How to Start Cognitive Ad Hoc Network Projects Using NS2

To start a Cognitive Ad-Hoc Network (CAN) project in NS2 is robust simulation tool which replicating an ad-hoc network including cognitive capabilities in which devices can be adjusted its behavior depends on the environment like spectrum sensing, spectrum management, and interference avoidance.

A Cognitive Ad-Hoc Network normally has Cognitive Radios (CRs), which can be identified frequency bands (spectrum holes) that are unused and adapt its transmission metrics actively. This ability creates them for dynamic spectrum access that enhances the spectrum efficiency including rare wireless resources within environments.

While NS2 doesn’t inherently support advanced Cognitive Radio functionalities, we can execute the numerous aspects like spectrum sensing, channel switching, and cognitive decision-making. Following is a detailed method to get started with a Cognitive Ad-Hoc Network (CAN) project in NS2.

Key Concepts for Cognitive Ad-Hoc Networks (CAN):

  1. Cognitive Radios (CRs): These radios can be detected the spectrum, identified unused channels (spectrum holes), and modified channels depends on prevent interference.
  2. Ad-Hoc Network: A decentralized network without a fixed infrastructure in which nodes directly interact.
  3. Spectrum Sensing: In the spectrum, method of identifying the existence of primary users (licensed users).
  4. Dynamic Spectrum Access (DSA): The capability of Cognitive Radios for adjusting dynamically available spectrum.
  5. Interference Avoidance: Cognitive radios modify its transmission metrics for preventing interference including primary users or other cognitive radios.

Steps to Start a Cognitive Ad-Hoc Network Project in NS2

  1. Install NS2 and Prerequisites

Initially, make sure that NS2 is installed on the system. Unless, we can adhere to provided installation guidance based on the operating system:

For Linux:

sudo apt-get install ns2

We will need to utilise package managers such as Cygwin (Windows) or Homebrew (macOS) for Windows and macOS.

When NS2 is installed then we should confirm the installation by executing a simple simulation script.

  1. Understand Cognitive Ad-Hoc Networks

We must know the crucial modules of Cognitive Ad-Hoc Network, such as:

  • Spectrum Sensing: In the network, devices would be capable of sense the spectrum and detect available channels.
  • Spectrum Access: When a spectrum hole is determined then the devices dynamically choose an available channel for interaction.
  • Ad-Hoc Network Topology: The network is made by nodes which directly interact with each other devoid of utilise the centralized infrastructure like access points or base stations.
  1. Model Cognitive Radio Features in NS2

While NS2 doesn’t directly support for Cognitive Radio or Ad-Hoc networks then we can replicate the Cognitive Radio behaviors via custom extensions and scripting.

Example: Cognitive Radio Nodes and Basic Spectrum Sensing

In NS2, we will need to design the cognitive nodes which are conscious of the spectrum. For example, we may replicate the spectrum sensing procedure by way of identifying whether a frequency band is engaged (by primary users) or available (a spectrum hole).

# Create the simulator

set ns [new Simulator]

# Create nodes (Cognitive Radio Nodes)

set crNode1 [$ns node]

set crNode2 [$ns node]

set crNode3 [$ns node]

# Create a simple ad-hoc network with cognitive radios

$ns duplex-link $crNode1 $crNode2 10Mb 10ms DropTail

$ns duplex-link $crNode2 $crNode3 10Mb 10ms DropTail

# Spectrum sensing procedure (simplified)

proc spectrum-sensing {node} {

global ns

# Simulate spectrum sensing at node, check for availability (0 = free, 1 = occupied)

set spectrumStatus [expr int(rand() * 2)]  ;# Randomly decide if spectrum is free or occupied

if {$spectrumStatus == 0} {

# Spectrum is free, so the node can transmit

$ns at 1.0 “$node start-transmission”

} else {

# Spectrum is occupied, so the node waits or changes channel

$ns at 1.0 “$node switch-channel”

}

}

# Create and run a simple simulation

$ns at 1.0 “spectrum-sensing $crNode1”

$ns at 2.0 “spectrum-sensing $crNode2”

$ns at 3.0 “spectrum-sensing $crNode3”

In this case:

  • Cognitive Radio Nodes (CRNs) are made like crNode1, crNode2, crNode3.
  • The spectrum-sensing procedure is replicated in which each node arbitrarily chooses if the spectrum is engaged or occupied.
  1. Implement Spectrum Sensing and Channel Switching

To prevent the interference including primary users or other cognitive nodes for Cognitive Radios then we can replicate the channel switching according to the availability of spectrum. Here’s how to execute this logic.

