How to Implement Inter Optical satellite in NS2

To implement the Inter-Optical Satellite Communication using NS2 (Network Simulator 2), we will replicate a situation in which the satellites communicate with each other using optical links that also called as Inter-Satellite Links (ISL). This satellite communication delivers high-speed data transfer including low latency and is frequently used in modern satellite constellations such as LEO or MEO for communication among the satellites.

Given below is a methods we will display on how to model a network in which satellites communicate using optical links and can relay data to ground stations. These setup contains the configuring optical links among the satellites and ground stations.

Steps to Implement Inter-Optical Satellite Communication in NS2:

  1. Set Up the Simulation Environment

Primarily, describe the satellite nodes and ground stations. Ascertain optical links among the satellites (ISLs) and also make a links among the satellites and ground stations for communication.

Example TCL Script for Basic Setup:

# Create a simulator instance

set ns [new Simulator]

# Set optical link parameters

set bw_optical 10Gb         ;# Bandwidth for inter-satellite optical links

set delay_optical 5ms       ;# Delay for optical satellite communication

# Set ground-satellite link parameters

set bw_ground_sat 1Gb       ;# Bandwidth for satellite-to-ground communication

set delay_ground_sat 50ms   ;# Delay for satellite-to-ground communication

# Create satellite nodes (optical communication enabled)

set sat1 [$ns node]

set sat2 [$ns node]

set sat3 [$ns node]

# Create ground station node

set ground1 [$ns node]

# Connect satellites with optical inter-satellite links (ISL)

$ns duplex-link $sat1 $sat2 $bw_optical $delay_optical DropTail

$ns duplex-link $sat2 $sat3 $bw_optical $delay_optical DropTail

$ns duplex-link $sat1 $sat3 $bw_optical $delay_optical DropTail

# Create uplink/downlink between satellite and ground station

$ns duplex-link $sat1 $ground1 $bw_ground_sat $delay_ground_sat DropTail

This configures makes 3 satellites are connected through the optical links. Satellite 1 is connected to a ground station for communication with Earth, whereas the satellites communicate with each other using optical inter-satellite links (ISLs).

  1. Configure Mobility for Satellites

As satellites are in constant motion, we can describe a basic mobility model to replicate the satellite movement in an orbit. The setdest function within NS2 permits to stipulate the new end of each satellite.

Example of Satellite Mobility Configuration:

# Set initial positions 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 10”  ;# Move sat1 to new coordinates at 10 m/s

$ns at 1.5 “$sat2 setdest 700 1000 10”  ;# Move sat2 to new coordinates at 10 m/s

$ns at 2.0 “$sat3 setdest 1200 1000 10” ;# Move sat3 to new coordinates at 10 m/s

This basic mobility model mimics the movement of satellites in this orbits. Every single satellite moves to new coordinates at a constant speed that can change as required.

  1. Configure Traffic between Satellites and Ground Stations

Here, we want to configure the traffic to replicate the data transmission between satellites and among satellites and ground stations. It can be completed using UDP or TCP agents, accompanied by CBR (Constant Bit Rate) traffic to model high-speed optical communication.

Example of Configuring Traffic Between Satellites and Ground Station:

# Create UDP agent for ground station (uplink to satellite 1)

set udp_ground1 [new Agent/UDP]

$ns attach-agent $ground1 $udp_ground1

# Create CBR traffic generator for ground station

set cbr_ground1 [new Application/Traffic/CBR]

$cbr_ground1 set packet_size_ 1000

$cbr_ground1 set rate_ 1Gb       ;# High-speed data transmission

$cbr_ground1 attach-agent $udp_ground1

# Create UDP sink for satellite 3 (downlink from satellite)

set null_sat3 [new Agent/Null]

$ns attach-agent $sat3 $null_sat3

# Connect ground station to satellite 3 through the satellite network

$ns connect $udp_ground1 $null_sat3

# Start and stop the traffic

$ns at 1.0 “$cbr_ground1 start”

$ns at 10.0 “$cbr_ground1 stop”

In this setup:

  • Ground station 1 transfers the data to satellite 3 via satellite 1 and satellite 2 through optical links.
  • The traffic is set up to emulate a high-speed data flow (1 Gbps), usual for optical communication.
  1. Simulate Handover between Satellites (Optional)

If we need to replicate a situation in which the ground station hands across communication from one satellite to another (e.g., due to satellite movement), we can actively swap the communication link when the simulation.

