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

Discrete Algs for Mobile Wireless Sys2 Overview  Mobile wireless systems are moving into your 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 Sys3 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 Sys4 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 Sys5 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 Sys6 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 Sys7 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 Sys8 Schedule  Part I: Basics physical layer MAC layer time synchronization localization  Part II: Communication global broadcast routing location services

Discrete Algs for Mobile Wireless Sys9 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 Sys10 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 Sys11 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 Sys12 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