/* -*-  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 "yans-wifi-phy.h"

#include "yans-wifi-channel.h"

#include "wifi-mode.h"

#include "wifi-preamble.h"

#include "wifi-phy-state-helper.h"

#include "ns3/simulator.h"

#include "ns3/packet.h"

#include "ns3/random-variable.h"

#include "ns3/assert.h"

#include "ns3/log.h"

#include "ns3/double.h"

#include "ns3/uinteger.h"

#include "ns3/enum.h"

#include "ns3/pointer.h"

#include <math.h>

NS_LOG_COMPONENT_DEFINE ("YansWifiPhy");

namespace ns3 {

/****************************************************************

 *       Phy event class

 ****************************************************************/

class RxEvent

{

public:

  RxEvent (uint32_t size, WifiMode payloadMode, 

           enum WifiPreamble preamble,

           Time duration, double rxPower)

    : m_size (size),

      m_payloadMode (payloadMode),

      m_preamble (preamble),

      m_startTime (Simulator::Now ()),

      m_endTime (m_startTime + duration),

      m_rxPowerW (rxPower),

      m_refCount (1)

  {}

  ~RxEvent ()

  {

    NS_ASSERT (m_refCount == 0);

  }

  void Ref (void) const {

    m_refCount++;

  }

  void Unref (void) const {

    m_refCount--;

    if (m_refCount == 0) {

      delete this;

    }

  }

  Time GetDuration (void) const {

    return m_endTime - m_startTime;

  }

  Time GetStartTime (void) const {

    return m_startTime;

  }

  Time GetEndTime (void) const {

    return m_endTime;

  }

  bool Overlaps (Time time) const {

    if (m_startTime <= time &&

        m_endTime >= time) {

      return true;

    } else {

      return false;

    }

  }

  double GetRxPowerW (void) const {

    return m_rxPowerW;

  }

  uint32_t GetSize (void) const {

    return m_size;

  }

  WifiMode GetPayloadMode (void) const {

    return m_payloadMode;

  }

  enum WifiPreamble GetPreambleType (void) const {

    return m_preamble;

  }

private:

  uint32_t m_size;

  WifiMode m_payloadMode;

  enum WifiPreamble m_preamble;

  Time m_startTime;

  Time m_endTime;

  double m_rxPowerW;

  mutable int m_refCount;

};

/****************************************************************

 *       Class which records SNIR change events for a 

 *       short period of time.

 ****************************************************************/

YansWifiPhy::NiChange::NiChange (Time time, double delta)

  : m_time (time), m_delta (delta) 

{}

Time

YansWifiPhy::NiChange::GetTime (void) const

{

  return m_time;

}

double 

YansWifiPhy::NiChange::GetDelta (void) const

{

  return m_delta;

}

bool 

YansWifiPhy::NiChange::operator < (YansWifiPhy::NiChange const &o) const

{

  return (m_time < o.m_time)?true:false;

}

/****************************************************************

 *       The actual YansWifiPhy class

 ****************************************************************/

NS_OBJECT_ENSURE_REGISTERED (YansWifiPhy);

TypeId 

YansWifiPhy::GetTypeId (void)

{

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

    .SetParent<WifiPhy> ()

    .AddConstructor<YansWifiPhy> ()

    .AddAttribute ("EnergyDetectionThreshold",

                   "The energy of a received signal should be higher than "

                   "this threshold (dbm) to allow the PHY layer to detect the signal.",

                   DoubleValue (-140.0),

                   MakeDoubleAccessor (&YansWifiPhy::SetEdThreshold,

                                       &YansWifiPhy::GetEdThreshold),

                   MakeDoubleChecker<double> ())

    .AddAttribute ("TxGain",

                   "Transmission gain (dB).",

                   DoubleValue (1.0),

                   MakeDoubleAccessor (&YansWifiPhy::SetTxGain,

                                       &YansWifiPhy::GetTxGain),

                   MakeDoubleChecker<double> ())

    .AddAttribute ("RxGain",

                   "Reception gain (dB).",

                   DoubleValue (1.0),

                   MakeDoubleAccessor (&YansWifiPhy::SetRxGain,

                                       &YansWifiPhy::GetRxGain),

                   MakeDoubleChecker<double> ())

    .AddAttribute ("TxPowerLevels",

                   "Number of transmission power levels available between "

                   "TxPowerBase and TxPowerEnd included.",

                   UintegerValue (1),

                   MakeUintegerAccessor (&YansWifiPhy::m_nTxPower),

                   MakeUintegerChecker<uint32_t> ())

    .AddAttribute ("TxPowerEnd",

                   "Maximum available transmission level (dbm).",

                   DoubleValue (16.0206),

                   MakeDoubleAccessor (&YansWifiPhy::SetTxPowerEnd, 

                                       &YansWifiPhy::GetTxPowerEnd),

                   MakeDoubleChecker<double> ())

