**How to Calculate Network Mobility Rate in NS2**

To calculate the Network Mobility Rate in Network Simulator 2 (NS2) represents the rate at which nodes adjust their locations over time inside the network. It is certainly crucial in simulations encompassing mobile ad hoc networks (MANETs), vehicular networks (VANETs) or any situation that has nodes can travel dynamically during the simulation. The given procedure will help you with the calculation of mobility rate in ns2:

**Formula for Mobility Rate:**

The **mobility rate** is usually estimated as the distance a node travels per unit of time (speed) over a specified period of time. For a network, the mobility rate can be stated as the average speed of all nodes in the simulation.

Mobility Rate=Total Distance Moved by Nodes (meters)Simulation Time (seconds)\text{Mobility Rate} = \frac{\text{Total Distance Moved by Nodes (meters)}}{\text{Simulation Time (seconds)}}Mobility Rate=Simulation Time (seconds)Total Distance Moved by Nodes (meters)

**Steps to Calculate Network Mobility Rate in NS2:**

**Define Mobility Model:**In NS2, node movement is controlled using mobility models like Random Waypoint, Random Walk, or other existed models. You can allot these mobility patterns to the nodes, which will lead them to travel inside the simulation area.**Track Node Movements:**The trace file created during the simulation records node locations at various timestamps. By assessing these positions, you can calculate the total distance dispatched by each node.**Calculate Mobility Rate:**Using the changes in position for each node over time, measure the distance traveled and average it over all nodes to obtain the network mobility rate.

**Example Tcl Script for NS2 Simulation with Mobility:**

Below is an example NS2 script where nodes travel according to a Random Waypoint mobility model. The mobility pattern for each node is stated by its speed and the time amongst differences in position.

# Create a new simulator instance

set ns [new Simulator]

# Define the simulation area

set opt(x) 500 ;# X dimension of the simulation area (meters)

set opt(y) 500 ;# Y dimension of the simulation area (meters)

# Define the number of mobile nodes

set num_nodes 5

# Open trace file to record events

set tracefile [open trace.tr w]

$ns trace-all $tracefile

# Create mobile nodes

for {set i 0} {$i < $num_nodes} {incr i} {

set node($i) [$ns node]

$node($i) set X_ [expr rand()*$opt(x)]

$node($i) set Y_ [expr rand()*$opt(y)]

$node($i) set Z_ 0.0

}

# Define mobility model (Random Waypoint)

for {set i 0} {$i < $num_nodes} {incr i} {

$ns at 0.0 “$node($i) setdest [expr rand()*$opt(x)] [expr rand()*$opt(y)] 10.0”

$ns at 5.0 “$node($i) setdest [expr rand()*$opt(x)] [expr rand()*$opt(y)] 15.0”

}

# Simulation end

$ns at 10.0 “finish”

proc finish {} {

global ns tracefile

$ns flush-trace

close $tracefile

exit 0

}

# Run the simulation

$ns run

In the above script:

- Nodes are distributed random destinations inside a 500×500 meter area.
- The mobility model is Random Waypoint, where nodes move to a new random location every 5 seconds.
- The speed is fixed to 10 meters per second initially and 15 meters per second after 5 seconds.

**Trace File Analysis for Mobility Rate:**

The trace file records the positions of the nodes when move. You can extract node positions at various timestamps to measure the distance travelled by each node.

**Example Trace File Output:**

The location of each node at any point in time is usually logged with M lines in the trace file:

M 0.1 _1_ 2.0 3.0 0.0

M 0.2 _1_ 4.0 7.0 0.0

M 0.3 _2_ 3.0 1.0 0.0

M 0.4 _1_ 6.0 10.0 0.0

- The format is M [timestamp] [node_id] [X_] [Y_] [Z_].

Compute the mobility rate by extracting the node locations at various times, estimate the Euclidean distance moved by each node, and total the distances over time.

**Formula for Distance Between Two Points:**

The Euclidean distance dispatched by a node amongst two time points can be measured as:

Distance=(X2−X1)2+(Y2−Y1)2\text{Distance} = \sqrt{(X_2 – X_1)^2 + (Y_2 – Y_1)^2}Distance=(X2−X1)2+(Y2−Y1)2

**Bash Script to Calculate Mobility Rate:**

You can process the trace file and calculate the sum distance travelled by each node over time by using Bash script or any scripting language.

# Extract mobility events from trace file (node positions with time)

grep “^M” trace.tr > mobility.txt

# Calculate the distance moved by node 1

awk ‘{

if (prev_time[$2] != “”) {

dx = $3 – prev_x[$2];

dy = $4 – prev_y[$2];

dist = sqrt(dx*dx + dy*dy);

total_distance[$2] += dist;

}

prev_time[$2] = $1;

prev_x[$2] = $3;

prev_y[$2] = $4;

} END {

for (node in total_distance) {

print “Node ” node ” Total Distance: ” total_distance[node] ” meters”;

}

}’ mobility.txt

# Sum distances for all nodes and calculate mobility rate

# Example calculation:

simulation_time=10 # Total simulation time in seconds

total_distance_moved=$(awk ‘{sum+=$5} END {print sum}’ mobility.txt)

mobility_rate=$(echo “scale=2; $total_distance_moved / $simulation_time” | bc)

echo “Mobility Rate: $mobility_rate meters/second”

**Calculate Mobility Rate:**

**Extract Positions:**Extract the node locations at various timestamps from the trace file.**Calculate Distance:**For each node, measure the total distance travelled during the simulation.**Calculate Mobility Rate:**Add up the total distance moved by all nodes and divide by the simulation time to obtain the mobility rate.

**Example Calculation:**

Let’s assume:

**Total distance moved by all nodes**= 1000 meters**Simulation time**= 10 seconds

Using the formula:

Mobility Rate=1000 meters10 seconds=100 meters/second\text{Mobility Rate} = \frac{1000 \text{ meters}}{10 \text{ seconds}} = 100 \text{ meters/second}Mobility Rate=10 seconds1000 meters=100 meters/second

Thus, the network mobility rate would be **100 meters/second**.

**Summary:**

**State a mobility model**for the nodes in the NS2 simulation (like Random Waypoint).**Generate a trace file**and extract node locations at various timestamps.**Compute the overall distance**travelled by each node using the Euclidean distance formula.**Add the distances**for all nodes and divide by the total simulation time to estimate the network mobility rate.

Now, you can get to know more about the mobility rate of the network and how to compute the distance travelled by each node using ns2 tool. We have provided the detailed guide and examples to help you calculate it including outputs. If needed, we will offer another computational process for you. To regulate the Network Mobility Rate using the NS2 tool, you can visit ns2project.com, where we offer excellent research ideas and topics. Just share your parameter details with us, and we’ll assist you with a comprehensive network comparison analysis.