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How to Implement Coexistence of OFDMA in ns3

To implement coexistence of OFDMA(Orthogonal Frequency Division Multiple Access) in ns3, we need to simulate scenarios where different networks (such as Wi-Fi and LTE) share the same frequency spectrum. This permits us to study how these networks coexist and how interference and resource allocation are managed.

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Here is a complete guide to implement this.

Steps for implementation

Step 1: Set up the simulation

  • Download and install ns3 : Make sure that ns3 is installed in the computer. If not, install it from the official ns3 website.
  • Ensure ns3 supports necessary modules: Ensure that your installation supports Wi-Fi and LTE modules.

Step 2: Create the network topology

Define a network topology that involves Wi-Fi and LTE base stations and user equipment (UE) nodes.

Create OFDMA Coexistence topology

#include “ns3/core-module.h”

#include “ns3/network-module.h”

#include “ns3/internet-module.h”

#include “ns3/point-to-point-module.h”

#include “ns3/lte-module.h”

#include “ns3/wifi-module.h”

#include “ns3/mobility-module.h”

#include “ns3/applications-module.h”

using namespace ns3;

NS_LOG_COMPONENT_DEFINE(“OFDMA_Coexistence_Simulation”);

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

{

CommandLine cmd;

cmd.Parse(argc, argv);

// Create nodes

NodeContainer ueNodes;

ueNodes.Create(10); // User equipment (UE) nodes

NodeContainer lteEnbNodes;

lteEnbNodes.Create(1); // LTE eNB (base station) node

NodeContainer wifiApNodes;

wifiApNodes.Create(1); // Wi-Fi AP node

NodeContainer pgwNode;

pgwNode.Create(1); // Packet Gateway node

// Set up LTE

Ptr<LteHelper> lteHelper = CreateObject<LteHelper>();

Ptr<PointToPointEpcHelper> epcHelper = CreateObject<PointToPointEpcHelper>();

lteHelper->SetEpcHelper(epcHelper);

InternetStackHelper internet;

internet.Install(pgwNode);

internet.Install(ueNodes);

Ptr<Node> pgw = epcHelper->GetPgwNode();

// Set up LTE network

NetDeviceContainer lteEnbDevs = lteHelper->InstallEnbDevice(lteEnbNodes);

NetDeviceContainer lteUeDevs = lteHelper->InstallUeDevice(ueNodes);

for (uint32_t i = 0; i < ueNodes.GetN(); ++i)

{

lteHelper->Attach(lteUeDevs.Get(i), lteEnbDevs.Get(0));

}

Ipv4InterfaceContainer lteUeIpIface;

lteUeIpIface = epcHelper->AssignUeIpv4Address(NetDeviceContainer(lteUeDevs));

// Set up Wi-Fi network

YansWifiChannelHelper wifiChannel = YansWifiChannelHelper::Default();

YansWifiPhyHelper wifiPhy = YansWifiPhyHelper::Default();

wifiPhy.SetChannel(wifiChannel.Create());

WifiHelper wifi;

wifi.SetRemoteStationManager(“ns3::AarfWifiManager”);

WifiMacHelper wifiMac;

Ssid ssid = Ssid(“ns3-ssid”);

wifiMac.SetType(“ns3::StaWifiMac”, “Ssid”, SsidValue(ssid), “ActiveProbing”, BooleanValue(false));

NetDeviceContainer wifiStaDevs = wifi.Install(wifiPhy, wifiMac, ueNodes);

wifiMac.SetType(“ns3::ApWifiMac”, “Ssid”, SsidValue(ssid));

NetDeviceContainer wifiApDevs = wifi.Install(wifiPhy, wifiMac, wifiApNodes);

// Assign IP addresses to Wi-Fi devices

Ipv4AddressHelper address;

address.SetBase(“192.168.1.0”, “255.255.255.0”);

Ipv4InterfaceContainer wifiInterfaces = address.Assign(wifiStaDevs);

wifiInterfaces.Add(address.Assign(wifiApDevs));

