WSN Simulation Template for OMNeT

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WSN Simulation Templatefor OMNeT

• Stefan Dulman
• s.o.dulman_at_utwente.nl

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Presentation Overview

• OMNeT Introduction
• Sensor Network Template
• Implementation Example
• Discussion and future work

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OMNeT Introduction
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OMNeT Features

• Simulator designed for fixed, wired, distributed
  systems (such as computer networks,
  multiprocessor systems)
• Discrete time simulator
• It is compatible with DOS, UNIX, WINDOWS (uses
  C and Tcl/Tk)
• Several graphical interfaces allows easy
  debugging and variables inspection
• Offers support for parallel execution

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OMNeT Features (2)

• Simulated objects are represented by modules
• Modules can be simple or composed (depth of
  module nesting is not limited)
• Modules communicate by messages (sent directly or
  via gates)
• One module description consists of
• Interface description (.NED file)
• Behavior description (C class)
• Modules, gates and links can be created
• Statically - at the beginning of the simulation
  (NED file)
• Dynamically during the simulation

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OMNeT Features (3)

• Support is offered for
• Recording data vectors and scalars in output
  files
• Random numbers (also from several distributions)
  with different starting seeds
• Tracing and debugging aids (displaying info about
  the modules activity, snapshots, breakpoints)
• Simulations are easy to configure using .ini file
• Batch execution of the same simulation for
  different parameters is also included

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OMNeT Features (4)

• What is missing or not working as wanted
• Mobile entities and wireless communication
  between them are not included
• Static data types not allowed
• For storing data needed by all the modules a
  central manager has to be created
• Communication with this entity goes by messages
  (slow!)
• Using pointers to it is not always good idea
  (parallel execution)
• Execution goes very slow with the increase of the
  number of messages and when using parameters
• Very slow 2D graphical interface made in Tk

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Sensor Network Template
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Template Description

• What is it
• A fully working project consisting of a network
  of mobile nodes that can communicate by wireless
  means. The user has only to implement the wanted
  algorithm, with no concern on how these issues
  are handled.
• All the parameters of the network can be changed
  without any need of rewriting any code
• Offers (a lot of) easy to use macros for
  accessing the main functionalities

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Template Description (2)

• Characteristics
• Implements mobility (Random Way Point alg.)
• Wireless communication
• Simulated by dynamically connecting modules
  within transmission range
• Unidirectional links
• Signal strength can be varied from within the
  nodes
• Energy management is also included
• Nodes have failing probabilities
• Map for area failures can be specified and used
• Other maps can easily used for obstacles, fading,
  etc. (implementation is similar)

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Network Architecture

• Central Manager
• Used as a central database
• Its main function stores the connectivity map
  and updates it upon request
• It takes care of reading additional configuration
  files and sending the information
• It is hidden from the display, communication with
  it is done only with sendDirect() function
• Sensor nodes

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Sensor Node Architecture

• Sensor node architecture
• Layer 0
• Sensor
• Energy manager
• Blackboard
• Application
• Custom network layers

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Mobility Issues

• Approaches to describe mobility
• Each node reports its position after a certain
  interval.
• Simulation precision depends on this interval.
• The smallest the interval the longest the
  simulation time
• Each node reports the equation of the curve of
  its movement
• Manager computes the interaction moments and
  schedules gates connect/disconnect at those
  moments
• Faster execution (almost 4 times in our
  simulations)
• More precise simulation
• Graphical display no longer linked to the
  simulator precision
• Random Way Point model as default

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Energy Management

• Implemented using the blackboard
• Consumed energy and of the current energy
• Data can be accessed from anywhere within a
  sensor node
• Estimation of the lifetime of the node (can be
  improved by using any desired estimation
  function)
• Warnings can be issued when no energy is left
  (special behaviours can be implemented in the
  energy manager e.g. stop certain components when
  energy goes beyond a treshhold)

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Reliability Issues

• Two kinds of failures implemented
• Node failure probability
• Can be specified for each node separately
• Available to all the layers inside a node
• Can be set to change over the time
• Area failure probability
• The failure zones are specified as rectangles
  inside a configuration file
• Data is available to all the layers
• It can be given any interpretation needed. Easy
  to extend to a set of maps

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Other features

• RWP algorithm is fully configurable by constants
  for speed and sleep time
• Discrete simulator problem update messages from
  the manager/layer0 for the topology update arrive
  in the same time with messages from the
  application.
• Solution usage of a constant defining the
  maximum time resolution used by the application
• Infrastructure update messages are scheduled
  before information messages
• Layer0 can check if the user has used time values
  that need a higher precision than allowed

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Other Features (2)

• Support for beacons is added (needed by the
  localization algorithms)
• A certain number of nodes have fixed positions
• Any node can find out if it is a beacon or not
• Each node can be displayed in several ways
  (useful for debugging and presentations to
  highlight the discovered paths, the clusters,
  etc.)
• 3 distinct graphical signs and 10 colors for each
  one
• Can be modified from anywhere inside the node
• Modifications are displayed immediately
• Simulation precision is no longer related to
  display update
• User can specify the display rate

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Work in progress

• Signal sources
• Support for fixed and mobile beacons
• Support for areas of interest
• Fixing minor bugs and optimizing the code
• Rather use new derived classes than parameters
• Finding the best places to place the
  functionality (manager or layer0)
• Trying to create a library of modules
• WANTED 3D graphical display !!!

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Work in Progress (2)

• Tcl/Tk script for
• Easy configuration of the network
• Designing the maps, node initial positions,
  initial values, etc.
• Generation of project files

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• Implementation example

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Example (1)

• Application example
• One node periodically broadcasts distinct
  messages (each 5 sec)
• Each other node re-broadcasts a received messages
  if this one is newer than the last heard one
  (after 1 second)
• In case of message collision, the incoming
  messages are discarded
• Step 1
• Adding the interface description for the custom
  layers

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Example (2)

• Step 2
• Creating the new module C class (using Tcl
  script)
• Step 3
• Writing the code for the message collision
• Step 4
• Writing the application code
• Step 5
• Verification by simulation

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Discussions

• Address where to download the template
• http//wwwhome.cs.utwente.nl/dulman/tools.htm
• Email address
• s.o.dulman_at_utwente.nl