How to Implement Network ISI mitigation in NS2

To implement the network Inter-Symbol Interference (ISI) mitigation in NS2, we need to simulate the impacts of ISI in wireless communication and then accomplishing methods to decrease or remove its influence. We can abstract effects of ISI on packet transmission and reception including model mitigation techniques like equalization or filtering because ns2 can’t simulate detailed signal-level phenomena like ISI natively. In below, we have offered the details and its accomplishing in the network simulation using ns2:

  1. Understanding ISI and Its Impact on Networks
  • Inter-Symbol Interference (ISI) happens when signal echoes or time dispersion cause symbols in a communication signal to intrudes with one another, leading to data errors.
  • In NS2, ISI can be modeled by lauching packet error rates or signal degradation in terms of channel conditions (like multipath fading or delay spread).
  • ISI Mitigation methods like equalization, filtering, or spread spectrum strategies can be abstracted in NS2 by influencing the packet reception probability in adverse channel conditions.
  1. Approach to Simulate ISI and Its Mitigation in NS2

Meanwhile NS2 doesn’t simulate signal-level interference directly, we can use packet error models to replicate ISI and modify error rates or transmission success in terms of various ISI mitigation strategies.

  1. Basic Steps for ISI Mitigation Simulation in NS2
  1. Model ISI in the Channel: Launch packet errors or decreased signal quality to simulate ISI.
  2. Apply ISI Mitigation Techniques: Imitate the probability of packet errors being mitigated using methods like equalization, filtering, or advanced coding schemes.
  1. Modifying the Physical Layer in NS2 to Simulate ISI

You can simulate the impacts of ISI by altering the physical layer (WirelessPhy) and using a packet error model that is relying on the ISI conditions in the network.

Step-by-Step Implementation

Step 1: Modify the Physical Layer to Introduce ISI Effects

  1. Open or Modify the Wireless Physical Layer File In NS2, the physical layer is defined in ~/ns-2.35/tcl/lib/wireless-phy.tcl. You will need to include a model for ISI that launches packet loss because of intrusion from previous symbols.

# Adding ISI effect simulation to the WirelessPhy class

# Define ISI effect parameters (higher values mean more interference)

set Phy/WirelessPhy/ISI_factor 0.05  ;# Base ISI effect (adjustable)

# Function to calculate packet error due to ISI

proc calc_isi_packet_error { packet_size modulation snr } {

# Example ISI calculation based on packet size, modulation scheme, and SNR

set isi_factor [Phy/WirelessPhy set ISI_factor]

set ber 0.0

# Adjust BER based on modulation and ISI (simplified model)

switch $modulation {

“BPSK” {

set ber [expr 0.001 * $isi_factor * 10 / $snr]

}

“QPSK” {

set ber [expr 0.01 * $isi_factor * 10 / $snr]

}

“QAM” {

set ber [expr 0.1 * $isi_factor * 10 / $snr]

}

default {

set ber [expr 0.01 * $isi_factor * 10 / $snr]  ;# Default for unknown modulations

}

}

# Calculate packet error probability

set packet_error_prob [expr 1.0 – pow((1.0 – $ber), $packet_size * 8)]

return $packet_error_prob

}

  1. Simulate ISI in Packet Reception Fine-tune the packet reception function in wireless-phy.tcl to present packet errors because of ISI and its mitigation.

proc Phy/WirelessPhy::recv {packet} {

# Get the size of the incoming packet

set packet_size [$packet size]

# Set a sample SNR (this can be dynamically adjusted based on the scenario)

set snr 10.0  ;# Signal-to-noise ratio (example)

# Choose the modulation scheme (you can dynamically change it or set it in the TCL script)

set modulation “QPSK”  ;# Example modulation scheme

# Calculate packet error due to ISI and modulation scheme

set isi_error_prob [calc_isi_packet_error $packet_size $modulation $snr]

# Generate a random value to simulate packet loss due to ISI

set random_val [expr rand()]

if {$random_val < $isi_error_prob} {

# Drop the packet due to ISI

drop $packet

return

}

# If the packet is not dropped, forward it to the upper layers

$self up-target $packet

}

Step 2: Implement ISI Mitigation Techniques

To mitigate ISI, we can alter the BER or packet error probability in terms of application of particular mitigation methods. Let’s model this using a function that reduces the error rate.

