minstrel-ht-wifi-manager.h

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/*
 * Copyright (c) 2009 Duy Nguyen
 * Copyright (c) 2015 Ghada Badawy
 *
 * 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: Duy Nguyen <duy@soe.ucsc.edu>
 *         Ghada Badawy <gbadawy@gmail.com>
 *         Matias Richart <mrichart@fing.edu.uy>
 *
 * MinstrelHt is a rate adaptation algorithm for high-throughput (HT) 802.11
 */
 
#ifndef MINSTREL_HT_WIFI_MANAGER_H
#define MINSTREL_HT_WIFI_MANAGER_H
 
#include "minstrel-wifi-manager.h"
 
#include "ns3/wifi-mpdu-type.h"
#include "ns3/wifi-remote-station-manager.h"
 
namespace ns3
{
 
/**
 * Data structure to save transmission time calculations per rate.
 */
typedef std::map<WifiMode, Time> TxTime;
 
/**
 * \enum McsGroupType
 * \brief Available MCS group types
 */
enum McsGroupType
{
    WIFI_MINSTREL_GROUP_HT = 0,
    WIFI_MINSTREL_GROUP_VHT,
    WIFI_MINSTREL_GROUP_HE
};
 
/**
 * \brief Stream insertion operator.
 *
 * \param os the stream
 * \param type the MCS group type
 * \returns a reference to the stream
 */
inline std::ostream&
operator<<(std::ostream& os, McsGroupType type)
{
    switch (type)
    {
    case WIFI_MINSTREL_GROUP_HT:
        return (os << "HT");
    case WIFI_MINSTREL_GROUP_VHT:
        return (os << "VHT");
    case WIFI_MINSTREL_GROUP_HE:
        return (os << "HE");
    default:
        return (os << "INVALID");
    }
}
 
/**
 * Data structure to contain the information that defines a group.
 * It also contains the transmission times for all the MCS in the group.
 * A group is a collection of MCS defined by the number of spatial streams,
 * if it uses or not Short Guard Interval, and the channel width used.
 */
struct McsGroup
{
    uint8_t streams;   ///< number of spatial streams
    uint16_t gi;       ///< guard interval duration (nanoseconds)
    uint16_t chWidth;  ///< channel width (MHz)
    McsGroupType type; ///< identifies the group, \see McsGroupType
    bool isSupported;  ///< flag whether group is  supported
    // To accurately account for TX times, we separate the TX time of the first
    // MPDU in an A-MPDU from the rest of the MPDUs.
    TxTime ratesTxTimeTable;          ///< rates transmit time table
    TxTime ratesFirstMpduTxTimeTable; ///< rates MPDU transmit time table
};
 
/**
 * Data structure for a table of group definitions.
 * A vector of McsGroups.
 */
typedef std::vector<McsGroup> MinstrelMcsGroups;
 
struct MinstrelHtWifiRemoteStation;
 
/**
 * A struct to contain all statistics information related to a data rate.
 */
struct MinstrelHtRateInfo
{
    /**
     * Perfect transmission time calculation, or frame calculation.
     * Given a bit rate and a packet length n bytes.
     */
    Time perfectTxTime;
    bool supported;      //!< If the rate is supported.
    uint8_t mcsIndex;    //!< The index in the operationalMcsSet of the WifiRemoteStationManager.
    uint32_t retryCount; //!< Retry limit.
    uint32_t adjustedRetryCount; //!< Adjust the retry limit for this rate.
    uint32_t numRateAttempt;     //!< Number of transmission attempts so far.
    uint32_t numRateSuccess;     //!< Number of successful frames transmitted so far.
    double prob; //!< Current probability within last time interval. (# frame success )/(# total
                 //!< frames)
    bool retryUpdated; //!< If number of retries was updated already.
    /**
     * Exponential weighted moving average of probability.
     * EWMA calculation:
     * ewma_prob =[prob *(100 - ewma_level) + (ewma_prob_old * ewma_level)]/100
     */
    double ewmaProb;
    double ewmsdProb;            //!< Exponential weighted moving standard deviation of probability.
    uint32_t prevNumRateAttempt; //!< Number of transmission attempts with previous rate.
    uint32_t prevNumRateSuccess; //!< Number of successful frames transmitted with previous rate.
    uint32_t numSamplesSkipped;  //!< Number of times this rate statistics were not updated because
                                 //!< no attempts have been made.
    uint64_t successHist;        //!< Aggregate of all transmission successes.
    uint64_t attemptHist;        //!< Aggregate of all transmission attempts.
    double throughput;           //!< Throughput of this rate (in packets per second).
};
 
/**
 * Data structure for a Minstrel Rate table.
 * A vector of a struct MinstrelHtRateInfo.
 */
typedef std::vector<MinstrelHtRateInfo> MinstrelHtRate;
 
/**
 * A struct to contain information of a group.
 */
struct GroupInfo
{
    /**
     * MCS rates are divided into groups based on the number of streams and flags that they use.
     */
    uint8_t m_col;               //!< Sample table column.
    uint8_t m_index;             //!< Sample table index.
    bool m_supported;            //!< If the rates of this group are supported by the station.
    uint16_t m_maxTpRate;        //!< The max throughput rate of this group in bps.
    uint16_t m_maxTpRate2;       //!< The second max throughput rate of this group in bps.
    uint16_t m_maxProbRate;      //!< The highest success probability rate of this group in bps.
    MinstrelHtRate m_ratesTable; //!< Information about rates of this group.
};
 
/**
 * Data structure for a table of groups. Each group is of type GroupInfo.
 * A vector of a GroupInfo.
 */
typedef std::vector<GroupInfo> McsGroupData;
 
/**
 * Constants for maximum values.
 */
 
static const uint8_t MAX_HT_SUPPORTED_STREAMS =
    4; //!< Maximal number of streams supported by the HT PHY layer.
static const uint8_t MAX_VHT_SUPPORTED_STREAMS =
    8; //!< Maximal number of streams supported by the VHT PHY layer.
static const uint8_t MAX_HE_SUPPORTED_STREAMS =
    8; //!< Maximal number of streams supported by the HE PHY layer.
static const uint8_t MAX_HT_STREAM_GROUPS =
    4; //!< Maximal number of groups per stream in HT (2 possible channel widths and 2 possible GI
       //!< configurations).
static const uint8_t MAX_VHT_STREAM_GROUPS =
    8; //!< Maximal number of groups per stream in VHT (4 possible channel widths and 2 possible GI
       //!< configurations).
static const uint8_t MAX_HE_STREAM_GROUPS =
    12; //!< Maximal number of groups per stream in HE (4 possible channel widths and 3 possible GI
        //!< configurations).
static const uint8_t MAX_HT_GROUP_RATES = 8;   //!< Number of rates (or MCS) per HT group.
static const uint8_t MAX_VHT_GROUP_RATES = 10; //!< Number of rates (or MCS) per VHT group.
static const uint8_t MAX_HE_GROUP_RATES = 12;  //!< Number of rates (or MCS) per HE group.
static const uint8_t MAX_HT_WIDTH = 40;        //!< Maximal channel width in MHz.
static const uint8_t MAX_VHT_WIDTH = 160;      //!< Maximal channel width in MHz.
static const uint8_t MAX_HE_WIDTH = 160;       //!< Maximal channel width in MHz.
 
