vht-phy.cc

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/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
/*
 * Copyright (c) 2020 Orange Labs
 *
 * 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
 *
 * Authors: Rediet <getachew.redieteab@orange.com>
 *          Sébastien Deronne <sebastien.deronne@gmail.com> (for logic ported from wifi-phy)
 */
 
#include "vht-phy.h"
#include "vht-ppdu.h"
#include "ns3/wifi-psdu.h"
#include "ns3/wifi-phy.h" //only used for static mode constructor
#include "ns3/wifi-utils.h"
#include "ns3/log.h"
#include "ns3/assert.h"
 
namespace ns3 {
 
NS_LOG_COMPONENT_DEFINE ("VhtPhy");
 
/*******************************************************
 *       VHT PHY (IEEE 802.11-2016, clause 21)
 *******************************************************/
 
/* *NS_CHECK_STYLE_OFF* */
const PhyEntity::PpduFormats VhtPhy::m_vhtPpduFormats {
  { WIFI_PREAMBLE_VHT_SU, { WIFI_PPDU_FIELD_PREAMBLE,      //L-STF + L-LTF
                            WIFI_PPDU_FIELD_NON_HT_HEADER, //L-SIG
                            WIFI_PPDU_FIELD_SIG_A,         //VHT-SIG-A
                            WIFI_PPDU_FIELD_TRAINING,      //VHT-STF + VHT-LTFs
                            WIFI_PPDU_FIELD_DATA } },
  { WIFI_PREAMBLE_VHT_MU, { WIFI_PPDU_FIELD_PREAMBLE,      //L-STF + L-LTF
                            WIFI_PPDU_FIELD_NON_HT_HEADER, //L-SIG
                            WIFI_PPDU_FIELD_SIG_A,         //VHT-SIG-A
                            WIFI_PPDU_FIELD_TRAINING,      //VHT-STF + VHT-LTFs
                            WIFI_PPDU_FIELD_SIG_B,         //VHT-SIG-B
                            WIFI_PPDU_FIELD_DATA } }
};
 
const VhtPhy::NesExceptionMap VhtPhy::m_exceptionsMap {
                 /* {BW,Nss,MCS} Nes */
  { std::make_tuple ( 80, 7, 2),  3 },   //instead of 2
  { std::make_tuple ( 80, 7, 7),  6 },   //instead of 4
  { std::make_tuple ( 80, 7, 8),  6 },   //instead of 5
  { std::make_tuple ( 80, 8, 7),  6 },   //instead of 5
  { std::make_tuple (160, 4, 7),  6 },   //instead of 5
  { std::make_tuple (160, 5, 8),  8 },   //instead of 7
  { std::make_tuple (160, 6, 7),  8 },   //instead of 7
  { std::make_tuple (160, 7, 3),  4 },   //instead of 3
  { std::make_tuple (160, 7, 4),  6 },   //instead of 5
  { std::make_tuple (160, 7, 5),  7 },   //instead of 6
  { std::make_tuple (160, 7, 7),  9 },   //instead of 8
  { std::make_tuple (160, 7, 8), 12 },   //instead of 9
  { std::make_tuple (160, 7, 9), 12 }    //instead of 10
};
/* *NS_CHECK_STYLE_ON* */
 
VhtPhy::VhtPhy (bool buildModeList /* = true */)
  : HtPhy (1, false) //don't add HT modes to list
{
  NS_LOG_FUNCTION (this << buildModeList);
  m_bssMembershipSelector = VHT_PHY;
  m_maxMcsIndexPerSs = 9;
  m_maxSupportedMcsIndexPerSs = m_maxMcsIndexPerSs;
  if (buildModeList)
    {
      BuildModeList ();
    }
}
 
