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

#include "wifi-mode.h"

#include "wifi-channel.h"

#include "wifi-preamble.h"

#include "ns3/simulator.h"

#include "ns3/packet.h"

#include "ns3/random-variable.h"

#include "ns3/assert.h"

#include "ns3/log.h"

#include "ns3/object-base.h"

#include "ns3/double.h"

#include "ns3/uinteger.h"

#include "ns3/enum.h"

#include "ns3/trace-source-accessor.h"

#include <math.h>

NS_LOG_COMPONENT_DEFINE ("WifiPhy");

namespace ns3 {

  // Define all the WifiMode needed for 802.11a

static WifiMode g_6mba = WifiModeFactory::CreateBpsk ("wifia-6mbs",

                                                      true,

                                                      20000000, 6000000, 12000000);

static WifiMode g_9mba = WifiModeFactory::CreateBpsk ("wifia-9mbs",

                                                      false,

                                                      20000000, 9000000, 12000000);

// XXX explain why Bpsk rather than Qpsk

static WifiMode g_12mba = WifiModeFactory::CreateBpsk ("wifia-12mbs",

                                                       true,

                                                       20000000, 12000000, 24000000);

static WifiMode g_18mba = WifiModeFactory::CreateBpsk ("wifia-18mbs",

                                                       false,

                                                       20000000, 18000000, 24000000);

static WifiMode g_24mba = WifiModeFactory::CreateBpsk ("wifia-24mbs",

                                                       true,

                                                       20000000, 24000000, 48000000);

static WifiMode g_36mba = WifiModeFactory::CreateBpsk ("wifia-36mbs",

                                                       false,

                                                       20000000, 36000000, 48000000);

static WifiMode g_48mba = WifiModeFactory::CreateBpsk ("wifia-48mbs",

                                                       false,

                                                       20000000, 48000000, 72000000);

static WifiMode g_54mba = WifiModeFactory::CreateBpsk ("wifia-54mbs",

                                                       false,

                                                       20000000, 54000000, 72000000);

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

 *       This destructor is needed.

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

WifiPhyListener::~WifiPhyListener ()

{}

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

 *       Phy event class

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

{

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.

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

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

  : m_time (time), m_delta (delta) 

{}

Time

WifiPhy::NiChange::GetTime (void) const

{

  return m_time;

}

double 

WifiPhy::NiChange::GetDelta (void) const

{

  return m_delta;

}

bool 

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

{

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

}

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

 *       The actual WifiPhy class

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

NS_OBJECT_ENSURE_REGISTERED (WifiPhy);

TypeId 

WifiPhy::GetTypeId (void)

{

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

    .SetParent<Object> ()

    .AddConstructor<WifiPhy> ()

    .AddAttribute ("EnergyDetectionThreshold",

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

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

                   Double (-140.0),

                   MakeDoubleAccessor (&WifiPhy::SetEdThreshold,

                                       &WifiPhy::GetEdThreshold),

                   MakeDoubleChecker<double> ())

    .AddAttribute ("TxGain",

                   "Transmission gain (dB).",

                   Double (1.0),

                   MakeDoubleAccessor (&WifiPhy::SetTxGain,

                                       &WifiPhy::GetTxGain),

                   MakeDoubleChecker<double> ())

    .AddAttribute ("RxGain",

                   "Reception gain (dB).",

                   Double (1.0),

                   MakeDoubleAccessor (&WifiPhy::SetRxGain,

                                       &WifiPhy::GetRxGain),

                   MakeDoubleChecker<double> ())

    .AddAttribute ("TxPowerLevels",

                   "Number of transmission power levels available between "

                   "TxPowerBase and TxPowerEnd included.",

                   Uinteger (1),

                   MakeUintegerAccessor (&WifiPhy::m_nTxPower),

                   MakeUintegerChecker<uint32_t> ())

    .AddAttribute ("TxPowerEnd",

                   "Maximum available transmission level (dbm).",

                   Double (16.0206),

                   MakeDoubleAccessor (&WifiPhy::SetTxPowerEnd, 

                                       &WifiPhy::GetTxPowerEnd),

                   MakeDoubleChecker<double> ())

    .AddAttribute ("TxPowerStart",

                   "Minimum available transmission level (dbm).",

                   Double (16.0206),

                   MakeDoubleAccessor (&WifiPhy::SetTxPowerStart, 

                                       &WifiPhy::GetTxPowerStart),

                   MakeDoubleChecker<double> ())

    .AddAttribute ("RxNoise",

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

                   Double (7),

                   MakeDoubleAccessor (&WifiPhy::SetRxNoise,

                                       &WifiPhy::GetRxNoise),

                   MakeDoubleChecker<double> ())

    .AddAttribute ("Standard", "XXX",

                   Enum (WIFI_PHY_STANDARD_80211a),

                   MakeEnumAccessor (&WifiPhy::SetStandard),

                   MakeEnumChecker (WIFI_PHY_STANDARD_80211a, "802.11a",

                                    WIFI_PHY_STANDARD_holland, "holland"))

    .AddTraceSource ("State",

                     "The WifiPhy state",

                     MakeTraceSourceAccessor (&WifiPhy::m_stateLogger))

    ;

  return tid;

}

WifiPhy::WifiPhy ()

  : m_syncing (false),

    m_endTx (Seconds (0)),

    m_endSync (Seconds (0)),

    m_endCcaBusy (Seconds (0)),

    m_startTx (Seconds (0)),

    m_startSync (Seconds (0)),

    m_startCcaBusy (Seconds (0)),

    m_previousStateChangeTime (Seconds (0)),

    m_endSyncEvent (),

    m_random (0.0, 1.0)

{}

WifiPhy::~WifiPhy ()

{}

void

WifiPhy::DoDispose (void)

{

  m_channel = 0;

  m_events.clear ();

  m_modes.clear ();

}

void

WifiPhy::SetStandard (enum WifiPhyStandard 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 

WifiPhy::SetRxNoise (double db)

{

  m_rxNoiseRatio = DbToRatio (db);

}

void 

WifiPhy::SetTxPowerStart (double start)

{

  m_txPowerBaseDbm = start;

}

void 

WifiPhy::SetTxPowerEnd (double end)

{

  m_txPowerEndDbm = end;

}

void 

WifiPhy::SetNTxPower (uint32_t n)

{

  m_nTxPower = n;

}

void 

WifiPhy::SetTxGain (double gain)

{

  m_txGainDb = gain;

}

void 

WifiPhy::SetRxGain (double gain)

{

  m_rxGainDb = gain;

}

void 

WifiPhy::SetEdThreshold (double threshold)

{

  m_edThresholdW = DbmToW (threshold);

}

double 

WifiPhy::GetRxNoise (void) const

{

  return RatioToDb (m_rxNoiseRatio);

}

double 

WifiPhy::GetTxPowerStart (void) const

{

  return m_txPowerBaseDbm;

}

double 

WifiPhy::GetTxPowerEnd (void) const

{

  return m_txPowerEndDbm;

}

double 

WifiPhy::GetTxGain (void) const

{

  return m_txGainDb;

}

double 

WifiPhy::GetRxGain (void) const

{

  return m_rxGainDb;

}

double 

WifiPhy::GetEdThreshold (void) const

{

  return WToDbm (m_edThresholdW);

}

Ptr<WifiChannel> 

WifiPhy::GetChannel (void) const

{

  return m_channel;

}

void 

WifiPhy::SetChannel (Ptr<WifiChannel> channel)

{

  m_channel = channel;

}

void 

WifiPhy::SetReceiveOkCallback (SyncOkCallback callback)

{

  m_syncOkCallback = callback;

}

void 

WifiPhy::SetReceiveErrorCallback (SyncErrorCallback callback)

{

  m_syncErrorCallback = callback;

}

void 

WifiPhy::StartReceivePacket (Ptr<Packet> packet, 

                             double rxPowerDbm,

                             WifiMode txMode,

                             enum WifiPreamble 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 (GetState ()) {

  case WifiPhy::SYNC:

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

                  rxPowerW<<"W)");

    if (endRx > m_endSync) 

      {

        goto maybeCcaBusy;

      }

    break;

  case WifiPhy::TX:

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

                  rxPowerW<<"W)");

    if (endRx > m_endTx) 

      {

        goto maybeCcaBusy;

      }

    break;

  case WifiPhy::CCA_BUSY:

  case WifiPhy::IDLE:

    if (rxPowerW > m_edThresholdW) 

      {

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

        // sync to signal

        NotifySyncStart (rxDuration);

        SwitchToSync (rxDuration);

        NS_ASSERT (m_endSyncEvent.IsExpired ());

        m_endSyncEvent = Simulator::Schedule (rxDuration, &WifiPhy::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) 

    {

      SwitchMaybeToCcaBusy (rxDuration);

      NotifyCcaBusyStart (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 ();

          SwitchMaybeToCcaBusy (delta);

          NotifyCcaBusyStart (delta);

        }

    }

}

void 

WifiPhy::SendPacket (Ptr<const Packet> packet, WifiMode txMode, WifiPreamble preamble, uint8_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 (!IsStateTx ());

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

  NotifyTxStart (txDuration);

  SwitchToTx (txDuration);

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

}

uint32_t 

WifiPhy::GetNModes (void) const

{

  return m_modes.size ();

}

WifiMode 

WifiPhy::GetMode (uint32_t mode) const

{

  return m_modes[mode];

}

uint32_t 

WifiPhy::GetNTxPower (void) const

{

  return m_nTxPower;

}

double 

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

{

  double low, high, precision;