Mobility and routing in a delay-tolerant network of unmanned aerial vehicies

86 Pages·2008·0.74 MB·English

by  by Erik Kuiper.

Linköping Studies in Science and Technology
Thesis No. 1356
Mobility and Routing in a Delay-tolerant Network of
Unmanned Aerial Vehicles
by
Erik Kuiper
Submitted to Linköping Institute of Technology at Linköping University in partial
fulfilment of the requirements for the degree of Licentiate of Engineering
Department of Computer and Information Science
Linköpings universitet
SE-581 83 Linköping, Sweden
Linköping 2008

Mobility and Routing in a Delay-tolerant Network of
Unmanned Aerial Vehicles
by
Erik Kuiper
April 2008
ISBN 978-91-7393-937-9
Linköping Studies in Science and Technology
Thesis No. 1356
ISSN 0280-7971
LiU-Tek-Lic-2008:14
ABSTRACT
Technology has reached a point where it has become feasible to develop unmanned aerial
vehicles (UAVs), that is aircraft without a human pilot on board. Given that future UAVs can
be autonomous and cheap, applications of swarming UAVs are possible. In this thesis we
have studied a reconnaissance application using swarming UAVs and how these UAVs can
communicate the reconnaissance data. To guide the UAVs in their reconnaissance mission we
have proposed a pheromone based mobility model that in a distributed manner guides the
UAVs to areas not recently visited. Each UAV has a local pheromone map that it updates
based on its reconnaissance scans. The information in the local map is regularly shared with a
UAV’s neighbors. Evaluations have shown that the pheromone logic is very good at guiding
the UAVs in their cooperative reconnaissance mission in a distributed manner.

Analyzing the connectivity of the UAVs we found that they were heavily partitioned which
meant that contemporaneous communication paths generally were not possible to establish.
This means that traditional mobile ad hoc network (MANET) routing protocols like AODV,
DSR and GPSR will generally fail. By using node mobility and the store-carry-forward
principle of delay-tolerant routing the transfer of messages between nodes is still possible. In
this thesis we propose location aware routing for delay-tolerant networks (LAROD). LAROD
is a beacon-less geographical routing protocol for intermittently connected mobile ad hoc
networks. Using static destinations we have shown by a comparative study that LAROD has
almost as good delivery rate as an epidemic routing scheme, but at a substantially lower
overhead.
This work has been supported by LinkLab, a research center for future aviation systems,
established by Saab and Linköping University, and the KK foundation through the industrial
graduate school SAVE-IT.
Department of Computer and Information Science
Linköpings universitet
SE-581 83 Linköping, Sweden

