How to Implement Network Channel Coding in NS2

To implement the Network Channel Coding within NS2, which encompasses simulating the error-correcting coding methods used to improve the reliability of data transmission across the noisy channels. These coding supports to identify and modify the errors triggered by noise, interference, or other impairments within the communication channel. However NS2 doesn’t natively present the comprehensive physical-layer channel coding mechanisms, we can replicate its impacts on the transmission quality and packet error rates. In this procedure, we will:

  1. Model the impact of channel coding in minimising the bit error rates (BER).
  2. Replicate the performance of the error finding or modifying for transmitted packets.
  3. Modify the packet error probability to mimic the use of Forward Error Correction (FEC) methods such as Convolutional Codes, Hamming Code, or Reed-Solomon Codes.

Step-by-Step Implementation:

  1. Understanding Channel Coding
  • Channel coding is used to identify and correct the errors while data transmission. General coding techniques comprise:
    • Hamming Code: Finds and corrects single-bit errors.
    • Convolutional Coding: It delivers error correction using a sliding window across the data stream.
    • Reed-Solomon Code: Corrects the burst errors.
  • The key aim of channel coding is to maximizing the probability of effectively decoding received data, even though some bits are corrupted because of the noise or interference.
  1. Approach to Simulate Channel Coding in NS2
  • Packet Error Rate Reduction: Replicate how channel coding minimises the packet error rate (PER) or bit error rate (BER) by applying correction methods.
  • Error Correction Mechanism: Integrate an abstraction of error detection and correction when packet transmission.
  • Modifying the Physical Layer: Alter the packet error rate (PER) in the physical layer rely on the kind of channel coding used.
  1. Steps for Implementing Channel Coding in NS2

Step 1: Modify the Physical Layer to Incorporate Channel Coding

  1. Open the Physical Layer Script (wireless-phy.tcl):
    • We will change how NS2 computes the packer errors while transmission. In specific, we will change the BER or PER depends on the channel coding scheme being used.
  2. Define Channel Coding Parameters:
    • Configure the parameters to denote the various channel coding schemes such as Hamming Code, Reed-Solomon, and so on. These parameters will impact the BER or PER.

# Set up channel coding parameters

set Phy/WirelessPhy/Hamming_code_ber_reduction 0.1  ;# Hamming code reduces BER by 90%

set Phy/WirelessPhy/Reed_Solomon_ber_reduction 0.05  ;# Reed-Solomon code reduces BER by 95%

set Phy/WirelessPhy/No_coding_ber 0.001  ;# Default BER without coding

  1. Function to Calculate Packet Error Rate Based on Channel Coding:

Execute a function, which computes the packet error rate (PER) depends on the kind of channel coding being used.

# Function to calculate packet error rate (PER) based on coding scheme

proc calc_packet_error_with_coding { coding_scheme packet_size ber } {

set ber_reduction 1.0

# Apply channel coding to reduce the BER

switch $coding_scheme {

“Hamming” {

set ber_reduction [Phy/WirelessPhy set Hamming_code_ber_reduction]

}

“Reed-Solomon” {

set ber_reduction [Phy/WirelessPhy set Reed_Solomon_ber_reduction]

}

default {

# No coding applied, use default BER

set ber_reduction 1.0

}

}

# Adjust the BER based on the selected coding scheme

set effective_ber [expr $ber * $ber_reduction]

# Calculate packet error probability (PER) based on the BER and packet size

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

return $packet_error_prob

}

  1. Adjust Packet Reception Based on Channel Coding:

Integrate the channel coding into the packet reception process, so as to packets with coding have a lower chance of being flowed because of the errors.

proc Phy/WirelessPhy::recv {packet} {

# Get the packet size

set packet_size [$packet size]

# Set the default BER (without coding)

set default_ber [Phy/WirelessPhy set No_coding_ber]

# Select the coding scheme (you can dynamically change this in the TCL script)

set coding_scheme “Hamming”  ;# Example: Hamming code applied

# Calculate the packet error probability based on the coding scheme

set packet_error_prob [calc_packet_error_with_coding $coding_scheme $packet_size $default_ber]

# Simulate packet loss due to transmission errors

set random_val [expr rand()]

if {$random_val < $packet_error_prob} {

# Drop the packet due to errors

drop $packet

return

}

# Forward the packet to the upper layers if no errors

$self up-target $packet

}

Step 2: Define a TCL Script to Simulate Network Traffic with Channel Coding

We will require a TCL script, which configures a simple wireless network, applies the channel coding, and replicates data transmission.

# Create a simulator instance

set ns [new Simulator]

# Create trace and nam files for output

set tracefile [open channel_coding.tr w]

set namfile [open channel_coding.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 in the network

# Set physical layer parameters

set Phy/WirelessPhy/No_coding_ber 0.001  ;# Default BER without coding

set Phy/WirelessPhy/Hamming_code_ber_reduction 0.1

set Phy/WirelessPhy/Reed_Solomon_ber_reduction 0.05

# Define node 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 and set initial positions

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

set node_($i) [$ns node]

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

}

# Set up traffic generation

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 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
  • Channel Coding Definition: Channel coding schemes such as Hamming Code and Reed-Solomon are abstracted as metrics, which minimise effective BER.
  • Packet Reception: The recv function verifies for packet errors rely on the chosen coding scheme and decides whether to drop or accept the packet.
  • Traffic Generation: The script makes constant bit rate (CBR) traffic among the nodes using UDP agents.
  1. Running the Simulation
  • We can save the altered wireless-phy.tcl and the TCL script (channel_coding.tcl).
  • Run the simulation using the below command:

ns channel_coding.tcl

  1. Analysing Results
  • To examine the trace file (channel_coding.tr) to estimate how the various channel coding schemes affects the packet error rates, after running the simulation.
  • We can liken the outcomes with and without coding to observe the enhancements in transmission reliability.
  1. Further Enhancements
  • Adaptive Coding: Execute the adaptive coding schemes, which switch among various coding rates or methods rely on the channel conditions (e.g., SNR).
  • FEC vs ARQ: Liken the Forward Error Correction (FEC) with Automatic Repeat Request (ARQ) by executing packet retransmission mechanisms.
  • Detailed Error Models: We can use more thorough physical layer models like fading, interference to well replicate real-world transmission environments and the impacts of channel coding.

As above we demonstrated the thorough process for execution the Network Channel Coding and analyse it in NS2 platform. Additional insights will be provided on this topic based on your needs. We emphasize contemporary research methodologies to ensure optimal results. Reach out to ns2project.com for superior outcomes in Network Channel Coding implementations for your initiatives. Our developers offer exceptional project support, working on thorough physical-layer channel coding strategies tailored to your needs, so you can obtain the finest topics and ideas from us.