A hierarchy in WLANs

[Varun Reddy]

Hi everyone,

Say I want to have 3 APs serving 60 users, and these APs are in turn wirelessly (Using Wifi) connected to the server. How would I create such a topology? At this moment, I was thinking that 'wifiStaNodes' can represent the users, 'wifiApNodes' can represent the APs, but how do I make these APs relay information to the server through Wifi? This is my attempt: I have created 'wifiAp2Nodes', which is a collection of the APs and the server.

I have attached my code in this thread. I receive the following error:
aborted. cond="!(networkHere == networkThere)", msg="GlobalRouter::ProcessSingleBroadcastLink(): Network number confusion", file=../src/internet/model/global-router-interface.cc, line=852

Thanks,
Varun

[Varun Reddy]

Alright so I've found the source of the problem.

The WiFi stations are installed with the 'StaWifiMac' Mac type:
NetDeviceContainer staDevices;
mac.SetType ("ns3::StaWifiMac","Ssid", SsidValue (ssid),"ActiveProbing", BooleanValue (false));
staDevices = wifi.Install (phy, mac, wifiStaNodes);

The WiFi APs are installed with the 'ApWifiMac' Mac type:
NetDeviceContainer apDevices;
mac.SetType ("ns3::ApWifiMac","Ssid", SsidValue (ssid));
apDevices  = wifi.Install (phy, mac, wifiApNodes);

In my scenario, I'm trying to make the APs act as Stations to another 'superior' AP. I'm guessing this wouldn't be possible?

[Tommaso Pecorella]

Hi,

it is possible, but you need to install multiple Wi-Fi devices on the APs, one to be the AP and one to be the STA for the "upper" level.

T.

[Varun Reddy]

Oh I see. I've tried to do that now, but can't seem to find the cause of the problem. I get the following error message: cond="!(networkHere == networkThere)", msg="GlobalRouter::ProcessSingleBroadcastLink(): Network number confusion", file=../src/internet/model/global-router-interface.cc, line=852
Here is a snippet of my code:

//Topology
// ------> denotes a Wifi Link

u0 u1 u2 .....   ------> AP1
..............
..............   ------> AP2  -----> Server
..............
...u58 u59 u60   ------> AP3   

int nWifi = 60;
int nAP = 3; 

NodeContainer allNodes;

NodeContainer wifiStaNodes; //User Nodes
wifiStaNodes.Create (nWifi);
allNodes.Add (wifiStaNodes);

NodeContainer wifiApNodes ; //Access Points
wifiApNodes.Create (nAP);
allNodes.Add (wifiApNodes);

NodeContainer wifiServer; //Server
wifiServer.Create (1);
allNodes.Add(wifiServer.Get(0));  

YansWifiChannelHelper channel = YansWifiChannelHelper::Default ();
YansWifiPhyHelper phy = YansWifiPhyHelper::Default ();
WifiHelper wifi;
wifi.SetRemoteStationManager ("ns3::ConstantRateWifiManager","DataMode", StringValue("VhtMcs9"), "ControlMode", StringValue("VhtMcs9"));
wifi.SetStandard (WIFI_PHY_STANDARD_80211af);
channel.AddPropagationLoss("ns3::TwoRayGroundPropagationLossModel","Frequency",DoubleValue(300e+06));

//Setting Physical layer parameters for the User Nodes
phy.Set("TxPowerStart",DoubleValue(20)); // 40mW = 16.02dBm
phy.Set("TxPowerEnd",DoubleValue(20));
phy.Set("TxPowerLevels", UintegerValue(1));
phy.Set("TxGain",DoubleValue(0));
phy.Set("RxGain",DoubleValue(-3));
phy.Set("EnergyDetectionThreshold",DoubleValue(-88));
phy.SetChannel (channel.Create ());

WifiMacHelper mac;
Ssid ssid = Ssid ("ns-3-ssid");

NetDeviceContainer staDevices;
mac.SetType ("ns3::StaWifiMac","Ssid", SsidValue (ssid),"ActiveProbing", BooleanValue (false));
staDevices = wifi.Install (phy, mac, wifiStaNodes);

//Setting Physical Layer parameters for Access Points and Server
phy.Set("TxPowerStart",DoubleValue(20)); // 40mW = 16.02dBm
phy.Set("TxPowerEnd",DoubleValue(20));
phy.Set("TxPowerLevels", UintegerValue(1));
phy.Set("TxGain",DoubleValue(30));
phy.Set("RxGain",DoubleValue(0));
phy.Set("EnergyDetectionThreshold",DoubleValue(-78));

