To Simulate Orthogonal Frequency Division Multiplexing (OFDM) wireless communication projects in NS3 have includes to configure a wireless network in which the OFDM is the underlying modulation scheme for routed the data. OFDM is broadly used in modern communication systems that contain LTE, Wi-Fi (802.11a/g/n/ac/ax), and 5G. In NS3, OFDM-based communication can be replicated using existing wireless modules like Wi-Fi, LTE, and mmWave.
Here’s a step-by-step guide to simulate an OFDM-based wireless communication project using Wi-Fi (802.11) and LTE modules, as both use OFDM for communication.
Step-by-Step Implementation
- Install NS3
Make sure that NS3 is installed with support for the Wi-Fi and LTE modules. We can validate if these modules are available by running:
./waf list-modules
Look for wifi, lte, or mmwave in the list of available modules.
- Simulating OFDM with Wi-Fi (802.11)
Wi-Fi standards like 802.11a/g/n/ac/ax use OFDM for data transmission. NS3 supports these standards, enables to replicate an OFDM-based Wi-Fi network.
Example Code for Simulating OFDM with Wi-Fi:
#include “ns3/core-module.h”
#include “ns3/network-module.h”
#include “ns3/internet-module.h”
#include “ns3/mobility-module.h”
#include “ns3/wifi-module.h”
#include “ns3/applications-module.h”
#include “ns3/flow-monitor-module.h”
using namespace ns3;
NS_LOG_COMPONENT_DEFINE (“OFDMWiFiSimulation”);
int main (int argc, char *argv[])
{
// Set up command-line arguments
CommandLine cmd;
cmd.Parse (argc, argv);
// Create two nodes: one AP and one client
NodeContainer wifiApNode;
wifiApNode.Create (1); // Access point
NodeContainer wifiStaNodes;
wifiStaNodes.Create (1); // Station (client)
// Set up Wi-Fi PHY and MAC layers using 802.11ac (OFDM-based)
WifiHelper wifi;
wifi.SetStandard (WIFI_PHY_STANDARD_80211ac); // Using 802.11ac for OFDM
YansWifiPhyHelper wifiPhy = YansWifiPhyHelper::Default ();
YansWifiChannelHelper wifiChannel = YansWifiChannelHelper::Default ();
wifiPhy.SetChannel (wifiChannel.Create ());
WifiMacHelper wifiMac;
Ssid ssid = Ssid (“ns3-80211-OFDM”);
wifiMac.SetType (“ns3::StaWifiMac”, “Ssid”, SsidValue (ssid), “ActiveProbing”, BooleanValue (false));
// Install Wi-Fi devices on the station (client)
NetDeviceContainer staDevices;
staDevices = wifi.Install (wifiPhy, wifiMac, wifiStaNodes);
// Configure AP (Access Point)
wifiMac.SetType (“ns3::ApWifiMac”, “Ssid”, SsidValue (ssid));
NetDeviceContainer apDevices;
apDevices = wifi.Install (wifiPhy, wifiMac, wifiApNode);
// Set up mobility models
MobilityHelper mobility;
mobility.SetPositionAllocator (“ns3::GridPositionAllocator”,
“MinX”, DoubleValue (0.0),
“MinY”, DoubleValue (0.0),
“DeltaX”, DoubleValue (5.0),
“DeltaY”, DoubleValue (5.0),
“GridWidth”, UintegerValue (1),
“LayoutType”, StringValue (“RowFirst”));
mobility.SetMobilityModel (“ns3::ConstantPositionMobilityModel”);
mobility.Install (wifiApNode);
mobility.Install (wifiStaNodes);
// Install the Internet stack
InternetStackHelper stack;
stack.Install (wifiApNode);
stack.Install (wifiStaNodes);
// Assign IP addresses
Ipv4AddressHelper ipv4;
ipv4.SetBase (“192.168.1.0”, “255.255.255.0”);
Ipv4InterfaceContainer apInterface = ipv4.Assign (apDevices);
Ipv4InterfaceContainer staInterface = ipv4.Assign (staDevices);
// Set up UDP server and client (representing data transmission)
UdpEchoServerHelper echoServer (9);
ApplicationContainer serverApp = echoServer.Install (wifiApNode.Get (0));
serverApp.Start (Seconds (1.0));
serverApp.Stop (Seconds (10.0));
UdpEchoClientHelper echoClient (apInterface.GetAddress (0), 9);
echoClient.SetAttribute (“MaxPackets”, UintegerValue (1000));
echoClient.SetAttribute (“Interval”, TimeValue (Seconds (0.1)));
echoClient.SetAttribute (“PacketSize”, UintegerValue (1024));
ApplicationContainer clientApp = echoClient.Install (wifiStaNodes.Get (0));
clientApp.Start (Seconds (2.0));
clientApp.Stop (Seconds (10.0));
// Enable PCAP tracing for Wi-Fi (OFDM)
wifiPhy.EnablePcapAll (“ofdm-wifi”);
// Enable FlowMonitor for performance analysis
FlowMonitorHelper flowmon;
Ptr<FlowMonitor> monitor = flowmon.InstallAll ();
// Run the simulation
Simulator::Run ();
// Print flow monitor statistics
monitor->SerializeToXmlFile (“ofdm-wifi-flowmon.xml”, true, true);
Simulator::Destroy ();
return 0;
}
Explanation of Code:
- OFDM-Based Wi-Fi (802.11ac): The code utilizes the WIFI_PHY_STANDARD_80211ac standard that is based on OFDM.
