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.