/**
 * \brief Implementation of Minstrel-HT Rate Control Algorithm
 * \ingroup wifi
 *
 * Minstrel-HT is a rate adaptation mechanism for the 802.11n/ac/ax standards
 * based on Minstrel, and is based on the approach of probing the channel
 * to dynamically learn about working rates that can be supported.
 * Minstrel-HT is designed for high-latency devices that implement a
 * Multiple Rate Retry (MRR) chain. This kind of device does
 * not give feedback for every frame retransmission, but only when a frame
 * was correctly transmitted (an Ack is received) or a frame transmission
 * completely fails (all retransmission attempts fail).
 * The MRR chain is used to advise the hardware about which rate to use
 * when retransmitting a frame.
 *
 * Minstrel-HT adapts the MCS, channel width, number of streams, and
 * short guard interval (enabled or disabled).  For keeping statistics,
 * it arranges MCS in groups, where each group is defined by the
 * tuple (streams, GI, channel width).  There is a vector of all groups
 * supported by the PHY layer of the transmitter; for each group, the
 * capabilities and the estimated duration of its rates are maintained.
 *
 * Each station maintains a table of groups statistics. For each group, a flag
 * indicates if the group is supported by the station. Different stations
 * communicating with an AP can have different capabilities.
 *
 * Stats are updated per A-MPDU when receiving AmpduTxStatus. If the number
 * of successful or failed MPDUs is greater than zero (a BlockAck was
 * received), the rates are also updated.
 * If the number of successful and failed MPDUs is zero (BlockAck timeout),
 * then the rate selected is based on the MRR chain.
 *
 * On each update interval, it sets the maxThrRate, the secondmaxThrRate
 * and the maxProbRate for the MRR chain. These rates are only used when
 * an entire A-MPDU fails and is retried.
 *
 * Differently from legacy minstrel, sampling is not done based on
 * "lookaround ratio", but assuring all rates are sampled at least once
 * each interval. However, it samples less often the low rates and high
 * probability of error rates.
 *
 * When this rate control is configured but non-legacy modes are not supported,
 * Minstrel-HT uses legacy Minstrel (minstrel-wifi-manager) for rate control.
 */
class MinstrelHtWifiManager : public WifiRemoteStationManager
{
  public:
    /**
     * \brief Get the type ID.
     * \return the object TypeId
     */
    static TypeId GetTypeId();
    MinstrelHtWifiManager();
    ~MinstrelHtWifiManager() override;
 
    void SetupPhy(const Ptr<WifiPhy> phy) override;
    void SetupMac(const Ptr<WifiMac> mac) override;
    int64_t AssignStreams(int64_t stream) override;
 
    /**
     * TracedCallback signature for rate change events.
     *
     * \param [in] rate The new rate.
     * \param [in] address The remote station MAC address.
     */
    typedef void (*RateChangeTracedCallback)(const uint64_t rate, const Mac48Address remoteAddress);
 
  private:
    void DoInitialize() override;
    WifiRemoteStation* DoCreateStation() const override;
    void DoReportRxOk(WifiRemoteStation* station, double rxSnr, WifiMode txMode) override;
    void DoReportRtsFailed(WifiRemoteStation* station) override;
    void DoReportDataFailed(WifiRemoteStation* station) override;
    void DoReportRtsOk(WifiRemoteStation* station,
                       double ctsSnr,
                       WifiMode ctsMode,
                       double rtsSnr) override;
    void DoReportDataOk(WifiRemoteStation* station,
                        double ackSnr,
                        WifiMode ackMode,
                        double dataSnr,
                        uint16_t dataChannelWidth,
                        uint8_t dataNss) override;
    void DoReportFinalRtsFailed(WifiRemoteStation* station) override;
    void DoReportFinalDataFailed(WifiRemoteStation* station) override;
    WifiTxVector DoGetDataTxVector(WifiRemoteStation* station, uint16_t allowedWidth) override;
    WifiTxVector DoGetRtsTxVector(WifiRemoteStation* station) override;
    void DoReportAmpduTxStatus(WifiRemoteStation* station,
                               uint16_t nSuccessfulMpdus,
                               uint16_t nFailedMpdus,
                               double rxSnr,
                               double dataSnr,
                               uint16_t dataChannelWidth,
                               uint8_t dataNss) override;
    bool DoNeedRetransmission(WifiRemoteStation* st,
                              Ptr<const Packet> packet,
                              bool normally) override;
 
    /**
     * Check the validity of a combination of number of streams, chWidth and mode.
     *
     * \param phy pointer to the wifi PHY
     * \param streams the number of streams
     * \param chWidth the channel width (MHz)
     * \param mode the wifi mode
     * \returns true if the combination is valid
     */
    bool IsValidMcs(Ptr<WifiPhy> phy, uint8_t streams, uint16_t chWidth, WifiMode mode);
 
