How to Calculate Coverage Time in NS2

To calculate coverage time in Network Simulator 2 (NS2), It refers to the amount of time taken for a particular area or point of interest is covered by one or more nodes. It is very useful in wireless sensor networks (WSN) or mobile networks in which the intent is to make sure that a region or target is constantly observed by the sensors or nodes. Below are the steps to follow to compute this using ns2:

Steps to Calculate Coverage Time in NS2

  1. Define Coverage Time:
  • Coverage Time is the growing time during which the target area or a certain point is inside the sensing range of at least one node.
  • It can be estimated for the whole region or for a specific point of interest.
  • The formula is: Coverage Time=∑(Intervals during which the area is covered)\text{Coverage Time} = \sum (\text{Intervals during which the area is covered})Coverage Time=∑(Intervals during which the area is covered)

You need to track when a node enters and exits the sensing range of the point/area and measure the time differences.

  1. Setup Simulation in NS2:

Compute the coverage time by configuring the network scenario and nodes in NS2. Here’s a simple TCL script setup:

# Create the Simulator

set ns [new Simulator]

# Create the Topography (e.g., 1000m x 1000m area)

set topo [new Topography]

$topo load_flatgrid 1000 1000

# Create two mobile nodes

set node_(0) [$ns node]

set node_(1) [$ns node]

# Define the sensing range for coverage (e.g., 30 meters)

set sensingRange 30

# Set initial positions of the nodes

$node_(0) set X_ 100

$node_(0) set Y_ 100

$node_(1) set X_ 500

$node_(1) set Y_ 200

# Set mobility (optional, if nodes are mobile)

$ns at 10.0 “$node_(0) setdest 500 500 10”  ;# Node 0 moves at 10 m/s

# Define traffic or events (if necessary)

  1. Tracking Coverage:

You need to track the locations of the nodes and verify either a point or area is in their sensing range over time. Here’s how you can do this:

  • Define the Point of Interest: Pick a certain point to observe (e.g., X = 300, Y = 300).
  • Check Coverage at Regular Intervals: At each time step, validate whether any node is within the sensing range of the point.

# Define the point of interest

set pointX 300

set pointY 300

# Function to check if a point is within the sensing range of any node

proc isCovered {x y} {

global ns node_ sensingRange

set covered 0

foreach nodeID [array names node_] {

set nodeX [$node_($nodeID) set X_]

set nodeY [$node_($nodeID) set Y_]

# Calculate Euclidean distance between the node and the point

set distance [expr sqrt(($nodeX – $x) * ($nodeX – $x) + ($nodeY – $y) * ($nodeY – $y))]

# If the point is within the sensing range, mark it as covered

if {$distance <= $sensingRange} {

set covered 1

break

}

}

return $covered

}

# Global variable to track coverage time

set coverageTime 0.0

set checkInterval 1.0  ;# Check coverage every 1 second

# Function to check coverage over time

proc checkCoverage {} {

global ns coverageTime checkInterval pointX pointY

# Check if the point is covered at the current time

if {[isCovered $pointX $pointY]} {

set coverageTime [expr $coverageTime + $checkInterval]

}

# Schedule the next coverage check

if {[$ns now] < 100.0} {   ;# Total simulation time = 100 seconds

$ns at [expr [$ns now] + $checkInterval] “checkCoverage”

}

}

# Start checking coverage at time 0

$ns at 0.0 “checkCoverage”

# Function to end the simulation and display results

proc finish {} {

global coverageTime

puts “Total Coverage Time: $coverageTime seconds”

exit 0

}

# End the simulation at 100 seconds

$ns at 100.0 “finish”

  1. Explanation of Key Functions:
  • isCovered {x y}: This function confirms whether the point at coordinates (x, y) is within the sensing range of any node. It returns 1 if covered, and 0 otherwise.
  • checkCoverage: This function is called at regular breaks (e.g., every 1 second) to check if the point is covered. It maximizes coverageTime if the point is covered during that interval.
  • finish: This function is called at the end of the simulation to show the total coverage time.
  1. Run the Simulation:
  • The simulation will execute for the defined time (e.g., 100 seconds).
  • The coverage is checked at regular intervals (e.g., every 1 second).
  • At the end of the simulation, the total coverage time is printed to the console.
  1. Output Analysis:
  • The coverage time indicates how long the point of interest was within the sensing range of any node.
  • By modifying the node location, sensing range, and mobility, you can learn how these factors impact the coverage time.

Considerations:

  • Mobility Models: If your nodes are mobile, use proper mobility models (for instance: random waypoint) to replicate real-world conditions.
  • Multiple Points/Regions: You can extend the script to estimate coverage time for several points or an entire area by apportioning it into grid points.
  • Energy Constraints: In sensor networks, you can consider the energy levels of nodes and finish counting coverage time if a node’s energy is depleted.

Make use of the provided steps and instructions to concentrate on the calculation of Coverage Time in the ns2 environment to discover the time taken by the nodes to cover the particular area in the wireless sensor networks (WSNs). Please provide us with the details of your parameters, and we will assist you in project performance accordingly.