/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */

/*

 * Copyright (c) 2010 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: Gary Pei <guangyu.pei@boeing.com>

 */

#include <cmath>

#include "nist-error-rate-model.h"

#include "wifi-phy.h"

#include "ns3/log.h"

NS_LOG_COMPONENT_DEFINE ("NistErrorRateModel");

namespace ns3 {

NS_OBJECT_ENSURE_REGISTERED (NistErrorRateModel);

TypeId

NistErrorRateModel::GetTypeId (void)

{

  static TypeId tid = TypeId ("ns3::NistErrorRateModel")

    .SetParent<ErrorRateModel> ()

    .AddConstructor<NistErrorRateModel> ()

  ;

  return tid;

}

NistErrorRateModel::NistErrorRateModel ()

{

}

double

NistErrorRateModel::GetBpskBer (double snr) const

{

  double z = std::sqrt (snr);

  double ber = 0.5 * erfc (z);

  NS_LOG_INFO ("bpsk snr=" << snr << " ber=" << ber);

  return ber;

}

double

NistErrorRateModel::GetQpskBer (double snr) const

{

  double z = std::sqrt (snr / 2.0);

  double ber = 0.5 * erfc (z);

  NS_LOG_INFO ("qpsk snr=" << snr << " ber=" << ber);

  return ber;

}

double

NistErrorRateModel::Get16QamBer (double snr) const

{

  double z = std::sqrt (snr / (5.0 * 2.0));

  double ber = 0.75 * 0.5 * erfc (z);

  NS_LOG_INFO ("16-Qam" << " snr=" << snr << " ber=" << ber);

  return ber;

}

double

NistErrorRateModel::Get64QamBer (double snr) const

{

  double z = std::sqrt (snr / (21.0 * 2.0));

  double ber = 7.0 / 12.0 * 0.5 * erfc (z);

  NS_LOG_INFO ("64-Qam" << " snr=" << snr << " ber=" << ber);

  return ber;

}

double

NistErrorRateModel::GetFecBpskBer (double snr, double nbits,

                                   uint32_t bValue) const

{

  double ber = GetBpskBer (snr);

  if (ber == 0.0)

    {

      return 1.0;

    }

  double pe = CalculatePe (ber, bValue);

  pe = std::min (pe, 1.0);

  double pms = std::pow (1 - pe, nbits);

  return pms;

}

double

NistErrorRateModel::GetFecQpskBer (double snr, double nbits,

                                   uint32_t bValue) const

{

  double ber = GetQpskBer (snr);

  if (ber == 0.0)

    {

      return 1.0;

    }

  double pe = CalculatePe (ber, bValue);

  pe = std::min (pe, 1.0);

  double pms = std::pow (1 - pe, nbits);

  return pms;

}

double

NistErrorRateModel::CalculatePe (double p, uint32_t bValue) const

{

  double D = std::sqrt (4.0 * p * (1.0 - p));

  double pe = 1.0;

  if (bValue == 1)

    {

      // code rate 1/2, use table 3.1.1

      pe = 0.5 * ( 36.0 * std::pow (D, 10.0)

                   + 211.0 * std::pow (D, 12.0)

                   + 1404.0 * std::pow (D, 14.0)

                   + 11633.0 * std::pow (D, 16.0)

                   + 77433.0 * std::pow (D, 18.0)

                   + 502690.0 * std::pow (D, 20.0)

                   + 3322763.0 * std::pow (D, 22.0)

                   + 21292910.0 * std::pow (D, 24.0)

                   + 134365911.0 * std::pow (D, 26.0)

                   );

    }

  else if (bValue == 2)

    {

      // code rate 2/3, use table 3.1.2

      pe = 1.0 / (2.0 * bValue) *

        ( 3.0 * std::pow (D, 6.0)

          + 70.0 * std::pow (D, 7.0)

          + 285.0 * std::pow (D, 8.0)

          + 1276.0 * std::pow (D, 9.0)

          + 6160.0 * std::pow (D, 10.0)

          + 27128.0 * std::pow (D, 11.0)

          + 117019.0 * std::pow (D, 12.0)

          + 498860.0 * std::pow (D, 13.0)

