Wireless Sensor Network Simulator


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Wireless Sensor Network Simulator

Deepa S, Mamatha C R, Rashmi R

UG Student1 ,Assistant Professor2, Assistant Professor3 Dept.computer science and engineering

Vemana Institute of Technology

Bangalore ,India

Abstract Wireless communication has been also bring many open issues in the network design.

evolving and growing rapidly during the last few years. In order to meet the demand of this growth

Normally, analyzing methods, computer simulation, and physical measurement are the three

researchers as well as industry have been working for main techniques used for analyzing the

new techniques and new standardizations. Wireless

sensor networks have been introduced to use in many

performance of wired and wireless networks. Setting up a network to do some reaal experiments is

application .They Provide a bridge between the the best way for studying about communication.

physical and virtual worlds. The main goal of this

paper is to learn how to use simulation for designing and studying wireless networks. Analyzing literature sources related to wireless communication networks

However, setting a network is not easy and costly. For this reason, a virtual network provided by network simulator is used for experiment in only one computer. Specially, NS2 which is free and easy to use is the popular all over the world. In our

and describing the basic wireless networks. Network project, NS-2 is chosen as our simulation

simulator-2 as a wireless simulator is being demonstrated in this paper. Network simulator ns-2

environment because it is the most widely used network simulator.

NS-2 has several key benefits which suitfor

and its detailed description along

programming languages used is

with the

explained.

doing the simulation:

Demonstration of the throughput ,delay and packet It provides extensive support for

dropped by the nodes is compared and the simulation simulating TCP/IP, Routing and multicast

is shown.

Keywords Wireless, sensors, ns-2 , simulation,

protocols over wired

network.

and wireless

network component . It provides a lot of standard modules to be used in sensor network.

  1. INTRODUCTION

    Wireless network is described as a network of

    • It is an object oriented provides a lot of documents.

    design which

    devices which communicate by using wireless technologies. Wireless network refers to any type of computer network that is wireless, and is commonly associated with a telecommunications network whose interconnections between nodes are implemented without the use of wires. The reasons for using wireless network are cost effectiveness of network deployment, and its applicability to environments where wiring is not possible or it is preferable solution compared with wired networks. When designing wireless networks and/or studying their behaviour under various conditions, software simulation tools are often used. In this paper the software tool Network Simulator (Version 2), widely known as ns-2, is described and used for the simulation. Optimizing a wireless sensor network

    • It uses OTcl to specify the components and OTcl to glue them together.

    Figure 1:Reality Network

    Figure 2:Network for simulation

  2. NETWORK SIMULATOR

    The network simulator (NS), which is a discrete event simulator for networks, is a simulated program developed by VINT (Virtual InterNetwork Testbed) project group (A Collaboration among USC/ISI, Xerox PARC, LBNL, and UCB). It

    supports simulations of TCP and UDP.

    Figure 3:Basic Structure of Network simulator

    To setup and run a simulation, a user writes an OTcl script, which is a simulation program to initiate an event scheduler, set up the network topology using the network objects and plumbing functions in the library, and to tell

    traffic sources when to start and stop transmitting packets through the event scheduler. When NS-2 which works as OTcl interpreter receives the OTcl script, it will set environment parameters following the received script. If a user wants to make a new network object, it will be easy to make a compound object from the object library, and plumb the data path through the object rather than write a new one. When the simulation is finished, the simulation results are produced in one or more text-based output files that contain detailed simulation data, which can be used to analyze directly or can be used in the graphical user interface Network Animator (NAM).

  3. PROGRAMMING LANGUAGES IN NS-2

    The reason for having two programming languages stems from the aim to have an easy to use, yet fast and powerful simulator. Object-oriented C++ forms an efficient class hierarchy core of ns-2 that takes care of handling packets, headers and algorithms. Object Tcl, or OTcl, is also an object oriented programming language utilized in ns-2 for network scenario creation, allowing fast modifications to scenario scripts. Simulation scenario contains network nodes, applications, topology and

    connections between the nodes. OTcl and C++ interact with each other through Tcl/C++ interface called TclCI. Tcl/Otcl is a language with very simple syntaxes that allows easy integration with other languages. Tcl was created by John Ousterhout. The characteristics of these languages are:

    • It allows a fast development.

    • It provides a graphic interface.

    • It is compatible with many platforms.

    • It is flexible for integration.

    • It is a scripting language.

    OTcl in ns-2 enables full control over simulation setup, configuration, and occasional actions (e.g. creating new TCP flows). It is a language that compromise between speed and abstraction level offered to the user. OTcl enables simulation scenarios of slightly varying parameters or configuration, where the main goal is to quickly Xplore a number of scenarios (change the model and re-run). Iteration time is an important aspect in OTcl [11]. C++ object oriented language is used for byte manipulation, packet processing and algorithm implementation. It is important to notice that detailed protocol simulations require the use of systems programming language. With C++ fast execution is enabled, so the Run time speed is important aspects in ns-2. Modularity of ns-2 is observed trough the Class hierarchy core of ns-2 written in C++. Modularity of simulation elements results in a compact simulation model, ns2 does not waste resources of the platform in vain. Compact design of elements opens up new space for the scalability of the elements of a simulation scenario.

