Institut Eurécom † Department of Mobile Communications Sophia Antipolis, France

1. Neighborhood Changing Rate: A Unifying Parameter to Characterize and Evaluate Data Dissemination Scenarios Institut Eurécom† Department of Mobile Communications Sophia Antipolis, France Jérôme Härri†, Biao Zhou‡, Mario Gerla‡, Fethi Filali†, Christian Bonnet† {haerri,filali,bonnet}@eurecom.fr {zhb,gerla}@cs.ucla.edu University of California‡ Department of Computer Science Los Angeles, USA 4th IEEE/IFIP Wireless On demand Network Systems and Services (WONS) Obergurgl, Austria January 24th 2007

2. Agenda • Data Dissemination in Mobile Ad Hoc Network • NCR • Definition • Example • Justification • The Mobeyes Protocol • Performance Results • Conclusion

3. Data Dissemination • A single car has a packet to spread • A car shares its packet with all vehicles reachable within its transmission range. • Objective:Disseminating the packet throughout the network • Example: Spreading factor: 2

4. Data Dissemination • At each encounter, the more vehicles the car meets, the more efficient is the spreading factor. • Example: Spreading factor: 5

5. Data Dissemination • In order to reduce the broadcast storm effect, no relaying. • Each car that receiving the set of data may in turn share it with any encountered vehicle. • Best dissemination Strategy: At each encounter point, a single car with data shares it with a large set of vehicles. • Group mobility does not help data dissemination, as in that case, a large set of cars containing data shares it with a potentially smaller set of vehicles. Data Dissemination Efficiency : Time needed to spread a given set of data to the entire network.

6. Data Dissemination • The data dissemination efficiency in therefore dependant to a large set of parameters: • The rate a car encounters other neighbors. • The number of vehicles met that do not follow a similar trajectory. • … Objective: Define a single universal metric including all these parameters In other terms, data dissemination efficiency may depend on a Neighborhood Changing Rate

7. Agenda • Data Dissemination in Mobile Ad Hoc Network • NCR • Definition • Example • Justification • The Mobeyes Protocol • Performance Results • Conclusion

8. Neighborhood Changing Rate (NCR) • Let’s define • : Sampling interval equal to the time needed for a node to move a distance equal to its transmission range • : Expected Neighbor entering node i’s neighborhood during the time interval • : Expected Neighbor leaving node i’s neighborhood during the time interval • : Node i’s nodal degree at time t. • Then,

9. Neighborhood ChangingRate (NCR) • Example: The NCR of Car 1 as a function of time, with t=1

10. Neighborhood ChangingRate (NCR) Definition (Uniform Mobility Model) : A Uniform Mobility Model (UMM) is a model preserving uniformly distributed velocities and densities Theorem : Defining speedav- representing and densityav– representing the average node density both generated by an UMM, NCR has the following features • 0 ≤ NCR(t) ≤ 1 • NCR speedav • NCR densityav Proof:See paper

11. Neighborhood ChangingRate (NCR) • The performance of protocols using data dissemination usually depends on multiple criteria • Speed • Velocity • Mobility pattern • … • Evaluating a protocol depending on multi-criteria is hard and gives arguable results. • More specifically, Mobility Patterns are not easily quantifiable because they depend on a too large set of parameters. • It would be preferable to evaluate it depending on a single criterion.

12. Neighborhood ChangingRate (NCR) • As NCR is independent to speedav and densityav, • In all models where the real speed and densitydiverge from the initial speedavand densityav, • NCR controls the set of parameters that generates the complex spatial and temporal dependencies we may observe in realistic mobility patterns • Specific Topologies or Mobility Patterns may become less relevant to evaluate the performance of dissemination protocols • With a given speedav, densityav, and NCR, we can perform cross-topology and cross-mobility patterns performance evaluation.

13. Neighborhood ChangingRate (NCR) • A similar situation also exists in Transportation Planning: • How to represent traffic flows in transportation that depend on multi-parameters such as: • Speed, density, volume/capacity ? • Level of Service (LOS) : Works like an American report card grade, using the letters A through F, with A being best and F being worst. • By using LOS classification and referring to a traffic situation as having a particular LOS , engineers can have a global knowledge of traffic condition in a particular area. • NCR is designed to have the same usage: • By referring to data dissemination as having a particular NCR, we can have an intuitive vision of its efficiency, and thus evaluate accurately VANET Protocols using this feature.

14. Agenda • Data Dissemination in Mobile Ad Hoc Network • NCR • Definition • Example • Justification • The Mobeyes Protocol • Performance Results • Conclusion

15. The Mobeyes Protocol • Mobeyes [1] is a protocol for sensed data mining in vehicular environments: • Periodic diffusion of a summary of sensed data • On demand harvesting of sensed data • Mobeyes Architecture • Mobeyes Sensing Interface (MSI) : Interface responsible for the access to the sensors or GPS • Mobeyes Data Processor (MDP): Reads raw data and generates the summaries • Mobeyes Diffusion/Harvesting Processor (MDHP): Opportunistically diffuses the summaries or on demand harvests the raw data. • Mobeyes uses epidemic dissemination to diffuse the summaries. So, it is an appropriate choice to validate NCR. [1] Uichin Lee et al. University of California, PerSeNS 2006

16. The Mobeyes Protocol • Example: Mobeyes Single Hop Passive Diffusion

17. Agenda • Data Dissemination in Mobile Ad Hoc Network • NCR • Definition • Example • Justification • The Mobeyes Protocol • Performance Results • Conclusion

18. Simulation Results 760m 2400m Urban Map Topology Triangle Topology Simulation Parameters Simulation Environment

19. Mobility Models Track Model Random Waypoint Model [1] Biao Zhou et al. University of California, MilCom 2004

20. Latency Latency on a Triangle Topology as a function of speed

21. Latency Latency on a Map Topology as a function of speed

22. Harvesting Efficiency NCR on a Triangle Topology with a speed of 5 m/s

23. Harvesting Efficiency NCR on a Triangle Topology with a speed of 15 m/s

24. Harvesting Efficiency NCR on a Triangle Topology with a speed of 25 m/s

25. Harvesting Efficiency • Mobeyes on a triangle topology: • Time before which 100% of the data is harvested NCR velocityav

26. Harvesting Efficiency NCR on a Map Topology with a speed of 5 m/s

27. Harvesting Efficiency NCR on a Map Topology with a speed of 15 m/s

28. Harvesting Efficiency NCR on a Map Topology with a speed of 5 m/s

29. Harvesting Efficiency • Mobeyes on a map topology: • Time before which 100% of the data is harvested NCR velocityav

30. Cross-Topology Comparison Latency for scenarios with same speed, density and NCR, and for different mobility models and topologies

31. Cross-Topology Comparison Harvesting rate for scenarios with same density, speed and NCR, and different mobility models and topologies

32. Cross-Topology Comparison • All Models having the same NCR • Time before which 100% of the data is harvested topology velocityav

33. Conclusion • NCR is a novel parameter describing data dissemination • NCR is able to describe spatial and temporal dependencies, not covered by speed or density. • NCR is an unifying parameter, as it regroup mobility patterns and topology parameters. • Data dissemination in any kind of topology and for any type of mobility pattern, can be the fully control by three parameters: • Average Speed • Average Density • NCR

34. Questions ? Jérôme Härri haerri@eurecom.fr