VhtPhy::~VhtPhy ()
{
  NS_LOG_FUNCTION (this);
}
 
void
VhtPhy::BuildModeList (void)
{
  NS_LOG_FUNCTION (this);
  NS_ASSERT (m_modeList.empty ());
  NS_ASSERT (m_bssMembershipSelector == VHT_PHY);
  for (uint8_t index = 0; index <= m_maxSupportedMcsIndexPerSs; ++index)
    {
      NS_LOG_LOGIC ("Add VhtMcs" << +index << " to list");
      m_modeList.emplace_back (CreateVhtMcs (index));
    }
}
 
const PhyEntity::PpduFormats &
VhtPhy::GetPpduFormats (void) const
{
  return m_vhtPpduFormats;
}
 
WifiMode
VhtPhy::GetSigMode (WifiPpduField field, const WifiTxVector& txVector) const
{
  switch (field)
    {
      case WIFI_PPDU_FIELD_TRAINING: //consider SIG-A mode for training (useful for InterferenceHelper)
      case WIFI_PPDU_FIELD_SIG_A:
        return GetSigAMode ();
      case WIFI_PPDU_FIELD_SIG_B:
        return GetSigBMode (txVector);
      default:
        return HtPhy::GetSigMode (field, txVector);
    }
}
 
WifiMode
VhtPhy::GetHtSigMode (void) const
{
  NS_ASSERT (m_bssMembershipSelector != HT_PHY);
  NS_FATAL_ERROR ("No HT-SIG");
  return WifiMode ();
}
 
WifiMode
VhtPhy::GetSigAMode (void) const
{
  return GetLSigMode (); //same number of data tones as OFDM (i.e. 48)
}
 
WifiMode
VhtPhy::GetSigBMode (const WifiTxVector& txVector) const
{
  NS_ABORT_MSG_IF (txVector.GetPreambleType () != WIFI_PREAMBLE_VHT_MU, "VHT-SIG-B only available for VHT MU");
  return GetVhtMcs0 ();
}
 
Time
VhtPhy::GetDuration (WifiPpduField field, const WifiTxVector& txVector) const
{
  switch (field)
    {
      case WIFI_PPDU_FIELD_SIG_A:
        return GetSigADuration (txVector.GetPreambleType ());
      case WIFI_PPDU_FIELD_SIG_B:
        return GetSigBDuration (txVector);
      default:
        return HtPhy::GetDuration (field, txVector);
    }
}
 
Time
VhtPhy::GetLSigDuration (WifiPreamble /* preamble */) const
{
  return MicroSeconds (4); //L-SIG
}
 
Time
VhtPhy::GetHtSigDuration (void) const
{
  return MicroSeconds (0); //no HT-SIG
}
 
Time
VhtPhy::GetTrainingDuration (const WifiTxVector& txVector,
                             uint8_t nDataLtf, uint8_t nExtensionLtf /* = 0 */) const
{
  NS_ABORT_MSG_IF (nDataLtf > 8, "Unsupported number of LTFs " << +nDataLtf << " for VHT");
  NS_ABORT_MSG_IF (nExtensionLtf > 0, "No extension LTFs expected for VHT");
  return MicroSeconds (4 + 4 * nDataLtf); //VHT-STF + VHT-LTFs
}
 
Time
VhtPhy::GetSigADuration (WifiPreamble /* preamble */) const
{
  return MicroSeconds (8); //VHT-SIG-A (first and second symbol)
}
 
Time
VhtPhy::GetSigBDuration (const WifiTxVector& txVector) const
{
  return (txVector.GetPreambleType () == WIFI_PREAMBLE_VHT_MU) ? MicroSeconds (4) : MicroSeconds (0); //HE-SIG-B only for MU
}
 
uint8_t
VhtPhy::GetNumberBccEncoders (const WifiTxVector& txVector) const
{
  WifiMode payloadMode = txVector.GetMode ();
  double maxRatePerCoder = (txVector.GetGuardInterval () == 800) ? 540e6 : 600e6;
  uint8_t nes = ceil (payloadMode.GetDataRate (txVector) / maxRatePerCoder);
 