    /**
     * Estimates the TxTime of a frame with a given mode and group (stream, guard interval and
     * channel width).
     *
     * \param phy pointer to the wifi PHY
     * \param streams the number of streams
     * \param gi guard interval duration (nanoseconds)
     * \param chWidth the channel width (MHz)
     * \param mode the wifi mode
     * \param mpduType the type of the MPDU
     * \returns the transmit time
     */
    Time CalculateMpduTxDuration(Ptr<WifiPhy> phy,
                                 uint8_t streams,
                                 uint16_t gi,
                                 uint16_t chWidth,
                                 WifiMode mode,
                                 MpduType mpduType);
 
    /**
     * Obtain the TxTime saved in the group information.
     *
     * \param groupId the group ID
     * \param mode the wifi mode
     * \returns the transmit time
     */
    Time GetMpduTxTime(uint8_t groupId, WifiMode mode) const;
 
    /**
     * Save a TxTime to the vector of groups.
     *
     * \param groupId the group ID
     * \param mode the wifi mode
     * \param t the transmit time
     */
    void AddMpduTxTime(uint8_t groupId, WifiMode mode, Time t);
 
    /**
     * Obtain the TxTime saved in the group information.
     *
     * \param groupId the group ID
     * \param mode the wifi mode
     * \returns the transmit time
     */
    Time GetFirstMpduTxTime(uint8_t groupId, WifiMode mode) const;
 
    /**
     * Save a TxTime to the vector of groups.
     *
     * \param groupId the group ID
     * \param mode the wifi mode
     * \param t the transmit time
     */
    void AddFirstMpduTxTime(uint8_t groupId, WifiMode mode, Time t);
 
    /**
     * Update the number of retries and reset accordingly.
     * \param station the wifi remote station
     */
    void UpdateRetry(MinstrelHtWifiRemoteStation* station);
 
    /**
     * Update the number of sample count variables.
     *
     * \param station the wifi remote station
     * \param nSuccessfulMpdus the number of successfully received MPDUs
     * \param nFailedMpdus the number of failed MPDUs
     */
    void UpdatePacketCounters(MinstrelHtWifiRemoteStation* station,
                              uint16_t nSuccessfulMpdus,
                              uint16_t nFailedMpdus);
 
    /**
     * Getting the next sample from Sample Table.
     *
     * \param station the wifi remote station
     * \returns the next sample
     */
    uint16_t GetNextSample(MinstrelHtWifiRemoteStation* station);
 
    /**
     * Set the next sample from Sample Table.
     *
     * \param station the wifi remote station
     */
    void SetNextSample(MinstrelHtWifiRemoteStation* station);
 
    /**
     * Find a rate to use from Minstrel Table.
     *
     * \param station the Minstrel-HT wifi remote station
     * \returns the rate in bps
     */
    uint16_t FindRate(MinstrelHtWifiRemoteStation* station);
 
    /**
     * Update the Minstrel Table.
     *
     * \param station the Minstrel-HT wifi remote station
     */
    void UpdateStats(MinstrelHtWifiRemoteStation* station);
 
    /**
     * Initialize Minstrel Table.
     *
     * \param station the Minstrel-HT wifi remote station
     */
    void RateInit(MinstrelHtWifiRemoteStation* station);
 
    /**
     * Return the average throughput of the MCS defined by groupId and rateId.
     *
     * \param station the Minstrel-HT wifi remote station
     * \param groupId the group ID
     * \param rateId the rate ID
     * \param ewmaProb the EWMA probability
     * \returns the throughput in bps
     */
    double CalculateThroughput(MinstrelHtWifiRemoteStation* station,
                               uint8_t groupId,
                               uint8_t rateId,
                               double ewmaProb);
 
    /**
     * Set index rate as maxTpRate or maxTp2Rate if is better than current values.
     *
     * \param station the Minstrel-HT wifi remote station
     * \param index the index
     */
    void SetBestStationThRates(MinstrelHtWifiRemoteStation* station, uint16_t index);
 
    /**
     * Set index rate as maxProbRate if it is better than current value.
     *
     * \param station the Minstrel-HT wifi remote station
     * \param index the index
     */
    void SetBestProbabilityRate(MinstrelHtWifiRemoteStation* station, uint16_t index);
 
