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

/*

 * Copyright (c) 2009 Duy Nguyen

 *

 * 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: Duy Nguyen <duy@soe.ucsc.edu>

 */

#ifndef MINSTREL_WIFI_MANAGER_H

#define MINSTREL_WIFI_MANAGER_H

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

#include "wifi-mode.h"

#include "ns3/nstime.h"

#include "ns3/random-variable-stream.h"

namespace ns3 {

struct MinstrelWifiRemoteStation;

/**

 * A struct to contain all information related to a data rate

 */

struct RateInfo

{

  /**

   * Perfect transmission time calculation, or frame calculation

   * Given a bit rate and a packet length n bytes

   */

  Time perfectTxTime;

  uint32_t retryCount;          ///< retry limit

  uint32_t adjustedRetryCount;  ///< adjust the retry limit for this rate

  uint32_t numRateAttempt;      ///< how many number of attempts so far

  uint32_t numRateSuccess;      ///< number of successful pkts

  uint32_t prob;                ///< (# pkts success )/(# total pkts)

  /**

   * EWMA calculation

   * ewma_prob =[prob *(100 - ewma_level) + (ewma_prob_old * ewma_level)]/100

   */

  uint32_t ewmaProb;

  uint32_t throughput;  ///< throughput of a rate

};

/**

 * Data structure for a Minstrel Rate table

 * A vector of a struct RateInfo

 */

typedef std::vector<struct RateInfo> MinstrelRate;

/**

 * Data structure for a Sample Rate table

 * A vector of a vector uint32_t

 */

typedef std::vector<std::vector<uint32_t> > SampleRate;

/**

 * \author Duy Nguyen

 * \brief Implementation of Minstrel Rate Control Algorithm

 * \ingroup wifi

 *

 * Porting Minstrel from Madwifi and Linux Kernel

 * http://linuxwireless.org/en/developers/Documentation/mac80211/RateControl/minstrel

 */

class MinstrelWifiManager : public WifiRemoteStationManager

{

public:

  static TypeId GetTypeId (void);

  MinstrelWifiManager ();

  virtual ~MinstrelWifiManager ();

  virtual void SetupPhy (Ptr<WifiPhy> phy);

  /**

   * Assign a fixed random variable stream number to the random variables

   * used by this model.  Return the number of streams (possibly zero) that

   * have been assigned.

   *

   * \param stream first stream index to use

   *

   * \return the number of stream indices assigned by this model

   */

  int64_t AssignStreams (int64_t stream);

private:

  //overriden from base class

  virtual WifiRemoteStation * DoCreateStation (void) const;

  virtual void DoReportRxOk (WifiRemoteStation *station,

                             double rxSnr, WifiMode txMode);

  virtual void DoReportRtsFailed (WifiRemoteStation *station);

  virtual void DoReportDataFailed (WifiRemoteStation *station);

  virtual void DoReportRtsOk (WifiRemoteStation *station,

                              double ctsSnr, WifiMode ctsMode, double rtsSnr);

  virtual void DoReportDataOk (WifiRemoteStation *station,

                               double ackSnr, WifiMode ackMode, double dataSnr);

  virtual void DoReportFinalRtsFailed (WifiRemoteStation *station);

  virtual void DoReportFinalDataFailed (WifiRemoteStation *station);

  virtual WifiTxVector DoGetDataTxVector (WifiRemoteStation *station, uint32_t size);

  virtual WifiTxVector DoGetRtsTxVector (WifiRemoteStation *station);

  virtual bool DoNeedDataRetransmission (WifiRemoteStation *st, Ptr<const Packet> packet, bool normally);

  virtual bool IsLowLatency (void) const;

  //for estimating the TxTime of a packet with a given mode

  Time GetCalcTxTime (WifiMode mode) const;

  /**

   * Add transmission time for the given mode to an internal list.

   *

   * \param mode Wi-Fi mode

   * \param t transmission time

   */

  void AddCalcTxTime (WifiMode mode, Time t);

  //update the number of retries and reset accordingly

  void UpdateRetry (MinstrelWifiRemoteStation *station);

  //getting the next sample from Sample Table

  uint32_t GetNextSample (MinstrelWifiRemoteStation *station);

  //find a rate to use from Minstrel Table

  uint32_t FindRate (MinstrelWifiRemoteStation *station);

  //updating the Minstrel Table every 1/10 seconds

  void UpdateStats (MinstrelWifiRemoteStation *station);

  //initialize Minstrel Table

  void RateInit (MinstrelWifiRemoteStation *station);

  /**

   * Estimate the time to transmit the given packet with the given number of retries.

   * This function is "roughly" the function "calc_usecs_unicast_packet" in minstrel.c

   * in the madwifi implementation.

   *

   * The basic idea is that, we try to estimate the "average" time used to transmit the

   * packet for the given number of retries while also accounting for the 802.11 congestion

   * window change. The original code in the madwifi seems to estimate the number of backoff

   * slots as the half of the current CW size.

   *

   * There are four main parts:

   *  - wait for DIFS (sense idle channel)

   *  - ACK timeouts

   *  - DATA transmission

   *  - backoffs according to CW

   */

  Time CalculateTimeUnicastPacket (Time dataTransmissionTime, uint32_t shortRetries, uint32_t longRetries);

  //initialize Sample Table

  void InitSampleTable (MinstrelWifiRemoteStation *station);

  //printing Sample Table

  void PrintSampleTable (MinstrelWifiRemoteStation *station);

  //printing Minstrel Table

  void PrintTable (MinstrelWifiRemoteStation *station);

  void CheckInit (MinstrelWifiRemoteStation *station);  ///< check for initializations

  /**

   * typedef for a vector of a pair of Time, WifiMode.

   * (Essentially a list for WifiMode and its corresponding transmission time

   * to transmit a reference packet.

   */

  typedef std::vector<std::pair<Time,WifiMode> > TxTime;

  TxTime m_calcTxTime;      ///< to hold all the calculated TxTime for all modes

  Time m_updateStats;       ///< how frequent do we calculate the stats (1/10 seconds)

  double m_lookAroundRate;  ///< the % to try other rates than our current rate

  double m_ewmaLevel;       ///< exponential weighted moving average

  uint32_t m_sampleCol;     ///< number of sample columns

  uint32_t m_pktLen;        ///< packet length used for calculate mode TxTime

  uint32_t m_nsupported;    ///< modes supported

  //Provides uniform random variables.

  Ptr<UniformRandomVariable> m_uniformRandomVariable;

};

} //namespace ns3

#endif /* MINSTREL_WIFI_MANAGER_H */