  //Handle exceptions to the rule
  auto iter = m_exceptionsMap.find (std::make_tuple (txVector.GetChannelWidth (),
                                                     txVector.GetNss (),
                                                     payloadMode.GetMcsValue ()));
  if (iter != m_exceptionsMap.end ())
    {
      nes = iter->second;
    }
  return nes;
}
 
Ptr<WifiPpdu>
VhtPhy::BuildPpdu (const WifiConstPsduMap & psdus, const WifiTxVector& txVector, Time ppduDuration)
{
  NS_LOG_FUNCTION (this << psdus << txVector << ppduDuration);
  return Create<VhtPpdu> (psdus.begin ()->second, txVector, ppduDuration, m_wifiPhy->GetPhyBand (),
                          ObtainNextUid (txVector));
}
 
PhyEntity::PhyFieldRxStatus
VhtPhy::DoEndReceiveField (WifiPpduField field, Ptr<Event> event)
{
  NS_LOG_FUNCTION (this << field << *event);
  switch (field)
    {
      case WIFI_PPDU_FIELD_SIG_A:
        return EndReceiveSigA (event);
      case WIFI_PPDU_FIELD_SIG_B:
        return EndReceiveSigB (event);
      default:
        return HtPhy::DoEndReceiveField (field, event);
    }
}
 
PhyEntity::PhyFieldRxStatus
VhtPhy::EndReceiveSigA (Ptr<Event> event)
{
  NS_LOG_FUNCTION (this << *event);
  NS_ASSERT (event->GetTxVector ().GetPreambleType () >= WIFI_PREAMBLE_VHT_SU);
  SnrPer snrPer = GetPhyHeaderSnrPer (WIFI_PPDU_FIELD_SIG_A, event);
  NS_LOG_DEBUG ("SIG-A: SNR(dB)=" << RatioToDb (snrPer.snr) << ", PER=" << snrPer.per);
  PhyFieldRxStatus status (GetRandomValue () > snrPer.per);
  if (status.isSuccess)
    {
      NS_LOG_DEBUG ("Received SIG-A");
      if (!IsAllConfigSupported (WIFI_PPDU_FIELD_SIG_A, event->GetPpdu ()))
        {
          status = PhyFieldRxStatus (false, UNSUPPORTED_SETTINGS, DROP);
        }
      status = ProcessSigA (event, status);
    }
  else
    {
      NS_LOG_DEBUG ("Drop packet because SIG-A reception failed");
      status.reason = SIG_A_FAILURE;
      status.actionIfFailure = DROP;
    }
  return status;
}
 
PhyEntity::PhyFieldRxStatus
VhtPhy::ProcessSigA (Ptr<Event> event, PhyFieldRxStatus status)
{
  NS_LOG_FUNCTION (this << *event << status);
  //TODO see if something should be done here once MU-MIMO is supported
  return status; //nothing special for VHT
}
 
PhyEntity::PhyFieldRxStatus
VhtPhy::EndReceiveSigB (Ptr<Event> event)
{
  NS_LOG_FUNCTION (this << *event);
  NS_ASSERT (event->GetPpdu ()->GetType () == WIFI_PPDU_TYPE_DL_MU);
  SnrPer snrPer = GetPhyHeaderSnrPer (WIFI_PPDU_FIELD_SIG_B, event);
  NS_LOG_DEBUG ("SIG-B: SNR(dB)=" << RatioToDb (snrPer.snr) << ", PER=" << snrPer.per);
  PhyFieldRxStatus status (GetRandomValue () > snrPer.per);
  if (status.isSuccess)
    {
      NS_LOG_DEBUG ("Received SIG-B");
      if (!IsAllConfigSupported (WIFI_PPDU_FIELD_SIG_A, event->GetPpdu ()))
        {
          status = PhyFieldRxStatus (false, UNSUPPORTED_SETTINGS, DROP);
        }
      status = ProcessSigB (event, status);
    }
  else
    {
      NS_LOG_DEBUG ("Drop reception because SIG-B reception failed");
      status.reason = SIG_B_FAILURE;
      status.actionIfFailure = DROP;
    }
  return status;
}
 