Example: Channel Switching Logic

# Channel Switching Logic

proc switch-channel {node} {

global ns

# Simulate the node switching to a new channel

set newChannel [expr int(rand() * 5)] ;# Randomly select a new channel (1 to 5)

puts “Node $node switching to channel $newChannel”

# You can add more logic here, such as waiting for the channel to become free

}

# Create a simple event to trigger channel switching

$ns at 5.0 “switch-channel $crNode1”

$ns at 6.0 “switch-channel $crNode2”

$ns at 7.0 “switch-channel $crNode3”

In this instance:

  • When the present one is engaged, switch-channel process replicates a node switching to a various channel.
  1. Simulate Communication in the Cognitive Ad-Hoc Network

When the spectrum sensing and channel switching are ready then we will need to replicate the data interaction among the Cognitive Radio Nodes. It encompasses to transmit the packets from one node to another node whereas make sure that the nodes are utilise channels that are available.

Example: Data Communication Between Cognitive Radio Nodes

# Create a simple application for communication between nodes

set app1 [new Application/Traffic/CBR]

$app1 set packetSize_ 512

$app1 set interval_ 0.01

$app1 attach-agent $crNode1

$ns at 2.0 “$app1 start”

set app2 [new Application/Traffic/CBR]

$app2 set packetSize_ 512

$app2 set interval_ 0.01

$app2 attach-agent $crNode2

$ns at 3.0 “$app2 start”

# Simple communication process from crNode1 to crNode2

$ns at 4.0 “$crNode1 send-packet $crNode2”

In this case:

  • CBR (Constant Bit Rate) traffic is utilised for interaction among the Cognitive Radio Nodes.
  1. Monitor and Analyze Performance

After executing the simulation then we would observe diverse performance parameters like:

  • Packet delivery ratio: How effectively packets are transmitted among the nodes.
  • Spectrum utilization: Estimate the spectrum usage effectiveness.
  • Latency: Measure the duration to move among the nodes for packets.
  • Interference: How successfully the cognitive radios prevent the interference from primary users.

Accumulate the information to utilise NS2 trace files and then examine it with the support of AWK or XGraph.

# Example: Using AWK to process trace files

awk ‘{if ($1 == “r”) print $0}’ cognitive_adhoc_simulation.tr | awk ‘{total+=1} END {print total}’

  1. Extend the Simulation

When basic simulation is configuring then we will need to improve the simulation by:

  • Integrating additional Cognitive Radio Nodes to build a larger ad-hoc network.
  • Simulating mobility: Design the cognitive radios movement and how it affects the network topology.
  • Advanced spectrum sensing algorithms: Execute additional sophisticated sensing methods like energy detection, matched filtering, or cyclostationary feature detection.
  • Multiple spectrum bands: Make use of more than one frequency band and mimic frequency reuse policies.
  • Cross-layer optimization: Execute the dynamic policies according to the network conditions for channel access and energy control.

Conclusion

Starting a Cognitive Ad-Hoc Network (CAN) project in NS2:

  1. In the network, make Cognitive Radio Nodes (CRNs).
  2. Execute spectrum sensing for identifying the available channels.
  3. Replicate channel switching to prevent interference and enhance the spectrum usage.
  4. Allow interaction among the nodes depends on the available spectrum channels.
  5. Observe performance parameters like packet delivery, latency, and spectrum utilization.

While NS2 doesn’t direct support for Cognitive Radio Networks then we will prolong their functionality to utilise custom procedures and logic for replicating the crucial behaviors of cognitive such as spectrum sensing, channel switching, and dynamic spectrum access. If we want further aspects then we could deliberate it to utilise NS3 including Cognitive Radio extensions or simulators such as OMNeT++ with MiXiM.

This step-by-step approach ensures a solid foundation for simulating Cognitive Ad Hoc Network projects in NS2 environment. We are ready to provide additional specifies upon request.