After setting cwMin and cwMax some stations are returning to default (StaWifiMac::Receive function)

[Klaudia Gądek]

After setting CwMin and CwMax. We can see that some Cw min and CW max values are returning to default. Could somebody tell me, why ns-3 is setting EDCA parameters during simulations, not only in initialization phase. It is set in StaWifiMac::Receive function(sta-wifi-mac.cc file). 

I would be grateful if you could tell my why it is implemented this way?

Thank, you in advance. 

More informations:

I am setting CwMin and CwMax in script: 

for (uint16_t i = 0; i < nnode+1; ++i)

{

Ptr<Node> node;

if (i==nnode){

        node = wifiApNode.Get(0);

}

else{

        node = wifiStaNode.Get(nnode - (i+1)); // Get station from node container 

}

Ptr<NetDevice> dev = node->GetDevice(0);

Ptr<WifiNetDevice> wifi_dev = DynamicCast<WifiNetDevice>(dev);

Ptr<WifiMac> mac = wifi_dev->GetMac();

        PointerValue ptr;

Ptr<EdcaTxopN> edca;

mac->GetAttribute("VO_EdcaTxopN", ptr);

edca = ptr.Get<EdcaTxopN>();

edca->SetMinCw(CWmin);

edca->SetMaxCw(CWmax);

mac->GetAttribute("VI_EdcaTxopN", ptr);

edca = ptr.Get<EdcaTxopN>();

edca->SetMinCw(CWmin);

edca->SetMaxCw(CWmax);

mac->GetAttribute("BE_EdcaTxopN", ptr);

edca = ptr.Get<EdcaTxopN>();

edca->SetMinCw(CWmin);

edca->SetMaxCw(CWmax);

mac->GetAttribute("BK_EdcaTxopN", ptr);

edca = ptr.Get<EdcaTxopN>();

edca->SetMinCw(CWmin);

edca->SetMaxCw(CWmax);

}

Logs(We can see that Cwmin and CWmax were set):

Line 2690: [mac=00:00:00:00:00:0a] EdcaTxopN:SetMinCw(0x2671e90, 1)

Line 2691: [mac=00:00:00:00:00:0a] EdcaTxopN:SetMaxCw(0x2671e90, 1)

Line 2692: [mac=00:00:00:00:00:0a] EdcaTxopN:SetMinCw(0x26725c0, 1)

Line 2693: [mac=00:00:00:00:00:0a] EdcaTxopN:SetMaxCw(0x26725c0, 1)

Line 2694: [mac=00:00:00:00:00:0a] EdcaTxopN:SetMinCw(0x2672d00, 1)

Line 2695: [mac=00:00:00:00:00:0a] EdcaTxopN:SetMaxCw(0x2672d00, 1)

Line 2696: [mac=00:00:00:00:00:0a] EdcaTxopN:SetMinCw(0x2673450, 1)

Line 2697: [mac=00:00:00:00:00:0a] EdcaTxopN:SetMaxCw(0x2673450, 1)

Line 2698: [mac=00:00:00:00:00:09] EdcaTxopN:SetMinCw(0x266e100, 1)

Line 2699: [mac=00:00:00:00:00:09] EdcaTxopN:SetMaxCw(0x266e100, 1)

Line 2700: [mac=00:00:00:00:00:09] EdcaTxopN:SetMinCw(0x266e830, 1)

Line 2701: [mac=00:00:00:00:00:09] EdcaTxopN:SetMaxCw(0x266e830, 1)

Line 2702: [mac=00:00:00:00:00:09] EdcaTxopN:SetMinCw(0x266ef70, 1)

Line 2703: [mac=00:00:00:00:00:09] EdcaTxopN:SetMaxCw(0x266ef70, 1)

Line 2704: [mac=00:00:00:00:00:09] EdcaTxopN:SetMinCw(0x266f6c0, 1)

Line 2705: [mac=00:00:00:00:00:09] EdcaTxopN:SetMaxCw(0x266f6c0, 1)

Line 2706: [mac=00:00:00:00:00:08] EdcaTxopN:SetMinCw(0x266a400, 1)

Line 2707: [mac=00:00:00:00:00:08] EdcaTxopN:SetMaxCw(0x266a400, 1)

Line 2708: [mac=00:00:00:00:00:08] EdcaTxopN:SetMinCw(0x266ab30, 1)

Line 2709: [mac=00:00:00:00:00:08] EdcaTxopN:SetMaxCw(0x266ab30, 1)

Line 2710: [mac=00:00:00:00:00:08] EdcaTxopN:SetMinCw(0x266b270, 1)

Line 2711: [mac=00:00:00:00:00:08] EdcaTxopN:SetMaxCw(0x266b270, 1)

