To simulate Telecommunication Projects using NS2 has includes generating a network setting which implement the real-world telecommunication systems like cellular networks, VoIP, multimedia streaming, and other kinds of data communication. We can design these systems using NS2 by setting up wired and wireless communication, transport protocols, traffic models, and mobility patterns.
Here is a step-by-step guide to simulate Telecommunication Projects in NS2.
Steps for Simulating Telecommunication Projects in NS2
- Install NS2: Install NS2 on a Linux system, as NS2 is best supported on Linux. We can install it using the following command:
sudo apt-get install ns2
- Understand the NS2 Structure: NS2 utilizes Tcl (Tool Command Language) to describe the simulation scenarios, contain network topologies, protocols, and traffic patterns. The key elements for telecommunication simulation in NS2 include:
- Wired and Wireless Channels: Depending on the project, we need to utilize wired (e.g., optical fiber or DSL) or wireless channels (e.g., Wi-Fi, cellular).
- Nodes: it denotes the network devices (like routers, base stations, mobile nodes).
- Traffic Models: Different traffic sources (such as VoIP, multimedia, HTTP, FTP) replicate real-world communication patterns.
- Routing Protocols: we need to utilize static routing, dynamic routing, or ad-hoc routing relay on your network type.
- Create a Telecommunication Network Scenario Using Tcl Script: Below is an instance Tcl script for replicating a VoIP (Voice over IP) telecommunication scenario, in which the voice traffic is replicated over a network using UDP.
Example Tcl Script for a VoIP Telecommunication Network Simulation:
# Create a new simulator object
set ns [new Simulator]
# Open trace and NAM files for logging
set tracefile [open voip_out.tr w]
$ns trace-all $tracefile
set namfile [open voip_out.nam w]
$ns namtrace-all $namfile
# Create the topology: two routers connected by a high-bandwidth link
set router1 [$ns node]
set router2 [$ns node]
$ns duplex-link $router1 $router2 100Mb 10ms DropTail
# Create two hosts: one for VoIP sender and one for receiver
set voip_sender [$ns node]
set voip_receiver [$ns node]
# Connect VoIP sender to router1 and receiver to router2
$ns duplex-link $voip_sender $router1 10Mb 5ms DropTail
$ns duplex-link $router2 $voip_receiver 10Mb 5ms DropTail
# Configure VoIP sender: UDP traffic over RTP (Real-Time Protocol)
set udp [new Agent/UDP]
$ns attach-agent $voip_sender $udp
# VoIP receiver: Null agent to receive packets
set null [new Agent/Null]
$ns attach-agent $voip_receiver $null
# Connect UDP to Null (VoIP data flow)
$ns connect $udp $null
# Create a traffic source for VoIP simulation using RTP
set rtp [new Application/Traffic/CBR]
$rtp set packetSize_ 160
$rtp set interval_ 0.02 ;# 20ms packet interval for voice
$rtp attach-agent $udp
# Schedule VoIP traffic to start and stop
$ns at 1.0 “$rtp start”
$ns at 10.0 “$rtp stop”
# Define finish procedure to end the simulation
proc finish {} {
global ns tracefile namfile
$ns flush-trace
close $tracefile
close $namfile
exec nam voip_out.nam &
exit 0
}
# Schedule the simulation to end after VoIP traffic stops
$ns at 11.0 “finish”
# Run the simulation
$ns run
Explanation of the Tcl Script:
- Simulator Object:
- The set ns [new Simulator] command starts the NS2 simulation engine.
- Trace and NAM Files:
- Simulation events are logged in a trace file (voip_out.tr), and the network animation is saved in a NAM (Network Animator) file (voip_out.nam).
- Network Topology:
- The network consists of two routers (router1 and router2), each associated to a host (voip_sender and voip_receiver) using duplex links with a bandwidth of 10Mbps and delay of 5ms.
- The link among the routers simulates a high-bandwidth backbone with 100Mbps and 10ms delay.
- Traffic Model (VoIP over UDP):
- VoIP traffic is designed using UDP as the transport protocol.
- A CBR (Constant Bit Rate) application is utilized to replicate real-time VoIP traffic. The packets are 160 bytes in size (which approximates an RTP voice packet), and the traffic is sent every 20ms (50 packets per second).
- Traffic Flow:
- The UDP agent attached to the VoIP sender transmits traffic to the Null agent on the receiver. The Null agent is utilized because it doesn’t create responses, simulating a simple VoIP environment.
- Start and Stop of VoIP Traffic:
- VoIP traffic begins at 1 second and terminates at 10 seconds. The simulation stop at 11 seconds.
- Running the Simulation:
Save the script as voip_simulation.tcl and execute it using NS2:
ns voip_simulation.tcl
After the simulation completes, view the animation using NAM:
nam voip_out.nam
- Analysing the Results:
- The trace file (voip_out.tr) comprises thorough information about packet transmission, packet drops, routing decisions, delays, etc. we need to utilize this trace file to estimate the significant parametric such as:
- Packet loss: Evaluate on how many packets are dropped in the course of transmission.
- End-to-end delay: The time taken for a packet to traverse the network.
- Throughput: The rate at which packets are successfully delivered.
- Trace file analysis can be completed using AWK scripts or other custom tools. Here’s an instance AWK script to estimate the throughput:
BEGIN {
sent_packets = 0
received_packets = 0
start_time = 0
end_time = 0
}
{
if ($1 == “s” && $4 == “AGT”) {
sent_packets++
if (start_time == 0) {
start_time = $2
}
}
if ($1 == “r” && $4 == “AGT”) {
received_packets++
end_time = $2
}
}
END {
duration = end_time – start_time
throughput = (received_packets * 160 * 8) / (duration * 1000)
printf(“Throughput: %.2f kbps\n”, throughput)
}
Extending the Model:
- Multimedia Streaming:
- Replace VoIP traffic with a multimedia streaming model using UDP, and adapt packet size and interval to replicate video frames.
- Cellular Network Simulation:
- Replicate a cellular network using mobile nodes, base stations, and wireless communication protocols (such as 3G/4G/5G).
- Establish mobility to simulate handovers among base stations.
- Traffic Variations:
- We can mimic different kinds of telecommunication traffic like FTP over TCP, HTTP, video streaming, or multicast.
- Realistic Network Models:
- Establish more routers, latency, and bandwidth constraints to replicate more complex telecommunication networks, like the backbone of a cellular or Internet service provider.
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