How to Simulate Cellular Topology Projects Using NS2

To simulate Cellular Topology in NS2 has series of steps to follow and it is usually defined to replicating a network structure usually utilized in mobile communication systems, in which the coverage area is divided into cells, each assisted by a base station (or access point). These base stations handle communications for mobile users contained by their respective cells, and interaction among cells can be managed by a central controller or through direct links among base stations.

Here’s how to simulate a Cellular Topology in NS2:

Steps to Simulate Cellular Topology Projects in NS2

1. Set up NS2 Environment:

Make sure that NS2 is installed and correctly configured. We will compose a TCL script which describes the cellular topology and replicates communication among mobile nodes and base stations.

2. Understanding Cellular Topology:

• In a Cellular Topology, each cell is handled by a base station. Mobile nodes in a cell interact with each other or with nodes in other cells across their respective base stations.
• The base stations can be interconnected directly or via a centralized network controller, liable on the network design.

3. Create a TCL Script for Cellular Topology:

Below is an instance of TCL script to replicate a Cellular Topology with 3 cells (each served by a base station) and mobile nodes in NS2:

# Create a new simulator instance

set ns [new Simulator]

# Open a NAM trace file for visualization

set nf [open out.nam w]

$ns namtrace-all $nf

# ======= create base stations =======

# These nodes represent the base stations for each cell

set base_station1 [$ns node]  ;# Base station for cell 1

set base_station2 [$ns node]  ;# Base station for cell 2

set base_station3 [$ns node]  ;# Base station for cell 3

# ======= Create mobile nodes =======

# Mobile nodes in different cells

set mobile_node1 [$ns node]    ;# Mobile node in cell 1

set mobile_node2 [$ns node]    ;# Mobile node in cell 2

set mobile_node3 [$ns node]    ;# Mobile node in cell 3

# ======= Connect base stations =======

# Base stations connected to each other to simulate inter-cell communication

$ns duplex-link $base_station1 $base_station2 10Mb 20ms DropTail

$ns duplex-link $base_station2 $base_station3 10Mb 20ms DropTail

$ns duplex-link $base_station1 $base_station3 10Mb 20ms DropTail

# ======= Connect mobile nodes to their respective base stations =======

$ns duplex-link $mobile_node1 $base_station1 5Mb 10ms DropTail

$ns duplex-link $mobile_node2 $base_station2 5Mb 10ms DropTail

$ns duplex-link $mobile_node3 $base_station3 5Mb 10ms DropTail

# ======= Traffic Generation =======

# Attach UDP agents to mobile nodes for communication

set udp1 [new Agent/UDP]

$ns attach-agent $mobile_node1 $udp1

set udp2 [new Agent/UDP]

$ns attach-agent $mobile_node2 $udp2

# Attach Null agents (traffic sinks) to other mobile nodes

set null1 [new Agent/Null]

$ns attach-agent $mobile_node3 $null1

set null2 [new Agent/Null]

$ns attach-agent $mobile_node1 $null2

# Connect the UDP agents to Null agents (mobile_node1 to mobile_node3, mobile_node2 to mobile_node1)

$ns connect $udp1 $null1

$ns connect $udp2 $null2

# Create Constant Bit Rate (CBR) traffic sources for each UDP agent

set cbr1 [new Application/Traffic/CBR]

$cbr1 attach-agent $udp1

$cbr1 set packetSize_ 512

$cbr1 set rate_ 100Kb

set cbr2 [new Application/Traffic/CBR]

$cbr2 attach-agent $udp2

$cbr2 set packetSize_ 512

$cbr2 set rate_ 100Kb

# Schedule traffic to start and stop

$ns at 1.0 “$cbr1 start”

$ns at 1.5 “$cbr2 start”

$ns at 5.0 “$cbr1 stop”

$ns at 5.5 “$cbr2 stop”

# End the simulation at 6 seconds

$ns at 6.0 “finish”

proc finish {} {

global ns nf

$ns flush-trace

close $nf

exec nam out.nam &

exit 0

}

# Run the simulation

$ns run

4. Explanation of the Code:

• Base Stations: Three base stations (base_station1, base_station2, base_station3) are generated, demonstrating the base stations that handle mobile nodes in their respective cells.
• Mobile Nodes: Three mobile nodes (mobile_node1, mobile_node2, mobile_node3) are created, each associated to a certain base station.
• Base Station Connectivity: Duplex links are generated among the base stations to replicate communication among cells (inter-cell communication).
• Mobile Node Connectivity: Each mobile node is associated to its respective base station using duplex links to replicate communication within a cell (intra-cell communication).
• UDP Traffic: UDP agents are attached to the mobile nodes, and Null agents are attached to the receiving nodes (traffic sinks).
• CBR Traffic: Constant Bit Rate (CBR) traffic generators transmit packets from mobile_node1 to mobile_node3 and from mobile_node2 to mobile_node1 with a data rate of 100Kb and packet sizes of 512 bytes.
• Traffic Scheduling: The traffic initiates at 1.0 seconds and 1.5 seconds and terminates at 5.0 seconds and 5.5 seconds, respectively.
• Simulation End: The simulation ends at 6 seconds, and the outcomes are saved in a .nam file for visualization.

5. Run the Simulation:

1. Save the script as cellular_topology.tcl.
2. Open a terminal and navigate to the folder in which the script is saved.
3. Execute the simulation using the following command:

ns cellular_topology.tcl

1. The simulation will create out.nam file that can be envisioned by using Network Animator (NAM).

6. Visualization in NAM:

• Open the out.nam file in NAM to envision the cellular topology. We will see three base stations associated to each other, with mobile nodes interacting with their respective base stations.

7. Customization and Enhancements:

• Increase the Number of Cells and Mobile Nodes: we can incorporate more base stations and mobile nodes by encompassing the code and adding more links to replicate a larger cellular network.
• Handover Simulation: we can mimic handover (or handoff) by transferring a mobile node from one base station to another.
• TCP Traffic: Change the UDP agents with TCP agents to mimic reliable communication:

set tcp1 [new Agent/TCP]

$ns attach-agent $mobile_node1 $tcp1

set sink1 [new Agent/TCPSink]

$ns attach-agent $mobile_node3 $sink1

$ns connect $tcp1 $sink1

• Different Traffic Types: we can replicate different kinds of traffic (such as FTP, HTTP) by using other traffic-generating agents.
• Performance Metrics: we can add tracing to evaluate parameters like packet loss, delay, and throughput:

set tracefile [open trace.tr w]

$ns trace-all $tracefile

8. Performance Analysis:

To measure the performance of the cellular topology, we can:

• Evaluate throughput by measuring the number of data successfully routed among base stations and mobile nodes.
• Analyse latency (delay) as data travels among cells and within cells.
• Evaluate packet loss to measure network reliability, specifically in heavy traffic loads.

Finally, we had successfully delivered the significant procedures to simulate the Cellular Topology in ns2 tool and also we deliver the sample snippets and their explanation. More information regarding Cellular Topology will be shared in upcoming manual. We specialize in simulating Cellular Topology Projects with the NS2 tool. Feel free to email us your project details, and we promise to provide you with top-notch research services.