    .AddAttribute ("TxPowerStart",

                   "Minimum available transmission level (dbm).",

                   DoubleValue (16.0206),

                   MakeDoubleAccessor (&YansWifiPhy::SetTxPowerStart, 

                                       &YansWifiPhy::GetTxPowerStart),

                   MakeDoubleChecker<double> ())

    .AddAttribute ("RxNoise",

                   "Ratio of energy lost by receiver (dB).",

                   DoubleValue (7),

                   MakeDoubleAccessor (&YansWifiPhy::SetRxNoise,

                                       &YansWifiPhy::GetRxNoise),

                   MakeDoubleChecker<double> ())

    .AddAttribute ("Standard", "The standard chosen configures a set of transmission modes"

                   " and some PHY-specific constants.",

                   EnumValue (WIFI_PHY_STANDARD_80211a),

                   MakeEnumAccessor (&YansWifiPhy::SetStandard),

                   MakeEnumChecker (WIFI_PHY_STANDARD_80211a, "802.11a",

                                    WIFI_PHY_STANDARD_holland, "holland"))

    .AddAttribute ("State", "The state of the PHY layer",

                   PointerValue (),

                   MakePointerAccessor (&YansWifiPhy::m_state),

                   MakePointerChecker<WifiPhyStateHelper> ())

    ;

  return tid;

}

YansWifiPhy::YansWifiPhy ()

 : m_endSyncEvent (),

   m_random (0.0, 1.0)

{

  NS_LOG_FUNCTION (this);

  m_state = CreateObject<WifiPhyStateHelper> ();

}

YansWifiPhy::~YansWifiPhy ()

{

  NS_LOG_FUNCTION (this);

}

void

YansWifiPhy::DoDispose (void)

{

  NS_LOG_FUNCTION (this);

  m_channel = 0;

  m_events.clear ();

  m_modes.clear ();

}

void

YansWifiPhy::SetStandard (enum WifiPhyStandard standard)

{

  NS_LOG_FUNCTION (this << standard);

  m_standard = standard;

  switch (standard) {

  case WIFI_PHY_STANDARD_80211a:

    Configure80211a ();

    break;

  case WIFI_PHY_STANDARD_holland:

    ConfigureHolland ();

    break;

  default:

    NS_ASSERT (false);

    break;

  }

}

void 

YansWifiPhy::SetRxNoise (double db)

{

  NS_LOG_FUNCTION (this << db);

  m_rxNoiseRatio = DbToRatio (db);

}

void 

YansWifiPhy::SetTxPowerStart (double start)

{

  NS_LOG_FUNCTION (this << start);

  m_txPowerBaseDbm = start;

}

void 

YansWifiPhy::SetTxPowerEnd (double end)

{

  NS_LOG_FUNCTION (this << end);

  m_txPowerEndDbm = end;

}

void 

YansWifiPhy::SetNTxPower (uint32_t n)

{

  NS_LOG_FUNCTION (this << n);

  m_nTxPower = n;

}

void 

YansWifiPhy::SetTxGain (double gain)

{

  NS_LOG_FUNCTION (this << gain);

  m_txGainDb = gain;

}

void 

YansWifiPhy::SetRxGain (double gain)

{

  NS_LOG_FUNCTION (this << gain);

  m_rxGainDb = gain;

}

void 

YansWifiPhy::SetEdThreshold (double threshold)

{

  NS_LOG_FUNCTION (this << threshold);

  m_edThresholdW = DbmToW (threshold);

}

double 

YansWifiPhy::GetRxNoise (void) const

{

  return RatioToDb (m_rxNoiseRatio);

}

double 

YansWifiPhy::GetTxPowerStart (void) const

{

  return m_txPowerBaseDbm;

}

double 

YansWifiPhy::GetTxPowerEnd (void) const

{

  return m_txPowerEndDbm;

}

double 

YansWifiPhy::GetTxGain (void) const

{

  return m_txGainDb;

}

double 

YansWifiPhy::GetRxGain (void) const

{

  return m_rxGainDb;

}

double 

YansWifiPhy::GetEdThreshold (void) const

{

  return WToDbm (m_edThresholdW);

}

Ptr<WifiChannel> 

YansWifiPhy::GetChannel (void) const

{

  return m_channel;

}

void 

YansWifiPhy::SetChannel (Ptr<YansWifiChannel> channel)

{

  m_channel = channel;

}

void 

YansWifiPhy::SetReceiveOkCallback (SyncOkCallback callback)

{

  m_state->SetReceiveOkCallback (callback);

}

void 

YansWifiPhy::SetReceiveErrorCallback (SyncErrorCallback callback)

{

  m_state->SetReceiveErrorCallback (callback);