Example of Simulating Handover Between Satellites:

# Initially, the ground station is connected to satellite 1

$ns duplex-link $ground1 $sat1 $bw_ground_sat $delay_ground_sat DropTail

# At time 5.0, handover the ground station connection 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 instance explains how the ground station can switch these communication link from satellite 1 to satellite 2, and replicated a handover event.

  1. Dynamic Routing Between Satellites

In the inter-satellite networks, dynamic routing make certain that data can be relayed via various satellites as required and we can use this routing protocol such as AODV (Ad hoc On-Demand Distance Vector) to handle the routing of traffic among the satellites.

Example of Enabling AODV for Dynamic Routing:

# Enable AODV routing protocol for the satellites

set val(rp) AODV

# Attach AODV routing protocol to all satellite nodes

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

set sat [set sat$i]

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

}

It allows AODV routing on all satellite nodes, permitting them to dynamically find the routes as the satellite topology alters because of the movement.

  1. Monitor and Trace the Simulation

Allow tracing to capture the performance of the optical satellite network that containing the packet transmissions, routing updates, and satellite handovers. It will permit to examine the behaviour of the inter-satellite optical communication network.

Enable Trace Files:

# Enable tracing for the simulation

set tracefile [open “inter_optical_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”

The trace file will capture packet transmissions, routing updates, and handover events, permits to investigate the behaviour and performance of the optical satellite network.

  1. Run the Simulation

At last, run the simulation to monitor the performance of the inter-optical satellite network.

# Run the simulation

$ns run

Example Complete TCL Script for Inter-Optical Satellite Communication Simulation

# Create a simulator instance

set ns [new Simulator]

# Set optical link parameters

set bw_optical 10Gb

set delay_optical 5ms

# Set ground-satellite link parameters

set bw_ground_sat 1Gb

set delay_ground_sat 50ms

# Create satellite nodes (optical communication enabled)

set sat1 [$ns node]

set sat2 [$ns node]

set sat3 [$ns node]

# Create ground station node

set ground1 [$ns node]

# Connect satellites with optical inter-satellite links (ISL)

$ns duplex-link $sat1 $sat2 $bw_optical $delay_optical DropTail

$ns duplex-link $sat2 $sat3 $bw_optical $delay_optical DropTail

$ns duplex-link $sat1 $sat3 $bw_optical $delay_optical DropTail

# Connect satellite 1 to the ground station

$ns duplex-link $sat1 $ground1 $bw_ground_sat $delay_ground_sat DropTail

# Set initial positions 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 10”

$ns at 1.5 “$sat2 setdest 700 1000 10”

$ns at 2.0 “$sat3 setdest 1200 1000 10”

# Create UDP agent for ground station (uplink to satellite 1)

set udp_ground1 [new Agent/UDP]

$ns attach-agent $ground1 $udp_ground1

# Create CBR traffic generator for ground station

set cbr_ground1 [new Application/Traffic/CBR]

$cbr_ground1 set packet_size_ 1000

$cbr_ground1 set rate_ 1Gb

$cbr_ground1 attach-agent $udp_ground1

# Create UDP sink for satellite 3 (downlink from satellite network)

set null_sat3 [new Agent/Null]

$ns attach-agent $sat3 $null_sat3

# Connect ground station to satellite 3 via satellite network

$ns connect $udp_ground1 $null_sat3

# Start and stop the traffic

$ns at 1.0 “$cbr_ground1 start”

$ns at 10.0 “$cbr_ground1 stop”

# Enable AODV routing protocol for the satellites

set val(rp) AODV

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

set sat [set sat$i]

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

}

# Enable tracing

set tracefile [open “inter_optical_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

Thus, we had expressed entire techniques that are helps you to execute effectively for the Inter Optical satellite using NS2 simulation environment. Also we will offer further materials about this topic in another manual.

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