stochastic characterization of mobile ad-hoc networks
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INFORMS 2004. Stochastic Characterization of Mobile Ad-hoc Networks. John P. Mullen and Timothy I. Matis Center for Stochastic Modeling Department of Industrial Engineering New Mexico State University. What Are MANETS ?. - PowerPoint PPT PresentationTRANSCRIPT
Primary Author: J.P. Mullen, Presented by: T.I. Matis, 10/26/2004
Stochastic Characterization of Mobile Ad-hoc Networks
John P. Mullen and Timothy I. MatisCenter for Stochastic ModelingDepartment of Industrial EngineeringNew Mexico State University
INFORMS 2004
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INFORMS 2004
Primary Author: J.P. Mullen, Presented by: T.I. Matis, 10/26/2004
What Are MANETS ?
A MANET is a mobile ad-hoc wireless communication network that is capable of autonomous operation Each node is capable of transmitting, receiving, and routing packets of
information. The network has no fixed backbone The nodes are able to enter, leave, and move around the network
independently and randomly
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INFORMS 2004
Primary Author: J.P. Mullen, Presented by: T.I. Matis, 10/26/2004
Mobile Ad Hoc Path Search
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INFORMS 2004
Primary Author: J.P. Mullen, Presented by: T.I. Matis, 10/26/2004
Same MANET After a While
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INFORMS 2004
Primary Author: J.P. Mullen, Presented by: T.I. Matis, 10/26/2004
NutshellMANET field performance differs greatly from simulation’s
Field & testbed performance is much poorer Developing MANET protocols in the field is very difficult Improving simulation fidelity increases the value of simulation in design. Higher fidelity earlier in the design process leads to better designs
Research focus: Significantly improve the fidelity of MANET simulations Without significantly increasing
Simulation run time or Modeling effort.
Research results Up to an order of magnitude improvement in fidelity Runtime increases are often insignificant, but generally less than 100% Very little added modeling effort
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INFORMS 2004
Primary Author: J.P. Mullen, Presented by: T.I. Matis, 10/26/2004
Overview
Multipath Fading and its impact on mobile ad hoc netsThe Stochastic Model
Objectives Implementation Validation
Demonstrations of the Model Small Models
Impact of Short Retry Limit (SRL) Comparing AODV and DSR
Large Models AODV vs. DSR AODV vs. DSR using GPS data Impact of SRL on DSR
Summary, Conclusions and Further Work
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INFORMS 2004
Primary Author: J.P. Mullen, Presented by: T.I. Matis, 10/26/2004
Shadowing and Fading
Shadowing Is caused by objects absorbing part of the signal Can be estimated by looking at the Line of Sight (LOS) path Causes a random reduction in signal strength.
Fading Is the result of the algebraic sum of signals from many paths Because movement of any object in the vicinity can change the sum
Multipath fading is extremely difficult to model and predict Would be very time consuming to simulate exactly And would have little predictive value.
This phenomena causes: Very rapid large-scale fluctuations in signal strength Can cause the signal to be significantly lesser or greater than expected.
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INFORMS 2004
Primary Author: J.P. Mullen, Presented by: T.I. Matis, 10/26/2004
Main causes of signal variation
R
T
Shadowing
Multipath
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INFORMS 2004
Primary Author: J.P. Mullen, Presented by: T.I. Matis, 10/26/2004
Measured Received Signal Strength(from Neskovic 2000)
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INFORMS 2004
Primary Author: J.P. Mullen, Presented by: T.I. Matis, 10/26/2004
Stochastic Variation Model
The Model Given mp(d), the expectation of power at distance d Rayleigh fading model of the instantaneous power, P(d)
Pr {P(d) ≤ p} = 1 – exp{-[p/mp(d)]} Inverse transform of the Rayleigh fading model
P(d) = -mp(d)ln(1-r)
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INFORMS 2004
Primary Author: J.P. Mullen, Presented by: T.I. Matis, 10/26/2004
Simulated vs. Real Power
Actual Measurements Simulated Values
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INFORMS 2004
Primary Author: J.P. Mullen, Presented by: T.I. Matis, 10/26/2004
Validation
Simulated reported field tests and compared results K.-W. Chin, J. Judge, A. Williams, and R. Kermode, "Implementation
experience with MANET routing protocols," ACM SIGCOMM Computer Communications Review, vol. 32, pp. 49 - 59, 2002.
I. D. Chakeres and E. M. Belding-Royer, "The Utility of Hello messages for determining link connectivity," Wireless Personal Multimedia Communications, vol. 2, pp. 504 - 508, 2003.
D. S. J. D. Couto, D. Aguayo, J. Bicket, and R. Morris, "A High Throughput Path Metric for MultiHop Wireless Routing," presented at MobiCom '03, San Diego, California, USA, 2003.
S. Desilva and S. Das, "Experimental evaluation of a wireless ad hoc network," 2000.
Simulations with Standard non-fading model were exceedingly optimistic Proposed fading model were very much more realistic.
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INFORMS 2004
Primary Author: J.P. Mullen, Presented by: T.I. Matis, 10/26/2004
Impact of Multipath Fading on MANETsHow does it affect MANETs?