    /**
     * Calculate the number of retransmissions to set for the index rate.
     *
     * \param station the Minstrel-HT wifi remote station
     * \param index the index
     */
    void CalculateRetransmits(MinstrelHtWifiRemoteStation* station, uint16_t index);
 
    /**
     * Calculate the number of retransmissions to set for the (groupId, rateId) rate.
     *
     * \param station the Minstrel-HT wifi remote station
     * \param groupId the group ID
     * \param rateId the rate ID
     */
    void CalculateRetransmits(MinstrelHtWifiRemoteStation* station,
                              uint8_t groupId,
                              uint8_t rateId);
 
    /**
     * 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
     *
     * \param dataTransmissionTime the data transmission time
     * \param shortRetries the short retries
     * \param longRetries the long retries
     * \returns the unicast packet time
     */
    Time CalculateTimeUnicastPacket(Time dataTransmissionTime,
                                    uint32_t shortRetries,
                                    uint32_t longRetries);
 
    /**
     * Perform EWMSD (Exponentially Weighted Moving Standard Deviation) calculation.
     *
     * \param oldEwmsd the old EWMSD
     * \param currentProb the current probability
     * \param ewmaProb the EWMA probability
     * \param weight the weight
     * \returns the EWMSD
     */
    double CalculateEwmsd(double oldEwmsd, double currentProb, double ewmaProb, double weight);
 
    /**
     * Initialize Sample Table.
     *
     * \param station the Minstrel-HT wifi remote station
     */
    void InitSampleTable(MinstrelHtWifiRemoteStation* station);
 
    /**
     * Printing Sample Table.
     *
     * \param station the Minstrel-HT wifi remote station
     */
    void PrintSampleTable(MinstrelHtWifiRemoteStation* station);
 
    /**
     * Printing Minstrel Table.
     *
     * \param station the Minstrel-HT wifi remote station
     */
    void PrintTable(MinstrelHtWifiRemoteStation* station);
 
    /**
     * Print group statistics.
     *
     * \param station the Minstrel-HT wifi remote station
     * \param groupId the group ID
     * \param of the output file stream
     */
    void StatsDump(MinstrelHtWifiRemoteStation* station, uint8_t groupId, std::ofstream& of);
 
    /**
     * Check for initializations.
     *
     * \param station the Minstrel-HT wifi remote station
     */
    void CheckInit(MinstrelHtWifiRemoteStation* station);
 
    /**
     * Count retries.
     *
     * \param station the Minstrel-HT wifi remote station
     * \returns the count of retries
     */
    uint32_t CountRetries(MinstrelHtWifiRemoteStation* station);
 
    /**
     * Update rate.
     *
     * \param station the Minstrel-HT wifi remote station
     */
    void UpdateRate(MinstrelHtWifiRemoteStation* station);
 
    /**
     * Return the rateId inside a group, from the global index.
     *
     * \param index the index
     * \returns the rate ID
     */
    uint8_t GetRateId(uint16_t index);
 
    /**
     * Return the groupId from the global index.
     *
     * \param index the index
     * \returns the group ID
     */
    uint8_t GetGroupId(uint16_t index);
 
    /**
     * Returns the global index corresponding to the groupId and rateId.
     *
     * For managing rates from different groups, a global index for
     * all rates in all groups is used.
     * The group order is fixed by BW -> SGI -> streams.
     *
     * \param groupId the group ID
     * \param rateId the rate ID
     * \returns the index
     */
    uint16_t GetIndex(uint8_t groupId, uint8_t rateId);
 
    /**
     * Returns the groupId of an HT MCS with the given number of streams, GI and channel width used.
     *
     * \param txstreams the number of streams
     * \param gi guard interval duration (nanoseconds)
     * \param chWidth the channel width (MHz)
     * \returns the HT group ID
     */
    uint8_t GetHtGroupId(uint8_t txstreams, uint16_t gi, uint16_t chWidth);
 
