Analysis of the Impact and Interactions of
Protocol and Environmental
Parameters on Overall MANET
Performance
Michael W. Totaro and Dmitri D. Perkins
Center for Advanced Computer Studies
University of Louisiana at Lafayette
Presented
by
Michael W. Totaro
Topics
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Introduction and Motivation
2k Factorial Design (A Brief Tutorial)
Related Work
Methodology
Analysis, Results, and Models
Future Work and Open Questions
Questions
References
Topics
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Introduction and Motivation
2k Factorial Design (A Brief Tutorial)
Related Work
Methodology
Analysis, Results, and Models
Future Work and Open Questions
Questions
References
Introduction and Motivation
 Important design challenge of MANETs:
maximize overall performance of protocols
operating in a MANET
 Impact that one or more factors have on
MANET performance?
 2k factorial design—an important tool that
may aid researchers in analyzing effect of
factors on MANET performance
Topics
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Introduction and Motivation
2k Factorial Design (A Brief Tutorial)
Related Work
Methodology
Analysis, Results, and Models
Future Work and Open Questions
Questions
References
2k Factorial Design
Process
 Code each factor to a “+” and a “-” level
 Design matrix: All possible combinations of factor levels
 Example for k = 3 factors:
Make the
8 simulation
runs, and
measure the
effects of
the factors!
2k Factorial Design
Main Effect of a Factor
Main effect of a factor is the average difference in the
response when this factor is at its “+” level as opposed
to its “-” level:
2k Factorial Design
Main Effect of a Factor – cont’d
The main effects measure the average change in the response
due to a change in an individual factor, with this average being
taken over all possible combinations of the other k-1 factors
(numbering 2k-1).
2k Factorial Design
Main Effect of a Factor – cont’d
We can rewrite the above as “Factor 1” column ● “Response” column / 2k-1
-R1 + R2 – R3 + R4 – R5 + R6 – R7 + R8
e1 =
4
2k Factorial Design
Factor Interaction
 Two factors A and B are said to interact if
the effect of one depends upon the level of
the other
 Conversely, these two factors, A and B, are
said to be noninteracting if the performance
of one is not affected by the level of the
other
 We shall look at examples of interacting
factors and noninteracting factors
2k Factorial Design
Examples of Noninteracting and Interacting Factors
Noninteracting Factors
A1
A2
B1
3
5
B2
6
8
As the factor A is changed
from level A1 to level A2,
the performance increases
by 2 regardless of the level
of factor B
Interacting Factors
A1
A2
B1
3
5
B2
6
9
As the factor A is changed
from level A1 to level A2,
the performance increases
either by 2 or 3 depending
upon whether B is at level
B1 or level B2, respectively
2k Factorial Design
Examples of Noninteracting and Interacting Factors – cont’d
Performance
8
Performance
B2
6
8
A2
6
B1
2
A1
2
A1
A2
B1
B2
(a) No Interaction
Performance
8
B2
6
Performance
8
A2
6
B1
2
A1
2
A1
A2
(b) Interaction
B1
Graphical representation of interacting and noninteracting factors.
B2
2k Factorial Design
Interaction Effects
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Addresses the question: “Does the effect of a factor depend on level of others?”
1 x 3 interaction effect: “Factor 1” ● “Factor 3” ● “Response” / 2k-1
R1 - R2 + R3 - R4 – R5 + R6 – R7 + R8
e13 =
4
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Sign of effect indicates direction of effect on response of moving that factor
from its “-” to its “+” level
Topics
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
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Introduction and Motivation
2k Factorial Design (A Brief Tutorial)
Related Work
Methodology
Analysis, Results, and Models
Future Work and Open Questions
Questions
References
Related Work
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Interest in cross-layer factor interaction in MANETs is not
entirely new.
Performance metrics for assessing the behavior of MANETs
are identified, discussed, and, most especially, partitioned
into three classification levels [1]
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Thread-task level metrics (algorithmic level) such as average
power expended and task completion time
Diagnostic packet level metrics such as end-to-end
throughput, end-to-end delay, link utilization, and packet loss,
which characterize network behavior at the packet level
Scenario metrics that describe the network environment and
define the scenario; these include: nodal movement/topology
rate of change, number of network nodes, area size of
network, density of nodes per unit area, offered load and
traffic patterns, and number of unidirectional links
Related Work – cont’d
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A comprehensive analysis of five factors—node speed, pause-time,
network size, number of traffic sources, and type of routing
(source vs. distributed)—was done using a factorial experimental
design in an effort to identify and quantify the effects and two-way
interactions of these factors on three performance responses:
throughput, average routing overhead, and power consumption [2]
Potential benefits may be derived by information exchange
between the lower layer, routing layer, and transport layer, which is
useful in the design and standardization of an adaptive
architecture that can exploit the interdependencies among link,
medium access, network, and applications protocols [3]
The underlying premise in cross-layer interaction analyses is that,
by learning more about factor and two-way interactions on the
performance of MANETs, researchers may want to consider taking
these effects into account in the design of future protocols
Topics
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Introduction and Motivation
2k Factorial Design (A Brief Tutorial)
Related Work
Methodology
Analysis, Results, and Models
Future Work and Open Questions
Questions
References
Methodology
Effects of factors?
Methodology – cont’d
Partial Design Grid (Coded)
Methodology – cont’d
Partial Design Grid (Uncoded)
Methodology – cont’d
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Simulation—QualNet
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26 factors = 64 experimental runs
Replications = 5
Total running time = 320 seconds
LAR1 routing protocol
Free-space model
2 Mbps
Packet size = 512 bytes
Pause time = 25 seconds
Transmission range = 250 meters
Terrain dimensions*: N = √ [ (MR2π / X) – 1 ]
where X = average number of neighbors
M = number of nodes
R2 = transmission range
*Using the formula for computing the average number of neighbors
for a node, derived by Ihklas Ajbar.
Topics
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Introduction and Motivation
2k Factorial Design (A Brief Tutorial)
Related Work
Methodology
Analysis, Results, and Models
Future Work and Open Questions
Questions
References
Analysis, Results, and Models
Scatterplot—Packet delivery ratio
Analysis, Results, and Models
Scatterplot—End-to-end delay
Analysis, Results, and Models
Scatterplot—Control packet overhead
Analysis, Results, and Models
Main effects—Packet delivery ratio
Analysis, Results, and Models – cont’d
Main effects—End-to-end delay
Analysis, Results, and Models – cont’d
Main effects—Control packet overhead
Analysis, Results, and Models – cont’d
Two-way factor interactions—Packet delivery ratio
Analysis, Results, and Models – cont’d
Two-way factor interactions—Control packet overhead
Analysis, Results, and Models – cont’d
Two-way factor interactions—End-to-end delay
Analysis, Results, and Models – cont’d
Response-surface plots
Analysis, Results, and Models – cont’d
Contour plots
Analysis, Results, and Models – cont’d
Predictive effects—Packet delivery ratio
Analysis, Results, and Models – cont’d
Predictive effects—End-to-end delay
Analysis, Results, and Models – cont’d
Predictive effects—Control packet overhead
Analysis, Results, and Models – cont’d
Prediction profile
Analysis, Results, and Models – cont’d
Regression Models—Packet delay ratio
Analysis, Results, and Models – cont’d
Regression Models—End-to-end delay
Analysis, Results, and Models – cont’d
Regression Models—Control packet overhead
Topics