PhyEntity::PhyFieldRxStatus
VhtPhy::ProcessSigB (Ptr<Event> event, PhyFieldRxStatus status)
{
  NS_LOG_FUNCTION (this << *event << status);
  //TODO see if something should be done here once MU-MIMO is supported
  return status; //nothing special for VHT
}
 
bool
VhtPhy::IsAllConfigSupported (WifiPpduField field, Ptr<const WifiPpdu> ppdu) const
{
  if (ppdu->GetType () == WIFI_PPDU_TYPE_DL_MU && field == WIFI_PPDU_FIELD_SIG_A)
    {
      return IsChannelWidthSupported (ppdu); //perform the full check after SIG-B
    }
  return HtPhy::IsAllConfigSupported (field, ppdu);
}
 
void
VhtPhy::InitializeModes (void)
{
  for (uint8_t i = 0; i < 10; ++i)
    {
      GetVhtMcs (i);
    }
}
 
WifiMode
VhtPhy::GetVhtMcs (uint8_t index)
{
#define CASE(x) \
case x: \
  return GetVhtMcs ## x (); \
 
  switch (index)
    {
      CASE ( 0)
      CASE ( 1)
      CASE ( 2)
      CASE ( 3)
      CASE ( 4)
      CASE ( 5)
      CASE ( 6)
      CASE ( 7)
      CASE ( 8)
      CASE ( 9)
      default:
        NS_ABORT_MSG ("Inexistent index (" << +index << ") requested for VHT");
        return WifiMode ();
    }
#undef CASE
}
 
#define GET_VHT_MCS(x) \
WifiMode \
VhtPhy::GetVhtMcs ## x (void) \
{ \
  static WifiMode mcs = CreateVhtMcs (x); \
  return mcs; \
}; \
 
GET_VHT_MCS (0)
GET_VHT_MCS (1)
GET_VHT_MCS (2)
GET_VHT_MCS (3)
GET_VHT_MCS (4)
GET_VHT_MCS (5)
GET_VHT_MCS (6)
GET_VHT_MCS (7)
GET_VHT_MCS (8)
GET_VHT_MCS (9)
#undef GET_VHT_MCS
 
WifiMode
VhtPhy::CreateVhtMcs (uint8_t index)
{
  NS_ASSERT_MSG (index <= 9, "VhtMcs index must be <= 9!");
  return WifiModeFactory::CreateWifiMcs ("VhtMcs" + std::to_string (index),
                                         index,
                                         WIFI_MOD_CLASS_VHT,
                                         false,
                                         MakeBoundCallback (&GetCodeRate, index),
                                         MakeBoundCallback (&GetConstellationSize, index),
                                         MakeCallback (&GetPhyRateFromTxVector),
                                         MakeCallback (&GetDataRateFromTxVector),
                                         MakeBoundCallback (&GetNonHtReferenceRate, index),
                                         MakeCallback (&IsAllowed));
}
 
WifiCodeRate
VhtPhy::GetCodeRate (uint8_t mcsValue)
{
  switch (mcsValue)
    {
      case 8:
        return WIFI_CODE_RATE_3_4;
      case 9:
        return WIFI_CODE_RATE_5_6;
      default:
        return HtPhy::GetCodeRate (mcsValue);
    }
}
 
uint16_t
VhtPhy::GetConstellationSize (uint8_t mcsValue)
{
  switch (mcsValue)
    {
      case 8:
      case 9:
        return 256;
      default:
        return HtPhy::GetConstellationSize (mcsValue);
    }
}
 
uint64_t
VhtPhy::GetPhyRate (uint8_t mcsValue, uint16_t channelWidth, uint16_t guardInterval, uint8_t nss)
{
  WifiCodeRate codeRate = GetCodeRate (mcsValue);
  uint64_t dataRate = GetDataRate (mcsValue, channelWidth, guardInterval, nss);
  return HtPhy::CalculatePhyRate (codeRate, dataRate);
}
 
