1. WSN Simulation Template for OMNeT++
Stefan Dulman

2. Presentation Overview
OMNeT++ Introduction
Sensor Network Template
Implementation Example
Discussion and future work

3. OMNeT++ Introduction

4. 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

5. 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

6. 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 module’s activity, snapshots, breakpoints)
Simulations are easy to configure using .ini file
Batch execution of the same simulation for different parameters is also included

7. 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

8. Sensor Network Template

9. 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

10. 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)

11. Network Architecture Central Manager Sensor nodes
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

12. Sensor Node Architecture
Layer 0
Sensor
Energy manager
Blackboard
Application
Custom network layers

13. 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

14. 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)

15. 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

16. 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

17. 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

18. 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: D graphical display !!!

19. 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

20. Implementation example

21. Example (1) Application example: Step 1
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

22. Example (2) Step 2 Step 3 Step 4 Step 5
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

23. Address where to download the template: Email address:
Discussions
Address where to download the template:
address: