/* -*-  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-net-device.h"

#include "wifi-preamble.h"

#include "wifi-default-parameters.h"

#include "ns3/simulator.h"

#include "ns3/packet.h"

#include "ns3/random-variable.h"

#include "ns3/assert.h"

#include "ns3/log.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 * 1 / 2, 6000000);

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

                                                      false,

                                                      20000000, 9000000 * 3 / 4, 9000000);

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

                                                       true,

                                                       20000000, 12000000 * 1 / 2, 12000000);

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

                                                       false,

                                                       20000000, 18000000 * 3 / 4, 18000000);

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

                                                       true,

                                                       20000000, 24000000 * 1 / 2, 24000000);

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

                                                       false,

                                                       20000000, 36000000 * 3 / 4, 36000000);

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

                                                       false,

                                                       20000000, 48000000 * 2 / 3, 48000000);

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

                                                       false,

                                                       20000000, 54000000 * 3 / 4, 54000000);

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

 *       This destructor is needed.

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

WifiPhyListener::~WifiPhyListener ()

{}

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

 *       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.

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

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

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

WifiPhy::WifiPhy (Ptr<WifiNetDevice> device)

  : m_edThresholdW (DbmToW (WifiDefaultParameters::GetPhyEnergyDetectionThresholdDbm ())),

    m_txGainDbm (WifiDefaultParameters::GetPhyTxGainDbm ()),

    m_rxGainDbm (WifiDefaultParameters::GetPhyRxGainDbm ()),

    m_rxNoiseRatio (DbToRatio (WifiDefaultParameters::GetPhyRxNoiseDb ())),

    m_txPowerBaseDbm (WifiDefaultParameters::GetPhyTxPowerBaseDbm ()),

    m_txPowerEndDbm (WifiDefaultParameters::GetPhyTxPowerEndDbm ()),

    m_nTxPower (WifiDefaultParameters::GetPhyTxPowerLevels ()),

    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_device (device),

    m_endSyncEvent (),

    m_random (0.0, 1.0)

{

  NS_ASSERT (WifiDefaultParameters::GetPhyStandard () == WifiDefaultParameters::PHY_STANDARD_80211a);

  Configure80211a ();

}

WifiPhy::~WifiPhy ()

{

  m_channel = 0;

  m_events.clear ();

  m_modes.clear ();

}

void 

WifiPhy::SetChannel (Ptr<WifiChannel> channel)

{

  m_channel = channel;

  m_channel->Add (m_device, MakeCallback (&WifiPhy::ReceivePacket, this));

}

void 

WifiPhy::SetReceiveOkCallback (SyncOkCallback callback)

{

  m_syncOkCallback = callback;

}

void 

WifiPhy::SetReceiveErrorCallback (SyncErrorCallback callback)

{

  m_syncErrorCallback = callback;

}

void 

WifiPhy::ReceivePacket (Packet const packet, 

                        double rxPowerDbm,

                        WifiMode txMode,

                        enum WifiPreamble preamble)

{

  rxPowerDbm += m_rxGainDbm;

  double rxPowerW = DbmToW (rxPowerDbm);

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

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

  m_startRxLogger (rxDuration, rxPowerW);

  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) 

      {

        // sync to signal

        NotifySyncStart (rxDuration);

        SwitchToSync (rxDuration);

        m_startSyncLogger (rxDuration, rxPowerW);

        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 (Packet const 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 ());

  if (IsStateSync ()) {

    m_endSyncEvent.Cancel ();

  }

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

  m_startTxLogger (txDuration, txMode.GetPhyRate (), GetPowerDbm (txPower));

  NotifyTxStart (txDuration);

  SwitchToTx (txDuration);

  m_channel->Send (m_device, packet, GetPowerDbm (txPower) + m_txGainDbm, 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;

  low = 1e-25;

  high = 1e25;

  precision = 1e-12;

  while (high - low > precision) 

    {

      NS_ASSERT (high >= low);

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

      if ((1 - GetChunkSuccessRate (txMode, middle, 1)) > ber) 

        {

          low = middle;

        } 

      else 

        {

          high = middle;

        }

    }

  return low;

}

void

WifiPhy::Configure80211a (void)

{

  m_plcpLongPreambleDelayUs = 20;

  m_plcpShortPreambleDelayUs = 20;

  m_longPlcpHeaderMode = g_6mba;

  m_shortPlcpHeaderMode = g_6mba;

  m_plcpHeaderLength = 4 + 1 + 12 + 1 + 6 + 16 + 6;

  /* 4095 bytes at a 6Mb/s rate with a 1/2 coding rate. */

  m_maxPacketDuration = Seconds (4095.0*8.0/6000000.0*(1.0/2.0));

  m_modes.push_back (g_6mba);

  m_modes.push_back (g_9mba);

  m_modes.push_back (g_18mba);

  m_modes.push_back (g_24mba);

  m_modes.push_back (g_36mba);

  m_modes.push_back (g_48mba);

  m_modes.push_back (g_54mba);

#ifdef PHY80211_DEBUG

  for (double db = 0; db < 30; db+= 0.5) {

    std::cout <<db<<" ";

    for (uint8_t i = 0; i < GetNModes (); i++) {

      WifiMode mode = GetMode (i);

      double ber = 1-GetChunkSuccessRate (mode, DbToRatio (db), 1);

      std::cout <<ber<< " ";

    }

    std::cout << std::endl;

  }

#endif

}

void 

WifiPhy::RegisterListener (WifiPhyListener *listener)

{

  m_listeners.push_back (listener);

}

bool 

WifiPhy::IsStateCcaBusy (void)

{

  return GetState () == CCA_BUSY;

}

bool 

WifiPhy::IsStateIdle (void)

{

  return (GetState () == IDLE)?true:false;

}

bool 

WifiPhy::IsStateBusy (void)

{

  return (GetState () != IDLE)?true:false;

}

bool 

WifiPhy::IsStateSync (void)

{

  return (GetState () == SYNC)?true:false;

}

bool 

WifiPhy::IsStateTx (void)

{

  return (GetState () == TX)?true:false;

}

Time

WifiPhy::GetStateDuration (void)

{

  return Simulator::Now () - m_previousStateChangeTime;

}

Time

WifiPhy::GetDelayUntilIdle (void)

{

  Time retval;

  switch (GetState ()) {

  case SYNC:

    retval = m_endSync - Simulator::Now ();

    break;

  case TX:

    retval = m_endTx - Simulator::Now ();

    break;

  case CCA_BUSY:

    retval = m_endCcaBusy - Simulator::Now ();

    break;

  case IDLE:

    retval = Seconds (0);

    break;

  default:

    NS_ASSERT (false);

    // NOTREACHED

    retval = Seconds (0);

    break;

  }

  retval = Max (retval, Seconds (0));

  return retval;

}

Time

WifiPhy::CalculateTxDuration (uint32_t size, WifiMode payloadMode, WifiPreamble preamble) const

{

  uint64_t delay = 0;

  switch (preamble) {

  case WIFI_PREAMBLE_LONG:

    delay += m_plcpLongPreambleDelayUs;

    delay += m_plcpHeaderLength * 1000000 / m_longPlcpHeaderMode.GetDataRate ();

    break;

  case WIFI_PREAMBLE_SHORT:

    delay += m_plcpShortPreambleDelayUs;

    delay += m_plcpHeaderLength * 1000000 / m_shortPlcpHeaderMode.GetDataRate ();

    break;

  }

  uint64_t nbits = size * 8;

  delay += nbits * 1000000 / payloadMode.GetDataRate ();