Line 2712: [mac=00:00:00:00:00:08] EdcaTxopN:SetMinCw(0x266b9c0, 1)

Line 2713: [mac=00:00:00:00:00:08] EdcaTxopN:SetMaxCw(0x266b9c0, 1)

Line 2714: [mac=00:00:00:00:00:07] EdcaTxopN:SetMinCw(0x2666700, 1)

Line 2715: [mac=00:00:00:00:00:07] EdcaTxopN:SetMaxCw(0x2666700, 1)

Line 2716: [mac=00:00:00:00:00:07] EdcaTxopN:SetMinCw(0x2666e30, 1)

Line 2717: [mac=00:00:00:00:00:07] EdcaTxopN:SetMaxCw(0x2666e30, 1)

Line 2718: [mac=00:00:00:00:00:07] EdcaTxopN:SetMinCw(0x2667570, 1)

Line 7419: [mac=00:00:00:00:00:0a] DcaTxop:SetMinCw(0x2671a20, 15)

Line 7420: [mac=00:00:00:00:00:0a] DcaTxop:SetMaxCw(0x2671a20, 1023)

Line 7423: [mac=00:00:00:00:00:0a] EdcaTxopN:SetMinCw(0x2672d00, 15)

Line 7424: [mac=00:00:00:00:00:0a] EdcaTxopN:SetMaxCw(0x2672d00, 1023)

Line 7427: [mac=00:00:00:00:00:0a] EdcaTxopN:SetMinCw(0x2673450, 15)

Line 7428: [mac=00:00:00:00:00:0a] EdcaTxopN:SetMaxCw(0x2673450, 1023)

Line 7431: [mac=00:00:00:00:00:0a] EdcaTxopN:SetMinCw(0x26725c0, 7)

Line 7432: [mac=00:00:00:00:00:0a] EdcaTxopN:SetMaxCw(0x26725c0, 15)

Line 7435: [mac=00:00:00:00:00:0a] EdcaTxopN:SetMinCw(0x2671e90, 3)

Line 7436: [mac=00:00:00:00:00:0a] EdcaTxopN:SetMaxCw(0x2671e90, 7)

Line 9113: [mac=00:00:00:00:00:0b] EdcaTxopN:GetMinCw(0x2676b50)

Line 9114: [mac=00:00:00:00:00:0b] EdcaTxopN:GetMaxCw(0x2676b50)

I am not sure why we are setting EDCA parameters here:

void

StaWifiMac::Receive (Ptr<Packet> packet, const WifiMacHeader *hdr)

{

  NS_LOG_FUNCTION (this << packet << hdr);

  NS_ASSERT (!hdr->IsCtl ());

  if (hdr->GetAddr3 () == GetAddress ())

    {

      NS_LOG_LOGIC ("packet sent by us.");

      return;

    }

  else if (hdr->GetAddr1 () != GetAddress ()

           && !hdr->GetAddr1 ().IsGroup ())

    {

      NS_LOG_LOGIC ("packet is not for us");

      NotifyRxDrop (packet);

      return;

    }

  else if (hdr->IsData ())

    {

      if (!IsAssociated ())

        {

          NS_LOG_LOGIC ("Received data frame while not associated: ignore");

          NotifyRxDrop (packet);

          return;

        }

      if (!(hdr->IsFromDs () && !hdr->IsToDs ()))

        {

          NS_LOG_LOGIC ("Received data frame not from the DS: ignore");

          NotifyRxDrop (packet);

          return;

        }

      if (hdr->GetAddr2 () != GetBssid ())

        {

          NS_LOG_LOGIC ("Received data frame not from the BSS we are associated with: ignore");

          NotifyRxDrop (packet);

          return;

        }

      if (hdr->IsQosData ())

        {

          if (hdr->IsQosAmsdu ())

            {

              NS_ASSERT (hdr->GetAddr3 () == GetBssid ());

              DeaggregateAmsduAndForward (packet, hdr);

              packet = 0;

            }

          else

            {

              ForwardUp (packet, hdr->GetAddr3 (), hdr->GetAddr1 ());

            }

        }

      else

        {

          ForwardUp (packet, hdr->GetAddr3 (), hdr->GetAddr1 ());

        }

      return;

    }

  else if (hdr->IsProbeReq ()

           || hdr->IsAssocReq ())

    {

      //This is a frame aimed at an AP, so we can safely ignore it.