}

void 

YansWifiPhy::StartReceivePacket (Ptr<Packet> packet, 

                             double rxPowerDbm,

                             WifiMode txMode,

                             enum WifiPreamble preamble)

{

  NS_LOG_FUNCTION (this << packet << rxPowerDbm << txMode << preamble);

  rxPowerDbm += m_rxGainDb;

  double rxPowerW = DbmToW (rxPowerDbm);

  Time rxDuration = CalculateTxDuration (packet->GetSize (), txMode, preamble);

  Time endRx = Simulator::Now () + rxDuration;

  Ptr<RxEvent> event = Create<RxEvent> (packet->GetSize (), 

                                        txMode,

                                        preamble,

                                        rxDuration,

                                        rxPowerW);

  AppendEvent (event);

  switch (m_state->GetState ()) {

  case YansWifiPhy::SYNC:

    NS_LOG_DEBUG ("drop packet because already in Sync (power="<<

                  rxPowerW<<"W)");

    if (endRx > Simulator::Now () + m_state->GetDelayUntilIdle ()) 

      {

        // that packet will be noise _after_ the reception of the

        // currently-received packet.

        goto maybeCcaBusy;

      }

    break;

  case YansWifiPhy::TX:

    NS_LOG_DEBUG ("drop packet because already in Tx (power="<<

                  rxPowerW<<"W)");

    if (endRx > Simulator::Now () + m_state->GetDelayUntilIdle ()) 

      {

        // that packet will be noise _after_ the transmission of the

        // currently-transmitted packet.

        goto maybeCcaBusy;

      }

    break;

  case YansWifiPhy::CCA_BUSY:

  case YansWifiPhy::IDLE:

    if (rxPowerW > m_edThresholdW) 

      {

        NS_LOG_DEBUG ("sync (power="<<rxPowerW<<"W)");

        // sync to signal

        m_state->SwitchToSync (rxDuration);

        NS_ASSERT (m_endSyncEvent.IsExpired ());

        m_endSyncEvent = Simulator::Schedule (rxDuration, &YansWifiPhy::EndSync, this, 

                                              packet,

                                              event);

      }

    else 

      {

        NS_LOG_DEBUG ("drop packet because signal power too Small ("<<

                      rxPowerW<<"<"<<m_edThresholdW<<")");

        goto maybeCcaBusy;

      }

    break;

  }

  return;

 maybeCcaBusy:

  if (rxPowerW > m_edThresholdW) 

    {

      m_state->SwitchMaybeToCcaBusy (rxDuration);

    } 

  else 

    {

      double threshold = m_edThresholdW - rxPowerW;

      NiChanges ni;

      CalculateNoiseInterferenceW (event, &ni);

      double noiseInterferenceW = 0.0;

      Time end = Simulator::Now ();

      for (NiChanges::const_iterator i = ni.begin (); i != ni.end (); i++) 

        {

          noiseInterferenceW += i->GetDelta ();

          if (noiseInterferenceW < threshold) 

            {

              break;

            }

          end = i->GetTime ();

        }

      if (end > Simulator::Now ()) 

        {

          Time delta = end - Simulator::Now ();

          m_state->SwitchMaybeToCcaBusy (delta);

        }

    }

}

void 

YansWifiPhy::SendPacket (Ptr<const Packet> packet, WifiMode txMode, WifiPreamble preamble, uint8_t txPower)

{

  NS_LOG_FUNCTION (this << packet << txMode << preamble << (uint32_t)txPower);

  /* Transmission can happen if:

   *  - we are syncing on a packet. It is the responsability of the

   *    MAC layer to avoid doing this but the PHY does nothing to 

   *    prevent it.

   *  - we are idle

   */

  NS_ASSERT (!m_state->IsStateTx ());

  Time txDuration = CalculateTxDuration (packet->GetSize (), txMode, preamble);

  if (m_state->IsStateSync ())

    {

      m_endSyncEvent.Cancel ();

    }

  m_state->SwitchToTx (txDuration, packet, txMode, preamble, txPower);

  m_channel->Send (this, packet, GetPowerDbm (txPower) + m_txGainDb, txMode, preamble);

}

uint32_t 

YansWifiPhy::GetNModes (void) const

{

  return m_modes.size ();

}

WifiMode 

YansWifiPhy::GetMode (uint32_t mode) const

{

  return m_modes[mode];

}

uint32_t 

YansWifiPhy::GetNTxPower (void) const

{

  return m_nTxPower;

}

double 

YansWifiPhy::CalculateSnr (WifiMode txMode, double ber) const

{

  double low, high, precision;

  low = 1e-25;

  high = 1e25;

  precision = 1e-12;

  while (high - low > precision) 

    {

      NS_ASSERT (high >= low);

      double middle = low + (high - low) / 2;

        {

          low = middle;

        } 

      else 

        {