NetDeviceContainer apDevices,serverDevice,ap_staDevices;

mac.SetType ("ns3::ApWifiMac","Ssid", SsidValue (ssid));

apDevices      = wifi.Install (phy, mac, wifiApNodes); // The APs
serverDevice   = wifi.Install (phy, mac, wifiServer);  // The Server

mac.SetType ("ns3::StaWifiMac","Ssid", SsidValue (ssid),"ActiveProbing", BooleanValue (false))

ap_staDevices  = wifi.Install (phy, mac, wifiApNodes); // The devices in the APs that are stations to the superior AP

Ptr<BasicEnergySource> energySource = CreateObject<BasicEnergySource>();
Ptr<SimpleDeviceEnergyModel> energyModel = CreateObject<SimpleDeviceEnergyModel>();

energySource->SetInitialEnergy (100);
energyModel->SetEnergySource (energySource);
energySource->AppendDeviceEnergyModel (energyModel);
energyModel->SetCurrentA (20);

// aggregate energy source to node
wifiServer.Get(0)->AggregateObject (energySource);

// Install internet stack
InternetStackHelper stack;
stack.Install (allNodes);

// Install Ipv4 addresses
Ipv4AddressHelper address;
address.SetBase ("10.1.0.0", "255.255.192.0");
address.Assign (staDevices);
address.Assign (apDevices);
address.SetBase ("10.2.0.0", "255.255.192.0");
Ipv4InterfaceContainer serverInterface;
serverInterface = address.Assign (serverDevice);
address.Assign (ap_staDevices);

// Install applications

UdpEchoServerHelper echoServer (9);
ApplicationContainer serverApps = echoServer.Install (wifiServer.Get(0));
serverApps.Start (Seconds (1.0));
serverApps.Stop (Seconds (5.0));
UdpEchoClientHelper echoClient (serverInterface.GetAddress(0), 9);
echoClient.SetAttribute ("MaxPackets", UintegerValue (10));
echoClient.SetAttribute ("Interval", TimeValue (Seconds (3)));
echoClient.SetAttribute ("PacketSize", UintegerValue (1024));
ApplicationContainer clientApps = echoClient.Install (wifiStaNodes);
clientApps.Start (Seconds (2.0));
clientApps.Stop (Seconds (5.0));

Ipv4GlobalRoutingHelper::PopulateRoutingTables ();
Simulator::Stop (Seconds (4.0));

P.S: Could the owner of this google group allow the members to edit their posts? At this moment, it seems like we have to delete the post and re-post it after correcting any errors.

[Tommaso Pecorella]

Hi,

the two "layers" should have different channel number / SSID.

If the error is still there try with ns-3-dev.

T.

PS: I'll ask about doing edits to posts.

[Varun Reddy]

Yes I tried that as well, and still no luck. I was wondering if the problem is because the different devices on the same node might have to be connected in some way? Do I need to modify the routing tables for the APs (the internal routing, between the two devices)?

Thanks,
Varun

[Tommaso Pecorella]

Without the full code it's not really possible to further investigate.

The error should be fixed in ns-3-dev, assuming that you did what I said. However, it is still possible that the bug wasn't fixed for good.

Nevertheless, without full code... 

T.

[Varun Reddy]

Hello,

I have attached a couple of files here. I will continue to look in ns-3-dev for fixes, but as of now I can't seem to find the relevant files.

Thank you,
Varun

[Tommaso Pecorella]

Hi,

let's forget that you should have cleaned the script to be built on a "standard" ns-3 release (you forgot to ad some header files)...

The issue (sorry, I didn't remember correctly) is that you can not have GlobalRouting on the STAs, or you'll end up with a loop.

The "trick" is to have GlobalRouting on the AP, and a StaticRouting only on the STAs. On the STAs you'll have to set a DefaultRoute to the AP. 

In your case, since one AP is also a STA, you'll need to use a little more tricks, basically adding more static routes to the other nodes, just to tell the whole network that the "bottom" network is there.

As a side note, this could be mitigated by DHCP (not yet in ns-3, work in progress), but it is ultimately a GlobalRouting enhancement.

T.

[Tommaso Pecorella]

Oh, I forgot...

when i said to use different channels and SSIDs, I meant one channel and one SSID for each Wi-Fi network. In your script there are 3 APs with the same channel and SSID...

T.

On Sunday, May 7, 2017 at 7:13:12 PM UTC+2, Varun Reddy wrote:

[Varun Reddy]

Ah alright! So it is a problem with the Routing method. I happened to notice some other users faced problems in AODV and OSLR implementations too.

Thanks a lot for your help Tommaso!

Varun