Ad-Hoc Networking Course
Instructor: Carlos Pomalaza-Ráez
D. D. Perkins, H. D. Hughes, and C. B. Owen:
”Factors Affecting the Performance of Ad Hoc
Networks”, in Proc. IEEE International Conference on Communications (ICC’02), pp. 2048-2052
Sami Koivu
Centre for Wireless Communications sami.koivu@ee.oulu.fi
20.1.2004

Outline
1. Introduction and Motivation
2. Methodology, Simulation, and Experimental
Design
3. Performance Metrics and Experimental Factors
4. Simulation Results and Design Analysis
5. Summary
© Sami Koivu: Presentation in Ad-Hoc Networking Course 20.1.2004
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Introduction and Motivation
• The goal of mobile ad hoc networks (MANETs) is to provide rapidly deployable means of communication without a pre-excisting infrastructure
• MANETs have a dynamic, multi-hop, and constantly changing structure
• The dynamic characteristics of ad-hoc networks cause great design challenges
• Therefore, the factors that affect the performance of the networks have to be studied
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Introduction and Motivation
• In this paper, the impact of five various factors are studied:
1. Node speed
2. Node pause time
3. Network size
4. Number of traffic sources
5. Routing protocol
• Source vs. distributed
• Additionally, the two-way interactions of these factors are examined, i.e., whether the effect of one factor is dependent on the level of another
• The impact of the factors are studied using a 2 k
( k =5, r =4) factorial design r
© Sami Koivu: Presentation in Ad-Hoc Networking Course 20.1.2004
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Methodology, Simulation, and
Experimental Design
• Since 2 k r ( k =5, r =4) factorial design is used, 32 separate experiments are done
• Each experiment is replicated 4 times resulting in 128 simulation runs
• Simulation study is carried out using Global Mobile
System Simulator (GloMoSim)
• Model is simulated for 200 seconds of simulated time
• Radio transmission range is approximately 250 m, free space propagation model is used
• Channel capacity is 2 Mbits/s
© Sami Koivu: Presentation in Ad-Hoc Networking Course 20.1.2004
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Methodology, Simulation, and
Experimental Design
• IEEE 802.11 Medium Access Control Protocol is used as the MAC protocol
• Sources transmit continuously 1024-byte data packets at a constant rate of 4 packets/s
• Utilized routing protocols are: Dynamic Source
Routing (DSR, source) and Ad-hoc on Demand
Distance Vector (AODV, distributed)
– Both the protocols are reactive
• The random waypoint mobility model is used
– Each node is placed randomly in the simulated area
(1600m*400m)
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Performance Metrics and Experimental
Factors
• The studied performance metrics are:
1. Throughput
• The effectiveness how well the network delivers the packets from the source to the destination
2. Average Routing Overhead
• The average number of control packets (route requests, replies, and error messages) produced per node
3. Average Power Consumption per node
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Performance Metrics and Experimental
Factors
• The main effect of a factor is the average change in the considered metric when the factor is changed from its level 1 (-) to its level 2 (+)
• The two-way interaction effect is the difference between the average values of a metric when two factors are at the same level and when they are at opposite levels
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Performance Metrics and Experimental
Factors
• The two-way interactions are denoted as label a x label b (for example the two way interaction of node speed and routing is 1x5)
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Simulation Results and Design Analysis
• The effects on control overhead
– The increase in node speed, number of sources, and utilization of distibuted routing increase the control overhead
– The two-way interactions of node speed – number of sources, node speed – routing, and number of sources – routing have also strong effects
© Sami Koivu: Presentation in Ad-Hoc Networking Course 20.1.2004
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Simulation Results and Design Analysis
• The effects on throughput
– Node speed, the number of sources, and their two-way interaction have a strong negative impact (when the factors increase the throughput of the network decreases)
– The increase in network size increases the throughput
– The type of routing has little effect on throughput
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Simulation Results and Design Analysis
• The effects on power consumption
– Network size has a negative impact
– Number of sources has a strong positive impact
– Their two-way interaction has small negative effect
© Sami Koivu: Presentation in Ad-Hoc Networking Course 20.1.2004
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Simulation Results and Design Analysis
• The importance of each factor is described in Table 2
– The proportion of variation in performance metric that is explained by the factor is presented
• The number of sources is the most important parameter when considering the overall performance of the network
• Node speed and network size are also quite important
• Routing protocol affects significantly only the average control overhead
• The last row includes the proportion of variation of experimental error
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Simulation Results and Design Analysis
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Summary
• The effect of five factors (node speed, pause-time, network size, number of sources, and routing protocol) on the performance of ad-hoc network was studied
• Three performance metrics (throughput, average routing overhead, and power consumption) were used
• The number of traffic sources is the most important factor when considering the performance, node speed and network size are also important
• Source routing more efficient than distributed one, because it achieves almost the same performance with much less control overhead
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