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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