wifi interference question

[minkyung park]

 Hello, I have a question.

I built a building, and put all nodes inside the building.

This is my topology. (There are N APs, and all APs and a source device are connected with each other (CSMA))

    AP1         AP2      ...       APn (802.11n wifi)

     |               |                     |

     --------------------------------------(CSMA channel)

        |

    source device

Source sends packets to the broadcast address. As soon as AP receives the packets, they forward the packets to connected stations.

 -->I used " Config::Connect ("/NodeList/APnodes/DeviceList/*/$ns3::CsmaNetDevice/MacRx", MakeBoundCallback (&PacketUpdate, recvSinkAp)); " (in PacketUpdate function)

I measured the throughput (like packet loss, data rate).

I thought that if the number of APs are increase, then the throughput would decrease, but didn't (it was not that different).

(I measured 1 APs, 2APs, 4APs, 8APs scenario)

I think it's because ns-3 does't support inter-channel interference, right?

Or i did something wrong?

[minkyung park]

 Sorry, and thanks for reply

I referenced "wifi-simple-interference.cc" example

I created UDP sockets in every node, and Source device(in topology) send packets to broadcast (AP1, ... APn receives it) using Simulator::Schedule. (every 1seconds interval )

a packet size is 2048, max packets size is 6MB.

these are part of my code

 81 static void GenerateTraffic (Ptr<Socket> socket, uint32_t pktSize,

 82         uint32_t totalPacketBytes, Time pktInterval )

 83 {

 87         if(totalPacketBytes <= pktSize){

 88             pktSize = totalPacketBytes;

 89             socket->Send (Create<Packet>(pktSize-32));

 90             totalPacketBytes -= pktSize;

 92         }

 93         else{

 94             socket->Send (Create<Packet>(pktSize-32));

 95             totalPacketBytes -= pktSize;

 97             Simulator::Schedule (pktInterval, &GenerateTraffic,

 98                     socket, pktSize, totalPacketBytes, pktInterval);

 99         }

.~~~~~

int main(){

~~~~~~ 

230     WifiHelper wifi = WifiHelper::Default ();

231     if(is5GHz)

232         wifi.SetStandard (WIFI_PHY_STANDARD_80211n_5GHZ);

233     else

234         wifi.SetStandard (WIFI_PHY_STANDARD_80211n_2_4GHZ);

235 

236     YansWifiChannelHelper channel = YansWifiChannelHelper::Default ();

237     channel.SetPropagationDelay ("ns3::ConstantSpeedPropagationDelayModel");

238 

239     YansWifiPhyHelper phy = YansWifiPhyHelper::Default ();

240     HtWifiMacHelper mac = HtWifiMacHelper::Default();

241 

245     Ptr<YansWifiChannel> channelNum[nAp];

246     Ssid ssid = Ssid ("wifi-ssid");

247     for(uint32_t i=0; i<nAp; i++){

248         channelNum[i] = channel.Create ();

249 

250         //set AP

251         phy.SetChannel (channelNum[i]);

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

253         wifi.SetRemoteStationManager ("ns3::ConstantRateWifiManager", "DataMode", DataRate,

254                 "ControlMode", DataRate);

255 

256         apDevices.Add(wifi.Install (phy, mac, wifiApNodes.Get(i)));

257     }

.

.

.~~~

373     Ptr<Socket> source = Socket::CreateSocket (sourceNodes.Get(0), tid);

374     source->SetAllowBroadcast (true);

375 

376     Ipv4Address broadcastAddr = Ipv4Address("10.1.1.1").GetSubnetDirectedBroadcast("/24");

377     InetSocketAddress remote = InetSocketAddress (broadcastAddr, 7778);

378     source->Connect (remote);

402     Simulator::Schedule (Seconds (0.0), &GenerateTraffic,

403             source, packetSize, totalPacketBytes, interPacketInterval);

404 

2015년 3월 13일 금요일 오후 4시 9분 52초 UTC+9, Tommaso Pecorella 님의 말:

Too few info to not say anything plainly obvious.

T.

[Tommaso Pecorella]

Been there, done that, discussed this topic too many times.

You're using a different channel instance for each AP. No interference is possible with this configuration.

T.

[Tommaso Pecorella]

Too few info to not say anything plainly obvious.

T.

On Friday, March 13, 2015 at 6:37:06 AM UTC+1, minkyung park wrote:

[Hendro Jio]

so.. Did NS3 can modelling the interference between 2 AP or more in same (overlapping) channel?

[Tommaso Pecorella]

Yes, with the SpectrumWifiPhy.

See examples//wireless/wifi-spectrum-per-example.cc

T.

[Con con]

Hello Tommaso,

I have written a simulation which is one AP and 4 wifi devices, which is more or less similar to /wifi-spectrum-per-example.cc. I did not used SpectrumWifiPhy but I used MonitorSnifferTx and YansWifiPhyRxDrop and compare the total packets transmitted to packets received so I calculate the interference. Do I have to use SpectrumWifiPhy  for this reason ?

thanks.

best regards!

[Con con]

The actual question here is : what is the difference between 
SpectrumWifiPhy and YansWifiPhy ?

thanks

[Tommaso Pecorella]

Hi,

the actual differences are:

1) SpectrumWifiPhy is slower.

2) SpectrumWifiPhy allows to calculate the interference between Wi-Fi and other technologies using the same frequencies (e.g., LTE-LAA and 802.15.4).

If you only have Wi-Fi, then YansWifiPhy is a good choice.

T.

[Con con]

Hello Tommaso,

I am interested in the second point 

2) SpectrumWifiPhy allows to calculate the interference between Wi-Fi and other technologies using the same frequencies (e.g., LTE-LAA and 802.15.4).

Is there any example, or how can I implement that ? I mean interference between 802.11 and 802.15.4. 

thanks!

[Con con]

Hello Tomasso,

I have attached an example which is one AP and multiple wifi nodes. I tried to find out how to measure interference between nodes of this example but it is not clear for me. 

I tried also to create another AP a different one with different ip and clients connected to that in the same channel expecting to see that throughput is decreased due to interference but with no success. The question is how can I add another ap in the same channel, and another AP in different channel which also may cause interference. ?? I am trying to find out this problem long time ago with no success. 

Thanks for help.