How to Implement Cognitive Radio Networks in ns2

To implement the Cognitive Radio Networks (CRNs) in ns2 (Network Simulator 2) has needs to important customization for the reason that ns2 does not natively support the advanced concepts that encompassed within CRNs, like spectrum sensing, dynamic spectrum access, or spectrum management. But, with certain adjustments and custom scripting, we can be estimated the behaviour of a Cognitive Radio Network within ns2.

Step-by-Step Implementations:

Step 1: Understanding Cognitive Radio Networks

Cognitive Radio Networks are permit secondary users (SUs) to use the spectrum assigned to primary users (PUs) without triggering interference. The main modules to mimic in a CRN that involve:

  1. Spectrum Sensing: Identifying the available channels.
  2. Dynamic Spectrum Access (DSA): Assigning the channels that are dynamically based on obtainability.
  3. Interference Management: Make sure that SUs do not interfere with the primary users.

Step 2: Create the Tcl Script

The following is an instance of how we mimic a basic CRN scenario within ns2. To mimicking the dynamic spectrum access part of a CRN which is focussing on this instance.

Example Tcl Script for Simulating Cognitive Radio Networks

# Create a simulator object

set ns [new Simulator]

# Define the topography object

set topo [new Topography]

$topo load_flatgrid 1000 1000

# Create the General Operations Director (GOD) for wireless simulations

create-god 4  # Two PUs and two SUs

# Configure the primary user (PU) and secondary user (SU) nodes

$ns node-config -adhocRouting AODV \

-llType LL \

-macType Mac/802_11 \

-ifqType Queue/DropTail/PriQueue \

-ifqLen 50 \

-antType Antenna/OmniAntenna \

-propType Propagation/TwoRayGround \

-phyType Phy/WirelessPhy \

-channelType Channel/WirelessChannel \

-topoInstance $topo \

-agentTrace ON \

-routerTrace ON \

-macTrace ON

# Open trace and NAM files for recording the simulation

set tracefile [open crn_out.tr w]

$ns trace-all $tracefile

set namfile [open crn_out.nam w]

$ns namtrace-all-wireless $namfile 1000 1000

# Define a finish procedure to close files and end the simulation

proc finish {} {

global ns tracefile namfile

$ns flush-trace

close $tracefile

close $namfile

exec nam crn_out.nam &

exit 0

}

# Create primary user nodes

set pu0 [$ns node]

set pu1 [$ns node]

# Set the positions for primary users

$pu0 set X_ 200.0

$pu0 set Y_ 500.0

$pu0 set Z_ 0.0

$pu1 set X_ 800.0

$pu1 set Y_ 500.0

$pu1 set Z_ 0.0

# Create secondary user nodes

set su0 [$ns node]

set su1 [$ns node]

# Set initial positions for secondary users

$su0 set X_ 300.0

$su0 set Y_ 550.0

$su0 set Z_ 0.0

$su1 set X_ 700.0

$su1 set Y_ 550.0

$su1 set Z_ 0.0

# Define the behavior of primary users (constant traffic)

set tcp_pu0 [new Agent/TCP]

$ns attach-agent $pu0 $tcp_pu0

set sink_pu0 [new Agent/TCPSink]

$ns attach-agent $pu1 $sink_pu0

$ns connect $tcp_pu0 $sink_pu0

set ftp_pu0 [new Application/FTP]

$ftp_pu0 attach-agent $tcp_pu0

$ftp_pu0 start

# Function to simulate spectrum sensing and dynamic access for SUs

proc cognitive_radio_access {su0 su1 pu0 pu1} {

global ns

# Simulate sensing period (e.g., 2 seconds)

$ns at 2.0 “$su0 setdest 300.0 500.0 10.0”

$ns at 2.0 “$su1 setdest 700.0 500.0 10.0”

# Simulate dynamic spectrum access after sensing

$ns at 4.0 “$su0 setdest 600.0 500.0 10.0”

$ns at 4.0 “$su1 setdest 400.0 500.0 10.0”

# Define secondary user traffic after accessing spectrum

set udp_su0 [new Agent/UDP]

$ns attach-agent $su0 $udp_su0

set null_su1 [new Agent/Null]

$ns attach-agent $su1 $null_su1

$ns connect $udp_su0 $null_su1

set cbr_su0 [new Application/Traffic/CBR]

$cbr_su0 attach-agent $udp_su0

$cbr_su0 set packetSize_ 512

$cbr_su0 set rate_ 1Mb

$cbr_su0 start 5.0

}

# Simulate cognitive radio access for SUs

cognitive_radio_access $su0 $su1 $pu0 $pu1

# Schedule the end of the simulation

$ns at 10.0 “finish”

# Run the simulation

$ns run

Step 3: Run the Tcl Script

Save the Tcl script including a .tcl extension, such as cognitive_radio_simulation.tcl. Then run the script using the below command in the terminal:

ns cognitive_radio_simulation.tcl

Step 4: Visualize the Simulation

We need to visualize the CRN, open the generated NAM file using:

nam crn_out.nam

It should show the nodes, the primary users, and the secondary users in the simulation.

Script Explanation

  • Primary Users (PUs): The nodes like pu0 and pu1 are denote the primary users that have a constant TCP connection, and mimicking licensed spectrum usage.
  • Secondary Users (SUs): The nodes such as su0 and su1 are signify the secondary users that execute the spectrum sensing and enthusiastically access the spectrum which is based on the obtainability of the primary users.
  • Cognitive Radio Access Function: The function that is cognitive_radio_access mimics the spectrum identifying by moving the secondary users nearer to the PUs and then we mimics the dynamic spectrum access by permitting the secondary users to begin communication after a sensing period.
  • Traffic Generation: TCP traffic is created among the PUs, and UDP traffic is made among the secondary users after spectrum access.

Customization

  • Advanced Spectrum Sensing: For modifying the timing and logic of the cognitive_radio_access function, to execute further sophisticated spectrum sensing algorithms.
  • Dynamic Channel Allocation: We mimic more realistic channel allocation approaches by changing how SUs select to access the spectrum.
  • Interference Management: We can add logic to manage the meddling scenarios in which SUs may trigger or permit interference with PUs.
  • Multiple PUs and SUs: Maximize the number of primary and secondary users to make a more difficult and realistic CRN setup.

Limitations

  • Simplified Model: The emulation is a high-level estimate. It does not fully execute the difficulties of cognitive radio networks, like real-time spectrum sensing, detailed interference management, advanced dynamic spectrum access.
  •  No True Spectrum Sensing: The script usages the node mobility to mimic spectrum sensing, that is an abstraction rather than a comprehensive emulation of real sensing mechanisms.
  • Lack of Standard Protocols: The tool ns2 does not natively help CRN-specific protocols, thus this simulation extracts those behaviours.

In this set up to understand more about the Cognitive Radio Networks containing their example tcl script, execution and simulation process in ns2. We will be presented additional details of these projects, if required.

Get Cognitive Radio Networks projects with implementation results at ns2projects.com. We also provide performance analysis for your projects. Explore unique research topics and ideas with comprehensive explanations. Our expertise work on all aspects of Cognitive Radio Networks.