary = timeAtBoundary - elapsedSuperframe;
 
    NS_LOG_DEBUG("Elapsed Superframe symbols: " << elapsedSuperframeSymbols << " ("
                                                << elapsedSuperframe.As(Time::S) << ")");
 
    NS_LOG_DEBUG("Next backoff period boundary in approx. "
                 << nextBoundary.GetSeconds() * symbolRate << " symbols ("
                 << nextBoundary.As(Time::S) << ")");
 
    return nextBoundary;
}
 
void
LrWpanCsmaCa::Start()
{
    NS_LOG_FUNCTION(this);
    m_NB = 0;
    if (IsSlottedCsmaCa())
    {
        // TODO: Check if the current PHY is using the Japanese band 950 Mhz:
        //       (IEEE_802_15_4_950MHZ_BPSK and IEEE_802_15_4_950MHZ_2GFSK)
        //       if in use, m_CW = 1.
        //       Currently 950 Mhz band PHYs are not supported in ns-3.
        //       To know the current used PHY, making the method for GetPhy()->GetMyPhyOption()
        //       public is necessary. Alternatively, the current PHY used
        //       can be known using phyCurrentPage variable.
 
        m_CW = 2;
 
        if (m_macBattLifeExt)
        {
            m_BE = std::min(static_cast<uint8_t>(2), m_macMinBE);
        }
        else
        {
            m_BE = m_macMinBE;
        }
 
        // m_coorDest to decide between incoming and outgoing superframes times
        m_coorDest = m_mac->isCoordDest();
 
        // Locate backoff period boundary. (i.e. a time delay to align with the next backoff period
        // boundary)
        Time backoffBoundary = GetTimeToNextSlot();
        m_randomBackoffEvent =
            Simulator::Schedule(backoffBoundary, &LrWpanCsmaCa::RandomBackoffDelay, this);
    }
    else
    {
        m_BE = m_macMinBE;
        m_randomBackoffEvent = Simulator::ScheduleNow(&LrWpanCsmaCa::RandomBackoffDelay, this);
    }
}
 
void
LrWpanCsmaCa::Cancel()
{
    m_randomBackoffEvent.Cancel();
    m_requestCcaEvent.Cancel();
    m_canProceedEvent.Cancel();
    m_mac->GetPhy()->CcaCancel();
}
 
void
LrWpanCsmaCa::RandomBackoffDelay()
{
    NS_LOG_FUNCTION(this);
 
    uint64_t upperBound = (uint64_t)pow(2, m_BE) - 1;
    Time randomBackoff;
    uint64_t symbolRate;
    Time timeLeftInCap;
 
    symbolRate = (uint64_t)m_mac->GetPhy()->GetDataOrSymbolRate(false); // symbols per second
 
    // We should not recalculate the random backoffPeriods if we are in a slotted CSMA-CA and the
    // transmission was previously deferred (m_randomBackoffPeriods != 0)
    if (m_randomBackoffPeriodsLeft == 0 || IsUnSlottedCsmaCa())
    {
        m_randomBackoffPeriodsLeft = (uint64_t)m_random->GetValue(0, upperBound + 1);
    }
 
    randomBackoff =
        Seconds((double)(m_randomBackoffPeriodsLeft * lrwpan::aUnitBackoffPeriod) / symbolRate);
 
    if (IsUnSlottedCsmaCa())
    {
        NS_LOG_DEBUG("Unslotted CSMA-CA: requesting CCA after backoff of "
                     << m_randomBackoffPeriodsLeft << " periods (" << randomBackoff.As(Time::S)
                     << ")");
        m_requestCcaEvent = Simulator::Schedule(randomBackoff, &LrWpanCsmaCa::RequestCCA, this);
    }
    else
    {
        // We must make sure there is enough time left in the CAP, otherwise we continue in
        // the CAP of the next superframe after the transmission/reception of the beacon (and the
        // IFS)
        timeLeftInCap = GetTimeLeftInCap();
 
        NS_LOG_DEBUG("Slotted CSMA-CA: proceeding after random backoff of "
                     << m_randomBackoffPeriodsLeft << " periods ("
                     << (randomBackoff.GetSeconds() * symbolRate) << " symbols or "
                     << randomBackoff.As(Time::S) << ")");
 
