SWIMMobility

SWIMMobility is an implementation of the Small Worlds in Motion (SWIM) [1] mobility model in the OMNeT++ Simulator [2]. This implementation work has been done as part of the student projects at Sustainable Communication Networks Group, University of Bremen, Germany.

Introduction

SWIM is a mobility model that mathematically characterises the movement patterns of humans. It uses 2 intuitions of human mobility, viz., people usually visit mostly locations close to their home location and if they visit a location far away from home, it is due to its popularity.

The mathematical formulations of these intuitions is based on an equation that considers the distance to a location and the popularity of that location. This code is an implementation of the SWIM mobility model in OMNeT++ Simulator for the INET framework [3].

Mobility Models in OMNeT++

OMNeT++ provides an interface (i.e., Abstract Class) that any mobility mechanism must implement to enable mobility in a node. This interface, called IMobility provides a set of methods that is invoked from other models that require mobility related information. An example is the wireless propagation models which require to know current coordinates, speed of mobility, etc. to determine the connectivity to other nodes.

To simplify the implementation of mobility, a set of base implementations are provided in OMNeT++ that implements some of the abstract methods of IMobility. These base implementations focus on implementing the basic functionality required in mobility patterns that could be generalised into categories.

This SWIM implementation extends the LineSegmentsMobilityBase class.

Building the SWIM Mobility Model

Place the following 3 files in the 'src/inet/mobility/single' folder of the INET framework code and rebuild.

• SWIMMobility.ned
• SWIMMobility.h
• SWIMMobility.cc

To rebuild INET framework (without rebuilding the whole INET framework), follow the steps below while in the root folder of the INET framework.

• make makefiles
• make MODE=release

The MODE=release is to create a non-debuggable version of the INET framework. For a debuggable version, use MODE=debug.

Using the SWIM Mobility Model

Check the examples provided by the INET Framework in the 'examples/mobility' folder to see how a mobility model is configured and used in a simulation.

The SWIM model has a number of configurable parameters that are defined in the 'SWIMMobility.ned'. Each of these parameters has a default value and if they are required to be changed, use the omnetpp.ini file to set these changed values. The following list provides the parameters specific to the SWIM model.

• alpha - The alpha value used in the SWIM model (default is 0.5);
• noOfLocations - The number of locations spread over the mobility area (default is 20);
• Hosts - The number of hosts in the scenario (defaults to the hosts defined in the network);
• popularityDecisionThreshold - The threshold used to decide between selecting a popular location or a not so popular location based on weights. The value range from 0 to 10 (default is 7). A higher value results in placing a more emphasis on a popular location;
• returnHomePercentage - Every node may move from location to location. If this variable is set, then the node returns home for the given percentage of times (defaults to 15 percent);
• neighbourLocationLimit - The radius within which all locations found are considered as being neighbouring locations. Outside this range are visiting locations (defaults to 300 meters)
• radius - This variable defines the radius within which a node should be located at selected neighbouring/visiting location. This is done to prevent nodes piling up at the same location (defaults to 5 meters).
• usedRNG - The number of the RNG to use for all SWIM related random numbers (defined in omnetpp.ini).
• waitTime - The duration of the pause time, after a destination is reached (in seconds).
• speed - The velocity of the movement of a node (in meters per second).
• recreateLocationsFile - The locations file is recreated (or the existing file is used) during a simulation (true or false, default is true). When created, it is not removed at the end of the simulation. IMPORTANT: Locations file creation process draws a series of random numbers from the same source used to decide location selections when moving. Therefore, the random number series used for moving nodes may differ from simulation to simulation, if this file has to be created in one simulation and not, in another.

Support

If you have any questions or comments regarding this code, please write to,

• Anas bin Muslim (anas1@uni-bremen.de),
• Asanga Udugama (adu@comnets.uni-bremen.de) or
• Anna Förster (anna.foerster@comnets.uni-bremen.de)