How to Implement Low Earth Orbit Satellite in NS2

To implement the Low Earth Orbit (LEO) Satellite Network within NS2 (Network Simulator 2) has includes the modeling satellites in motion that normally in circular orbits at heights ranging from 500 to 2,000 km above the Earth. In a LEO satellite network, the satellites endlessly move relation to the Earth’s surface, and its interconnections (via inter-satellite links) alter as they move. The ground stations can be connected to these satellites to transfer and obtain data.

The key stepwise procedure in mimicking LEO satellites contain setting up satellite mobility, ascertaining inter-satellite and satellite-to-ground communication links, and also handling satellite handovers as the satellites move.

Steps to Implement a LEO Satellite Network in NS2:

  1. Set up the Simulation Environment

Initially, make a nodes are signifying satellites and ground stations. Configure the LEO satellites with dynamic positions to replicate an orbital movement.

Example TCL Script for Basic Setup:

# Create a simulator instance

set ns [new Simulator]

# Set link parameters (optical or RF communication links)

set bw 1Gb          ;# Bandwidth for inter-satellite and ground links

set delay 20ms      ;# Initial delay for satellite communication

# Create satellite nodes (LEO satellites)

set sat1 [$ns node]

set sat2 [$ns node]

set sat3 [$ns node]

# Create ground station node

set ground1 [$ns node]

# Connect satellites with inter-satellite links (ISL)

$ns duplex-link $sat1 $sat2 $bw $delay DropTail

$ns duplex-link $sat2 $sat3 $bw $delay DropTail

# Create uplink/downlink between satellite and ground station

$ns duplex-link $sat1 $ground1 $bw $delay DropTail

This configures a simple topology with three LEO satellites connected via inter-satellite links (ISL) and one ground station communicating including sat1 through an uplink/downlink.

  1. Define Satellite Mobility for LEO Orbits

The LEO satellites are in constant motion. To mimic the motion of LEO satellites, we can be described a mobility model in which the satellites are move in a circular or elliptical path around the Earth. In the environment NS2, we can modify the positions actively to replicate the movement of satellites in orbit.

Example of Defining Satellite Mobility:

# Set initial positions for satellites

 

for satellites

$sat1 set X_ 0

$sat1 set Y_ 1000

$sat2 set X_ 500

$sat2 set Y_ 1000

$sat3 set X_ 1000

$sat3 set Y_ 1000

# Simulate satellite movement (circular orbit)

$ns at 1.0 “$sat1 setdest 200 1000 20”  ;# Move sat1 to new coordinates at 20 m/s

$ns at 1.5 “$sat2 setdest 700 1000 20”  ;# Move sat2 to new coordinates at 20 m/s

$ns at 2.0 “$sat3 setdest 1200 1000 20” ;# Move sat3 to new coordinates at 20 m/s

# You can continue updating positions based on the satellite’s orbital path.

This configures moves the satellites along predefined paths, replicating their orbital behaviour.

  1. Configure Traffic between Satellites and Ground Stations

In the LEO satellite networks, traffic is routed among the satellites through inter-satellite links or downlinked to ground stations. We can mimic data transfer using UDP or TCP traffic.

Example of Creating Traffic from Ground Station to Satellites:

# Create a UDP agent at ground station (uplink traffic)

set udp_ground [new Agent/UDP]

$ns attach-agent $ground1 $udp_ground

# Create CBR traffic generator to simulate data from ground station to satellite

set cbr_ground [new Application/Traffic/CBR]

$cbr_ground set packet_size_ 1000

$cbr_ground set rate_ 1Gb       ;# Data rate to simulate high-speed transmission

$cbr_ground attach-agent $udp_ground

# Create a UDP sink at satellite 1 (receiver for uplink)

set null_sat1 [new Agent/Null]

$ns attach-agent $sat1 $null_sat1

# Connect ground station to satellite 1

$ns connect $udp_ground $null_sat1

# Start and stop the traffic

$ns at 1.0 “$cbr_ground start”

$ns at 10.0 “$cbr_ground stop”

In this instance, the ground station transfers traffic to sat1 through an uplink, replicating communication among an Earth and the satellite.

  1. Simulate Handover between Satellites

Since LEO satellites move, they could move out of range of a ground station that need a handover to other satellite. This procedure can replicate by actively altering the satellite-to-ground connections when the simulation.

Example of Simulating Handover:

# Initially, the ground station is connected to satellite 1

$ns duplex-link $ground1 $sat1 $bw $delay DropTail

# At time 5.0, handover ground station from satellite 1 to satellite 2

$ns at 5.0 “$ns rtmodel-at 5.0 down $ground1 $sat1”

$ns at 5.0 “$ns rtmodel-at 5.0 up $ground1 $sat2”

This replicates the handover process that the ground station connection is swapped from sat1 to sat2 at the time 5.0 seconds.

