To simulate Orthogonal Frequency Division Multiplexing (OFDM) in NS2 can be difficult because NS2 does not directly support OFDM modulation that is a key technology in wireless communication systems like Wi-Fi (802.11), WiMAX, and 4G LTE. But, we can replicate the core context of OFDM wireless communication by approximating the feature of OFDM over custom models or by using community-developed patches that allow OFDM functionality.
Here’s how we can simulate OFDM Wireless Communication projects using NS2, concentrate on approximating OFDM behaviour, like multi-carrier transmission, high data rates, and wireless channel characteristics.
Key Components for Simulating OFDM in NS2:
- OFDM Modulation: Replicate multi-carrier transmission by adapt the transmission rate, bandwidth, and packet size to signify OFDM.
- Wireless Channel: Replicate the wireless channel with proper propagation models that involves models for multipath fading and interference.
- Access Points and Mobile Nodes: Model wireless communication among access points (APs) and mobile nodes (MNs).
- Traffic Models: Replicate different traffic patterns, like video streaming, VoIP, or data transmission, using proper applications over TCP/UDP.
Steps for Simulating OFDM Wireless Communication in NS2
- Install NS2: initially, make sure that NS2 is installed on the system. We can install it on Linux using:
sudo apt-get install ns2
Validate the installation by typing:
ns -version
- Extend NS2 for OFDM Capabilities: while NS2 does not directly support OFDM modulation, we can estimated OFDM by:
- Custom Scripting: We can adapt performance metrics like bandwidth, packet size, and delay to replicate the high data rates and effectiveness of OFDM systems.
- Using a Propagation Model: establish a propagation model that contain multipath effects and fading that are significant for replicate wireless OFDM systems.
- Create an OFDM Wireless Communication Scenario Using a Tcl Script: The following Tcl script emulate a basic OFDM wireless communication system using high data rates and bandwidth to approximate the features of OFDM.
Example Tcl Script for Simulating OFDM in NS2
# Create a new simulator object
set ns [new Simulator]
# Open trace and NAM files for output
set tracefile [open ofdm_out.tr w]
$ns trace-all $tracefile
set namfile [open ofdm_out.nam w]
$ns namtrace-all-wireless $namfile 500 500
# Define the wireless channel and propagation model for OFDM simulation
set val(chan) Channel/WirelessChannel ;# Wireless channel model for OFDM
set val(prop) Propagation/TwoRayGround ;# TwoRayGround propagation model
set val(netif) Phy/WirelessPhy ;# Wireless PHY layer (approximating OFDM)
set val(mac) Mac/802_11 ;# Wi-Fi MAC layer (approximating OFDM)
set val(ifq) Queue/DropTail/PriQueue ;# Interface Queue
set val(ll) LL ;# Link Layer
set val(ant) Antenna/OmniAntenna ;# Antenna model
set val(ifqlen) 50 ;# Interface Queue length
set val(nn) 3 ;# Number of mobile nodes (MNs and APs)
set val(bw) 20Mb ;# Bandwidth approximating OFDM channel
set val(delay) 2ms ;# Low delay to represent high-speed OFDM systems
set val(x) 500 ;# X dimension of the simulation area
set val(y) 500 ;# Y dimension of the simulation area
# Define the topology object for OFDM wireless communication
set topo [new Topography]
$topo load_flatgrid $val(x) $val(y)
# Configure the nodes for OFDM wireless communication
$ns node-config -llType $val(ll) \
-macType $val(mac) \
-ifqType $val(ifq) \
-ifqLen $val(ifqlen) \
-antType $val(ant) \
-propType $val(prop) \
-phyType $val(netif) \
-channelType $val(chan) \
-topoInstance $topo \
-agentTrace ON \
-routerTrace ON \
-macTrace ON
# Create access point (AP) and mobile nodes (MNs)
set ap [$ns node] ;# Access Point (AP) representing the OFDM transmitter
set mn_0 [$ns node] ;# Mobile Node 0 (OFDM receiver)
set mn_1 [$ns node] ;# Mobile Node 1 (another OFDM receiver)
# Set initial positions for AP and mobile nodes
$ap set X_ 250.0
$ap set Y_ 250.0
$mn_0 set X_ 150.0
$mn_0 set Y_ 200.0
$mn_1 set X_ 350.0
$mn_1 set Y_ 300.0
# Create links between access point and mobile nodes
$ns duplex-link $ap $mn_0 $val(bw) $val(delay) DropTail
$ns duplex-link $ap $mn_1 $val(bw) $val(delay) DropTail
# Define UDP traffic between AP and mobile nodes (approximating OFDM data transmission)
set udp_ap [new Agent/UDP]
