1 Pervasive & Ubiquitous Computing Hao Chu ( 朱浩華 ) Lecture #2 2/23/2004.

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Pervasive & Ubiquitous Computing

Hao Chu (朱浩華 )

Lecture #2

2/23/2004

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Administrative Announcements

• Course homepage is up.– http://www.csie.ntu.edu.tw/~hchu/ubicomp_course/ubi

comp_course.htm– Reading list, project overview, project ideas, …

• Course WIKI page is up.

• “How to use WIKI?” by James

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Vision and Challenges

• M. Weiser, “The Computer for the 21th Century", Scientific American, September 1991.

• M. Weiser, “Some Computer Science Issues in Ubiquitous Computing”, Communications of the ACM, 36(7):75-85, July 1993.

• M. Weiser, J. S. Brown, "The Coming Age of Calm Technology“, 1996.

• M. Satyanarayanan. "Fundamental Challenges in Mobile Computing", Fifteenth ACM Symposium on Principles of Distributed Computing, May 1996.

• M. Satyanarayanan. “Pervasive Computing: Vision and Challenges”, IEEE Personal Communications, August, 2001.

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M. Weiser. “The Computer for the 21th Century", Scientific America

n, September 1991.

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Two Key Points

• Ubiquitous computing is about computing so well integrated with our physical environment such that people fail to take notice of them.– Computing being everywhere, yet fading into the back

ground– Computing becoming disappearing and invisible

• Location and scale are important issues.– Adapt their behavior intelligentlly without complex AI– Scale suitable to different tasks

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Examples of Disappearing Technologies

• Writing• Electric Motors• Micro-controllers in CEs• They are everywhere (embedding & hidden into

physical objects), yet invisible.• When a technology matures, they disappear!

– Maturity = cheap, small, widely applicable, good usability, …

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Why Good Technology Is Invisible?

• “Invisible” stays out of the way of task– Like a good pencil stays out of the way of the writing– Like a good car stays out of the way of the driving

• Bad technology draws attention to itself:– Like a broken, or skipping, or dull pencil– Like a car that needs frequent tune-ups

• Computers are mostly not invisible– They dominate interaction with them.

• Ubicomp is about making computers invisible.

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Ubicomp vs. Virtual Reality

• Should we live in virtual computing world? Or should computing come out and live in our physical world?

• VR is about simulating physical world & putting people inside virtual computing world.– Limited applications & activities

• Ubicomp is about bringing computing to people’s physical world.– Integrating with everyday objects and activities

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Ubicomp vs. Multimedia

• Multimedia grabs user attention for entertainment purpose.

• Ubicomp reduces user distraction, allowing people to focus on tasks.

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Intelligence

• Computing embedded and enhancing physical objects

• Achieve intelligence through interconnection of physical objects– Wall talking to heating or projector

• Achieve intelligence through location awareness (without AI)– Automated call forwarding, lighting control

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PARC Ubicomp Work (1991)

• Focus on devices that transmit & display information.

• Device scale targets different tasks.– Consider three sizes: tabs,

pads, boards.

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Tabs• Inch-scale Ubicomp devices

– Post-It notes

• Carried around by a person• Hundreds in a room

– Credit cards, ID cards– Remote controllers– Badges– Tags / Labels (RFID)– Locating system (tags as library catalogs)– Animate static physical objects (active calendar, active

map)

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Pads

• Foot-scale Ubicomp devices– A sheet of paper / tablet PC

• Tens in a room– Like scrap papers that can

be grabbed and used anywhere, no unique ID.

• Like windows in Apple Macintosh, but can spread them out on a real desk.

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Boards

• Yard-scale Ubicomp device• One in a room• White board with e-chalk

– Shared white board with remote participants

• Video screen• Electronic Bookcases

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Hardware Challenges (1991)

• High resolution flat panel display (cheap)• High speed processor• High capability storage• High bandwidth wireless Network• Lower power consumption• How well do today’s HW technologies meet

these challenges?

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Software Challenges (1991)

• Dynamic configuration of HW/SW in ubicomp environments (device mobility)

• Application migration across heterogeneous ubicomp environments (user mobility)

• Transparent linking of wired and wireless networks– Tiny range wireless, long range wireless, high speed

wired

• How well do today’s SW technologies meet these challenges?

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Sal Scenario

• Proactively brew coffee• Electronic Trails of

neighbor coming and going (Privacy issue)

• Automatic recording pen • Email locating garbage

door opener• Window tells weather• Share location info with

Joe (Privacy Issue)

• Share tabs/pads with Joe (Miniaturization)

• Gesture to project blinking tab to projector.

• Memory augmentation on meeting with Mary.

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Privacy Issue

• Hundreds and thousands of invisible computers sensing and watching people– A bit scaring?

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Misc

• Ubicomp as a Savor to Healthy Social Interaction?– People don’t have to hole up in windowless offices bef

ore computer screens all days.

• Ubicomp as relaxing as “talking a walk in the woods”

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Discussion

• Tradeoff between intelligence and privacy• Tradeoff between invisibility and privacy• What are killer ubicomp applications?• Think about interesting scenarios for interconnecting ho

me appliances• AI & ubicomp?• Should computing stay out of the physical world?

– Human dependency on computing– Environmental impacts– Social impacts

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M. Weiser. “Some computer science issues in ubiquitous computing.”Communications of the ACM,

36(7):75-85, July 1993.

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Key Point

• Based on their PARC experiments with tabs, pads, and boards, this paper tries to define some ubicomp challenges and where ubicomp is going.

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Ubicomp as Experimental CS

• Construct working prototype• Evaluate working prototype in everyday use.• Importance of “working prototype”

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Hardware Prototype Issues

• Power consumption: impossible to change batteries to many ubicomp devices frequently.