    /**
     * Returns the groupId of a VHT MCS with the given number of streams, GI and channel width used.
     *
     * \param txstreams the number of streams
     * \param gi guard interval duration (nanoseconds)
     * \param chWidth the channel width (MHz)
     * \returns the VHT group ID
     */
    uint8_t GetVhtGroupId(uint8_t txstreams, uint16_t gi, uint16_t chWidth);
 
    /**
     * Returns the groupId of an HE MCS with the given number of streams, GI and channel width used.
     *
     * \param txstreams the number of streams
     * \param gi guard interval duration (nanoseconds)
     * \param chWidth the channel width (MHz)
     * \returns the HE group ID
     */
    uint8_t GetHeGroupId(uint8_t txstreams, uint16_t gi, uint16_t chWidth);
 
    /**
     * Returns the lowest global index of the rates supported by the station.
     *
     * \param station the Minstrel-HT wifi remote station
     * \returns the lowest global index
     */
    uint16_t GetLowestIndex(MinstrelHtWifiRemoteStation* station);
 
    /**
     * Returns the lowest global index of the rates supported by in the group.
     *
     * \param station the Minstrel-HT wifi remote station
     * \param groupId the group ID
     * \returns the lowest global index
     */
    uint16_t GetLowestIndex(MinstrelHtWifiRemoteStation* station, uint8_t groupId);
 
    /**
     * Returns a list of only the HE MCS supported by the device.
     * \returns the list of the HE MCS supported
     */
    WifiModeList GetHeDeviceMcsList() const;
 
    /**
     * Returns a list of only the VHT MCS supported by the device.
     * \returns the list of the VHT MCS supported
     */
    WifiModeList GetVhtDeviceMcsList() const;
 
    /**
     * Returns a list of only the HT MCS supported by the device.
     * \returns the list of the HT MCS supported
     */
    WifiModeList GetHtDeviceMcsList() const;
 
    /**
     * Given the index of the current TX rate, check whether the channel width is
     * not greater than the given allowed width. If so, the index of the current TX
     * rate is returned. Otherwise, try halving the channel width and check if the
     * MCS group with the same number of streams and same GI is supported. If a
     * supported MCS group is found, return the index of the TX rate within such a
     * group with the same MCS as the given TX rate. If no supported MCS group is
     * found, the simulation aborts.
     *
     * \param txRate the index of the current TX rate
     * \param allowedWidth the allowed width in MHz
     * \return the index of a TX rate whose channel width is not greater than the
     *         allowed width, if found (otherwise, the simulation aborts)
     */
    uint16_t UpdateRateAfterAllowedWidth(uint16_t txRate, uint16_t allowedWidth);
 
    Time m_updateStats;            //!< How frequent do we calculate the stats.
    Time m_legacyUpdateStats;      //!< How frequent do we calculate the stats for legacy
                                   //!< MinstrelWifiManager.
    uint8_t m_lookAroundRate;      //!< The % to try other rates than our current rate.
    uint8_t m_ewmaLevel;           //!< Exponential weighted moving average level (or coefficient).
    uint8_t m_nSampleCol;          //!< Number of sample columns.
    uint32_t m_frameLength;        //!< Frame length used to calculate modes TxTime in bytes.
    uint8_t m_numGroups;           //!< Number of groups Minstrel should consider.
    uint8_t m_numRates;            //!< Number of rates per group Minstrel should consider.
    bool m_useLatestAmendmentOnly; //!< Flag if only the latest supported amendment by both peers
                                   //!< should be used.
    bool m_printStats;             //!< If statistics table should be printed.
 
    MinstrelMcsGroups m_minstrelGroups; //!< Global array for groups information.
 
    Ptr<MinstrelWifiManager> m_legacyManager; //!< Pointer to an instance of MinstrelWifiManager.
                                              //!< Used when 802.11n/ac/ax not supported.
 
    Ptr<UniformRandomVariable> m_uniformRandomVariable; //!< Provides uniform random variables.
 
    TracedValue<uint64_t> m_currentRate; //!< Trace rate changes
};
 
} // namespace ns3
 
#endif /* MINSTREL_HT_WIFI_MANAGER_H */