How to Start Cognitive Radio Networks Projects Using NS2

To start Cognitive Radio Networks (CRNs) in NS2 (Network Simulator 2) that needs to replicate the dynamic spectrum access, spectrum sensing, and cognitive radio approaches, which allow more effective usage of radio spectrum. This kind of simulation can be utilised for experimenting diverse CRN protocols like spectrum sensing, dynamic spectrum access, and spectrum management policies.

NS2 environment doesn’t have direct support for Cognitive Radio Networks by default, however there are extensions and components are obtainable to replicate the CRNs. Following is sequential steps to start a Cognitive Radio Network project using NS2:

Steps to Start CRNs Projects in NS2

  1. Install NS2

Make sure that NS2 is installed on the machine. We should download and install it using official NS2 website or through a package manager on Linux:

  • For Linux: We can install NS2 through package managers, such as:

sudo apt-get install ns2

  • For Windows or macOS: Install NS2 on a virtual machine or via Cygwin (Windows).

Make sure that NS2 is functioning by executing a sample script for verifying their functionality.

  1. Cognitive Radio Extensions for NS2

NS2 doesn’t directly support Cognitive Radio (CR) networks by default, but we can determine and install the essential extensions, which execute the CR mechanisms. Common extension is CRN (Cognitive Radio Networks) that integrates simple functionalities of CR simulations for NS2.

We will need to download the CRN extensions using repositories such as GitHub or SourceForge. For NS2, some projects offer CRNs are:

The process to install these extensions that contain:

  • To download the code.
  • Obtaining it to the ns-allinone directory (where NS2 is installed).
  • Executing to compile the code.

If we can select a GitHub repo or any other source then we can adhere to the installation guidance incorporating it including NS2.

  1. Understand the Cognitive Radio Concepts

We acquire more knowledge about the Cognitive Radio Networks key concepts like:

  • Cognitive Radio (CR): A smart radio, which can be detected their environment, adjusts its operation dynamically, and utilise the unused spectrum such as spectrum holes.
  • Primary Users (PU): It is also called licensed users of the spectrum.
  • Secondary Users (SU): The unlicensed users, which opportunistically apply spectrum that is not to be utilised by the PUs.
  • Spectrum Sensing: The process of identifying if a spectrum band is to be utilised by the PU.
  • Spectrum Access: The method of accessing and using the spectrum bands by the SU.
  • Dynamic Spectrum Access (DSA): Approaches for spectrum sharing among the PU and SU devoid of triggering interference to PUs.
  1. Set Up Your CRN Topology

Cognitive Radio Networks contain unique topologies in which Primary and Secondary Users (PUs and SUs) should be designed. A simple CRN topology has:

  • Primary Base Stations (PBS): These are the spreaders or base stations, which utilise the licensed spectrum.
  • Secondary Base Stations (SBS): These are the nodes, which can be opportunistically accessed spectrum according to the whether the spectrum is inactive.
  • Secondary Users (SUs): Devices or users, which use the available spectrum, however only when the spectrum is not to be utilised by Primary Users.

Example Topology in NS2: In a basic CRN simulation, we could contain numerous nodes that are denoting PUs and SUs. For instance:

  • Make one node for a Primary User (PU).
  • Generate several Secondary Users (SUs), which can be utilised spectrum opportunistically.

Example script for creating a basic CRN topology:

# Load NS2 Cognitive Radio Network module

package require ns2-cr

# Create the simulator

set ns [new Simulator]

# Create nodes for Primary Users (PUs) and Secondary Users (SUs)

set PU [list]

set SU [list]

# Create one Primary User (PU) and one Secondary User (SU)

set PU1 [$ns node]

set SU1 [$ns node]

lappend PU $PU1

lappend SU $SU1

# Create more Secondary Users if needed

for {set i 2} {$i <= 5} {incr i} {

set temp_node [$ns node]

lappend SU $temp_node

}

# Set up Spectrum Access Mechanisms (example: Dynamic Spectrum Access)

# You will need to define sensing periods, access protocols, etc.

# Create the spectrum sensing and sharing logic (simplified example)

# Here we simulate that SU1 listens for idle spectrum, and only then starts transmission.

$ns at 1.0 “puts \”SU1 listens for available spectrum\””

