ofdm-ppdu.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
 *
 * Author: Rediet <getachew.redieteab@orange.com>
 *         Muhammad Iqbal Rochman <muhiqbalcr@uchicago.edu>
 *         Sébastien Deronne <sebastien.deronne@gmail.com> (LSigHeader)
 */

#include "ns3/wifi-phy.h"
#include "ns3/wifi-psdu.h"
#include "ofdm-phy.h"
#include "ofdm-ppdu.h"
#include "ns3/log.h"

namespace ns3 {

NS_LOG_COMPONENT_DEFINE ("OfdmPpdu");

OfdmPpdu::OfdmPpdu (Ptr<const WifiPsdu> psdu, const WifiTxVector& txVector,
                    WifiPhyBand band, uint64_t uid,
                    bool instantiateLSig /* = true */)
  : WifiPpdu (psdu, txVector, uid),
    m_band (band),
    m_channelWidth (txVector.GetChannelWidth ())
{
  NS_LOG_FUNCTION (this << psdu << txVector << band << uid);
  if (instantiateLSig)
    {
      m_lSig.SetRate (txVector.GetMode ().GetDataRate (txVector), m_channelWidth);
      m_lSig.SetLength (psdu->GetSize ());
    }
}

OfdmPpdu::~OfdmPpdu ()
{
}

WifiTxVector
OfdmPpdu::DoGetTxVector (void) const
{
  WifiTxVector txVector;
  txVector.SetPreambleType (m_preamble);
  //OFDM uses 20 MHz, unless PHY channel width is 5 MHz or 10 MHz
  uint16_t channelWidth = m_channelWidth < 20 ? m_channelWidth : 20;
  txVector.SetMode (OfdmPhy::GetOfdmRate (m_lSig.GetRate (m_channelWidth), channelWidth));
  txVector.SetChannelWidth (channelWidth);
  return txVector;
}

Time
OfdmPpdu::GetTxDuration (void) const
{
  Time ppduDuration = Seconds (0);
  const WifiTxVector& txVector = GetTxVector ();
  ppduDuration = WifiPhy::CalculateTxDuration (m_lSig.GetLength (), txVector, m_band);
  return ppduDuration;
}

Ptr<WifiPpdu>
OfdmPpdu::Copy (void) const
{
  return Create<OfdmPpdu> (GetPsdu (), GetTxVector (), m_band, m_uid);
}

OfdmPpdu::LSigHeader::LSigHeader ()
  : m_rate (0b1101),
    m_length (0)
{
}

OfdmPpdu::LSigHeader::~LSigHeader ()
{
}

TypeId
OfdmPpdu::LSigHeader::GetTypeId (void)
{
  static TypeId tid = TypeId ("ns3::LSigHeader")
    .SetParent<Header> ()
    .SetGroupName ("Wifi")
    .AddConstructor<LSigHeader> ()
  ;
  return tid;
}

TypeId
OfdmPpdu::LSigHeader::GetInstanceTypeId (void) const
{
  return GetTypeId ();
}

void
OfdmPpdu::LSigHeader::Print (std::ostream &os) const
{
  os << "SIGNAL=" << GetRate ()
     << " LENGTH=" << m_length;
}

uint32_t
OfdmPpdu::LSigHeader::GetSerializedSize (void) const
{
  return 3;
}

void
OfdmPpdu::LSigHeader::SetRate (uint64_t rate, uint16_t channelWidth)
{
  if (channelWidth == 5)
    {
      rate *= 4; //corresponding 20 MHz rate if 5 MHz is used
    }
  else if (channelWidth == 10)
    {
      rate *= 2; //corresponding 20 MHz rate if 10 MHz is used
    }
  /* Here is the binary representation for a given rate:
   * 6 Mbit/s: 1101
   * 9 Mbit/s: 1111
   * 12 Mbit/s: 0101
   * 18 Mbit/s: 0111
   * 24 Mbit/s: 1001
   * 36 Mbit/s: 1011
   * 48 Mbit/s: 0001
   * 54 Mbit/s: 0011
   */
  switch (rate)
    {
      case 6000000:
        m_rate = 0b1101;
        break;
      case 9000000:
        m_rate = 0b1111;
        break;
      case 12000000:
        m_rate = 0b0101;
        break;
      case 18000000:
        m_rate = 0b0111;
        break;
      case 24000000:
        m_rate = 0b1001;
        break;
      case 36000000:
        m_rate = 0b1011;
        break;
      case 48000000:
        m_rate = 0b0001;
        break;
      case 54000000:
        m_rate = 0b0011;
        break;
      default:
        NS_ASSERT_MSG (false, "Invalid rate");
        break;
    }
}

uint64_t
OfdmPpdu::LSigHeader::GetRate (uint16_t channelWidth) const
{
  uint64_t rate = 0;
  switch (m_rate)
    {
      case 0b1101:
        rate = 6000000;
        break;
      case 0b1111:
        rate = 9000000;
        break;
      case 0b0101:
        rate = 12000000;
        break;
      case 0b0111:
        rate = 18000000;
        break;
      case 0b1001:
        rate = 24000000;
        break;
      case 0b1011:
        rate = 36000000;
        break;
      case 0b0001:
        rate = 48000000;
        break;
      case 0b0011:
        rate = 54000000;
        break;
      default:
        NS_ASSERT_MSG (false, "Invalid rate");
        break;
    }
  if (channelWidth == 5)
    {
      rate /= 4; //compute corresponding 5 MHz rate
    }
  else if (channelWidth == 10)
    {
      rate /= 2; //compute corresponding 10 MHz rate
    }
  return rate;
}

void
OfdmPpdu::LSigHeader::SetLength (uint16_t length)
{
  NS_ASSERT_MSG (length < 4096, "Invalid length");
  m_length = length;
}

uint16_t
OfdmPpdu::LSigHeader::GetLength (void) const
{
  return m_length;
}

void
OfdmPpdu::LSigHeader::Serialize (Buffer::Iterator start) const
{
  uint8_t byte = 0;
  uint16_t bytes = 0;

  byte |= m_rate;
  byte |= (m_length & 0x07) << 5;
  start.WriteU8 (byte);

  bytes |= (m_length & 0x0ff8) >> 3;
  start.WriteU16 (bytes);
}

uint32_t
OfdmPpdu::LSigHeader::Deserialize (Buffer::Iterator start)
{
  Buffer::Iterator i = start;

  uint8_t byte = i.ReadU8 ();
  m_rate = byte & 0x0f;
  m_length = (byte >> 5) & 0x07;

  uint16_t bytes = i.ReadU16 ();
  m_length |= (bytes << 3) & 0x0ff8;

  return i.GetDistanceFrom (start);
}

} //namespace ns3