  4. IMPLEMENTATION OF NS-2 BASED WIRELESS SENSOR NETWORK

    SIMULATOR

    1. Basic structure of wireless networks

      Wireless networks consist of numerous mobile nodes which communicate with each other via wireless channels, while in wireless sensor networks, these mobiles nodes are attached with sensors to sense the physical target and processors to generate data packets from sensing data and transmit them to their neighbours. Wireless network is described as a network of devices which communicate by using wireless technologies wireless is a concept of relating to data communications using radio waves; operating by means of transmitted electromagnetic waves.

      Wireless communication is used as a term for transmission of information from one place to another without using cables.

      Figure 4:Basic Structure of wireless sensor etwork

    2. Simulation model of wireless sensor network

      Figure 5:simulation model of sensor network

    3. Network inside NS-2

    The node (terminal, router) in real network have 4 layer using TCP/IP model . Actually, forwarding router have only 2 bottom layer. In the otherwise, 4 layers of TCP/IP model in NS2 are shown in. Two bottom layers are ready automatically when a node setting up. TCP or UDP in transport layer are shown as Agent. FTP, CBR are in application layers. Actually, the sender will set the application for creating data while the receive will not because it is no need to simulate the receiving data in application layer. Realistic network use cable for link between 2 node. One cable is available for biconnection. In NS2, a link is use for one connection.

    Two lines are needed for biconnection. Each link has a queue which similar to buer in realistic network. Packet, which is sent from node should be queuing in queue. When queue is empty, it will be send to other node via link.

    Figure 6:Network inside NS-2

  5. SIMULATION EXPERIMENT DESIGN

Simulation Scenario Wireless network performance depends mainly on the end to end throughput and average delay. Different applications place different requirements on the network. Real time applications such as voice over IP are highly sensitive to delay but function satisfactorily with little bandwidth. At the other hand data transfer applications like FTP are insensitive to delay but require as much bandwidth as possible. In this section we are going to present simulation scenario aimed at stimulating the network performance through network throughput, packet drop rate and average packets end to end delay. Determining the throughput, packet drop rate and average packets end to end delay

The nodes in our scenario use IEEE 802.11 standards (CSMA/CA) to communicate with each other.

We are going to use the simulation for: Determining the throughput for each node; ns-2 should calculate the bytes received by each node.

Determining the packet loses; ns-2 should calculate

the bytes that are transmitted and not receive by any node. Determining the average packets end to end delay; ns-2 should calculate the difference time of the last packet received and the number of all packets received.

we will present results of simulation obtained by using ns- 2 simulator where the experiment setup is aimed primarily at demonstration of ns-2 features and illustrations of some basic performance for simulated network.

  1. The network throughput

    In this section we are showing the simulation results illustrating the network throughput. We will see the throughput of nodes to see how nodes affect each other as a result of different emitting times of the node. Figure 7 show the relation between throughput and transmission rate. Here, the X axis represents the time of simulation and Y axis represents the throughput

    Figure 7:Throughput for two nodes (Node_1 is red line and

    Node_2 is green line)

    B . Packet drop rate

    Packet drop occurs when one or more packets of data travelling across a computer network fail to reach their destination. Here, the X axis represents the time of simulation and Y axis

    represents the number of packets dropped

    Figure 8: Packet drop for two nodes (Node_1 is a red line and

    Node_2 is a green line)

    C. Average packet end to end delay

    Packet delay is the difference in end-to-end delay between selected packets in a flow with any lost packets being ignored. . Here, the X axis represents the time of simulation and Y axis represents the average delay packets

    Figure 9:Delay for two nodes (Node_1 is a red line and Node_2 is a green

    line)

    VI . CONCLUSION

    Network Simulator (Version 2) is a discrete event driven network simulation tool for studying the dynamic nature of communication networks. Ns-2 provides a highly modular platform for wired and wireless simulations supporting different network elements, protocols, traffic and routing types. In general, Ns-2 provides users with a way of

    specifying network protocols and simulating their behaviour. The results of the simulation are stored in a trace file that records data about all events that occurred during the simulation process. In the master thesis we have used ns-2 to simulate the end user performance of the wireless network consisting of two APs and five nodes for variable throughput and transmission rate for the nodes. The simulation results in following conclusions about network behavior:

    • For throughput and transmission rate for the nodes, the performance of network remains constant and there is high fluctuation for single node.

    • Another comparative study between packet drop rate and transmission rate for the nodes shows that the performances of the observed networks differ and there is high fluctuation in the node .

    • Third important feature of performance study is average packets end to end delay and transmission rate for the nodes is that the performance of the whole network is finding to be transient initially, but it comes to a stable state after a certain amount of time.

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