      NotifyRxDrop (packet);

      return;

    }

  else if (hdr->IsBeacon ())

    {

      MgtBeaconHeader beacon;

      packet->RemoveHeader (beacon);

      CapabilityInformation capabilities = beacon.GetCapabilities ();

      bool goodBeacon = false;

      if (GetSsid ().IsBroadcast ()

          || beacon.GetSsid ().IsEqual (GetSsid ()))

        {

          NS_LOG_LOGIC ("Beacon is for our SSID");

          goodBeacon = true;

        }

      SupportedRates rates = beacon.GetSupportedRates ();

      bool bssMembershipSelectorMatch = false;

      for (uint32_t i = 0; i < m_phy->GetNBssMembershipSelectors (); i++)

        {

          uint32_t selector = m_phy->GetBssMembershipSelector (i);

          if (rates.IsBssMembershipSelectorRate (selector))

            {

              NS_LOG_LOGIC ("Beacon is matched to our BSS membership selector");

              bssMembershipSelectorMatch = true;

            }

        }

      if (m_phy->GetNBssMembershipSelectors () > 0 && bssMembershipSelectorMatch == false)

        {

          NS_LOG_LOGIC ("No match for BSS membership selector");

          goodBeacon = false;

        }

      if ((IsWaitAssocResp () || IsAssociated ()) && hdr->GetAddr3 () != GetBssid ())

        {

          NS_LOG_LOGIC ("Beacon is not for us");

          goodBeacon = false;

        }

      if (goodBeacon)

        {

          Time delay = MicroSeconds (beacon.GetBeaconIntervalUs () * m_maxMissedBeacons);

          RestartBeaconWatchdog (delay);

          SetBssid (hdr->GetAddr3 ());

          bool isShortPreambleEnabled = capabilities.IsShortPreamble ();

          if (m_erpSupported)

            {

              ErpInformation erpInformation = beacon.GetErpInformation ();

              isShortPreambleEnabled &= !erpInformation.GetBarkerPreambleMode ();

              if (erpInformation.GetUseProtection() == true)

                {

                  m_stationManager->SetUseNonErpProtection (true);

                }

              else

                {

                  m_stationManager->SetUseNonErpProtection (false);

                }

              if (capabilities.IsShortSlotTime () == true)

                {

                  //enable short slot time

                  SetSlot (MicroSeconds (9));

                }

              else

                {

                  //disable short slot time

                  SetSlot (MicroSeconds (20));

                }

            }

           // if (m_qosSupported)

           // {

           //   EdcaParameterSet edcaParameters = beacon.GetEdcaParameterSet ();

          //    //The value of the TXOP Limit field is specified as an unsigned integer, with the least significant octet transmitted first, in units of 32 μs.

          //    SetEdcaParameters (AC_BE, edcaParameters.GetBeCWmin(), edcaParameters.GetBeCWmax(), edcaParameters.GetBeAifsn(), 32 * MicroSeconds (edcaParameters.GetBeTXOPLimit()));

          //    SetEdcaParameters (AC_BK, edcaParameters.GetBkCWmin(), edcaParameters.GetBkCWmax(), edcaParameters.GetBkAifsn(), 32 * MicroSeconds (edcaParameters.GetBkTXOPLimit()));

          //    SetEdcaParameters (AC_VI, edcaParameters.GetViCWmin(), edcaParameters.GetViCWmax(), edcaParameters.GetViAifsn(), 32 * MicroSeconds (edcaParameters.GetViTXOPLimit()));

          //    SetEdcaParameters (AC_VO, edcaParameters.GetVoCWmin(), edcaParameters.GetVoCWmax(), edcaParameters.GetVoAifsn(), 32 * MicroSeconds (edcaParameters.GetVoTXOPLimit()));

          //  }

          m_stationManager->SetShortPreambleEnabled (isShortPreambleEnabled);

          m_stationManager->SetShortSlotTimeEnabled (capabilities.IsShortSlotTime ());

        }

      if (goodBeacon && m_state == BEACON_MISSED)

        {

          SetState (WAIT_ASSOC_RESP);

          SendAssociationRequest ();

        }

      return;

    }

  else if (hdr->IsProbeResp ())

    {

      if (m_state == WAIT_PROBE_RESP)

        {

          MgtProbeResponseHeader probeResp;

          packet->RemoveHeader (probeResp);

          CapabilityInformation capabilities = probeResp.GetCapabilities ();

          if (!probeResp.GetSsid ().IsEqual (GetSsid ()))

            {

              //not a probe resp for our ssid.

              return;

            }

          SupportedRates rates = probeResp.GetSupportedRates ();

          for (uint32_t i = 0; i < m_phy->GetNBssMembershipSelectors (); i++)

            {

              uint32_t selector = m_phy->GetBssMembershipSelector (i);

              if (!rates.IsSupportedRate (selector))

                {

                  return;

