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Localized Algorithms and Their Applications in Ad Hoc Wireless

Networks

Jie Wu

Dept. of Computer Science & Engineering

Florida Atlantic University

Boca Raton, FL 33431

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Classification of Communication Networks

• Wired Networks– LAN, MAN, WAN, and Internet

• Wireless Networks– Infrastructured networks

(cellular networks)– Infrastructureless networks

(ad hoc wireless networks)

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Wired/Wireless Networks

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Wireless and Mobile Networks• 200 million wireless telephone handsets

(purchased annually)

• A billion wireless communication devices in use

• The first decade of 21st Century: mobile computing

• "anytime, anywhere"

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• Self-organizing: without centralized control

• Scarce resources: bandwidth and batteries

• Dynamic network topology

• Unit disk graph models: host connection based on geographical distance

Characteristics

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Unit Disk Graph

A simple ad hoc wireless network of six wireless mobile hosts.

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• Mobility management – Addressing and routing

• Location tracking– Absolute vs. Relative, GPS

• Network management– Merge and split

• Resource management– Network resource allocation and energy efficiency

• QoS management– Dynamic advance reservation and adaptive error control techniques

Major Issues in Ad Hoc Networks

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• MAC protocols– Contention-base, controlled

• Applications and middleware– Measurement and experimentation

• Security– Authentication, encryption, anonymity, and intrusion detection

• Error control and failure– Error correction and retransmission, deployment of back-up

systems

Major Issues in Ad Hoc Networks (Cont’d.)

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Localized Algorithms (Estrin, 99)• Processors (hosts) only interact with others in a

restricted vicinity.• Each processor performs exceedingly simple tasks

(such as maintaining and propagating information markers).

• Collectively these processors achieve a desired global objective.

• There is no (or limited) sequential propagation of information.

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Localized Algorithms (Con’t)

• Differ from traditional distributed algorithms• Complexity

– Communication: number of rounds

– Communication: size of message

– Computation: plays a lesser rule

• Quality – Average case: probabilistic analysis/simulation

– Worst case: bound/approximation ratio

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Application I: Connected Dominating Set (CDS)

(Wu and Li, 1999)

• CDS as a virtual backbone

• Marking process: A node is marked true if it has two unconnected neighbors

.

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Marking Process (Cont’d.)

A sample ad hoc wireless network

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Application II: Broadcasting(Wu and Dai, 2003 and 2004)

• Promiscuous receive mode

• Coverage & efficiency

• Flooding: each node forwards the message once

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Application II: Broadcasting (Con’t)

• Localized solution via self-pruning

(INFOCOM 2003)• Localized solution via neighbor designation

(ICDCS 2003)• Mobility management and consistent view

(INFOCOM 2004)• Computation complexity reduction in dense mode (ICDCS 2004)

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A Sample Broadcasting(n=100, d=6, r=16, k=2)

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Other Applications

• Energy-Efficient Communication• MAC layer protocols• Topology control• Directional antenna• Sensor coverage• Data gathering and dissemination• …

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Security in Ad Hoc Networks

• Key management

• Routing security

• Light-weight cryptography

• Intrusion detection

• Trust: incentive-based

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Cross-Disciplinary Issues

• NSF Sensor Network Program (March, 2003)

• Sponsored by multiple divisions/programs (including CISE)• Encouraging multi-disciplinary team effort• 1,000 submissions with an acceptance rate of around 5%

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Example: Multi-Disciplinary Team

• Hitch-hiking Model (INFOCOM 2004) • Energy-efficient design in sensor networks• Multiple institutions: UMass- FAU • Multiple disciplines

• physical layer• MAC layer• network layer

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Vision of the Field• Convergence of Multiple Disciplines

– Parallel processing

– Distributed systems

– Network computing

• Wireless network and mobile computing as an important component in Cyberinfrastructure and Cybertrust

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Vision of the FieldUltimate Cyberinfrastructure• Petascale computing, exabyte storage, and terabit

networksNetwork-Centric • Supernetworks: networks are faster than the

computers attached to them• Endpoints scale to bandwidth-match the network

with multiple-10Gbps lambdas

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Major Conferences in the fields

• General: IEEE INFOCOM

• Mobile Computing: ACM MobiCom

• Ad Hoc Networks: ACM MobiHoc

• Distributed Systems: IEEE ICDCS

• Sensor Networks: IEEE MASS (Mobile Ad-hoc and Sensor Networks)

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Some Related Events

• IEEE Computer– Special issue on Ad Hoc Networking

– Feb. 2004, guest editors: J. Wu. & I. Stojmenovic

• NSF Workshop on Theoretical Aspects of Ad hoc, Sensor, and Peer-to-Peer Networks– Feb. 2004, http://www.cse.fau.edu/~jie

– Book published by CRC and special issue in JPDC