How to Implement Physical Layer in ns2

 

To implement the physical layer using the simulation NS2 (Network Simulator 2) has needs to encompass comprehending the role of the physical layer in the network simulation and how NS2 manages the physical layer. This layer in terms of the simulation NS2 that normally connects to the mimicking how the signals propagate and interact with the situation then how the nodes are communicate over the channels such as wireless mediums. Obtain engaging project concepts from our team of researchers. Receive customized support for the implementation of the Physical Layer in ns2. We provide comprehensive network analysis information for your projects; please share your project specifics with us for further assistance.

The simulation NS2 is previously contains a wireless physical layer for mimicking wireless networks. The physical layer can be tailored, but it mainly deals with:

  • Transmission power
  • Propagation models
  • Antenna models
  • Interference and noise models

Steps to Implement or Customize the Physical Layer in NS2:

  1. NS2 Physical Layer Overview

This layer in NS2 is executed under the Phy/WirelessPhy class that simulations how signals are transferred and received across a wireless medium. The physical layer interacts with:

  • Channel/WirelessChannel: The medium for the communication.
  • Antenna/OmniAntenna: The antenna model.
  • Propagation models: Models are like FreeSpace and TwoRayGround that describe how signals propagate.
  1. TCL Script Configuration for Physical Layer

Once configures a network in the NS2, we can stipulate the physical layer in the TCL script using node-config. Given below is an example of how to set up the physical layer in a simple wireless simulation:

# Create a simulator instance

set ns [new Simulator]

# Open trace and nam files

set tracefile [open “phy_layer.tr” w]

$ns trace-all $tracefile

set namfile [open “phy_layer.nam” w]

$ns namtrace-all-wireless $namfile

# Define network topology

set topo [new Topography]

$topo load_flatgrid 500 500

# Configure the nodes with the physical layer parameters

$ns node-config -adhocRouting DSR \

-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

# Create nodes

set n0 [$ns node]

set n1 [$ns node]

set n2 [$ns node]

# Set up wireless links between nodes

$ns duplex-link $n0 $n1 1Mb 10ms DropTail

$ns duplex-link $n1 $n2 1Mb 10ms DropTail

# Set up a traffic generator (UDP)

set udp [new Agent/UDP]

$ns attach-agent $n0 $udp

set null [new Agent/Null]

$ns attach-agent $n2 $null

$ns connect $udp $null

# Define a CBR traffic source

set cbr [new Application/Traffic/CBR]

$cbr set packetSize_ 512

$cbr set interval_ 0.05

$cbr attach-agent $udp

# Schedule events

$ns at 0.1 “$cbr start”

$ns at 4.0 “$cbr stop”

# End simulation

proc finish {} {

global ns tracefile namfile

$ns flush-trace

close $tracefile

close $namfile

exec nam phy_layer.nam &

exit 0

}

$ns at 5.0 “finish”

# Run the simulation

$ns run

Explanation of TCL Script:

  • node-config: This segment is stipulates the physical layer setup in which:
    • -phyType Phy/WirelessPhy: Specifies the physical layer model (in this situation, the wireless physical layer).
    • -propType Propagation/TwoRayGround: Describes the propagation model used by the physical layer. We can modify it to other models such as FreeSpace or Shadowing.
    • -antType Antenna/OmniAntenna: Sets the antenna model.
    • -channelType Channel/WirelessChannel: Sets the communication channel type (wireless).
  1. Physical Layer Models in NS2

We can setup the numerous features of the physical layer by tweaking propagation models, transmission power, and more:

  • Propagation Models:
    • FreeSpace: Considers, a clear, line-of-sight communication path.
    • TwoRayGround: Assumes, both direct path and ground reflection.
    • Shadowing: Launches the variability because of obstacles.

Sample TCL command to set the propagation model:

$ns node-config -propType Propagation/FreeSpace

  • Transmission Power: We can set up the transmission power (TxPower) at the physical layer using C++ or via TCL:

Phy/WirelessPhy set Pt_ 0.2818   ;# Set transmission power (in watts)

  • Antenna Models: We can also test with various antenna models:

$ns node-config -antType Antenna/OmniAntenna

  1. Modifying Physical Layer Behavior in C++

If we want to change the physical layer performance such as how signal propagation is handled, we can edit the given NS2 files:

  • wireless-phy.cc: The primary file in which the physical layer logic is executed.
  • propagation.cc: Manages the propagation models.
  • antenna.cc: Deals with antenna types.

For instance, if we need to change the signal reception logic in the physical layer, we would alter the recv() function in the wireless-phy.cc file:

void WirelessPhy::recv(Packet* p, Handler* h) {

// Custom physical layer handling logic

}

Once changes are created, recompile NS2:

cd ns-allinone-2.35/ns-2.35/

./configure

make clean

make

  1. Visualizing and Analyzing Results

We can open the NAM file to visualize how packets propagate in the network, after running the TCL simulation:

nam phy_layer.nam

Moreover, we can evaluate the trace file (phy_layer.tr) to test the physical layer events such as packet transmission, reception, and loss because of propagation effects.

  1. Enhancing the Physical Layer Simulation

To improve the simulation, we could:

  • Test with various antenna configurations like directional antennas.
  • Mimic mobility models to monitor how node movement impacts the physical layer.
  • Launch the interference and noise models to replicate a more realistic communication environment.

The comprehensive procedure for executing and enforcing the Physical layer in NS2 has been demonstrated. Further specific information will be provided later depending on your needs.