**How to Calculate Network Transmission Power in NS2**

To calculate transmission power in ns2 has a series of steps to follow and it is the performance metrics in wireless communication that regulates the strength of the signal routed by a node like a base station or a mobile device. The transmission power impacts the Signal-to-Noise Ratio (SNR), link quality, coverage, and interference in a network.

NS2 permits to setting up and estimate the transmission power for wireless nodes that specifically in the scenarios in which we are emulated an energy-efficient protocols, power control, or wireless network performance.

The below are the procedures to calculate the transmission power in ns2:

**Steps to Calculate Network Transmission Power in NS2**

**Configure Transmission Power in NS2**

To estimate the transmission power in NS2, we need to first configure the **transmission power** for the wireless nodes. NS2 utilize the Phy/WirelessPhy class to describe the physical layer parameters that involves the transmission power, reception threshold, and other features.

We can set up the transmission power using the set Pt_ parameter that denotes the transmission power in **Watts**.

**Example TCL Script to Set Transmission Power:**

# Create a new simulator object

set ns [new Simulator]

# Configure the channel and physical layer

set val(chan) Channel/WirelessChannel ;# Wireless channel

set val(prop) Propagation/TwoRayGround ;# Propagation model

set val(netif) Phy/WirelessPhy ;# Wireless PHY layer

set val(mac) Mac/802_11 ;# MAC layer

set val(ifq) Queue/DropTail/PriQueue ;# Queue type

set val(ll) LL ;# Link layer

set val(ant) Antenna/OmniAntenna ;# Antenna model

set val(x) 500 ;# X range of the simulation

set val(y) 500 ;# Y range of the simulation

# Define transmission power (in Watts)

set tx_power 0.2818 ;# Default transmission power (in Watts)

# Configure nodes with the transmission power

for {set i 0} {$i < 2} {incr i} {

set node($i) [$ns node]

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

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

$node($i) set Z_ 0.0

# Configure the transmission power for each node’s PHY layer

$node($i) set Pt_ $tx_power

}

# Create a simple wireless link between nodes

$ns at 1.0 “$node(0) setdest 250 250 5”

$ns at 2.0 “$node(1) setdest 250 250 5”

# Run the simulation

$ns run

In this script:

**Pt_**is the metric for**transmission power**. In the above sample, the transmission power is set to**0.2818 Watts**(defaulting for some wireless configurations in NS2).- The wireless nodes are simulated with simple settings like channel type, propagation model (TwoRayGround in this case), and antenna model.

**Monitor Transmission Power in NS2**

We can enthusiastically observe or print the transmission power of a node in the course of the simulation using the get approaches to recover the value of the Pt_ parameter.

**Example TCL Script to Monitor Transmission Power:**

# Function to monitor and print transmission power of a node

proc monitor_transmission_power {node_id} {

global ns node

set tx_power [$node($node_id) set Pt_]

puts “Time: [$ns now], Node: $node_id, Transmission Power: $tx_power Watts”

# Re-schedule this procedure to check the transmission power every 10 seconds

$ns at [expr [$ns now] + 10.0] “monitor_transmission_power $node_id”

}

# Start monitoring the transmission power for Node 0

$ns at 0.0 “monitor_transmission_power 0”

In this script:

- The transmission power of
**Node 0**is monitored and printed at regular intervals (every 10 seconds). - We can track the transmission power in course of the replication to measure changes or adapt the power dynamically if we are mimic power control protocols.

**Calculate Transmission Power Based on Path Loss and Received Power**

In some scenarios, we need to estimate the **transmission power** according to the **received power** and **path loss**. The relationship among the transmission power, received power, and path loss is given by:

Pr=Pt×Gt×Gr×(λ4πd)2P_r = P_t \times G_t \times G_r \times \left(\frac{\lambda}{4 \pi d}\right)^2Pr=Pt×Gt×Gr×(4πdλ)2

Where:

- PrP_rPr is the received power.
- PtP_tPt is the transmission power.
- GtG_tGt and GrG_rGr are the antenna gains for the transmitter and receiver.
- λ\lambdaλ is the wavelength of the transmitted signal.
- ddd is the distance between the transmitter and receiver.

To calculate the transmission power based on the received power and path loss, we can reorder the equation:

Pt=PrGt×Gr×(λ4πd)2P_t = \frac{P_r}{G_t \times G_r \times \left(\frac{\lambda}{4 \pi d}\right)^2}Pt=Gt×Gr×(4πdλ)2Pr

**TCL Script to Calculate Transmission Power Based on Received Power:**

# Function to calculate transmission power based on received power and path loss

proc calculate_transmission_power {received_power distance frequency} {

# Constants

set c 3.0e8 ;# Speed of light in m/s

set Gt 1.0 ;# Transmit antenna gain

set Gr 1.0 ;# Receive antenna gain

# Calculate wavelength (λ = c / f)

set wavelength [expr $c / $frequency]

# Calculate transmission power

set path_loss_factor [expr ($wavelength / (4 * 3.1416 * $distance)) ** 2]

set transmission_power [expr $received_power / ($Gt * $Gr * $path_loss_factor)]

return $transmission_power

}

# Example usage

set received_power 1e-9 ;# Received power in Watts (1 nW)

set distance 100 ;# Distance between nodes in meters

set frequency 2.4e9 ;# Frequency in Hz (2.4 GHz for Wi-Fi)

set tx_power [calculate_transmission_power $received_power $distance $frequency]

puts “Calculated Transmission Power: $tx_power Watts”

This script estimate the **transmission power** according to the given **received power**, **distance**, and **frequency**. We can utilize this approach if we need to dynamically estimate the necessary transmission power during the simulation.

**Adjust Transmission Power Dynamically (Power Control)**

If we need to mimic **power control algorithms** in which nodes adapt their transmission power dynamically, we can compose a script that adapts the transmission power according to network conditions such as distance or interference.

**Example of Dynamic Power Adjustment:**

# Function to dynamically adjust transmission power based on distance

proc adjust_transmission_power {node_id distance} {

global node

set tx_power [expr 0.1 + ($distance / 500.0)] ;# Adjust transmission power based on distance

$node($node_id) set Pt_ $tx_power

puts “Node: $node_id, Adjusted Transmission Power: $tx_power Watts”

}

# Example usage: Adjust transmission power for Node 0 based on a distance of 200 meters

adjust_transmission_power 0 200

In this example:

- The transmission power is adapted according to the distance among nodes. The closer the nodes are, the lower the transmission power needed.
- This can be helpful for mimic energy-efficient or interference-aware protocols in which the nodes dynamically adapt their transmission power.

**Log Transmission Power to a File**

To evaluate the transmission power over time or through nodes, we can log the transmission power to a file during the simulation.

**Example TCL Script to Log Transmission Power:**

# Open a log file for transmission power

set tx_log [open tx_power_log.txt w]

# Function to log transmission power

proc log_transmission_power {node_id} {

global ns node tx_log

set tx_power [$node($node_id) set Pt_]

puts $tx_log “Time: [$ns now], Node: $node_id, Transmission Power: $tx_power Watts”

# Schedule the next logging event

$ns at [expr [$ns now] + 1.0] “log_transmission_power $node_id”

}

# Start logging transmission power for Node 0 every second

$ns at 0.0 “log_transmission_power 0”

This script logs the **transmission power** of **Node 0** to a file every second. We can utilize this log to evaluate on how transmission power changes during the simulation.

In this page, we understand the concepts and deliver the clear computation procedures that will help you to calculate the network transmission power analysis in ns2 tool. We plan to deliver the more information about how the network power analysis calculated in other simulation tools.

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