  1. Dynamic Routing Between Satellites

In a LEO satellite network, inter-satellite routing make certain that data is sent among the satellites to maintain communication with the ground station. We can be used a routing protocol like AODV (Ad hoc On-Demand Distance Vector) to manage the dynamic routing among satellites.

Example of Setting up AODV Routing:

# Enable AODV routing on the satellite nodes

set val(rp) AODV

# Attach the routing protocol to all satellites

for {set i 1} {$i <= 3} {incr i} {

$ns at 0.0 “$sat$i set ragent [new Agent/AODV]”

}

This set up AODV on all satellites, permitting them to find actively routes as the topology changes by reason of satellite movement.

  1. Monitor and Trace the Simulation

Allow tracing to take network performance, like packet delivery, routing changes, and satellite handover events. It will support to examine the network’s performance while satellite movement and handover.

Enable Trace Files:

# Enable tracing for the simulation

set tracefile [open “leo_satellite_trace.tr” w]

$ns trace-all $tracefile

# Define a finish procedure to end the simulation and close the trace file

proc finish {} {

global ns tracefile

$ns flush-trace

close $tracefile

exit 0

}

# Set the simulation end time

$ns at 20.0 “finish”

This trace file will capture the events such as packet transmissions, handover, and routing updates.

  1. Run the Simulation

At last, we run the simulation to monitor the performance of the LEO satellite network.

# Run the simulation

$ns run

Example Complete TCL Script for LEO Satellite Network Simulation

# Create a simulator instance

set ns [new Simulator]

# Set link parameters (for inter-satellite and ground-satellite links)

set bw 1Gb

set delay 20ms

# Create satellite nodes (LEO satellites)

set sat1 [$ns node]

set sat2 [$ns node]

set sat3 [$ns node]

# Create ground station node

set ground1 [$ns node]

# Connect satellites with inter-satellite links (ISL)

$ns duplex-link $sat1 $sat2 $bw $delay DropTail

$ns duplex-link $sat2 $sat3 $bw $delay DropTail

# Connect ground station to satellite 1 (uplink/downlink)

$ns duplex-link $sat1 $ground1 $bw $delay DropTail

# Set initial positions for satellites (example coordinates)

$sat1 set X_ 0

$sat1 set Y_ 1000

$sat2 set X_ 500

$sat2 set Y_ 1000

$sat3 set X_ 1000

$sat3 set Y_ 1000

# Simulate satellite movement (circular orbit)

$ns at 1.0 “$sat1 setdest 200 1000 20”

$ns at 1.5 “$sat2 setdest 700 1000 20”

$ns at 2.0 “$sat3 setdest 1200 1000 20”

# Create UDP agent for uplink traffic from ground station

set udp_ground [new Agent/UDP]

$ns attach-agent $ground1 $udp_ground

# Create CBR traffic for ground-to-satellite communication

set cbr_ground [new Application/Traffic/CBR]

$cbr_ground set packet_size_ 1000

$cbr_ground set rate_ 1Gb

$cbr_ground attach-agent $udp_ground

# Create UDP sink at satellite 1

set null_sat1 [new Agent/Null]

$ns attach-agent $sat1 $null_sat1

# Connect ground station to satellite 1

$ns connect $udp_ground $null_sat1

# Start and stop the traffic

$ns at 1.0 “$cbr_ground start”

$ns at 10.0 “$cbr_ground stop”

# Simulate handover of ground station from sat1 to sat2

$ns at 5.0 “$ns rtmodel-at 5.0 down $ground1 $sat1”

$ns at 5.0 “$ns rtmodel-at 5.0 up $ground1 $sat2”

# Enable AODV routing on the satellite nodes

set val(rp) AODV

for {set i 1} {$i <= 3} {incr i} {

$ns at 0.0 “$sat$i set ragent [new Agent/AODV]”

}

# Enable tracing

set tracefile [open “leo_satellite_trace.tr” w]

$ns trace-all $tracefile

# End simulation

$ns at 20.0 “finish”

proc finish {} {

global ns tracefile

$ns flush-trace

close $tracefile

exit 0

}

# Run the simulation

$ns run

Therefore, we shown the simplified step-by-step process on how to setup the network environment, how to define this LEO satellite and how to monitor and run the simulation with sample examples in NS2. Further specific details will be provided later, if required.

Contact ns2project.com to get the best Low Earth Orbit Satellite implementation outcomes for your projects. Regarding your projects, we focus on establishing satellite mobility, determining inter-satellite and satellite-to-ground communication links, and using the most recent research approaches to provide the best results.