• Balance of HW/SW feature: display, network, processing, memory, storage capability, multitasking, QoS, etc.

• Ease of expansion & modification (integration vs. modular design)

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Hardware Issues

• Low-power computing• High-speed wireless bandwidth (802.11g 54

Mbps)• Pens for very large display

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Network Issues

• Wireless Media Access (802.11, Bluetooth, Cellular Networks)

• Quality of Services (RSVP, etc)• Ubicomp devices changing network attachment

(Mobile IP)

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Interaction Substrate Issues

• Interaction substrates are UI software for pens and screens.– Handprinting recognition– Voice recognition– Display migration (follow-me display)

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Application Issues

• “Applications are of course the whole point of ubiquitous computing”.

• Locating people (active badges)– Automated call forwarding– Tracking down people for meeting– Watching general activity in a building (feel in touch

with surrounding environments)

• Shared drawing in virtual meeting– Scalability to 5000 peoples (multicast for bandwidth

efficiency)

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Location Privacy

• Centralized location database as one possible solution, but not scalable, single point of attack, one break-in reveals all.

• Move toward more distributed approach.

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Computational Method Issue

• Due to unpredictable network to ubicomp devices, (file) caching can be used to improve performance.

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Discussion

• Open ….

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M. Weiser, J. S. Brown. "The Coming Age of Calm Technology." 1

996.

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Key Points

• The computing trends is moving toward many (hundreds of) computers sharing each of us. Since computers are everywhere, they better stay out of our ways. Weiser called it Calm technology.

• A proposed solution (Calm technology) is to place most information in periphery of our attention, but allow fast & easy moving to center of our attention.

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Computing Trends

These trends are results of computing getting smaller, faster, and cheapers.

• Mainframe Era: many people sharing a computer.

• PC Era: one computer per person• Internet Era: (interconnecting PCs)• Ubicomp Era:

– many computers (everyday objects) sharing one person

– interconnecting everyday objects

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Ubicomp Era

• Cheap “Thin servers” in every household appliances.

• Average home appliances (Microwaves, TV, DVD players, etc.) have embedded processors, but they are not Ubicomp devices, because– They are not networked.– They are not connected to the Internet.

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Calm Technology

• Calm and uncalm technology differs how to engage our attention.– Divide our attention into two parts: periphery and cent

er.

• Periphery is informing without overburdening– E.g., driving a car, center = roads and radio, periphery

= engine noise

• Calm technology can move easily & quickly between periphery and center.

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Examples of Calm Technology

• Inner Office Windows– Extend periphery to what are going on the hallway– E.g., notice lunch gathering, meeting, but not

distracting to work

• In comparison to open cubicles with low partitions– Force too much to the center– E.g., noises in the hallway can become distracting to

work

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Dangling String

• Represent bits flowing over a wire through motion and sound.

• The output is (beautifully?) integrated with our physical environment.

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Discussion

• Is Ubicomp defined by the devices or user experience?

• Are inner office window and dangling string really calm and relaxing?

• Does Calm give more or less information?• This is related to ambient display research. UI P

eople know more about this research area?

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M. Satyanarayanan. "Fundamental Challenges in Mobile Computing", Fifteenth ACM Symposium on Principles of Distributed Computi

ng, May 1996.

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Key Points

• What are fundamental challenges in mobile computing (What is so special about mobile computing)?– Resource-limited mobile devices– Mobility is hazardous– Unpredictable wireless networks– Finite power source

• Adaptation is key to mobility.

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Evolution from Distributed Systems to Mobile Computing

• What are fundamental differences between Distributed Systems and Mobile Computing?– Distributed systems = Applications running over

Computers Connected Over Network– Mobile systems = Applications running over mobile

devices connected over wireless networks– Mobile devices constraints: resource-limited, finite

power source, easy-to-lose (weak security)– Wireless network constraints: unpredictability

bandwidth and frequent disconnections

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Adaptation is Key to Mobility

• Adapt applications to continuously changing computing environment (due to mobility):– Power, network bandwidth / availability, …

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Adaptation Strategies

• Need resource management at the system layer to allocate resources to different applications.

• Need application level semantics, e.g., frame-rate, resolution, etc.

• The best approach is to have both application and system supports.

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Extended Client Server Model

• Traditional (thin) client (fat) server model in distributed computing needed adjustments to address unpredictable network, finite power, and performance.

• Extended client-server model (called smart client model) places some server functionalities to client.

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Coda & Odyssey

• Coda supports application-transparent adaptation.– It is distributed file system (FS).– It can cache/hoard some parts of FS on client.– It can support disconnected operations from FS

cache.

• Odyssey supports application-aware adaptation.– Adapt application quality/fidelity (e.g., video

framework, resolution) based on dynamic network condition, power saving, and processing loads.

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Research Topics for Exploration

• Caching metrics (what to cache/hoard?)• Caching coherence (Semantic callbacks and vali

dators)• Algorithms for resource revocation

• Agility (靈敏 ) vs. stability (Analysis of adaptation)

• (Global) Resource estimation from local observations

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M. Satyanarayanan. “Pervasive Computing: Vision and Challenges”, IEEE Personal Communications,

August, 2001.

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Key Points

• What are fundamental challenges in pervasive/ubicomp computing (What is so special about pervasive computing)?– Effective use of smart spaces– Invisibility– Localized Scalability– Masking Uneven Conditioning

• We will hear a distinguished talk from author directly.– http://www.cs.uiuc.edu/news/dls/distlectpst.html

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Discussion

• What exactly is proactivity? How does it differ from adaptation?

• Is Ubicomp still about old technical issues ..– Integrating different technologies, devices and service

s.– Resource discovery protocol– Optimization (different parameters such as power)– Adaptation (with environments)