                }

            }

          for (uint32_t i = 0; i < m_phy->GetNModes (); i++)

            {

              WifiMode mode = m_phy->GetMode (i);

              uint8_t nss = 1; // Assume 1 spatial stream

              if (rates.IsSupportedRate (mode.GetDataRate (m_phy->GetChannelWidth (), false, nss)))

                {

                  m_stationManager->AddSupportedMode (hdr->GetAddr2 (), mode);

                  if (rates.IsBasicRate (mode.GetDataRate (m_phy->GetChannelWidth (), false, nss)))

                    {

                      m_stationManager->AddBasicMode (mode);

                    }

                }

            }

            

          bool isShortPreambleEnabled = capabilities.IsShortPreamble ();

          if (m_erpSupported)

            {

              bool isErpAllowed = false;

              for (uint32_t i = 0; i < m_phy->GetNModes (); i++)

              {

                WifiMode mode = m_phy->GetMode (i);

                if (mode.GetModulationClass () == WIFI_MOD_CLASS_ERP_OFDM && rates.IsSupportedRate (mode.GetDataRate (m_phy->GetChannelWidth (), false, 1)))

                  {

                    isErpAllowed = true;

                    break;

                  }

              }

              if (!isErpAllowed)

                {

                  //disable short slot time and set cwMin to 31

                  SetSlot (MicroSeconds (20));

                  //ConfigureContentionWindow (31, 1023);

                }

              else

                {

                  ErpInformation erpInformation = probeResp.GetErpInformation ();

                  isShortPreambleEnabled &= !erpInformation.GetBarkerPreambleMode ();

                  if (m_stationManager->GetShortSlotTimeEnabled ())

                    {

                      //enable short slot time

                      SetSlot (MicroSeconds (9));

                    }

                  else

                    {

                      //disable short slot time

                      SetSlot (MicroSeconds (20));

                    }

                  //ConfigureContentionWindow (15, 1023);

                }

            }

          m_stationManager->SetShortPreambleEnabled (isShortPreambleEnabled);

          m_stationManager->SetShortSlotTimeEnabled (capabilities.IsShortSlotTime ());

          SetBssid (hdr->GetAddr3 ());

          Time delay = MicroSeconds (probeResp.GetBeaconIntervalUs () * m_maxMissedBeacons);

          RestartBeaconWatchdog (delay);

          if (m_probeRequestEvent.IsRunning ())

            {

              m_probeRequestEvent.Cancel ();

            }

          SetState (WAIT_ASSOC_RESP);

          SendAssociationRequest ();

        }

      return;

    }

  else if (hdr->IsAssocResp ())

    {

      if (m_state == WAIT_ASSOC_RESP)

        {

          MgtAssocResponseHeader assocResp;

          packet->RemoveHeader (assocResp);

          if (m_assocRequestEvent.IsRunning ())

            {

              m_assocRequestEvent.Cancel ();

            }

          if (assocResp.GetStatusCode ().IsSuccess ())

            {

              SetState (ASSOCIATED);

              NS_LOG_DEBUG ("assoc completed");

              CapabilityInformation capabilities = assocResp.GetCapabilities ();

              SupportedRates rates = assocResp.GetSupportedRates ();

              bool isShortPreambleEnabled = capabilities.IsShortPreamble ();

              if (m_erpSupported)

                {

                  bool isErpAllowed = false;

                  for (uint32_t i = 0; i < m_phy->GetNModes (); i++)

                  {

                    WifiMode mode = m_phy->GetMode (i);

                    if (mode.GetModulationClass () == WIFI_MOD_CLASS_ERP_OFDM && rates.IsSupportedRate (mode.GetDataRate (m_phy->GetChannelWidth (), false, 1)))

                      {

                        isErpAllowed = true;

                        break;

                      }

                  }

                  if (!isErpAllowed)

                    {

                      //disable short slot time and set cwMin to 31

                      SetSlot (MicroSeconds (20));

                      //ConfigureContentionWindow (31, 1023);

                    }

                  else

                    {

                      ErpInformation erpInformation = assocResp.GetErpInformation ();

                      isShortPreambleEnabled &= !erpInformation.GetBarkerPreambleMode ();

                      if (m_stationManager->GetShortSlotTimeEnabled ())

                        {

                          //enable short slot time

                          SetSlot (MicroSeconds (9));

                        }

                      else

                        {

                          //disable short slot time

                          SetSlot (MicroSeconds (20));

                        }

                      //ConfigureContentionWindow (15, 1023);

                    }

                }

[Rediet]

It's up to the AP to define the parameters that'll be used on its BSS. Why not set the AP's parameters also so that they may be notified later on?