# ISI Mitigation Function (e.g., equalization or filtering)

proc mitigate_isi { isi_error_prob mitigation_factor } {

# Adjust the error probability based on mitigation factor

return [expr $isi_error_prob * (1.0 – $mitigation_factor)]

}

# Modify the packet reception process to include mitigation

proc Phy/WirelessPhy::recv {packet} {

set packet_size [$packet size]

set snr 10.0

set modulation “QPSK”

# Calculate initial ISI error probability

set isi_error_prob [calc_isi_packet_error $packet_size $modulation $snr]

# Apply ISI mitigation (example mitigation factor: 50%)

set mitigation_factor 0.5  ;# 50% improvement due to mitigation

set mitigated_error_prob [mitigate_isi $isi_error_prob $mitigation_factor]

# Randomly decide if the packet is dropped or not based on mitigated error

set random_val [expr rand()]

if {$random_val < $mitigated_error_prob} {

drop $packet

return

}

# If the packet is not dropped, forward it to the upper layers

$self up-target $packet

}

Step 3: Update the TCL Simulation Script

TCL script is used to simulate a network scenario where ISI is present and then apply ISI mitigation methods.

# Create a simulator instance

set ns [new Simulator]

# Create trace and nam files for output

set tracefile [open isi_mitigation.tr w]

set namfile [open isi_mitigation.nam w]

$ns trace-all $tracefile

$ns namtrace-all $namfile

# Define network topology

set topo [new Topography]

$topo load_flatgrid 1000 1000  ;# Simulation area: 1000×1000 meters

# Create the General Operations Director (GOD)

set god_ [create-god 10]  ;# 10 nodes

# Set physical layer parameters

set Phy/WirelessPhy/ISI_factor 0.05

# Define node configuration parameters

set opt(chan)       Channel/WirelessChannel

set opt(prop)       Propagation/TwoRayGround

set opt(netif)      Phy/WirelessPhy

set opt(mac)        Mac/802_11

set opt(ifq)        Queue/DropTail/PriQueue

set opt(ll)         LL

set opt(ant)        Antenna/OmniAntenna

set opt(x)          1000

set opt(y)          1000

# Set number of nodes

set opt(nn) 10  ;# Number of nodes

# Create nodes

for {set i 0} {$i < $opt(nn)} {incr i} {

set node_($i) [$ns node]

$node_($i) random-motion 1  ;# Enable random motion for nodes

}

# Start traffic generation and simulation

proc start_traffic {} {

global ns node_ opt

# Create UDP agents and attach them to nodes

for {set i 0} {$i < $opt(nn)} {incr i} {

set udp_($i) [new Agent/UDP]

set null_($i) [new Agent/Null]

$ns attach-agent $node_($i) $udp_($i)

$ns attach-agent $node_($i) $null_($i)

# Generate CBR traffic

set cbr_($i) [new Application/Traffic/CBR]

$cbr_($i) set packetSize_ 512

$cbr_($i) set interval_ 0.1

$cbr_($i) attach-agent $udp_($i)

# Connect UDP agents for communication between nodes

$ns connect $udp_($i) $null_($i)

}

}

# Start the traffic at 1.0 second

$ns at 1.0 “start_traffic”

# Run the simulation

$ns at 100.0 “finish”

# End simulation procedure

proc finish {} {

global ns tracefile namfile

close $tracefile

close $namfile

$ns halt

}

# Run the simulation

$ns run

  1. Explanation of the Script
  • ISI Simulation: A basic model of ISI is simulated by modifying packet error rates based on modulation and SNR.
  • ISI Mitigation: The mitigate_isi function decreased the ISI-induced error rate by accomplishing a mitigation factor (like equalization, filtering).
  • TCL Script: A basic wireless network simulation is generated with 10 nodes generating traffic, and ISI impacts are applied during packet reception.
  1. Running the Simulation
  • Store the altered wireless-phy.tcl file and the TCL script (isi_mitigation.tcl).
  • Execute the simulation using:

ns isi_mitigation.tcl

  1. Analyzing Results
  • After running the simulation, Monitor how ISI impacts packet reception and how effective the mitigation strategies are by assessing the trace file (isi_mitigation.tr).
  • Metrics to consider include:
    • Packet Delivery Ratio: How many packets successfully reach their destination.
    • Packet Loss: The amount of packets lost because of ISI and after mitigation.
  1. Further Enhancements
  • Adaptive ISI Mitigation: Execute adaptive algorithms that modify the mitigation factor based on real-time network conditions (for instance: dynamic equalization).
  • Multi-hop Networks: Add multi-hop networks in which ISI may aggregate through numerous transmissions by extending the simulation.
  • Advanced Modulation and Coding: Integrate more advanced modulation schemes and forward error correction (FEC) methods to further mitigate ISI.

Through this demonstration, we have completely delivered the steps which are essential for the implementation of Inter-Symbol Interference (ISI) mitigation within the simulated environment using ns2 tool. You can analyze their outputs and include the advanced mechanisms into the network. Rely on ns2project.com to effectively implement Network ISI mitigation in NS2, tailored specifically for your needs. Our team will take care of the project performance analysis with ease tailored to your project.