802.11 MAC - Modify CW

[Sampath]

Hi Everyone,

I am trying to change the contention window (CW) size of 802.11 MAC protocol and observe the changes in the throughput. 

My topology is a simple infrastructure Wifi. One AP and several STAs.

I tried the following options

1) Config::Set ("/NodeList/*/DeviceList/*/$ns3::WifiNetDevice/Mac/$ns3::RegularWifiMac/DcaTxop/MinCw", UintegerValue (7));

2) Ptr<NetDevice> dev1 = wifiApNode.Get (0)->GetDevice (0);

  Ptr<WifiNetDevice> wifi_dev1 = DynamicCast<WifiNetDevice> (dev1);

  Ptr<WifiMac> wifi_mac1 = wifi_dev1->GetMac ();

  PointerValue ptr1;

  wifi_mac1->GetAttribute("DcaTxop", ptr1);

  Ptr<DcaTxop> dca1 = ptr1.Get<DcaTxop>();

  dca1->SetMinCw(7);

  dca1->SetMaxCw(1023);

However none of these worked. Could you please give me some ideas on how to do this?

Thanks in advance.

Sampath

[Rediet]

Hello Sampath,

It's odd because if you perform this once the RegularWifiMac objects have been instantiated (i.e. once WifiHelper::Install has been called), you should be able to modify these parameters.

Could you please join a simplified script for the first option?

BR,

Rediet

[Sampath]

Hi Rediet,

Thank you for the quick reply. I think I found the problem. 

Both the methods are working.

Problem was in the time resolution. Time resolution was not small enough to reflect the changes in the throughput.

So I increased the number of users. Now I can observe the effects.

Thanks again

Regards,

Sampath