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First I want to thank Saab, and then especially Anders Pettersson and Gunnar
Holmberg, for giving me this opportunity to pursue a PhD. With this thesis I
should be half way. Without the connection to a practically applicable
problem domain I would probably not have chosen to pursue a PhD. I also
want to thank my industrial advisor Mats Ekman. I might not have sought
your advice that extensively, but the discussions we had gave me some things
to think about.
To my academic advisor and supervisor Simin Nadjm-Tehrani I would like to
extend a thank for guiding me to this point. You especially taught me how to
write for an academic audience and not only to report my findings. I might
not entirely agree with the anatomy of academic articles, but hopefully I now
understand it reasonably well.
I also want to thank the other members of RTSlab for your friendship and
valuable comments. You helped me to become aware of some of the
assumptions I hade made and you pushed me to clarify and further
investigate some issues. I hope you will continue to take a coffee break at
three even after I am gone.
I am grateful to SAVE-IT and the KK foundation for partially funding my
research. You might not be in my thoughts every day, but without you this
research might never have been done.
Finally I want to thank my friend C. Without you I might never have selected
to work for Saab, and then this would never have happened.
Erik Kuiper
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1 Introduction....................................................................................................1
1.1 Mobile Ad-hoc Networks.....................................................................1
1.2 Intermittently connected MANETs.....................................................3
1.3 Problem Description..............................................................................4
1.4 Contributions.........................................................................................6
1.5 Thesis Outline........................................................................................7
2 Background.....................................................................................................9
2.1 Mobility Models.....................................................................................9
2.1.1 Synthetic Mobility Models.............................................................10
2.1.2 Real-World Mobility Models.........................................................14
2.2 Routing..................................................................................................17
2.2.1 DTN Routing in Opportunistic Networks...................................18
2.2.2 Beacons-less Routing......................................................................20
3 Reconnaissance Mobility............................................................................23
3.1 Scenario.................................................................................................23
3.2 Random Mobility Model....................................................................24
3.3 Distributed Pheromone Repel Mobility Model...............................25
3.4 Evaluation.............................................................................................29
3.4.1 Scan Coverage.................................................................................30
3.4.2 Scan Characteristic..........................................................................34
3.4.3 Communication...............................................................................37
4 Routing in DTNs..........................................................................................41
4.1 LAROD.................................................................................................41
4.2 Broadcast Delay-tolerant Routing (BDTR).......................................46
4.3 Broadcast Routing (BR).......................................................................48
4.4 Evaluation.............................................................................................48
4.4.1 Node density...................................................................................50
4.4.2 Node speed......................................................................................52
4.4.3 Time to live......................................................................................53
4.4.4 Network load...................................................................................55
5 Conclusions and Future Work...................................................................57
5.1 Conclusions..........................................................................................57
5.2 Future Work.........................................................................................58
6 Acronyms.......................................................................................................59
7 References.....................................................................................................61
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Figure 1. Change of average direction near the edges..................................12
Figure 2. Forwarding areas...............................................................................21
Figure 3. Local pheromone map after 3600 seconds of simulation.............26
Figure 4. Global pheromone view after 3600 seconds of simulation..........26
Figure 5. Local pheromone map after 7200 seconds of simulation.............27
Figure 6. Global pheromone view after 7200 seconds of simulation..........27
Figure 7. Pheromone search pattern................................................................28
Figure 8. Pheromone mobility coverage with global pheromone map......31
Figure 9. Pheromone mobility coverage with 100% transfer probability...32
Figure 10. Pheromone mobility coverage with 50% transfer probability.....32
Figure 11. Pheromone mobility coverage with 10% transfer probability.....32
Figure 12. Pheromone mobility coverage with 0% transfer probability.......33
Figure 13. Random mobility coverage..............................................................33
Figure 14. Random Waypoint mobility coverage............................................33
Figure 15. Comparison of average coverage....................................................34
Figure 16. Pheromone mobility with global pheromone map.......................35
Figure 17. Pheromone mobility with 100% transfer probability....................35
Figure 18. Pheromone mobility with 50% transfer probability......................36
Figure 19. Pheromone mobility with 10% transfer probability......................36
Figure 20. Pheromone mobility with 0% transfer probability.......................36
Figure 21. Random mobility...............................................................................37
Figure 22. Random Waypoint mobility.............................................................37
Figure 23. Pheromone mobility with global pheromone map.......................38
Figure 24. Pheromone mobility with 100% transfer probability....................39
Figure 25. Pheromone mobility with 50% transfer probability......................39
Figure 26. Pheromone mobility with 10% transfer probability......................39
Figure 27. Pheromone mobility with 0% transfer probability.......................40
Figure 28. Random mobility...............................................................................40
Figure 29. Random Waypoint mobility.............................................................40
Figure 30. LAROD forwarding areas................................................................42
Figure 31. Illustration of vectors used for delay time computations............44
Figure 32. LAROD pseudo code........................................................................45
Figure 33. BDTR pseudo code............................................................................47
Figure 34. Delivery ratio for different node densities.....................................51
Figure 35. Overhead for different node densities............................................51
Figure 36. Delay for different node densities...................................................51
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Figure 37. Delivery ratio for different node speeds........................................52
Figure 38. Overhead for different node speeds...............................................53
Figure 39. Delay for different node speeds......................................................53
Figure 40. Delivery ratio for different packet life times..................................54
Figure 41. Overhead for different packet life times........................................54
Figure 42. Delay for different packet life times................................................55
Figure 43. Delivery ratio for different network loads.....................................56
Figure 44. Overhead for different network loads............................................56
Figure 45. Delay for different network loads...................................................56

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