isa5428: 普及計算 research issues
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ISA5428: 普及計算Research Issues
金仲達教授清華大學資訊系統與應用研究所
九十三學年度第一學期
Pervasive Computing Research Issues-2
Source “Pervasive Computing: Vision and Challenges
”M. Satyanarayanan, Carnegie Mellon UniversityIEEE Personal Communications,pp. 10-17, August 2001
Pervasive Computing Research Issues-3
Outline Related fields
Distributed System Mobile Computing Pervasive Computing
Example scenario Drill down Conclusion
Pervasive Computing Research Issues-4
Distributed Systems Research involving two or more computers
connected by a network Areas foundational to pervasive computing:
Remote communication: protocol layering, RPC, end-to-end argument
Fault tolerance: atomic transactions, two phase commit
High availability: replica control, mirrored execution, recovery
Remote information access: caching, function shipping, distributed file system
Security: authentication, privacy
Pervasive Computing Research Issues-5
Mobile Computing (1/2) Research on building distributed systems
with mobile clients Principles in distributed system design still
apply 4 constraints to distinguish it from distributed
systems and demand new research Unpredictable variation in network quality Lowered trust and robustness of mobile elements Limited local resources imposed by weight and
size Battery power consumption
Pervasive Computing Research Issues-6
Mobile Computing (2/2) Research areas:
Mobile networking: mobile IP, ad hoc protocols, improving TCP performance in wireless networks
Mobile information access: selective control of data consistency
Support for adaptive applications: transcoding by proxies
System-level energy saving techniques: energy-aware adaptation, variable speed processor scheduling
Location sensitivity: location sensing, location-aware system behavior
Pervasive Computing Research Issues-7
Pervasive Computing Pervasive computing environment:
An environment saturated with computing and communication capability, yet so gracefully integrated with users that it becomes a “technology that disappears”
Subsume distributed computing and mobile computing, but incorporate 4 additional research thrusts (next figure)
Pervasive Computing Research Issues-8
Pervasive Computing Research Issues-9
4 Additional Research Areas (1/2) Effective use of smart spaces:
Space: an enclosed area or a well-defined open area Smart space: embedding computing infrastructure in
building infrastructure => physical/virtual converge Enable sensing and control of one world by the other
Example? Invisibility:
Minimal user distraction is a more practical goal Ex.: the environment continuously meets user
expectations and rarely presents him with surprises Some alerts may still be needed
Pervasive Computing Research Issues-10
4 Additional Research Areas (2/2) Localized scalability:
Increasing complexity in interactions between a user’s personal computing space and surroundings as well as other persons
Must consider scalability with physical distance Masking uneven conditioning
Different environments will have huge differences in their smartness, causing user distraction
One solution: have user’s personal computing space to compensate
Complete invisibility may be impossible, but reduced variability is possible
Pervasive Computing Research Issues-11
Outline Related fields Example scenario
Scenario 1 Scenario 2 Miss Capabilities
Drill down Conclusion
Pervasive Computing Research Issues-12
Scenario 1 Jane is at Gate 23 of an airport and would like to
e-mail her edited files through wireless connection, but the bandwidth is miserable
Aura, the pervasive computing environment, detects the situation, consults airport servers, and finds Gate 15 will have no flight in 1.5 hour
Aura suggests Jane to go to Gate 15 and prioritize her email
Jane accepts the suggestions Files are transmitted at Gate 15 and Aura
informs Jane when she needs to be back to gate
Pervasive Computing Research Issues-13
Scenario 2 Fred has to walk to a meeting from his office to
give a presentation, but he is not quite ready yet Fred grabs a handheld computer and starts
walking to the meeting Aura transfers his state from desktop to
handheld, and Fred does final editing with voice Aura infers Fred’s schedule, downloads materials
to projection computer and warms up projector Room’s face detection system recognizes some
unfamiliar faces and advises Fred not to show sensitive data
Pervasive Computing Research Issues-14
Some Key Aspects Scenario 1:
Proactivity: Aura can estimate how long the whole process takes and look ahead on her behalf
Combining knowledge from different layers: wireless congestion and boarding time
Smart space: provide information of wireless BW, flight time and gates, distance between gates
Scenario 2: Moving execution state across diverse platforms Automatic adjusting behavior to fit circumstances:
voice inputs Proactivity and smart space
Pervasive Computing Research Issues-15
Missing Capabilities Component technologies are simple and
basic They are available today
The challenge:The seamless integration of component technologies into a pervasive computing system Architecture Component synthesis System-level engineering
Pervasive Computing Research Issues-16
Outline Related fields Example scenario Drill down
User intent Cyber foraging Adaptation strategy High-level energy management Client thickness Context awareness Balancing proactivity and transparency Privacy and trust Impact on layering
Conclusion
Pervasive Computing Research Issues-17
The Model Each user is immersed in a personal
computing space that mediates all interactions with the pervasive computing elements in surroundings
As a command center System design: wearable computer? personal
assistant? thicker or thinner? what sensors and networking?
Context aware: how to know user’s state and surrounding, and modify behavior
How to cooperate and interact with infrastructure? with other persons?
How to roam and adapt? reconfigurable? => PDA with 802.11b, Java
Pervasive Computing Research Issues-18
Issue: Smart Object/Environment Provide services
System design: which embedded system? web server? sensors and actuators? NW?