Unnecessary route searches Selection of false routes
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INFORMS 2004
Primary Author: J.P. Mullen, Presented by: T.I. Matis, 10/26/2004
Impact of Multipath Fading On MANETs
NominalRange
(r0)
OK
StubCellular
DroppedPackets
Fadingmargin
FalseRoutesOK
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INFORMS 2004
Primary Author: J.P. Mullen, Presented by: T.I. Matis, 10/26/2004
Impact of Multiple Retries on MANETs
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INFORMS 2004
Primary Author: J.P. Mullen, Presented by: T.I. Matis, 10/26/2004
The MANET fading Trade-off
Protocol
ImproveReliability
OnGood Routes
IncreaseRisk of
SelectingBad Routes
MANET:Nominal range is amatter of balance.
Most Wireless:Nominal range is amatter of design.
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INFORMS 2004
Primary Author: J.P. Mullen, Presented by: T.I. Matis, 10/26/2004
Demonstrations
Small Models (validations of field tests) Scenario 1 – Performance vs. distance.
Used for the two cases above Scenario 2 – Routing Test Focus mainly on fading effects Models:
Fading vs. nonfading simulations of AODV DSR vs. AODV with fading model
Large models (exploration) Scenario 3 – 24 nodes. Also consider other effects, such as interference Models: Fading and non-fading versions of
AODV vs. DSR AODV vs. DSR using GPS data Impact of SRL on DSR
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INFORMS 2004
Primary Author: J.P. Mullen, Presented by: T.I. Matis, 10/26/2004
Scenario 2: Routing test(from Chin et. al., 2002)
10 pps
0.5 m/s
r0 = 39m
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INFORMS 2004
Primary Author: J.P. Mullen, Presented by: T.I. Matis, 10/26/2004
Sc 2: Fading vs. Nonfading: AODV
Notes: Default values for AODV SRL = 7
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INFORMS 2004
Primary Author: J.P. Mullen, Presented by: T.I. Matis, 10/26/2004
Sc 2: AODV vs. DSR
Notes: Default protocol values SRL = 7
Nonfading model shows no difference
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INFORMS 2004
Primary Author: J.P. Mullen, Presented by: T.I. Matis, 10/26/2004
Scenario 3: Larger Scale Test
Features:•More nodes (24)•Random r-t pairs•Interference•Higher loads
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INFORMS 2004
Primary Author: J.P. Mullen, Presented by: T.I. Matis, 10/26/2004
Mean Throughput: AODV vs. DSR
Notes:•Default protocol values•SRL = 7
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INFORMS 2004
Primary Author: J.P. Mullen, Presented by: T.I. Matis, 10/26/2004
Mean Delay: AODV vs. DSR
Notes:•Default protocol values•SRL = 7
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INFORMS 2004
Primary Author: J.P. Mullen, Presented by: T.I. Matis, 10/26/2004
Using GPS data
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Ar0
Use GPS to block unreliable routes
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INFORMS 2004
Primary Author: J.P. Mullen, Presented by: T.I. Matis, 10/26/2004
Impact of GPSWithout GPS With GPS
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INFORMS 2004
Primary Author: J.P. Mullen, Presented by: T.I. Matis, 10/26/2004
Mean Throughput: Impact of SRL on DSR
Notes:•Default protocol values
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INFORMS 2004
Primary Author: J.P. Mullen, Presented by: T.I. Matis, 10/26/2004
Mean Delay: Impact of SRL on DSR
Notes:•Default protocol values
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INFORMS 2004
Primary Author: J.P. Mullen, Presented by: T.I. Matis, 10/26/2004
Execution Time in Scenario 3 (Virtually no differences in Scenarios 1 & 2)
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INFORMS 2004
Primary Author: J.P. Mullen, Presented by: T.I. Matis, 10/26/2004
Summary
Non fading modelOverestimates field performance Is very insensitive to all the contrasts shown here and more.
Fading modelProvides more realistic estimatesBetter predicts impacts of protocol and parameter changesShows promise of new techniques.Requires little or no additional modelingHas little impact on execution time
(Alternative is a testbed or a field trial)
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INFORMS 2004
Primary Author: J.P. Mullen, Presented by: T.I. Matis, 10/26/2004
Conclusions
Multipath Fading has a great impact on mobile ad hoc nets
Including its effects in simulation greatly improves fidelity
Stochastic Modeling of Multipath Fading Is a practical way to include the impact of fading
Minor modifications to code (in OPNET, at least)Without great increases in
Modeling effort orExecution time
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INFORMS 2004
Primary Author: J.P. Mullen, Presented by: T.I. Matis, 10/26/2004
Future Work
More Fading ModelsRayleigh Ricean Nakagami
Other significant RF effects e.g. exponential decay factor
Better user interface Allow selection of models & parameters without need to recompile.
ValidationReplicating published studies Set up own testbed and field trials
Better modeling of fading impacts Hello vs. control vs. data packet results Other significant measurable elements.
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INFORMS 2004
Primary Author: J.P. Mullen, Presented by: T.I. Matis, 10/26/2004
Acknowledgements
OPNET TechnologiesSoftware license research grantTechnical assistance
Center for Stochastic ModelingTechnical resources
Klipsch School of Electrical and Computer EngineeringDr. Steve HoranDr. Hong Huang (also CSM member)
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INFORMS 2004
Primary Author: J.P. Mullen, Presented by: T.I. Matis, 10/26/2004
Final Questions?