/* -*-  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 "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 = 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 = 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 = 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 = 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 = 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 = pow (1 - pe, nbits);
  return pms;
}
double
NistErrorRateModel::CalculatePe (double p, uint32_t bValue) const
{
  double D = 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 * pow (D, 10.0)
                   + 211.0 * pow (D, 12.0)
                   + 1404.0 * pow (D, 14.0)
                   + 11633.0 * pow (D, 16.0)
                   + 77433.0 * pow (D, 18.0)
                   + 502690.0 * pow (D, 20.0)
                   + 3322763.0 * pow (D, 22.0)
                   + 21292910.0 * pow (D, 24.0)
                   + 134365911.0 * 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 * pow (D, 6.0)
          + 70.0 * pow (D, 7.0)
          + 285.0 * pow (D, 8.0)
          + 1276.0 * pow (D, 9.0)
          + 6160.0 * pow (D, 10.0)
          + 27128.0 * pow (D, 11.0)
          + 117019.0 * pow (D, 12.0)
          + 498860.0 * pow (D, 13.0)
          + 2103891.0 * pow (D, 14.0)
          + 8784123.0 * 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 * pow (D, 5.0)
          + 201.0 * pow (D, 6.0)
          + 1492.0 * pow (D, 7.0)
          + 10469.0 * pow (D, 8.0)
          + 62935.0 * pow (D, 9.0)
          + 379644.0 * pow (D, 10.0)
          + 2253373.0 * pow (D, 11.0)
          + 13073811.0 * pow (D, 12.0)
          + 75152755.0 * pow (D, 13.0)
          + 428005675.0 * 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 = pow (1 - pe, 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 = pow (1 - pe, nbits);
  return pms;
}
double 
NistErrorRateModel::GetChunkSuccessRate (WifiMode mode, double snr, uint32_t nbits) const
{
  if (mode.GetModulationClass () == WIFI_MOD_CLASS_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
