Opnet Wirless Mobile Network

CEG 4286 Wireless Mobile Networks LABORATORY 2

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Introduction to OPNET OPNET modeler is used for wireless network lab simulations of this course. You will learn how to use OPNET first by reviewing this tutorial. Further information can be obtained by studying OPNET documentations or consulting TAs. The purpose of this laboratory it to explain general structure of the OPNET modeler, how information flow during network simulations and view some of the capabilities of OPNET. This tutorial mainly concentrates on the parts of OPNET that we will utilize for CEG 4286 class. Definitions and screen shots of all the advanced OPNET editors are also given in this tutorial.

Overview

OPNET work flow OPNET Basics and Structure Network Model Editor Node Model Editor Process Model Editor Other OPNET Editors

OPNET Work flow

While using OPNET, you should follow certain steps in order to simulate a network configuration. First, you should create the network model that you want to work on. (Details of creating a network

model is given in the following sections). An example wireless LAN network connected through bridges is given in the figure below:

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CEG 4286 Wireless Mobile Networks After creating the network, you should choose network statistics that you want to work on or observe as

you change the simulation parameters. For instance, for WLANs, these statistics could be communication delay, system throughput, packet error rate etc. You can choose wanted statistics by right clicking the on the network model window and choosing “Choose individual statistics” option as illustrated below in figure 2.

Illustration 2: Choosing the simulation statistics to observe

Running the simulation would be the next step after choosing statistics to analyze. Running the simulation can be accomplished by calling “Configure Discrete Event Simulation” option from the “Simulation” tab in the Network model window.

CEG 4286 Wireless Mobile Networks

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Illustration 3: Example network simulation set-up

st step in simulating a network is analyzing the results of the network. Analyzing results means ing the change of selected network statistics relative to different simulation parameters. For a example this could be the change of network throughput relative to time as the load of the

rk changes, as illustrated in the figure below. Simulation results can be observed by right clicking twork window and choosing “view results” option from the drop down menu. The variation chosen statistics relative to time is shown in a graph.

llustration 4: Analyzing network simulation results

CEG 4286 Wireless Mobile Networks OPNET Basics and Structure

• OPNET has three-tiered hierarchy

Network model: Specifies actual network components (e.g. computers, hubs, routers) Node model: Specifies objects in network components (e.g. source in transmitter, queue) Process model: Specifies the algorithm and behavior of the node models

Illustration 5: OPNET hierarchy

• Project editor is the first interface that you come across with, when you start OPNET. You can specify network topology, choose statistics to analyze, run simulations and view results by this editor.

• Node editor specifies the internal structure of the components in project model. (e.g. router or hub) • Process editor implements the algorithm in node models. (e.g. ARQ algorithms)

Network Model Editor • Network models consist of nodes, links and subnets • Nodes can represent any network device, e.g. servers, mobile stations, routers, etc. • Subnets are used to cluster group of devices, e.g. Consider a WLAN network of school and you can

represent a room with a subnet where there are multiple wireless computers in each room.

CEG 4286 Wireless Mobile Networks

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Node Mod • Node mo• Basic bui• Processor• Nodes int• Node mo

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Illustration 6: An example network model

ble the connection between nodes, e.g. An Ethernet link connecting multiple computers.

el Editor

del includes basic build blocks of network components lding blocks might include source, sink, queue, link and processor modules modules can be fully programmable. (e.g. MAC interface) erface with other network components with transceivers and receivers dules can be connected with packet streams for data transmission and statistics wires for data

Illustration 7: An example node model

odel Editor

CEG 4286 Wireless Mobile Networks • Process model determines the behavior of the nodes by state transition diagrams, C-modules and built-in

functions (i.e. Kernel procedures) • Process model consists of

Finite state machine or state transition diagrams Chunks of C-codes called C modules State/Temporary variables

• Every action taken by process model is called process • In finite state machine, every state has enter executives (top half) and exit executives (bottom half) • The states can be forced (green) and unforced (red). Unforced state waits for an interrupt to continue

execution of exit executives. • Example for green (forced) state:

When first entered it performs enter execs in the first state Without any wait, it executes the exit execs (i.e. The reason it is called forced). (That is the only

difference between the unforced state. Unforced [Red] state passes the control to kernel after enter execs and waits for a signal [interrupt] in order to continue with exit execs.)

Evaluates the condition for transition. If the conditions are true it continues with the second state

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llustration 8: Example state diagram of process model

PNET Editors

s many advanced editors to be used in specific network modeling. For the labs that we are going to will not use all of its capabilities. Therefore in this section we will mention those editors. For more about these editors, please refer to OPNET help files.

Model Editor ink model editor lets you create new types of wired link objects, i.e. Ethernet connection. Each new f link can have different type of attributes, i.e. connection speed, duplex etc. The link model editor

window as illustrated below.

CEG 4286 Wireless Mobile Networks

Illustration 9: Link Model Editor

• The Path Editor

The path editor is used to create new path objects that define a traffic route.

Illustration 10: Path editor window

• The Packet Format Editor

CEG 4286 Wireless Mobile Networks The packet format editor lets you define the fields and the length of fields of a packet. For example IEEE 802.11 wireless channel simulations requires two types of packet formats, namely control packet format and information packet format. Different fields are color coded for illustration and the length of fields are proportional to the number of bits each field contains.

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llustration 11: Packet format editor window

e PDF Editor e probability density function (pdf) editor lets you analyze the probability distribution of an event. It resents the spread of probability of any outcome over the range of probabilities.

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e Probe E

llustration 12: PDF editor window

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CEG 4286 Wireless Mobile Networks The probe editor lets you choose the statistics to be collected during the simulation. With probe editor you can specify, save and load the statistics to be collected for any simulation.

Illustration 13: Probe editor window

• The Simulation Sequence Editor With OPNET, you can run simulations within the project editor. But you may want to simulate the same simulation with different constraints and conditions. For example, considering the wireless networks, you might want to get the throughput results for the same network with different loading conditions. You can specify the simulation editor to run the same simulation multiple times with the specified system parameters.

CEG 4286 Wireless Mobile Networks

Illustration 14: Simulation sequence window

• The Analysis Tool With analysis tool, you can create scalar graphs for parametric studies and define templates to which you apply statistical data and create analysis configurations that you can save and view later.

Illustration 15: Analysis tool