home/Research Interests/Mobility Models

Mobility Models

(Main collaborators: Prof. J. Virtamo and Dr. P. Lassila)

A mobility model (or a trace file) is needed for analysis and simulation of mobile networks. Commonly used synthetic mobility models include Brownian motion, different random walk patterns (cf. Lévy flight), and group mobility models.

Random Waypoint Model

Perhaps the most popular elementary mobility model is the so-called Random Waypoint (RWP) model, where each node moves independently of the other nodes towards the next waypoint. Upon reaching the waypoint, a node chooses the next waypoint uniformly in random from the given area. The resulting movement pattern may not resemble well an actual human mobility, but nonetheless, it is often used due to its simplicity and ease of analysis.

The important quantities that one should be aware of when, e.g., defining a simulation scenario are the following:

  • Spatial node distribution in stationarity [3,4],
  • Arrival rates, e.g., to a cell (cf. handovers in mobile networks) [2],
  • Contact rates, mean inter-meeting times and contact durations [1].

 Stationary node distribution of RWP
Figure: Stationary node distribution of RWP.

For example, when simulating a cellular network, it is important to adjust the handover rates to an appropriate level [3]. Spatial node distribution, on the other hand, is a relevant quantity when considering connectivity in a mobile ad-hoc network [6].

References

[1]  M. S. Desta, E. Hyytiä, J. Ott and J. Kangasharju, Characterizing Content Sharing Properties for Mobile Users in Open City Squares, 10th Annual IEEE/IFIP Conference on Wireless On-Demand Network Systems and Services (WONS), Banff, Canada. March 2013.
[2]  E. Hyytiä, J. Virtamo, P. Lassila, J. Kangasharju and J. Ott, When Does Content Float? Characterizing Availability of Anchored Information in Opportunistic Content Sharing, in IEEE INFOCOM, pp. 3123-3131, 2011, Shanghai, China. (pdf)
[3] E. Hyytiä, P. Lassila and J. Virtamo, A Markovian Waypoint Mobility Model with Application to Hotspot Modeling, in IEEE ICC, 2006, Istanbul, Turkey. (pdf)
[4] E. Hyytiä and J. Virtamo, Random Waypoint Mobility Model in Cellular Networks, Wireless Networks, vol. 13, no. 2, Springer, 2007. (pdf)
[5] E. Hyytiä, P. Lassila and J. Virtamo, Spatial Node Distribution of the Random Waypoint Mobility Model With Applications, IEEE Trans. on Mobile Computing, 5(6), 680-694, 2006. (pdf)
[6] E. Hyytiä and J. Virtamo, Random Waypoint Model in n-Dimensional Space, Operations Research Letters, vol. 33/6, pp. 567-571, 2005. (pdf)
[7] P. Lassila, E. Hyytiä and H. Koskinen, Connectivity Properties of Random Waypoint Mobility Model for Ad Hoc Networks, in The Fourth annual Mediterranean workshop on Ad Hoc Networks (Med-Hoc-Net 2005), 2005, Île de Porquerolles, France. (pdf)

See the Random Waypoint model in action (a simple java applet).