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Mobile Computing and Wireless Networking

CS 851 Seminar 2002 Fall

University of Virginia

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First Thing to Do !

Everything is in the Web Syllabus, materials,

http://www.cs.virginia.edu/~cs851-2/course.html

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What Are We Going to Learn?

What are the challenges facing Mobile Computing? What are fundamental principles in Mobile Computing What is the state-of-the-art research for Mobile Computing? What are the open problems?

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Selected Topics Vision and Challenges

Wireless  Medium Access  Control

  IEEE 802.11

  Mobile Ad Hoc  Routing 

  Mobile IP

  TCP over Wireless Link

Energy Efficient  and Power Aware Protocols

  Capacity of Wireless Network

  Mobile Data Access/Dissemination

  Address auto configuration

  Location Discovery/Tracking 

  Multicast in Mobile Ad Hoc Network (option)

  Security (option)

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How Are We Going to Learn?

Select new and representative papers for each topic Each student needs to do two presentations Each presentation will cover one or two papers (begin at Sep 10) Before each lecture, every student needs to hand in a simple

summary about the presented papers (begin at Sep 10) Term project performed in small group which consists of two

students. (Suggested topics will be provided before Sep. 15)

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Challenges of Mobile Computing

[1] “Some computer science issues in Ubiquitous Computing” by M. Weiser 1993

[2] “The challenges of Mobile Computing” by G. H. Forman & J. Zahorjan 1994

[3] “On some principles of Nomadic Computing and Multi-Access Communications” by L. Kleinrock 2000

[4] “Pervasive Computing: Vision and Challenges” by M. Satyanarayanan 2001

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What is Mobile Computing?

Building distributed systems with portable computers and wireless communications to allow mobile users to access services and resources at anytime from anywhere

Advances of wireless communication & portable computers make computers users do not need to maintain a fixed position in the network and enables almost unrestricted mobility. However, network resources and application software do not follow mobile users. There are many problems to provide computing and communication capacities to mobile users.

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Buzzwords

Ubiquitous Computing, Mobile Computing, Nomadic Computing, Pervasive Computing

Mobile Computing and Nomadic Computing are about building distributed systems with portable computers and wireless communications Mobile Computing: focus on out-door mobility with pedestrian or vehicular speed Nomadic Computing: focus on in-door mobility with pedestrian speed

Ubiquitous Computing ==Pervasive Computing (AI + Mobile Computing) creating environments saturated with computing and communication capacity yet

gracefully integrated with human users (or enhancing computer use by making many computers available throughout the physical environment, but making them effectively invisible to the users)

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Many Applications

Military environments soldiers, tanks, planes

Civilian environments taxi cab network meeting rooms sports stadiums boats, small aircraft

Emergency operations search-and-rescue policing and fire fighting

Killer application Anywhere and anytime access to the Internet

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Evolution of Computing

Freedom from Collocation (space & time)

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Single UserOS

Time Sharing

Networked Computing

Mobile Computing

Pervasive Computing

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Three Challenges

Wireless communication

Mobility

Poor local resources due to portability

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Wireless Communication

Limited transmission range (IEEE 802.11 < 300 meters) Limited bandwidth

o IEEE 802.11 ~ 2 mbps

o IEEE 802.11a ~54 mbps

o IEEE 802.11b ~ 11 mbps

o IEEE 802.11g ~ 20mbps

Frequent disconnections or network partitions Uncertainty of performance

Variance of bit error Variance of latency Variance of bandwidth

Easier for intruders to insert themselves into networks

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Mobility

Mobility Dynamic Environment Network

oAddress migration (network access point varies)

oHigh performance variability (error rate, latency, cost, connectivity …) Hardware

oLighter

oMore robust

oLower power Available resources change Correctness of information changes

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Poor local resources due to portability

CPU Memory limited battery life time

All these challenges are instinct and need innovative and system-wide solutions

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Five Areas for Achieved Results

Mobile networking

Mobile information management

Adaptive techniques

Power management and energy saving

Location sensitivity

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Mobile Networking

Mobile Ad-Hoc networksMultiple Access ControlDistributed scheduling algorithmsMobile ad-hoc routingSecurity

Mobile IP

Wireless TCP I-TCPSnoop TCP

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Mobile Data Management

Data delivery modesServer pushClient pullHybrid

Data organization Data consistency management

Disconnected operationWeak connected operation

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Adaptive Techniques

Exploiting dynamical (networking, physical, users) information to perform effective mobile computing

Adaptive resource management

Adaptive networking

Application-aware adaptations

oExample: a videoconferencing application can display only the speaker if bandwidth is low, else all participants

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Power Management and Energy Saving

Topology control of ad-hoc networks using transmit power adjustment

Power aware routing protocols Power aware MAC protocols

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Location Sensitivity

Location-aware applicationso Discover and take advantage of contextual information such as

user location, nearby people and devices, and user activity

o Ex.

• What resources (printers, ect.) are available “here”?

• Where is the “nearest” hospital?

• How do I get from “here” to the nearby public library

Location information systemso Indoor location tracking system

o Outdoor logical location determination system without GPS

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Summary

Mobile computing Very active and evolving research field Plenty of interesting research problems

We will learn a lot in this course Understand the state of the art New ideas and new results New ways of using mobile computing

It will be Very Rewarding

Dedicate your time and make contributions

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Evolution of Computing

Freedom from Collocation (space & time)

Fle

xib

le R

eso

urc

e U

sa

ge

Single UserOS

Time Sharing

Networked Computing

Mobile Computing

Pervasive Computing