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

/*

 * Copyright (c) 2009 IITP RAS

 *

 * 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

 *

 * Authors: Kirill Andreev <andreev@iitp.ru>

 */

#include "airtime-metric.h"

#include "ns3/wifi-remote-station-manager.h"

#include "ns3/wifi-mode.h"

namespace ns3 {

namespace dot11s {

NS_OBJECT_ENSURE_REGISTERED (AirtimeLinkMetricCalculator);

TypeId

AirtimeLinkMetricCalculator::GetTypeId ()

{

  static TypeId tid = TypeId ("ns3::dot11s::AirtimeLinkMetricCalculator")

    .SetParent<Object> ()

    .AddConstructor<AirtimeLinkMetricCalculator> ()

    .AddAttribute ( "TestLength",

                    "Rate should be estimated using test length.",

                    UintegerValue (1024),

                    MakeUintegerAccessor (

                      &AirtimeLinkMetricCalculator::SetTestLength),

                    MakeUintegerChecker<uint16_t> (1)

                    )

    .AddAttribute ( "Dot11MetricTid",

                    "TID used to calculate metric (data rate)",

                    UintegerValue (0),

                    MakeUintegerAccessor (

                      &AirtimeLinkMetricCalculator::SetHeaderTid),

                    MakeUintegerChecker<uint8_t> (0)

                    )

    .AddAttribute ( "Dot11sMeshHeaderLength",

                    "Length of the mesh header",

                    UintegerValue (6),

                    MakeUintegerAccessor (

                      &AirtimeLinkMetricCalculator::m_meshHeaderLength),

                    MakeUintegerChecker<uint16_t> (0)

                    )

  ;

  return tid;

}

AirtimeLinkMetricCalculator::AirtimeLinkMetricCalculator () :

  m_overheadNanosec (0)

{

}

void

AirtimeLinkMetricCalculator::SetHeaderTid (uint8_t tid)

{

  m_testHeader.SetDsFrom ();

  m_testHeader.SetDsTo ();

  m_testHeader.SetTypeData ();

  m_testHeader.SetQosTid (tid);

}

void

AirtimeLinkMetricCalculator::SetTestLength (uint16_t testLength)

{

  m_testFrame = Create<Packet> (testLength + 6 /*Mesh header*/ + 36 /*802.11 header*/);

}

uint32_t

AirtimeLinkMetricCalculator::CalculateMetric (Mac48Address peerAddress, Ptr<MeshWifiInterfaceMac> mac)

{

  /* Airtime link metric is defined in 11B.10 of 802.11s Draft D3.0 as:

   *

   * airtime = (O + Bt/r) /  (1 - frame error rate), where

   * o  -- the PHY dependent channel access which includes frame headers, training sequences,

   *       access protocol frames, etc.

   * bt -- the test packet length in bits (8192 by default),

   * r  -- the current bitrate of the packet,

   *

   * Final result is expressed in units of 0.01 Time Unit = 10.24 us (as required by 802.11s draft)

   */

  NS_ASSERT (!peerAddress.IsGroup ());

  //obtain current rate:

  //obtain frame error rate:

  double failAvg = mac->GetWifiRemoteStationManager ()->GetInfo (peerAddress).GetFrameErrorRate ();

  if (failAvg == 1)

    {

      // Retrun max metric value when frame error rate equals to 1

      return (uint32_t)0xffffffff;

    }

  NS_ASSERT (failAvg < 1.0);

  //calculate metric

  uint32_t metric = (uint32_t)((double)( /*Overhead + payload*/

                                 mac->GetPifs () + mac->GetSlot () + mac->GetEifsNoDifs () + //DIFS + SIFS + AckTxTime = PIFS + SLOT + EifsNoDifs

                                 ).GetMicroSeconds () / (10.24 * (1.0 - failAvg)));

  return metric;

}

} // namespace dot11s

} // namespace ns3