uint64_t
VhtPhy::GetPhyRateFromTxVector (const WifiTxVector& txVector, uint16_t /* staId */)
{
  return GetPhyRate (txVector.GetMode ().GetMcsValue (),
                     txVector.GetChannelWidth (),
                     txVector.GetGuardInterval (),
                     txVector.GetNss ());
}
 
uint64_t
VhtPhy::GetDataRateFromTxVector (const WifiTxVector& txVector, uint16_t /* staId */)
{
  return GetDataRate (txVector.GetMode ().GetMcsValue (),
                      txVector.GetChannelWidth (),
                      txVector.GetGuardInterval (),
                      txVector.GetNss ());
}
 
uint64_t
VhtPhy::GetDataRate (uint8_t mcsValue, uint16_t channelWidth, uint16_t guardInterval, uint8_t nss)
{
  NS_ASSERT (guardInterval == 800 || guardInterval == 400);
  NS_ASSERT (nss <= 8);
  NS_ASSERT_MSG (IsCombinationAllowed (mcsValue, channelWidth, nss), "VHT MCS " << +mcsValue << " forbidden at " << channelWidth << " MHz when NSS is " << +nss);
  return HtPhy::CalculateDataRate (3.2, guardInterval,
                                   GetUsableSubcarriers (channelWidth),
                                   static_cast<uint16_t> (log2 (GetConstellationSize (mcsValue))),
                                   HtPhy::GetCodeRatio (GetCodeRate (mcsValue)), nss);
}
 
uint16_t
VhtPhy::GetUsableSubcarriers (uint16_t channelWidth)
{
  switch (channelWidth)
    {
      case 80:
        return 234;
      case 160:
        return 468;
      default:
        return HtPhy::GetUsableSubcarriers (channelWidth);
    }
}
 
uint64_t
VhtPhy::GetNonHtReferenceRate (uint8_t mcsValue)
{
  WifiCodeRate codeRate = GetCodeRate (mcsValue);
  uint16_t constellationSize = GetConstellationSize (mcsValue);
  return CalculateNonHtReferenceRate (codeRate, constellationSize);
}
 
uint64_t
VhtPhy::CalculateNonHtReferenceRate (WifiCodeRate codeRate, uint16_t constellationSize)
{
  uint64_t dataRate;
  switch (constellationSize)
    {
      case 256:
        if (codeRate == WIFI_CODE_RATE_3_4 || codeRate == WIFI_CODE_RATE_5_6)
          {
            dataRate = 54000000;
          }
        else
          {
            NS_FATAL_ERROR ("Trying to get reference rate for a MCS with wrong combination of coding rate and modulation");
          }
        break;
      default:
        dataRate = HtPhy::CalculateNonHtReferenceRate (codeRate, constellationSize);
    }
  return dataRate;
}
 
bool
VhtPhy::IsAllowed (const WifiTxVector& txVector)
{
  return IsCombinationAllowed (txVector.GetMode ().GetMcsValue (),
                               txVector.GetChannelWidth (),
                               txVector.GetNss ());
}
 
bool
VhtPhy::IsCombinationAllowed (uint8_t mcsValue, uint16_t channelWidth, uint8_t nss)
{
  if (mcsValue == 9 && channelWidth == 20 && nss != 3)
    {
      return false;
    }
  if (mcsValue == 6 && channelWidth == 80 && nss == 3)
    {
      return false;
    }
  return true;
}
 
uint32_t
VhtPhy::GetMaxPsduSize (void) const
{
  return 4692480;
}
 
} //namespace ns3
 
namespace {
 
static class ConstructorVht
{
public:
  ConstructorVht ()
  {
    ns3::VhtPhy::InitializeModes ();
    ns3::WifiPhy::AddStaticPhyEntity (ns3::WIFI_MOD_CLASS_VHT, ns3::Create<ns3::VhtPhy> ());
  }
} g_constructor_vht; 
 
}