Naming, registration, discovery Physical/virtual mapping Mobile management, energy management Service composition, I/O matching, adaptation,
environment monitoring
Pervasive Computing Research Issues-19
Issue: Infrastructure Support Infrastructures in real life
e.g., electricity, roads, ... Just there or even invisible, open platform
Internet infrastructure Domain name service (DNS registry) Services: cooperating routers, time servers TCP/IP: common formats/protocols Web standards
Extend the Internet to everyday objects
Pervasive Computing Research Issues-20
Infrastructure for Smart Objects Guarantee
Security, privacy, availability, reliability Provide services
Location (Where am I?) Context (Are we in a meeting?) Event delivery (Tell me when... happens) Brokering (Find something that…) Directory, discovery, registry Mobility, roaming, ...
How do we organize billions of mobile smart objects that are highly dynamic, short living,…?
For applications
built with smart objects
For smart objects
Pervasive Computing Research Issues-21
Issue: User Intent (1/2) A pervasive computing system must track
user intent Determine which actions will help, not hinder,
user Ex.: suppose a user is viewing video over a
network, whose bandwidth suddenly drops. Should the system
Reduce the fidelity of the video? Pause briefly to find another higher-bandwidth
connection? Advise the user that the task can no longer be
accomplished?Correct choice depends on what user is trying to
accomplish
Pervasive Computing Research Issues-22
User Intent (2/2) Today’s applications either have no idea abo
ut user intent (e.g. to support adaptation and proactivity), or do it badly
Issues: Can user intent be inferred, or does it have to be ex
plicitly provided? How is user intent represented internally? What are
represented? How does one characterize accuracy of knowledge?
Is incomplete or imprecise information useful? Will obtaining intent place an burden on the user?
Pervasive Computing Research Issues-23
Issue: Cyber Foraging (1/2) Dynamically augment computing
resources of end user devices with wired hardware infrastructure => surrogate
Usage: On entering a neighborhood, a device detects
the presence of surrogates and negotiates its use
Surrogates serve as gateway to the Internet and server for heavy computation
When the device leaves the neighborhood, surrogate binding is broken and staged data are discarded
Pervasive Computing Research Issues-24
Cyber Foraging (2/2) Issues:
How to discover the presence of surrogates? How to establish an appropriate level of trust?
How to amortize the cost of establishing trust? How to balance the load of surrogates? How to minimize latency in serving devices? How to deploy surrogates? How scalable? How to make surrogate uses seamless and
minimally intrusive for a user?
Pervasive Computing Research Issues-25
Issue: Adaptation Strategy (1/2) Necessary when there is significant
mismatch between the supply and demand of a resource, e.g. bandwidth, energy, computing cycles, ...
Three strategies for adaptation The client guides applications in changing their
behavior The client asks the environment to guarantee a
certain level of a resource The client suggests a corrective action to the
user
Pervasive Computing Research Issues-26
Adaptation Strategy (2/2) Issues:
How does a client choose between adaptation strategies? How strategies be changed seamlessly as user moves?
How to do resource reservation in a smart space? What are appropriate admission control policies? What API are needed to make reservation?
Will corrective actions be intrusive? How to do it, e.g. API, programming model?
What is the relationship between lowing fidelity and adaptation?
Pervasive Computing Research Issues-27
Issue: High-Level Energy Management Necessary because low-level techniques,
e.g. battery and circuit design, are insufficient
Issues: What high-level systems can be managed for
energy efficiency? (memory, application adaptation, …)
Are they intrusive to the user? Can user intent help?
Can smart spaces and surrogates be used to reduce energy demand on a mobile device?
How to tradeoff the energy used in remote execution with wireless connection?
Pervasive Computing Research Issues-28
Issue: Client Thickness How powerful does a mobile client need to be?
From bare-bones devices (high-resolution displays thru wireless to servers) to full-function clients (standalone & disconnected operation)
Issues: How to quantify thickness with env. conditioning, e.g., sensor
s added and better networking? How to migrate app. between clients of different thickness? How to cooperate with infrastructure? Can clients be reconfigurable to adapt to env.? Semi-portable infrastructure for less hospitable env.? How to roam transparently? especially from a benign environ
ment to a poor one? How to lower the cost of diversity in devices?
Pervasive Computing Research Issues-29
Issue: Context Awareness Needed for an environment minimally intrusive
Recognize user state and surroundings Make decisions proactively, modify behavior
accordingly Issues:
Obtaining information needed to function How to represent context internally? How to combine
it with system and application state? Where to store? How often to update and consult context
information? What services does the infrastructure have to
provide? How to track location? sense surroundings?
Pervasive Computing Research Issues-30
Issue: Proactivity and Transparency How not to annoy a user in a proactive
system?=> self-tuning according to user expertise and experiences
Issues: How are user preferences and tolerances
specified and taken into account? How to determine the right level of balance?
Pervasive Computing Research Issues-31
Issue: Privacy and Trust A pervasive computing environment needs
to monitor user actions almost continuously in order to be effective
Need mutual trust between environment and user
Issues: Tradeoff between seamless system behavior
and privacy/trust enforcement Any appropriate authentication techniques? How to specify security constraints? How to
specify one’s identity?
Pervasive Computing Research Issues-32
Issue: Impact on Layering Pervasive computing often requires
merging information from different layers a system
Issues: Relationship between layering and pervasive
computing How to create a new layer?
Pervasive Computing Research Issues-33
Conclusions Almost all sub domains in CS are affected
System infrastructures, networking, security, user interfaces, embedded systems, AI, perception, speech recognition,...
We are already moving in this direction XML, UDDI, mobile IP, Jini, ...
Systems integration is the key Many new and fascinating research problems
emerge!
Pervasive Computing Research Issues-34
The Field Is Burgeoning IEEE Pervasive magazine Springer Personal and Ubiquitous Computing Ubicomp Various links to universities, research institute
s, companies
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