$ns at 2.0 “puts \”SU1 starts using the spectrum\””

# Set up some traffic flow (for example, between Secondary User and Primary User)

set udp [new Agent/UDP]

$ns attach-agent $SU1 $udp

set cbr [new Application/Traffic/CBR]

$cbr attach-agent $udp

$ns at 3.0 “$cbr start”

$ns at 5.0 “$cbr stop”

# Run the simulation

$ns run

Explanation:

  • The script makes PUs and SUs within the network.
  • Spectrum access is managed by a basic collection of rules. For instance, SU1 pays attention for spectrum availability before establishing the transmission.
  • The application transmits the information among SUs to utilise CBR (constant bit rate) traffic.
  1. Implement Spectrum Sensing and Access Mechanisms

Cognitive Radio needs the spectrum sensing simulation that is normally designed in two ways they are:

  • Energy Detection: The SU pays attention to the radio spectrum and identifies if there is a signal from the PU.
  • Matched Filtering: The SU suits a signal model that is known for identifying the existence of the PU.

Instance of Spectrum Sensing:

  • We need to utilise the timers or events for designing the sensing process (once SU verifies if spectrum is inactive or engaged by PU).
  • When the spectrum is determined idle then the secondary user can be accessed the spectrum.

Example code to simulate energy detection in NS2 might look like:

# Spectrum sensing period for Secondary Users (SU)

$ns at 1.0 “puts \”SU1 starts spectrum sensing\””

$ns at 2.0 “puts \”SU1 finds idle spectrum and starts transmission\””

  1. Traffic Generation and Data Transmission

We will want to configure the traffic generation among PUs and SUs or between two SUs. According to the kind of traffic, we can utilise TCP, UDP, or Constant Bit Rate (CBR) applications to replicate.

Example of generating CBR traffic:

set udp [new Agent/UDP]

$ns attach-agent $SU1 $udp

set cbr [new Application/Traffic/CBR]

$cbr attach-agent $udp

$ns at 3.0 “$cbr start”

$ns at 5.0 “$cbr stop”

  1. Run the Simulation

When we need inscribed the script then we execute the CRN simulation. After executing the simulation, NS2 will be created trace files in which we may observe the CRN performance like throughput, packet loss, and spectrum efficiency.

To execute the simulation:

ns cognitive_radio_simulation.tcl

  1. Analyze the Results
  • Throughput: Estimate the throughput of Secondary Users (SUs) and how successfully they get into spectrum.
  • Delay: During spectrum access and sensing, verify the delay among the SUs and PUs.
  • Spectrum Utilization: Observe how frequently the spectrum is utilised by PUs and SUs.

Examine and envision the information to utilise tools such as AWK or XGraph.

  1. Extend the Simulation

After executing a basic simulation then we need to prolong the project to:

  • Execute advanced spectrum sensing mechanisms.
  • Replicate the spectrum handovers or dynamic spectrum allocation.
  • Experiment interference management among the PUs and SUs.
  • Mimic several spectrum bands and multi-cell networks.
  • Discover cooperative spectrum sensing between the SUs.
  1. Documentation and Reporting

Make sure that we provide more insights like network topology, sets up, outcomes, and conclusions from the simulation. Contain graphs, analysis of throughput, packet loss, and the effect of various CR mechanisms.

Common Issues You Might Encounter:

  • Compatibility: Make sure that the Cognitive Radio extension is matching with the new version of NS2.
  • Complexity: To replicate the CRNs can be concentrated computationally; make certain for enhancing the simulations.
  • Debugging: Sort out complex CR algorithms issues to verify event scheduling and traffic generation carefully within NS2 scripts.

In this guide, we can make, replicate and analyse the Cognitive Radio Networks using NS2 with the support of above methods and discover the spectrum sharing, sensing, and access behavior in dynamic wireless environments. As well, we will present required details about this process in the next manual.