        NS_LOG_DEBUG("Backoff periods left in CAP: "
                     << ((timeLeftInCap.GetSeconds() * symbolRate) / lrwpan::aUnitBackoffPeriod)
                     << " (" << (timeLeftInCap.GetSeconds() * symbolRate) << " symbols or "
                     << timeLeftInCap.As(Time::S) << ")");
 
        if (randomBackoff >= timeLeftInCap)
        {
            uint64_t usedBackoffs =
                (double)(timeLeftInCap.GetSeconds() * symbolRate) / lrwpan::aUnitBackoffPeriod;
            m_randomBackoffPeriodsLeft -= usedBackoffs;
            NS_LOG_DEBUG("No time in CAP to complete backoff delay, deferring to the next CAP");
            m_endCapEvent =
                Simulator::Schedule(timeLeftInCap, &LrWpanCsmaCa::DeferCsmaTimeout, this);
        }
        else
        {
            m_canProceedEvent = Simulator::Schedule(randomBackoff, &LrWpanCsmaCa::CanProceed, this);
        }
    }
}
 
Time
LrWpanCsmaCa::GetTimeLeftInCap()
{
    Time currentTime;
    uint64_t capSymbols;
    Time endCapTime;
    uint64_t activeSlot;
    uint64_t symbolRate;
    Time rxBeaconTime;
 
    // At this point, the currentTime should be aligned on a backoff period boundary
    currentTime = Simulator::Now();
    symbolRate = (uint64_t)m_mac->GetPhy()->GetDataOrSymbolRate(false); // symbols per second
 
    if (m_coorDest)
    { // Take Incoming frame reference
        activeSlot = m_mac->m_incomingSuperframeDuration / 16;
        capSymbols = activeSlot * (m_mac->m_incomingFnlCapSlot + 1);
        endCapTime = m_mac->m_macBeaconRxTime + Seconds((double)capSymbols / symbolRate);
    }
    else
    { // Take Outgoing frame reference
        activeSlot = m_mac->m_superframeDuration / 16;
        capSymbols = activeSlot * (m_mac->m_fnlCapSlot + 1);
        endCapTime = m_mac->m_macBeaconTxTime + Seconds((double)capSymbols / symbolRate);
    }
 
    return (endCapTime - currentTime);
}
 
void
LrWpanCsmaCa::CanProceed()
{
    NS_LOG_FUNCTION(this);
 
    Time timeLeftInCap;
    uint16_t ccaSymbols;
    uint32_t transactionSymbols;
    Time transactionTime;
    uint64_t symbolRate;
 
    ccaSymbols = 0;
    m_randomBackoffPeriodsLeft = 0;
    symbolRate = (uint64_t)m_mac->GetPhy()->GetDataOrSymbolRate(false);
    timeLeftInCap = GetTimeLeftInCap();
 
    // TODO: On the 950 Mhz Band (Japanese Band)
    //       only a single CCA check is performed;
    //       the CCA check duration time is:
    //
    //       CCA symbols = phyCCADuration * m_CW (1)
    //       other PHYs:
    //       CCA symbols = 8 * m_CW(2)
    //
    //       note: phyCCADuration & 950Mhz band PHYs are
    //             not currently implemented in ns-3.
    ccaSymbols += 8 * m_CW;
 
    // The MAC sublayer shall proceed if the remaining CSMA-CA algorithm steps
    // can be completed before the end of the CAP.
    // See IEEE 802.15.4-2011 (Sections 5.1.1.1 and 5.1.1.4)
    // Transaction = 2 CCA + frame transmission (SHR+PHR+PPDU) + turnaroudtime*2 (Rx->Tx & Tx->Rx) +
    // IFS (LIFS or SIFS) and Ack time (if ack flag true)
 
    transactionSymbols = ccaSymbols + m_mac->GetTxPacketSymbols();
 
    if (m_mac->isTxAckReq())
    {
        NS_LOG_DEBUG("ACK duration symbols: " << m_mac->GetMacAckWaitDuration());
        transactionSymbols += m_mac->GetMacAckWaitDuration();
    }
    else
    {
        // time the PHY takes to switch from Rx to Tx and Tx to Rx
        transactionSymbols += (lrwpan::aTurnaroundTime * 2);
    }
    transactionSymbols += m_mac->GetIfsSize();
 
    // Report the transaction cost
    if (!m_lrWpanMacTransCostCallback.IsNull())
    {
        m_lrWpanMacTransCostCallback(transactionSymbols);
    }
 
    transactionTime = Seconds((double)transactionSymbols / symbolRate);
    NS_LOG_DEBUG("Total required transaction: " << transactionSymbols << " symbols ("
                                                << transactionTime.As(Time::S) << ")");
 
    if (transactionTime > timeLeftInCap)
    {
        NS_LOG_DEBUG("Transaction of "
                     << transactionSymbols << " symbols "
                     << "cannot be completed in CAP, deferring transmission to the next CAP");
 