// Set up mobility

MobilityHelper mobility;

mobility.SetPositionAllocator(“ns3::GridPositionAllocator”,

“MinX”, DoubleValue(0.0),

“MinY”, DoubleValue(0.0),

“DeltaX”, DoubleValue(5.0),

“DeltaY”, DoubleValue(10.0),

“GridWidth”, UintegerValue(3),

“LayoutType”, StringValue(“RowFirst”));

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

mobility.Install(lteEnbNodes);

mobility.Install(wifiApNodes);

mobility.SetMobilityModel(“ns3::RandomWalk2dMobilityModel”,

“Bounds”, RectangleValue(Rectangle(-50, 50, -50, 50)));

mobility.Install(ueNodes);

// Install and start applications on UEs

uint16_t dlPort = 1234;

ApplicationContainer clientApps, serverApps;

for (uint32_t i = 0; i < ueNodes.GetN(); ++i)

{

UdpClientHelper dlClient(lteUeIpIface.GetAddress(i), dlPort);

dlClient.SetAttribute(“Interval”, TimeValue(MilliSeconds(100)));

dlClient.SetAttribute(“MaxPackets”, UintegerValue(1000));

clientApps.Add(dlClient.Install(pgwNode.Get(0)));

UdpServerHelper dlServer(dlPort);

serverApps.Add(dlServer.Install(ueNodes.Get(i)));

}

serverApps.Start(Seconds(0.01));

clientApps.Start(Seconds(0.01));

// Enable tracing

lteHelper->EnableTraces();

wifiPhy.EnablePcap(“wifi”, wifiApDevs.Get(0));

Simulator::Run();

Simulator::Destroy();

return 0;

}

Step 3: Configure Mobility

To simulate realistic scenarios where UEs can move between different network technologies, set up mobility models.

// Set up mobility

MobilityHelper mobility;

mobility.SetPositionAllocator(“ns3::GridPositionAllocator”,

“MinX”, DoubleValue(0.0),

“MinY”, DoubleValue(0.0),

“DeltaX”, DoubleValue(5.0),

“DeltaY”, DoubleValue(10.0),

“GridWidth”, UintegerValue(3),

“LayoutType”, StringValue(“RowFirst”));

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

mobility.Install(lteEnbNodes);

mobility.Install(wifiApNodes);

mobility.SetMobilityModel(“ns3::RandomWalk2dMobilityModel”,

“Bounds”, RectangleValue(Rectangle(-50, 50, -50, 50)));

mobility.Install(ueNodes);

Step 4: Implement Coexistence Mechanisms

Handling coexistence of OFDMA between LTE and Wi-Fi involves ensuring that they share the spectrum without causing significant interference to each other. One approach is to use listen-before-talk (LBT) mechanisms or dynamically adjust the power and frequency used by the networks.

Step 5: Enable Tracing

To analyze the network performance and coexistence, enable tracing.

// Enable tracing

lteHelper->EnableTraces();

wifiPhy.EnablePcap(“wifi”, wifiApDevs.Get(0));

Complete Example Code

Here is an example code by combining all the steps

#include “ns3/core-module.h”

#include “ns3/network-module.h”

#include “ns3/internet-module.h”

#include “ns3/point-to-point-module.h”

#include “ns3/lte-module.h”

#include “ns3/wifi-module.h”

#include “ns3/mobility-module.h”

#include “ns3/applications-module.h”

using namespace ns3;

NS_LOG_COMPONENT_DEFINE(“OFDMA_Coexistence_Simulation”);

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

{

CommandLine cmd;

cmd.Parse(argc, argv);

// Create nodes

NodeContainer ueNodes;

ueNodes.Create(10); // User equipment (UE) nodes

NodeContainer lteEnbNodes;

lteEnbNodes.Create(1); // LTE eNB (base station) node

NodeContainer wifiApNodes;

wifiApNodes.Create(1); // Wi-Fi AP node

NodeContainer pgwNode;

pgwNode.Create(1); // Packet Gateway node

// Set up LTE

Ptr<LteHelper> lteHelper = CreateObject<LteHelper>();

