/* -*-  Mode: C++; c-file-style: "gnu"; indent-tabs-mode:nil; -*- */

/*

 * Copyright (c) 2003,2007 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 "amrr-mac-stations.h"

#include "ns3/default-value.h"

#include "ns3/time-default-value.h"

#include "ns3/simulator.h"

#include "ns3/log.h"

NS_LOG_COMPONENT_DEFINE ("AmrrMacStation");

namespace ns3 {

static TimeDefaultValue g_updatePeriod

("WifiAmrrUpdatePeriod",

 "The interval between decisions about rate control changes",

 Seconds (1.0));

static NumericDefaultValue<double> g_failureRatio

("WifiAmrrFailureRatio",

 "Ratio of erronous transmissions needed to switch to a lower rate",

 1.0/3.0);

static NumericDefaultValue<double> g_successRatio

("WifiAmrrSuccessRatio",

 "Ratio of successful transmissions needed to switch to a higher rate",

 1.0/10.0);

static NumericDefaultValue<uint32_t> g_maxSuccessThreshold

("WifiAmrrMaxSuccessThreshold",

 "maximum number of consecutive success periods needed to switch to a higher rate",

 10);

static NumericDefaultValue<uint32_t> g_minSuccessThreshold

("WifiAmrrMinSuccessThreshold",

 "minimum number of consecutive success periods needed to switch to a higher rate",

 1);

AmrrMacStations::AmrrMacStations (WifiMode defaultTxMode)

  : MacStations (defaultTxMode),

    m_updatePeriod (g_updatePeriod.GetValue ()),

    m_failureRatio (g_failureRatio.GetValue ()),

    m_successRatio (g_successRatio.GetValue ()),

    m_maxSuccessThreshold (g_maxSuccessThreshold.GetValue ()),

    m_minSuccessThreshold (g_minSuccessThreshold.GetValue ())

{}

MacStation *

AmrrMacStations::CreateStation (void)

{

  return new AmrrMacStation (this);

}

AmrrMacStation::AmrrMacStation (AmrrMacStations *stations)

  : m_stations (stations),

    m_nextModeUpdate (Simulator::Now () + stations->m_updatePeriod),

    m_tx_ok (0),

    m_tx_err (0),

    m_tx_retr (0),

    m_retry (0),

    m_txrate (0),

    m_successThreshold (m_stations->m_minSuccessThreshold),

    m_success (0),

    m_recovery (false)

{}

AmrrMacStation::~AmrrMacStation ()

{}

void 

AmrrMacStation::ReportRxOk (double rxSnr, WifiMode txMode)

{}

void 

AmrrMacStation::ReportRtsFailed (void)

{}

void 

AmrrMacStation::ReportDataFailed (void)

{

  m_retry++;

  m_tx_retr++;

}

void 

AmrrMacStation::ReportRtsOk (double ctsSnr, WifiMode ctsMode, double rtsSnr)

{}

void 

AmrrMacStation::ReportDataOk (double ackSnr, WifiMode ackMode, double dataSnr)

{

  m_retry = 0;

  m_tx_ok++;

}

void 

AmrrMacStation::ReportFinalRtsFailed (void)

{}

void 

AmrrMacStation::ReportFinalDataFailed (void)

{

  m_retry = 0;

  m_tx_err++;

}

bool

AmrrMacStation::IsMinRate (void) const

{

  return (m_txrate == 0);

}

bool

AmrrMacStation::IsMaxRate (void) const

{

}

bool

AmrrMacStation::IsSuccess (void) const

{

  return m_tx_ok > (m_tx_retr + m_tx_err) * m_stations->m_successRatio;

}

bool

AmrrMacStation::IsFailure (void) const

{

  return (m_tx_retr + m_tx_err) > m_tx_ok * m_stations->m_failureRatio;

}

bool

AmrrMacStation::IsEnough (void) const

{

  return (m_tx_retr + m_tx_err + m_tx_ok) > 10;

}

void 

AmrrMacStation::ResetCnt (void)

{

  m_tx_ok = 0;

  m_tx_err = 0;

  m_tx_retr = 0;

}

void 

AmrrMacStation::IncreaseRate (void)

{

  m_txrate++;

  NS_ASSERT (m_txrate < GetNSupportedModes ());

}

void 

AmrrMacStation::DecreaseRate (void)

{

  m_txrate--;

}

void

AmrrMacStation::UpdateMode (void)

{

  if (Simulator::Now () < m_nextModeUpdate)

    {

      return;

    }

  m_nextModeUpdate = Simulator::Now () + m_stations->m_updatePeriod;

  bool needChange = false;

  if (IsSuccess () && IsEnough ()) 

    {

      m_success++;

      if (m_success >= m_successThreshold &&

          !IsMaxRate ()) 

        {

          m_recovery = true;

          m_success = 0;

          IncreaseRate ();

          needChange = true;

        } 

      else 

        {

          m_recovery = false;

        }

    } 

  else if (IsFailure ()) 

    {

      m_success = 0;

      if (!IsMinRate ()) 

        {

          if (m_recovery) 

            {

              m_successThreshold *= 2;

              m_successThreshold = std::min (m_successThreshold,

                                             m_stations->m_maxSuccessThreshold);

            } 

          else 

            {

              m_successThreshold = m_stations->m_minSuccessThreshold;

            }

          m_recovery = false;

          DecreaseRate ();

          needChange = true;

        } 

      else 

        {

          m_recovery = false;

        }

    }

  if (IsEnough () || needChange) 

    {

      ResetCnt ();

    }

}

AmrrMacStations *

AmrrMacStation::GetStations (void) const

{

  return m_stations;

}

WifiMode 

AmrrMacStation::DoGetDataMode (uint32_t size)

{

  UpdateMode ();

  NS_ASSERT (m_txrate < GetNSupportedModes ());

  uint32_t rateIndex;

  if (m_retry < 1)

    {

      rateIndex = m_txrate;

    }

  else if (m_retry < 2)

    {

      if (m_txrate > 0)

        {

          rateIndex = m_txrate - 1;

        }

      else

        {

          rateIndex = m_txrate;

        }

    }

  else if (m_retry < 3)

    {

      if (m_txrate > 1)

        {

          rateIndex = m_txrate - 2;

        }

      else

        {

          rateIndex = m_txrate;

        }

    }

  else

    {

      if (m_txrate > 2)

        {

          rateIndex = m_txrate - 3;

        }

      else

        {

          rateIndex = m_txrate;

        }

    }

  return GetSupportedMode (rateIndex);

}

WifiMode 

AmrrMacStation::DoGetRtsMode (void)

{

  UpdateMode ();

  // XXX: can we implement something smarter ?

  return GetSupportedMode (0);

}

} // namespace ns3