ContactBased Mobility Metrics for DelayTolerant Ad Hoc Networking

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Contact-Based Mobility Metrics for Delay-Tolerant
Ad Hoc Networking

• A. Khelil, P.J. Marrón, K. Rothermel
• MASCOTS, Sept 29 2005

2
Outline

• Motivation
• Related Work
• Contact-Based Mobility (CBM) Metrics
• Statistical and Theoretical Analysis for Random
  Waypoint
• Uses of CBM Metrics
• Conclusion

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Motivation

• Mobile ad hoc network (MANET)
• In MANETs mobility can be exploited
• to increase the capacity of the network )
• to overcome network partitioning
• New class of protocols and applications
• Physical transport of messages (mobility-aided)
• Tolerate higher E2E transmission delays
  (delay-tolerant)
• Delay-tolerant protocols and appl. act on a large
  time-scale
• ? Investigation of mobility on a large time-scale
  is crucial

) M. Grossglauser et al. Mobility Increases the
Capacity of Ad Hoc Networks Trans. on Netw.,
2002.
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Related Work

• Existing mobility metrics
• Velocity-based e.g. speed, relative speed
• Link-based e.g. link change rate, link duration
  )
• Route-based e.g. route change rate, route
  duration )
• Metrics defined for (non-delay-tolerant) ad hoc
  routing
• Metrics model mobility instantaneously and do not
  support detection of mobility patterns a large
  time-scale

) J. Boleng et al. Metrics to Enable Adaptive
Protocols for Mobile Ad Hoc Networks ICWN, 2002.
) N. Sadagopan et al. Paths Analysis of Path
Duration Distributions in MANET and their Impact
on Routing Protocols Mobihoc, 2003.
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Outline

• Motivation
• Related Work
• Contact-Based Mobility (CBM) Metrics
• Methodology and Terminology
• Metrics Definition
• Statistical and Theoretical Analysis for Random
  Waypoint
• Uses of CBM Metrics
• Conclusion

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Methodology and Terminology (1)

• Observation Epidemiology uses contacts to model
  mobility of individuals
• We use contacts between nodes to quantify the
  mobility on a large time-scale

• Assumption Nodes are uniquely identified (e.g.
  MAC addr.)
• Definitions
• Encounter between nodes n and m occurs if
  distance(n,m) lt com. range
• enmn, m, tstart, duration
• Contact
• cnmenm

2nd E
3rd E
1st E
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Methodology and Terminology (2)

• Node manages a contact table for the time of
  interest T
• Cncnm
• set of contacts of node n in T
• Enenm
• set of encounters of node n in T

time of interest T
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Def. of Contact-Based Mobility (CBM) Metrics

• Node-centric vs. network-wide
• Metrics
• Avg. Encounter Frequency ( 1.4)
• Encounter Rate ( 7/40 encounters/s)
• Contact Rate ( 5/40 contacts/s)
• Avg. Encounter Duration
• Avg. Contact Duration

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9
Outline

• Motivation
• Related Work
• Contact-Based Mobility (CBM) Metrics
• Statistical and Theoretical Analysis for Random
  Waypoint
• Uses of CBM Metrics
• Conclusion

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Simulation Parameters
Area
R










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Average Encounter Frequency

• AEF is independent from node density
• AEF increases with Vmax

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Average Encounter Rate Average Contact Rate

• Linear increase with node density
• Non linear increase with Vmax

• Linear increase with node density
• linear increase with Vmax

AER / ACR AEF
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Avg. Contact Duration Avg. Encounter Duration

• Independent from node density
• Decreases with Vmax

• Independent from node density
• Decreases with Vmax

ACD / AED AEF
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Analytical Model for Random Waypoint
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Comparison Analytical Simulation Results

• Results are very comparable
• Differences are due to
• - Spatial node distribution is not exactly
  uniform, since nodes are more likely to locate in
  the middle of movement area Bettstetter
• - Average nodal speed decreases over time
  Yoon

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Outline

• Motivation
• Related Work
• Contact-Based Mobility (CBM) Metrics
• Statistical and Theoretical Analysis for Random
  Waypoint
• Uses of CBM Metrics
• CBM Metrics in Network Simulator ns-2
• Conclusion

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Uses of CBM Metrics

• Design and adaptation of delay-tolerant
  mobility-aided protocols
• Detect large time-scale
  mobility patterns, examples
• Node src encounters dest-1 periodically
• Nodes src and x move in a group
• At run-time HELLO beaconing

x

• Performance analysis of delay-tolerant
  mobility-aided protocols
• Classification of mobility scenario
• Performance evaluation and comparison

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The Network Simulator ns-2

• Ns-2 discrete event simulator for wired
  wireless networks
• General Operations Director (GOD) central
  instance
• Stores global state information
• nodes
• node position
• number of hops between 2 nodes
• partitioning information
• GOD simplifies (global view) evaluation of
  wireless protocols

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CBM Metrics in ns-2
Arbitrary ns-2 movement trace
Basic communication model
A and B communicate if distance(A,B) lt comm_range
Before simulation
Annotation Tool
Movement trace annotated with CBM information
ns-2
GeneralOperationsDirector(GOD)
Delay- Tolerant Protocol Evaluation
Query()
During simulation
Simulation trace
CBM metrics
http//canu.informatik.uni-stuttgart.de/cbm
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Conclusion

• We introduced novel metrics to quantify mobility
  on a large time- scale
• Based on contacts between nodes
• Important for evaluation of mobility-aided
  delay-tolerant networking
• Detailed statistical analysis for random waypoint
• First steps towards an analytical model for
  random waypoint
• We provide implementation for ns-2

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• Thank you for your attention!
• http//canu.informatik.uni-stuttgart.de/cbm

khelil,marron,rothermel_at_informatik.uni-stuttgart
.de