CPSC 689: Discrete Algorithms for Mobile and Wireless Systems

1. CPSC 689: Discrete Algorithms for Mobile and Wireless Systems Spring 2009 Prof. Jennifer Welch

2. Overview • Mobile wireless systems are moving intoyour neighborhood! Robots, vehicular networks, sensor networks, etc. • How can we ensure they are correct and properly evaluate their performance? What are inherent limitations on solvability of problems in this domain? • We will study algorithms for such systems emphasizing those with well-defined correctness and performance properties: • MAC layer, localization, time synchronization, topology control, routing, location services, middleware, applications Discrete Algs for Mobile Wireless Sys

3. Course Goals • Understand nature of wireless ad hoc network setting • what can be assumed about correctness, reliability, and performance? • what are appropriate complexity measures? • Identify important, well-defined problems that can be solved with distributed algorithms • communication, synchronization, localization, etc. • Learn about existing algorithms for these problems • identify where more algorithmic work is needed • Identify inherent limitations (lower bounds, impossibility results) • Identify useful abstraction layers for programming wireless networks Discrete Algs for Mobile Wireless Sys

4. Motivation • Mobile ad hoc network: collection of computing devices (nodes) that communicate via wireless broadcasts • Nodes may have sensors and/or actuators • Nodes move spontaneously or under advice/control from software • No available infrastructure • Possible uses: rescue workers, robots exploring a new location, aircraft over ocean Discrete Algs for Mobile Wireless Sys

5. Motivation • Programming such networks is hard! • Mobility, nodes leaving and joining, failing and recovering • Need good distributed algorithms for problems from basic communication to high level applications • reliable communication, establishing and maintaining structures, providing layers of abstraction, managing data and resources, controlling and coordinating physical entities Discrete Algs for Mobile Wireless Sys

6. Approach • We will take a theoretical, mathematical viewpoint: • define clean computational models • define abstract problems • describe algorithms clearly • analyze complexity of algorithms • identify inherent limitations • Try to develop a theory that "fits" practical assumptions Discrete Algs for Mobile Wireless Sys

7. Challenge • Practical algorithms often provide few hard-and-fast guarantees • hard to get them, since network is so poorly behaved • Theoretical algorithms usually can give good guarantees • but sometimes based on questionable assumptions • Can we find algorithms that work in practice and still satisfy some provable guarantees? Discrete Algs for Mobile Wireless Sys

8. Schedule • Part I: Basics • physical layer • MAC layer • time synchronization • localization • Part II: Communication • global broadcast • routing • location services Discrete Algs for Mobile Wireless Sys

9. Schedule • Part III: Building and Maintaining Network Structures • topology control • clustering • unit disk graphs and related models • wakeup problem • maximal independent sets, coloring, etc. Discrete Algs for Mobile Wireless Sys

10. Schedule • Part IV: Middleware • local infrastructure • token circulation, leader election, resource allocation, group communication • compulsory protocols • virtual node layers • Applications • data aggregation • implementing atomic memory • robot and vehicle motion coordination Discrete Algs for Mobile Wireless Sys

11. How the Class Will Work • Source material consists of: • papers in the research literature (available through the course web page) • drafts of two books (paper copies will be made available) • For each class, we will read 1 or 2 papers/book chapters and discuss them Discrete Algs for Mobile Wireless Sys

12. Course Requirements • Do the assigned reading before each class: • turn in a 1-page summary of each paper at the beginning of class • may have a few questions to answer also • Attend each class and participate in the discussion • Term project: go into more depth with supplementary reading or tackle an original research problem • written report • oral presentation Discrete Algs for Mobile Wireless Sys