/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
/*
* Copyright (c) 2005,2006 INRIA
*
* 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: Mathieu Lacage <mathieu.lacage@sophia.inria.fr>
*/
#include <cmath>
#include "yans-error-rate-model.h"
#include "wifi-phy.h"
#include "ns3/log.h"
NS_LOG_COMPONENT_DEFINE ("YansErrorRateModel");
namespace ns3 {
NS_OBJECT_ENSURE_REGISTERED (YansErrorRateModel)
;
TypeId
YansErrorRateModel::GetTypeId (void)
{
static TypeId tid = TypeId ("ns3::YansErrorRateModel")
.SetParent<ErrorRateModel> ()
.AddConstructor<YansErrorRateModel> ()
;
return tid;
}
YansErrorRateModel::YansErrorRateModel ()
{
}
double
YansErrorRateModel::Log2 (double val) const
{
return std::log (val) / std::log (2.0);
}
double
YansErrorRateModel::GetBpskBer (double snr, uint32_t signalSpread, uint32_t phyRate) const
{
double EbNo = snr * signalSpread / phyRate;
double z = std::sqrt (EbNo);
double ber = 0.5 * erfc (z);
NS_LOG_INFO ("bpsk snr=" << snr << " ber=" << ber);
return ber;
}
double
YansErrorRateModel::GetQamBer (double snr, unsigned int m, uint32_t signalSpread, uint32_t phyRate) const
{
double EbNo = snr * signalSpread / phyRate;
double z = std::sqrt ((1.5 * Log2 (m) * EbNo) / (m - 1.0));
double z1 = ((1.0 - 1.0 / std::sqrt (m)) * erfc (z));
double z2 = 1 - std::pow ((1 - z1), 2.0);
double ber = z2 / Log2 (m);
NS_LOG_INFO ("Qam m=" << m << " rate=" << phyRate << " snr=" << snr << " ber=" << ber);
return ber;
}
uint32_t
YansErrorRateModel::Factorial (uint32_t k) const
{
uint32_t fact = 1;
while (k > 0)
{
fact *= k;
k--;
}
return fact;
}
double
YansErrorRateModel::Binomial (uint32_t k, double p, uint32_t n) const
{
double retval = Factorial (n) / (Factorial (k) * Factorial (n - k)) * std::pow (p, static_cast<double> (k)) * std::pow (1 - p, static_cast<double> (n - k));
return retval;
}
double
YansErrorRateModel::CalculatePdOdd (double ber, unsigned int d) const
{
NS_ASSERT ((d % 2) == 1);
unsigned int dstart = (d + 1) / 2;
unsigned int dend = d;
double pd = 0;
for (unsigned int i = dstart; i < dend; i++)
{
pd += Binomial (i, ber, d);
}
return pd;
}
double
YansErrorRateModel::CalculatePdEven (double ber, unsigned int d) const
{
NS_ASSERT ((d % 2) == 0);
unsigned int dstart = d / 2 + 1;
unsigned int dend = d;
double pd = 0;
for (unsigned int i = dstart; i < dend; i++)
{
pd += Binomial (i, ber, d);
}
pd += 0.5 * Binomial (d / 2, ber, d);
return pd;
}
double
YansErrorRateModel::CalculatePd (double ber, unsigned int d) const
{
double pd;
if ((d % 2) == 0)
{
pd = CalculatePdEven (ber, d);
}
else
{
pd = CalculatePdOdd (ber, d);
}
return pd;
}
double
YansErrorRateModel::GetFecBpskBer (double snr, double nbits,
uint32_t signalSpread, uint32_t phyRate,
uint32_t dFree, uint32_t adFree) const
{
double ber = GetBpskBer (snr, signalSpread, phyRate);
if (ber == 0.0)
{
return 1.0;
}
double pd = CalculatePd (ber, dFree);
double pmu = adFree * pd;
pmu = std::min (pmu, 1.0);
double pms = std::pow (1 - pmu, nbits);
return pms;
}
double
YansErrorRateModel::GetFecQamBer (double snr, uint32_t nbits,
uint32_t signalSpread,
uint32_t phyRate,
uint32_t m, uint32_t dFree,
uint32_t adFree, uint32_t adFreePlusOne) const
{
double ber = GetQamBer (snr, m, signalSpread, phyRate);
if (ber == 0.0)
{
return 1.0;
}
/* first term */
double pd = CalculatePd (ber, dFree);
double pmu = adFree * pd;
/* second term */
pd = CalculatePd (ber, dFree + 1);
pmu += adFreePlusOne * pd;
pmu = std::min (pmu, 1.0);
double pms = std::pow (1 - pmu, static_cast<double> (nbits));
return pms;
}
double
YansErrorRateModel::GetChunkSuccessRate (WifiMode mode, double snr, uint32_t nbits) const
{
if (mode.GetModulationClass () == WIFI_MOD_CLASS_ERP_OFDM
|| mode.GetModulationClass () == WIFI_MOD_CLASS_OFDM)
{
if (mode.GetConstellationSize () == 2)
{
if (mode.GetCodeRate () == WIFI_CODE_RATE_1_2)
{
return GetFecBpskBer (snr,
nbits,
mode.GetBandwidth (), // signal spread
mode.GetPhyRate (), // phy rate
10, // dFree
11 // adFree
);
}
else
{
return GetFecBpskBer (snr,
nbits,
mode.GetBandwidth (), // signal spread
mode.GetPhyRate (), // phy rate
5, // dFree
8 // adFree
);
}
}
else if (mode.GetConstellationSize () == 4)
{
if (mode.GetCodeRate () == WIFI_CODE_RATE_1_2)
{
return GetFecQamBer (snr,
nbits,
mode.GetBandwidth (), // signal spread
mode.GetPhyRate (), // phy rate
4, // m
10, // dFree
11, // adFree
0 // adFreePlusOne
);
}
else
{
return GetFecQamBer (snr,
nbits,
mode.GetBandwidth (), // signal spread
mode.GetPhyRate (), // phy rate
4, // m
5, // dFree
8, // adFree
31 // adFreePlusOne
);
}
}
else if (mode.GetConstellationSize () == 16)
{
if (mode.GetCodeRate () == WIFI_CODE_RATE_1_2)
{
return GetFecQamBer (snr,
nbits,
mode.GetBandwidth (), // signal spread
mode.GetPhyRate (), // phy rate
16, // m
10, // dFree
11, // adFree
0 // adFreePlusOne
);
}
else
{
return GetFecQamBer (snr,
nbits,
mode.GetBandwidth (), // signal spread
mode.GetPhyRate (), // phy rate
16, // m
5, // dFree
8, // adFree
31 // adFreePlusOne
);
}
}
else if (mode.GetConstellationSize () == 64)
{
if (mode.GetCodeRate () == WIFI_CODE_RATE_2_3)
{
return GetFecQamBer (snr,
nbits,
mode.GetBandwidth (), // signal spread
mode.GetPhyRate (), // phy rate
64, // m
6, // dFree
1, // adFree
16 // adFreePlusOne
);
}
else
{
return GetFecQamBer (snr,
nbits,
mode.GetBandwidth (), // signal spread
mode.GetPhyRate (), // phy rate
64, // m
5, // dFree
8, // adFree
31 // adFreePlusOne
);
}
}
}
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