- Node Setup: One Access Point (AP) and one Station (STA) are generated for communication.
- Mobility: The mobility of nodes is set using a simple grid-based allocation, with both AP and STA being stationary.
- Application Layer: A simple UDP echo server-client model is utilized to mimic the data transmission.
- Performance Monitoring: The FlowMonitor tool is used to measure the parameters such as throughput, delay, and packet loss. PCAP tracing is also enabled for detailed analysis of packet-level behavior.
- Simulating OFDM with LTE
NS3’s LTE module mimics 4G cellular networks, in which OFDM is used for the downlink and SC-FDMA (Single Carrier Frequency Division Multiple Access) for the uplink. LTE deliver more advanced features for replicating OFDM-based communication in a cellular environment.
Example Code for Simulating OFDM with LTE:
#include “ns3/core-module.h”
#include “ns3/network-module.h”
#include “ns3/internet-module.h”
#include “ns3/mobility-module.h”
#include “ns3/lte-module.h”
#include “ns3/applications-module.h”
using namespace ns3;
NS_LOG_COMPONENT_DEFINE (“OFDM_LTE_Simulation”);
int main (int argc, char *argv[])
{
CommandLine cmd;
cmd.Parse (argc, argv);
// Create the LTE helper
Ptr<LteHelper> lteHelper = CreateObject<LteHelper> ();
Ptr<PointToPointEpcHelper> epcHelper = CreateObject<PointToPointEpcHelper> ();
lteHelper->SetEpcHelper (epcHelper);
// Create nodes: one eNodeB and two UEs
NodeContainer enbNodes;
enbNodes.Create (1); // One base station (eNodeB)
NodeContainer ueNodes;
ueNodes.Create (2); // Two user equipment (UEs)
// Set mobility for eNodeB and UEs
MobilityHelper mobility;
mobility.SetMobilityModel (“ns3::ConstantPositionMobilityModel”);
mobility.Install (enbNodes);
mobility.SetMobilityModel (“ns3::ConstantPositionMobilityModel”);
mobility.Install (ueNodes);
// Install LTE devices on the nodes
NetDeviceContainer enbLteDevs = lteHelper->InstallEnbDevice (enbNodes);
NetDeviceContainer ueLteDevs = lteHelper->InstallUeDevice (ueNodes);
// Attach UEs to eNodeB
lteHelper->Attach (ueLteDevs, enbLteDevs.Get (0));
// Install Internet stack on UEs
InternetStackHelper internet;
internet.Install (ueNodes);
// Assign IP addresses to UEs
Ipv4AddressHelper ipv4;
ipv4.SetBase (“7.0.0.0”, “255.0.0.0”);
Ipv4InterfaceContainer ueIpIface;
ueIpIface = epcHelper->AssignUeIpv4Address (NetDeviceContainer (ueLteDevs));
// Set up an application (UDP) on one of the UEs
uint16_t dlPort = 10000;
UdpClientHelper dlClient (ueIpIface.GetAddress (0), dlPort);
dlClient.SetAttribute (“MaxPackets”, UintegerValue (1000));
dlClient.SetAttribute (“Interval”, TimeValue (Seconds (0.1)));
dlClient.SetAttribute (“PacketSize”, UintegerValue (1024));
ApplicationContainer clientApps = dlClient.Install (ueNodes.Get (1));
clientApps.Start (Seconds (2.0));
clientApps.Stop (Seconds (10.0));
UdpServerHelper dlPacketSinkHelper (dlPort);
ApplicationContainer serverApps = dlPacketSinkHelper.Install (ueNodes.Get (0));
serverApps.Start (Seconds (1.0));
serverApps.Stop (Seconds (10.0));
// Enable PCAP tracing
lteHelper->EnablePcapAll (“ofdm-lte”);
// Run the simulation
Simulator::Run ();
Simulator::Destroy ();
return 0;
}
Explanation of Code:
- LTE Setup: The code configures an eNodeB (base station) and two User Equipments (UEs) for LTE communication.
- OFDM in LTE: LTE utilizes OFDM for the downlink, and this is systematically simulated using the NS3 LTE module.
- Mobility: Both the eNodeB and UEs are stationary in this setup; however we can easily change this by implementing different mobility models.
- Application Layer: A UDP client-server application is utilized to mimic data transmission from one UE to another.
- Analysing Performance in OFDM-based Simulations
For both Wi-Fi and LTE simulations, we can measure parameters such as:
- Throughput: Evaluate on how much data is successfully transmitted.
- Latency: Time taken for packets to travel from the sender to the receiver.
- Packet Loss: Count the number of packets dropped in the course of transmission.
- Signal-to-Noise Ratio (SNR): measure the effects of channel conditions on the performance.
- Using mmWave for OFDM
If you are interested in replicating OFDM for 5G networks that utilize millimeter waves (mmWave), NS3 has an mmWave module. This module supports 5G and contains an advanced OFDM-based communication, enabling for high-frequency, high-bandwidth simulations.
You can install and utilize the mmWave module in NS3 by following its setup guide and process the example simulations for 5G.
In the end of the simulation, we completely learn how to simulate and execute the OFDM wireless communication that was successfully executed in ns3 tool. More information regarding the OFDM wireless communication will also be provided.
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