Ptr<PointToPointEpcHelper> epcHelper = CreateObject<PointToPointEpcHelper>();

lteHelper->SetEpcHelper(epcHelper);

InternetStackHelper internet;

internet.Install(pgwNode);

internet.Install(ueNodes);

Ptr<Node> pgw = epcHelper->GetPgwNode();

// Set up LTE network

NetDeviceContainer lteEnbDevs = lteHelper->InstallEnbDevice(lteEnbNodes);

NetDeviceContainer lteUeDevs = lteHelper->InstallUeDevice(ueNodes);

for (uint32_t i = 0; i < ueNodes.GetN(); ++i)

{

lteHelper->Attach(lteUeDevs.Get(i), lteEnbDevs.Get(0));

}

Ipv4InterfaceContainer lteUeIpIface;

lteUeIpIface = epcHelper->AssignUeIpv4Address(NetDeviceContainer(lteUeDevs));

// Set up Wi-Fi network

YansWifiChannelHelper wifiChannel = YansWifiChannelHelper::Default();

YansWifiPhyHelper wifiPhy = YansWifiPhyHelper::Default();

wifiPhy.SetChannel(wifiChannel.Create());

WifiHelper wifi;

wifi.SetRemoteStationManager(“ns3::AarfWifiManager”);

WifiMacHelper wifiMac;

Ssid ssid = Ssid(“ns3-ssid”);

wifiMac.SetType(“ns3::StaWifiMac”, “Ssid”, SsidValue(ssid), “ActiveProbing”, BooleanValue(false));

NetDeviceContainer wifiStaDevs = wifi.Install(wifiPhy, wifiMac, ueNodes);

wifiMac.SetType(“ns3::ApWifiMac”, “Ssid”, SsidValue(ssid));

NetDeviceContainer wifiApDevs = wifi.Install(wifiPhy, wifiMac, wifiApNodes);

// Assign IP addresses to Wi-Fi devices

Ipv4AddressHelper address;

address.SetBase(“192.168.1.0”, “255.255.255.0”);

Ipv4InterfaceContainer wifiInterfaces = address.Assign(wifiStaDevs);

wifiInterfaces.Add(address.Assign(wifiApDevs));

// Set up mobility

MobilityHelper mobility;

mobility.SetPositionAllocator(“ns3::GridPositionAllocator”,

“MinX”, DoubleValue(0.0),

“MinY”, DoubleValue(0.0),

“DeltaX”, DoubleValue(5.0),

“DeltaY”, DoubleValue(10.0),

“GridWidth”, UintegerValue(3),

“LayoutType”, StringValue(“RowFirst”));

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

mobility.Install(lteEnbNodes);

mobility.Install(wifiApNodes);

mobility.SetMobilityModel(“ns3::RandomWalk2dMobilityModel”,

“Bounds”, RectangleValue(Rectangle(-50, 50, -50, 50)));

mobility.Install(ueNodes);

// Install and start applications on UEs

uint16_t dlPort = 1234;

ApplicationContainer clientApps, serverApps;

for (uint32_t i = 0; i < ueNodes.GetN(); ++i)

{

UdpClientHelper dlClient(lteUeIpIface.GetAddress(i), dlPort);

dlClient.SetAttribute(“Interval”, TimeValue(MilliSeconds(100)));

dlClient.SetAttribute(“MaxPackets”, UintegerValue(1000));

clientApps.Add(dlClient.Install(pgwNode.Get(0)));

UdpServerHelper dlServer(dlPort);

serverApps.Add(dlServer.Install(ueNodes.Get(i)));

}

serverApps.Start(Seconds(0.01));

clientApps.Start(Seconds(0.01));

// Enable tracing

lteHelper->EnableTraces();

wifiPhy.EnablePcap(“wifi”, wifiApDevs.Get(0));

Simulator::Run();

Simulator::Destroy();

return 0;

}

Overall, we had an analysis on the implementation of coexistence of OFDMA using ns3 by simulating scenarios where different networks share the same frequency spectrum.