Bug 871: Rework construction of Wi-Fi rates
This patch attempts to lay some groundwork for enhancements to the Wi-Fi module
by bringing the representation of transmit rates more in line with the
standard.
The key part of the patch is the introduction of a type that corresponds to the
notion of Modulation Class described in IEEE 802.11-2007, Section 9.6.1, Table
9-2.
It also adds coding rate information to the WifiModes and centralises their
construction into a single WifiModeFactory method. The rates are also renamed
with reference to their Modulation Class.
WifiModes no longer have a WifiStandard, but the latter type still exists and is
used to imply the set of WifiModes that a MAC/PHY pair will support.
/* -*- 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