Writing simulation scripts in Tcl (Tool Command Language) is included in the process of simulation Wireless Sensor Networks (WSNs) with the help of NS-2 (Network Simulator 2). By permitting users to simulate several protocols and network topologies, NS-2 is mostly utilized for the investigation in networking. Here, we provide a simple example of the process of establishing a basic WSN simulation in NS-2. Through this example we enclose the concepts of developing a network topology, describing a wireless channel, formation of nodes and configuring an easy interaction among nodes.

Step 1: Define the Environment

       Initially, you should establish the simulation setting along with the network topology, trace files and simulator object.

# Create Simulator instance

set ns [new Simulator]

# Set up the file for tracing

set tracefile [open wsn.tr w]

$ns trace-all $tracefile

# Define a procedure to finish the simulation that closes the trace file

proc finish {} {

    global ns tracefile

    $ns flush-trace

    close $tracefile

    exit 0

}

# Define the simulation area (e.g., 500×500 meters)

set val(x) 500

set val(y) 500

Step 2: Create the Wireless Channel

       To maintain the path of the network topology, NS-2 employs a “God” object.

# Create the topology object

create-god 10

# Setup the wireless channel

Phy/WirelessPhy set bandwidth_ 2Mb

Phy/WirelessPhy set freq_ 2.4e9

Step 3: Configure Node and Network Properties

       You can assign the features of the node by configuring the kind of ad hoc routing protocol like AODV in this phase.

# Configuration for wireless communication

set opt(adhocRouting) AODV

set opt(ll) LL

set opt(mac) Mac/802_11

set opt(ifq) Queue/DropTail/PriQueue

set opt(ifqlen) 50

set opt(ant) Antenna/OmniAntenna

set opt(prop) Propagation/TwoRayGround

set opt(netif) Phy/WirelessPhy

set opt(channel) Channel/WirelessChannel

set opt(x) 500

set opt(y) 500

set opt(cp) “”

set opt(sc) “”

# Create a node

set node0 [$ns node]

$node0 set X_ 250

$node0 set Y_ 250

$node0 set Z_ 0

Step 4: Define Nodes and Their Communication

       Develop various nodes and then use an application protocol to establish a straightforward or clear interaction flow among them.

# Creating another node

set node1 [$ns node]

$node1 set X_ 300

$node1 set Y_ 300

$node1 set Z_ 0

# Define a UDP connection from node0 to node1

set udp [new Agent/UDP]

$ns attach-agent $node0 $udp

set null [new Agent/Null]

$ns attach-agent $node1 $null

$ns connect $udp $null

# Set up a data source

set cbr [new Application/Traffic/CBR]

$cbr set packetSize_ 512

$cbr set interval_ 0.05

$cbr attach-agent $udp

# Start the application

$ns at 1.0 “$cbr start”

# Schedule the end of the simulation

$ns at 30.0 “finish”

# Run the simulation

$ns run

       A fundamental WSN with two nodes is initiated by this script and these nodes in which one node transfers data to another node beyond a UDP link through the AODV routing protocol. According to your project needs, you can configure various routing protocols, refine the simulation parameters and include many nodes to extend this simulation. To assist in modifying your simulation to particular WSN situations, consider the NS-2 which provides huge records and public resources.

How to run a NS2 simulator on a Mac?

       As NS-2 (Network Simulator 2) is mainly built for Linux/Unix platforms, executing NS-2 on a Mac contains some procedures. By installing Linux virtual setups or implementing terminal emulators, you can still get it running on MacOS however. We give you the procedural flow direction to get NS-2 up and executing on your Mac:

Option 1: Using Homebrew and XQuartz

       To install NS-2, this approach includes implementing a package manager called Homebrew for macOS. Specifically for X11 applications, you will also require XQuartz. Meanwhile, for its graphical elements, NS-2 depends on it.

Step 1: Install Homebrew

       Open the Terminal app and run the below direction, when you have not installed Homebrew until now:

/bin/bash -c “$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install.sh)”

       To finish the installation, stick to the displaying directions.

Step 2: Install XQuartz

       NS-2 needs X11 forwarding that is offered by the XQuartz. Using https://www.xquartz.org/, download and install XQuartz.

Step 3: Install NS-2 Using Homebrew

       You can install NS-2 with Homebrew by executing the following command after the installation of Homebrew and XQuartz:

       brew install ns 

Step 4: Verify the Installation

       Once NS-2 is installed, check whether NS-2 is installed appropriately by executing:

       Ns

       This specified command must open the NS-2 command line. Leave it by typing exit.

Option 2: Using a Virtual Machine

       Alternative procedure that offers highly compatible platforms for NS-2 is executing a Linux virtual machine (VM) on your Mac.

Step 1: Install a Virtualization Tool

       Install VMware Fusion (https://www.vmware.com/products/fusion.html) or VirtualBox (https://www.virtualbox.org/) as a virtualization tool. VMware Fusion is costly software that includes multiple properties, but VirtualBox is completely free.

Step 2: Download a Linux ISO

       It is necessary to download a Linux distribution ISO image. For simple utilization, Ubuntu is a famous decision. Through this link https://ubuntu.com/download, you can download it.

Step 3: Create a New Virtual Machine

       Design a novel VM by opening your virtualization tool. In place of the startup disk, you can implement the downloaded Linux ISO.

Step 4: Install Linux

       Install Linux on your VM by tracking the on-screen guidelines.

Step 5: Install NS-2 on Linux

       By utilizing the package manager or compiling it from source, you can install NS-2 after the installation of Linux. You can execute the following codes for Ubuntu or Debian-central dispersions:

       sudo apt-get update

       sudo apt-get install ns2

Step 6: Verify the Installation

       Check the installation through executing:

       Ns

       The above command must open the NS-2 command line. To leave the setting, type exit.

Note

       On NS-2, executing simulations needs writing scripts in Tcl. Through the ns command afterwards the script name, you can perform these scripts, for example, ns myscript.tcl.

       Either straight on your Mac or using a virtual Linux platform, you must be capable of running NS-2 simulations by adhering to these procedures.