How to Implement Frequency Hopping in ns3

To implement frequency hopping in ns3, we need to change the frequency channel dynamically which is used by nodes during the simulation. This is helpful in mitigating interference and improve communication reliability.

Here is a complete guide in implementing frequency hopping in ns3.

Steps for implementation

Step 1: Set up the simulation

Make sure that ns3 is installed in the computer. If not, install it from the official ns3 website.

Step 2: Create a New Simulation Script

In the scratch directory of our ns3, we should create a simulation script. In our example, let’s create a file named frequency_hopping.cc.

Step 3: Include Necessary Headers

Include all the necessary ns3 headers in our script.

#include “ns3/core-module.h”

#include “ns3/network-module.h”

#include “ns3/internet-module.h”

#include “ns3/wifi-module.h”

#include “ns3/mobility-module.h”

#include “ns3/applications-module.h”

using namespace ns3;

Step 4: Define Command-Line Arguments for Parameterization

Define parameters that can be set through the command line.

int main(int argc, char *argv[])

{

uint32_t numNodes = 2;

double simTime = 10.0;

double hopInterval = 1.0; // Interval in seconds for frequency hopping

CommandLine cmd;

cmd.AddValue(“numNodes”, “Number of nodes”, numNodes);

cmd.AddValue(“simTime”, “Simulation time (seconds)”, simTime);

cmd.AddValue(“hopInterval”, “Frequency hopping interval (seconds)”, hopInterval);

cmd.Parse(argc, argv);

NodeContainer nodes;

nodes.Create(numNodes);

YansWifiChannelHelper wifiChannel = YansWifiChannelHelper::Default();

YansWifiPhyHelper wifiPhy = YansWifiPhyHelper::Default();

wifiPhy.SetChannel(wifiChannel.Create());

WifiHelper wifi;

wifi.SetStandard(WIFI_STANDARD_80211n);

WifiMacHelper wifiMac;

wifiMac.SetType(“ns3::AdhocWifiMac”);

NetDeviceContainer devices = wifi.Install(wifiPhy, wifiMac, nodes);

MobilityHelper mobility;

mobility.SetMobilityModel(“ns3::ConstantPositionMobilityModel”);

mobility.Install(nodes);

InternetStackHelper stack;

stack.Install(nodes);

Ipv4AddressHelper address;

address.SetBase(“10.1.1.0”, “255.255.255.0”);

Ipv4InterfaceContainer interfaces = address.Assign(devices);

// Install applications

uint16_t port = 9;

OnOffHelper onoff(“ns3::UdpSocketFactory”, Address(InetSocketAddress(interfaces.GetAddress(numNodes-1), port)));

onoff.SetConstantRate(DataRate(“500kbps”));

ApplicationContainer apps = onoff.Install(nodes.Get(0));

apps.Start(Seconds(1.0));

apps.Stop(Seconds(simTime));

PacketSinkHelper sink(“ns3::UdpSocketFactory”, Address(InetSocketAddress(Ipv4Address::GetAny(), port)));

apps = sink.Install(nodes.Get(numNodes-1));

apps.Start(Seconds(0.0));

apps.Stop(Seconds(simTime));

// Implement frequency hopping

for (uint32_t i = 0; i < numNodes; ++i)

{

Simulator::ScheduleWithContext(nodes.Get(i)->GetId(), Seconds(hopInterval), &ChangeFrequency, devices.Get(i), hopInterval);

}

Simulator::Stop(Seconds(simTime));

Simulator::Run();

Simulator::Destroy();

return 0;

}

Step 5: Implement the Frequency Hopping Function

Change the frequency channel of the nodes periodically by implementing a function.

void ChangeFrequency(Ptr<NetDevice> device, double hopInterval)

{

Ptr<WifiNetDevice> wifiDevice = DynamicCast<WifiNetDevice>(device);

Ptr<WifiPhy> wifiPhy = wifiDevice->GetPhy();

static uint32_t currentChannel = 1;

currentChannel = (currentChannel % 11) + 1; // Assuming 11 channels

wifiPhy->SetChannelNumber(currentChannel);

NS_LOG_UNCOND(“Node ” << device->GetNode()->GetId() << ” changed to channel ” << currentChannel);

// Schedule the next frequency change

Simulator::Schedule(Seconds(hopInterval), &ChangeFrequency, device, hopInterval);

}

Step 6: Compile and Run Your Simulation

Compile your simulation script using waf:

./waf configure

./waf build

./waf –run scratch/frequency_hopping

Step 7: Analyze the Output

To ensure that the nodes are changing frequency channels at the specified intervals, analyze the log output.

Overall, we had an analysis on the implementation of frequency hopping using ns3 by changing the frequency channel dynamically which is used by nodes during the simulation

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