Change GI, MCS value, Channel width and propagation model dynamically

[Durgesh Kshirsagar]

Hello everyone!

I am puzzled to know that if we can change GI, MCS value,   Channel width and propagation model dynamically in NS3.

Thank you!

[Samir Si-Mohammed]

Hello,

I guess you’re talking about Wi-Fi. I do not know if it can help, but you can change those parameters using:

// Set channel width

Config::Set ("/NodeList/*/DeviceList/*/$ns3::WifiNetDevice/+\

Phy/ChannelWidth",

UintegerValue (channelWidth));

// Set guard interval

Config::Set ("/NodeList/*/DeviceList/*/$ns3::WifiNetDevice/+\

HtConfiguration/ShortGuardIntervalSupported",

BooleanValue (sgi));

std::ostringstream oss;

oss << "VhtMcs" << MCS;

wifi.SetRemoteStationManager ("ns3::ConstantRateWifiManager",

"DataMode", StringValue (oss.str ()),

"ControlMode", StringValue (oss.str ()));

For MCS, the second line depends on the Wi-Fi amendment you are in. For instance, the given code is for 802.11ac (« VhtMcs »), for 802.11ac it would be HE (« HeMcs »), etc.

For the propagation models you must specify it when you create your physical channel, for instance with the YansWifiChannelHelper: 

 

YansWifiChannelHelper channel = YansWifiChannelHelper::Default ();

channel.AddPropagationLoss("ns3::LogDistancePropagationLossModel");

Regards,

Samir 

--

Samir SI-MOHAMMED

Researcher/PhD Candidate
ENS Lyon - Labex MILyon - STACKEO
LIP UMR CNRS - INRIA DANTE Team

http://perso.ens-lyon.fr/samir.si-mohammed/

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[Durgesh Kshirsagar]

Thank you for you answer. But can we change these values dynamically? Is it theoretically and practically correct/feasible?

[Samir Si-Mohammed]

Hello,

You can do so by creating a simple function like the one below:

void changeParameters (double channelWidth, double sgi) {

Config::Set ("/NodeList/*/DeviceList/*/$ns3::WifiNetDevice/Phy/ChannelWidth", UintegerValue (channelWidth));

Config::Set ("/NodeList/*/DeviceList/*/$ns3::WifiNetDevice/HtConfiguration/ShortGuardIntervalSupported", BooleanValue (sgi));

}

And calling it with a scheduling before running the simulation:

Simulator::Schedule(Seconds(5), &changeParameters, 40, 1);

Simulator::Stop (Seconds (simulationTime));

Simulator::Run ();

I think that the MCS dynamic update must be a bit more complicated since you have to pass the WifiHelper object to the function. Regarding the practical correctness I think that parameters like MCS are more chosen by the transmitter device after a negotiation phase (See this video for more details).

Hope this will help.

Regards,

Samir 

--

Samir SI-MOHAMMED

Researcher/PhD Candidate
ENS Lyon - Labex MILyon - STACKEO
LIP UMR CNRS - INRIA DANTE Team

http://perso.ens-lyon.fr/samir.si-mohammed/

To view this discussion on the web visit https://groups.google.com/d/msgid/ns-3-users/992a5ffa-bc90-4a9e-90d0-1b078c803f94n%40googlegroups.com.

[Durgesh Kshirsagar]

Thank you so much for your help! I will definitely go through video.

[Shivam Garg]

Hi Durgesh,

Were you able to figure out how to change the values dynamically?

Regards,

Shivam