$ns attach-agent $ap $udp_ap
set udp_sink_0 [new Agent/Null]
$ns attach-agent $mn_0 $udp_sink_0
set udp_sink_1 [new Agent/Null]
$ns attach-agent $mn_1 $udp_sink_1
# Connect AP to the mobile nodes (MNs)
$ns connect $udp_ap $udp_sink_0
$ns connect $udp_ap $udp_sink_1
# Create CBR (Constant Bit Rate) application to simulate OFDM traffic from AP to MNs
set cbr_ap [new Application/Traffic/CBR]
$cbr_ap set packetSize_ 1024 ;# Larger packet size to represent high OFDM throughput
$cbr_ap set interval_ 0.001 ;# Frequent transmission (high data rate)
$cbr_ap attach-agent $udp_ap
# Schedule the traffic
$ns at 1.0 “$cbr_ap start”
$ns at 5.0 “$cbr_ap stop”
# Simulation ends at 10 seconds
$ns at 10.0 “finish”
# Define the finish procedure to close files and launch NAM
proc finish {} {
global ns tracefile namfile
$ns flush-trace
close $tracefile
close $namfile
exec nam ofdm_out.nam &
exit 0
}
# Run the simulation
$ns run
Explanation of the Tcl Script:
- Simulator Object:
- The set ns [new Simulator] command generates the simulation object.
- Wireless Channel and Propagation Model:
- A wireless channel (Channel/WirelessChannel) is defined to replicate the wireless environment, and the TwoRayGround model is utilized for propagation, approximating real-world wireless conditions.
- Access Point (AP) and Mobile Nodes (MNs):
- The AP act as the OFDM transmitter, since the mobile nodes (mn_0 and mn_1) perform as OFDM receivers.
- UDP Traffic with CBR (Constant Bit Rate):
- UDP agents are attached to replicate the OFDM traffic flow from the AP to the mobile nodes.
- The CBR application design continuous data transmission with large packet sizes and high transmission frequency, replication the high throughput of OFDM systems.
- Simulation End:
- The simulation executes for 10 seconds, after which the finish procedure closes the trace and establish NAM for visualization.
- Running the Simulation:
Save the script as ofdm_simulation.tcl and execute it using NS2:
ns ofdm_simulation.tcl
After the simulation completes, open NAM to envision the network:
nam ofdm_out.nam
- Analysing the Results:
- The trace file (ofdm_out.tr) logs events like packet transmissions, receptions, and packet drops, enabling you to estimate parameters like:
- Throughput
- Latency
- Packet delivery ratio
- Example AWK script to estimate throughput:
BEGIN {
packet_count = 0;
start_time = 0;
end_time = 0;
}
{
if ($1 == “r” && $4 == “AGT”) {
packet_count++;
if (start_time == 0) {
start_time = $2;
}
end_time = $2;
}
}
END {
duration = end_time – start_time;
throughput = (packet_count * 1024 * 8) / (duration * 1000); # kbps
printf(“Throughput: %.2f kbps\n”, throughput);
}
Extending the Simulation:
- Advanced Propagation Models:
- Establish more sophisticated propagation models like Rayleigh fading or Rician fading to replicate multipath effects in OFDM wireless communication.
- Modulation and Coding Techniques:
- Execute custom modules for modulation schemes (such as QAM, PSK) and channel coding (such as convolutional coding, turbo codes) to precisely signify OFDM’s transmission behavior.
- Adaptive OFDM:
- Execute adaptive OFDM by enthusiastically adapting the transmission parameters (such as bandwidth, modulation scheme) in terms of channel conditions.
- Multiple Access in OFDM (OFDMA):
- Replicate OFDMA (Orthogonal Frequency-Division Multiple Access) in which multiple users distribute the same OFDM subcarriers concurrently.
- Mobility Models:
- Establish mobility models for the mobile nodes to replicate real-world mobile wireless communication, like in Wi-Fi or LTE systems.
In this setup simulation, we had successfully and efficiently replicate the Orthogonal Frequency Division Multiplexing in ns2 environment and provide the elaborated procedures to simulate the execution. Additional specific details regarding the Orthogonal Frequency Division Multiplexing project will be shared in upcoming manual. phdprime.com provide extensive information about the OFDM Wireless Communication Projects. Please share your details with us, and we’ll assist you in achieving the best simulation results. Our technical team is here to offer you top-notch guidance on technologies in wireless communication systems, including Wi-Fi (802.11), WiMAX, and 4G LTE.