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

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Introduction and Motivation
2k Factorial Design (A Brief Tutorial)
Related Work
Methodology
Analysis, Results, and Models
Future Work and Open Questions
Questions
References
Future Work and Open Questions
 Validation of prediction (regressions)
models
 Other factors (e.g., power
consumption, etc.)?
 Other empirical models (e.g., neural
networks, time-series prediction)?
Topics








Introduction and Motivation
2k Factorial Design (A Brief Tutorial)
Related Work
Methodology
Analysis, Results, and Models
Future Work and Open Questions
Questions
References
Questions
 Thank you!
Topics








Introduction and Motivation
2k Factorial Design (A Brief Tutorial)
Related Work
Methodology
Analysis, Results, and Models
Future Work and Open Questions
Questions
References
References
1. M. W. Subbarao, “Ad Hoc Networking Critical Features
and Performance Metrics”. White paper, Wireless
Communications Technology Group, National
Institutes of Standards and Technology, September
15, 1999
2. D. D. Perkins, H. D. Hughes, and C. B. Owen, “Factors
Affecting the Performance of Ad Hoc Networks”.
Proceedings of IEEE International Conference on
Communications (ICC 2002), New York, April 2002
3. J. Lee, S. Singh, and Y. Roh, “Interlayer Interactions
and Performance in Wireless Ad Hoc Networks,”
Internet – Draft, IRTF ANS Working Group;
http://www.flarion.com/ans-research/Drafts/draft-irtfans-interlayer-performance-00.txt, accessed
1/29/2004