        NS_LOG_DEBUG("Symbols left in CAP: " << (timeLeftInCap.GetSeconds() * symbolRate) << " ("
                                             << timeLeftInCap.As(Time::S) << ")");
 
        m_endCapEvent = Simulator::Schedule(timeLeftInCap, &LrWpanCsmaCa::DeferCsmaTimeout, this);
    }
    else
    {
        m_requestCcaEvent = Simulator::ScheduleNow(&LrWpanCsmaCa::RequestCCA, this);
    }
}
 
void
LrWpanCsmaCa::RequestCCA()
{
    NS_LOG_FUNCTION(this);
    m_ccaRequestRunning = true;
    m_mac->GetPhy()->PlmeCcaRequest();
}
 
void
LrWpanCsmaCa::DeferCsmaTimeout()
{
    NS_LOG_FUNCTION(this);
    m_lrWpanMacStateCallback(MAC_CSMA_DEFERRED);
}
 
void
LrWpanCsmaCa::PlmeCcaConfirm(LrWpanPhyEnumeration status)
{
    NS_LOG_FUNCTION(this << status);
 
    // Only react on this event, if we are actually waiting for a CCA.
    // If the CSMA algorithm was canceled, we could still receive this event from
    // the PHY. In this case we ignore the event.
    if (m_ccaRequestRunning)
    {
        m_ccaRequestRunning = false;
        if (status == IEEE_802_15_4_PHY_IDLE)
        {
            if (IsSlottedCsmaCa())
            {
                m_CW--;
                if (m_CW == 0)
                {
                    // inform MAC channel is idle
                    if (!m_lrWpanMacStateCallback.IsNull())
                    {
                        NS_LOG_LOGIC("Notifying MAC of idle channel");
                        m_lrWpanMacStateCallback(CHANNEL_IDLE);
                    }
                }
                else
                {
                    NS_LOG_LOGIC("Perform CCA again, m_CW = " << m_CW);
                    m_requestCcaEvent = Simulator::ScheduleNow(&LrWpanCsmaCa::RequestCCA,
                                                               this); // Perform CCA again
                }
            }
            else
            {
                // inform MAC, channel is idle
                if (!m_lrWpanMacStateCallback.IsNull())
                {
                    NS_LOG_LOGIC("Notifying MAC of idle channel");
                    m_lrWpanMacStateCallback(CHANNEL_IDLE);
                }
            }
        }
        else
        {
            if (IsSlottedCsmaCa())
            {
                m_CW = 2;
            }
            m_BE = std::min(static_cast<uint16_t>(m_BE + 1), static_cast<uint16_t>(m_macMaxBE));
            m_NB++;
            if (m_NB > m_macMaxCSMABackoffs)
            {
                // no channel found so cannot send pkt
                NS_LOG_DEBUG("Channel access failure");
                if (!m_lrWpanMacStateCallback.IsNull())
                {
                    NS_LOG_LOGIC("Notifying MAC of Channel access failure");
                    m_lrWpanMacStateCallback(CHANNEL_ACCESS_FAILURE);
                }
                return;
            }
            else
            {
                NS_LOG_DEBUG("Perform another backoff; m_NB = " << static_cast<uint16_t>(m_NB));
                m_randomBackoffEvent =
                    Simulator::ScheduleNow(&LrWpanCsmaCa::RandomBackoffDelay,
                                           this); // Perform another backoff (step 2)
            }
        }
    }
}
 
void
LrWpanCsmaCa::SetLrWpanMacTransCostCallback(LrWpanMacTransCostCallback c)
{
    NS_LOG_FUNCTION(this);
    m_lrWpanMacTransCostCallback = c;
}
 
void
LrWpanCsmaCa::SetLrWpanMacStateCallback(LrWpanMacStateCallback c)
{
    NS_LOG_FUNCTION(this);
    m_lrWpanMacStateCallback = c;
}
 
void
LrWpanCsmaCa::SetBatteryLifeExtension(bool batteryLifeExtension)
{
    m_macBattLifeExt = batteryLifeExtension;
}
 
int64_t
LrWpanCsmaCa::AssignStreams(int64_t stream)
{
    NS_LOG_FUNCTION(this);
    m_random->SetStream(stream);
    return 1;
}
 
uint8_t
LrWpanCsmaCa::GetNB() const
{
    return m_NB;
}
 
bool
LrWpanCsmaCa::GetBatteryLifeExtension() const
{
    return m_macBattLifeExt;
}
 
} // namespace ns3