Additional Parameters

The main basis of a wireless network is that data is sent between nodes through a wireless medium (such as radio waves, infrared, etc.). It has several challenges such as the movement of nodes, signal quality, and the mobility of the network topology, which need to be properly modeled in the simulation.

In addition to traditional network parameters, wireless networks also have some additional parameters that have a profound impact on the performance of the network. These parameters are designed keeping in mind the dynamic nature of wireless networks.

In a wireless network, nodes are usually not static, but they move. A mobility model is used to determine in which direction, at what speed, and in what way the nodes will move. The most common mobility model is:

Random Waypoint Model: This model selects a random direction and speed for each node, and the node moves in that direction for a certain period of time. Then the node selects a new direction and speed. The code for this model is as follows:

$ns_ at 2.0 "$node_(1) setdest 75 200 15.0"

In this, the setdest command sets the destination position (x, y) and speed (m/s) of the node.

The characteristics of the antenna are also important in a wireless network because it affects the transmission and reception of radio signals. Two types of antenna models are commonly used in NS2:

Omni-directional Antenna: This sends signals in all directions. It is set as follows:

Directional Antenna: This sends signals only in a specific direction, and it is used when the network requires more targeted communication.

A radio propagation model determines how a signal will propagate through the air and what kind of obstacles it will encounter. This greatly affects the performance of the network because it determines how a signal will be received between nodes.

There are three main propagation models in NS2:

Free Space Model: This model assumes that the signal is transmitted in a straight line, and there are no obstacles on it. It is used when the nodes are in direct line of sight of each other:

Two-ray Ground Model: This model takes into account the direct and ground reflection paths of the signal. It is more accurate for long distances:

Shadowing Model: This model takes into account the signal fading due to various obstacles:

Each node in a wireless network has a specific transmission range, within which it can send signals to other nodes. In addition, there is also an interference range, in which a node can send a signal, but it can interfere with the signals of other nodes in that range. These ranges are set as follows:

Phy/WirelessPhy set freq_ 914e6 ;# Signal frequency

Phy/WirelessPhy set L_ 1.0      ;# System loss

A MAC protocol is used to control the use of the media between nodes in a wireless network. The most commonly used MAC protocol in NS2 is:

MAC 802.11: This is based on the IEEE 802.11 standard, which is used in Wi-Fi networks. Its setup is as follows:

Energy management in wireless nodes is a major challenge, especially in mobile and ad-hoc networks. It is necessary to manage the information of the battery capacity and energy consumption of the nodes. The battery model is set as follows:

Node/MobileNode set initialEnergy_ 100.0

Node/MobileNode set txPower_ 0.5

Node/MobileNode set rxPower_ 0.3

In this, initialEnergy_ represents the initial battery level of the node, while txPower_ and rxPower_ represent the energy consumption during transmission and reception.

Animation is used to see the activities of the network in the simulation of a wireless network. In NS2, this process is done through NAM (Network Animator), which graphically displays the movement of nodes, signals, and packets.

$ns namtrace-all-wireless $namtrace $val(x) $val(y)