User Mobility for Opportunistic Ad Hoc Networking WMCSA 2004 Jing - - PowerPoint PPT Presentation

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User Mobility for Opportunistic Ad Hoc Networking WMCSA 2004 Jing - - PowerPoint PPT Presentation

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User Mobility for Opportunistic Ad Hoc Networking WMCSA 2004 Jing Su, Alvin Chin, Anna Popivanova, Ashvin Goel , Eyal de Lara Department of Computer Science Department of Electrical and Computer Engineering University of Toronto

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User Mobility for Opportunistic Ad Hoc Networking

WMCSA 2004

Jing Su, Alvin Chin, Anna Popivanova, Ashvin Goel†, Eyal de Lara Department of Computer Science

†Department of Electrical and Computer Engineering

University of Toronto http://www.cs.toronto.edu/~jingsu

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WMCSA 2004 -- University of Toronto -- Jing Su 2

Overview

Motivation Experiment Results Conclusions Related Work

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WMCSA 2004 -- University of Toronto -- Jing Su 3

Motivation

Can a network be built on pairwise interaction? Can routing algorithms be improved?

Exploit predictability in user mobility Explore replication and latency trade-off

Evaluate research using real mobility

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WMCSA 2004 -- University of Toronto -- Jing Su 4

Applications

ZebraNET, SWIM Infrastructure-less research or military networks Supplement to infrastructure networks

Improve power or cost Extend coverage and availability

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WMCSA 2004 -- University of Toronto -- Jing Su 5

Methodology

Collect traces of pairwise contact

Give devices to human test subjects Devices search for other test subjects Collect data at end of study

Trace-based simulation to determine network

characteristics

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WMCSA 2004 -- University of Toronto -- Jing Su 6

Requirements

Provide incentive to carry device

Use currently available mobile devices Instrumentation software shouldn't disrupt user

Go for whole work-day on single charge Catch serendipitous contact

even when user is not aware

Chose Palm devices, using Bluetooth

802.11 has 10x power requirement over Bluetooth

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WMCSA 2004 -- University of Toronto -- Jing Su 7

Experimental Setup

20 Mobile Devices

Palm Tungsten T Given to subjects to carry around

3 Stationary Devices

Palm m125 Placed near high-traffic locations Simulate infrastructure

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WMCSA 2004 -- University of Toronto -- Jing Su 8

Search Frequency

“Pings” have to be spaced for power management Want to catch serendipitous contact

Need to search at least once every 10 seconds

10 meters

2 m/s

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WMCSA 2004 -- University of Toronto -- Jing Su 9

Search Frequency

“Pings” have to be spaced for power management Want to catch serendipitous contact

Need to search at least once every 10 seconds

10 meters

2 m/s

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WMCSA 2004 -- University of Toronto -- Jing Su 10

Search Frequency

“Pings” have to be spaced for power management Want to catch serendipitous contact

Need to search at least once every 10 seconds

10 meters

2 m/s

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WMCSA 2004 -- University of Toronto -- Jing Su 11

Search Frequency

“Pings” have to be spaced for power management Want to catch serendipitous contact

Need to search at least once every 10 seconds

10 meters

2 m/s

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WMCSA 2004 -- University of Toronto -- Jing Su 12

Search Frequency

“Pings” have to be spaced for power management Want to catch serendipitous contact

Need to search at least once every 10 seconds

2 m/s

10 meters

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WMCSA 2004 -- University of Toronto -- Jing Su 13

Search Protocol

Synchronized clocks Bluetooth is half duplex Gives 8-10 hours battery life May miss data Our results are conservative

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WMCSA 2004 -- University of Toronto -- Jing Su 14

User Studies

18 Graduate students

2.5 weeks, Autumn 2003 9 in CS, 9 in ECE

20 Undergraduate students

8 weeks, Spring 2004 10 in CS, 10 in ECE

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WMCSA 2004 -- University of Toronto -- Jing Su 15

Results

Reachability End-to-end latency Latency versus replication trade-off User experiences

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Reachability (study #1)

User Study #1 21 nodes total

18 Mobile 3 Stationary

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WMCSA 2004 -- University of Toronto -- Jing Su 17

Reachability (study #2)

User Study #2 23 nodes total

20 Mobile 3 Stationary

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Trace-Based Simulation

Packet creation

When node meets new node

Packet propagation

Epidemic Unlimited bandwidth Unlimited memory

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WMCSA 2004 -- University of Toronto -- Jing Su 19

End-to-End Latency (All Packets)

User Study #1

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WMCSA 2004 -- University of Toronto -- Jing Su 20

A Closer Look

Most nodes communicated infrequently Look at select node pairs that communicate

frequently

Called “social nodes” 18 to 08 , 15 to 02

We expect our best-case to be representative of

average case in a larger network

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WMCSA 2004 -- University of Toronto -- Jing Su 21

End-to-End Latency for Social Nodes

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Distribution of Intermediaries

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Latency versus Replication Trade-off

Minimal replication

Who should be the next hop neighbour? Prefer certain neighbours

Efficient source routing using biased handoff

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Biased Handoff Neighbors

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WMCSA 2004 -- University of Toronto -- Jing Su 25

User Experiences

Graduate students

Used devices sparingly Treated them very carefully Power conservation protocol worked well

Undergraduate students

Frequently used device Many filled the memory with games Power conservation protocol was not sufficient

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WMCSA 2004 -- University of Toronto -- Jing Su 26

Related Work

Jetcheva et al 2003 , Ad Hoc City Buses Zhao et al 2004 , Message Ferries Kotz et al 2002 , Analysis of Wireless Networks Herrmann 2003 , Modeling Sociological Aspects Wang et al 2004 , Postmanet Jain et al 2004 , Delay Tolerant Networks

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WMCSA 2004 -- University of Toronto -- Jing Su 27

Conclusion

Lessons

Current wireless devices need better application-level

control/hints for power management

Context aware computing will be a challenge

Pairwise contact enables building network for

latency insensitive packets

Biased handoff can be used to improve routing

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WMCSA 2004 -- University of Toronto -- Jing Su 28

Future Work

Want “denser” data Practical algorithm to determine biased handoff Using data to evaluate mobility models

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Questions?

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WMCSA 2004 -- University of Toronto -- Jing Su 30

Reachability (user study #1)

All Lecture Times Removed Stationary Nodes Removed Stationary Devices Only 2 4 6 8 10 12 14 16 18 20

Max Median Min

Number of other nodes reachable

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WMCSA 2004 -- University of Toronto -- Jing Su 31

Reachability (user study #2)

All Lecture Times Removed Stationary Nodes Removed Stationary Devices Only 2 4 6 8 10 12 14 16 18 20 22

Max Median Min

Number of other nodes reachable