          + 2103891.0 * std::pow (D, 14.0)

          + 8784123.0 * std::pow (D, 15.0)

        );

    }

  else if (bValue == 3)

    {

      // code rate 3/4, use table 3.1.2

      pe = 1.0 / (2.0 * bValue) *

        ( 42.0 * std::pow (D, 5.0)

          + 201.0 * std::pow (D, 6.0)

          + 1492.0 * std::pow (D, 7.0)

          + 10469.0 * std::pow (D, 8.0)

          + 62935.0 * std::pow (D, 9.0)

          + 379644.0 * std::pow (D, 10.0)

          + 2253373.0 * std::pow (D, 11.0)

          + 13073811.0 * std::pow (D, 12.0)

          + 75152755.0 * std::pow (D, 13.0)

          + 428005675.0 * std::pow (D, 14.0)

        );

    }

  else

    {

      NS_ASSERT (false);

    }

  return pe;

}

double

NistErrorRateModel::GetFec16QamBer (double snr, uint32_t nbits,

                                    uint32_t bValue) const

{

  double ber = Get16QamBer (snr);

  if (ber == 0.0)

    {

      return 1.0;

    }

  double pe = CalculatePe (ber, bValue);

  pe = std::min (pe, 1.0);

  double pms = std::pow (1 - pe, static_cast<double> (nbits));

  return pms;

}

double

NistErrorRateModel::GetFec64QamBer (double snr, uint32_t nbits,

                                    uint32_t bValue) const

{

  double ber = Get64QamBer (snr);

  if (ber == 0.0)

    {

      return 1.0;

    }

  double pe = CalculatePe (ber, bValue);

  pe = std::min (pe, 1.0);

  double pms = std::pow (1 - pe, static_cast<double> (nbits));

  return pms;

}

double

NistErrorRateModel::GetChunkSuccessRate (WifiMode mode, double snr, uint32_t nbits) const

{

  if (mode.GetModulationClass () == WIFI_MOD_CLASS_ERP_OFDM

    {

      if (mode.GetConstellationSize () == 2)

        {

          if (mode.GetCodeRate () == WIFI_CODE_RATE_1_2)

            {

              return GetFecBpskBer (snr,

                                    nbits,

                                    1 // b value

                                    );

            }

          else

            {

              return GetFecBpskBer (snr,

                                    nbits,

                                    3 // b value

                                    );

            }

        }

      else if (mode.GetConstellationSize () == 4)

        {

          if (mode.GetCodeRate () == WIFI_CODE_RATE_1_2)

            {

              return GetFecQpskBer (snr,

                                    nbits,

                                    1 // b value

                                    );

            }

          else

            {

              return GetFecQpskBer (snr,

                                    nbits,

                                    3 // b value

                                    );

            }

        }

      else if (mode.GetConstellationSize () == 16)

        {

          if (mode.GetCodeRate () == WIFI_CODE_RATE_1_2)

            {

              return GetFec16QamBer (snr,

                                     nbits,

                                     1 // b value

                                     );

            }

          else

            {

              return GetFec16QamBer (snr,

                                     nbits,

                                     3 // b value

                                     );

            }

        }

      else if (mode.GetConstellationSize () == 64)

        {

          if (mode.GetCodeRate () == WIFI_CODE_RATE_2_3)

            {

              return GetFec64QamBer (snr,

                                     nbits,

                                     2 // b value

                                     );

            }

          else

            {

              return GetFec64QamBer (snr,

                                     nbits,

                                     3 // b value

                                     );

            }

        }

    }

  else if (mode.GetModulationClass () == WIFI_MOD_CLASS_DSSS)

    {

      switch (mode.GetDataRate ())

        {

        case 1000000:

          return DsssErrorRateModel::GetDsssDbpskSuccessRate (snr, nbits);

        case 2000000:

          return DsssErrorRateModel::GetDsssDqpskSuccessRate (snr, nbits);

        case 5500000:

          return DsssErrorRateModel::GetDsssDqpskCck5_5SuccessRate (snr, nbits);

        case 11000000:

          return DsssErrorRateModel::GetDsssDqpskCck11SuccessRate (snr, nbits);

        }

    }

  return 0;

}

} // namespace ns3