Mobile and Ubiquitous Computing A background and overview

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Mobile and Ubiquitous Computing A background and
overview

• Vision of Mark Weiser
• Challenges and Issues of Mobile Computing
• Challenges and Issues of Ubiquitous Computing

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Reference Papers

• 1 The Computer for the 21st Century
• Mark Weiser, Palo Alto Research Center
• 1991, Scientific American
• Reprinted in Pervasive Computing
• January March 2002
• 2 Fundamental Challenges in Mobile Computing
• M. Satyanarayanan, Carnegie Mellon University
• Published in 1996 in ACM (PODC96)
• 3 Pervasive Computing Vision and Challenges
• M. Satyanarayanan, Carnegie Mellon University
• Published in IEEE Personal
  Communications August
  2001

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Preview

• The convergence of technologies
• Issues pointed to by Mark Weiser
• Problems and issues of Mobile Computing
• Five major research areas
• Problems of Ubiquitous Computing
• Integration of different technologies
• Major areas of research

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• An Interesting Scenario
• Jane is at Gate 23 at the Pittsburgh airport,
  waiting for her connecting flight
• She would like to use her wireless connection to
  e-mail a number of large documents
• Many passengers at Gates 22 and 23 are surfing
  the Web
• Aura observes that Jane wont be able to finish
  sending her documents before her flight departs
• After consulting the airports flight schedule
  service, Aura discovers that wireless bandwidth
  is excellent at Gate 15
• A dialog box pops up on Janes screen suggesting
  that she go to Gate 15, which is only three
  minutes away
• It also asks her to prioritize her e-mail, so
  that the most critical messages are transmitted
  first
• Jane accepts Auras advice and walks to Gate 15
• Aura informs her that it is close to being done
  with her messages, and that she can start walking
  back
• The last message is transmitted during her walk,
  and she is back at Gate 23 in time for her
  boarding call 3

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Vision of Mark Weiser

• Specialized elements of hardware and
  software, connected by wires, radio waves and
  infrared, will be so ubiquitous that no one will
  notice their presence
• Ubiquitous
• Invisible computers embedded in everyday objects
  that would replace PCs
• Technology should disappear to make computers
  ubiquitous
• Issues
• Scale and the knowledge of where the
  user is located to adapt to the surroundings

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Vision of Mark Weiser

• Embodied virtuality
• Modified virtual reality
• Process of drawing computers out of their
  electronic shells
• Devices that implement the technology
• Interaction between devices is more important
  than making them
• Parts that build a ubiquitous system
• Low cost and low power computers
• Software
• Network that ties the computer together

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Vision of Mark Weiser

• The Computer Hardware is satisfactory
• The Operating System needs a change Microkernel
  approach
• Network requirements
• Transparent and wireless link between modules
• Protocols that are efficient in mobile networks
• A large number of channels
• A future where computers disappear

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Problems and issues of mobile computing

• Constraints of mobile computing and their impact
  on distributed systems
• All constraints are intrinsic to mobility
• Mobile elements are resource poor
• Mobility is inherently hazardous
• Mobile connectivity is highly variable
• Mobile elements rely on a finite energy source
• Solution lies in the mobile client being
• ADAPTIVE

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Problems and issues of mobile computing

• Adaptive implementation has two extremes
• Total autonomy Adaptation is the responsibility
  of the individual application
• Application transparent adaptation
  Responsibility of adaptation lies entirely
  on the system
• Actual implementation lies between the two
  extremes Application aware adaptation
• Use an extended client-server model to implement
  mobile application
• The client may have to take the role of a server

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Problems and issues of mobile computing

• Experimental results on Coda file system
• Experiment conducted to study the effect of
  mobility and application transparent adaptation
• Disconnected operation is feasible, effective and
  usable
• Use techniques of hoarding, update logging and
  reintegration on reconnection
• Optimistic replica control strategy is applicable
  
• Use techniques of log-based directory
  resolution, application-specific file
  resolution, containment and manual repair

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Problems and issues of mobile computing

• Experimental results on Coda file system.
• 3. Support weak connectivity to avoid the
  limitations of disconnected operations
• Use techniques of adaptive transport
  protocols, rapid cache validation mechanism,
  trickle reintegration mechanism and model-based
  cache miss handling
• 4. Use isolation-only transaction to cope with
  detection and handling of read-write conflicts
  during disconnected operations
• Use database transactions
• 5. Server replication can be used to complement
  disconnected operation

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Areas of research in mobile computing

• Five areas of research are identified
• Caching Metrics
• Problems of common metric - Miss ratio
• Should be consistent and easy to monitor
• Open problems
• What is an appropriate set of caching metrics for
  mobile computing?
• Under what circumstances does one use each
  metric?
• How does one efficiently monitor these metrics?
• What are the implications of these alternative
  metrics for caching algorithms?

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Areas of research in mobile computing

• 2. Use cache validation instead of maintaining
  cache coherence to reduce remote communication
• Use callbacks
• Maintain cache coherence at multiple levels of
  granularity
• Use semantic validation to maintain cache
  coherence at multiple levels of granularity
• Open questions are related to predicate Q that is
  a function of the block value P
• How useful are semantic validation and callbacks?
• What forms can P and Q take for data types?

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Areas of research in mobile computing

• 3. Algorithms for resource revocation
• Application aware adaptation complicates the
  problem of resource management
• Open problems are
• How does one formulate the resource revocation
  problem?
• How does one characterize the differential impact
  of revocation on different applications?
• What strategies does one use if multiple
  resources must be simultaneously revoked?
• How does one distinguish between resources whose
  revocation is easy to recover from and those
  which are expensive or impossible to recover
  from?
• How does one handle deadlocks during revocation

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Areas of research in mobile computing

• 4. Analysis of adaptation
• Primary figure of merit for mobile clients
  Agility
• Ideal mobile client is highly agile and very
  stable
• Open questions
• What are the right metrics to measure agility?
• Are there systematic techniques to improve the
  agility of a system?
• How does one decide when a mobile system is
  agile enough?
• What are the right metrics to measure system
  stability?
• Can one develop design guidelines to ensure
  stability?
• Can one analytically derive the agility and
  stability properties of an adaptive system
  without building it?

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Areas of research in mobile computing

• 5. Global estimation from local observations
• Adaptive mobile clients should have the
  capability to infer global changes by detecting
  local changes
• Issues are
• Are there systematic ways to perform global
  estimation from local observations?
• Can one bind the error in global estimates?
• What is the relationship between global
  estimation and agility of adaptation?
• Can one provide system support to improve global
  estimation?
• Can one quantify the benefits of out-of-band
  channels?

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Problems and Issues of Ubiquitous Computing

• Pervasive Computing
• Technology that disappears
• Relationship with distributed systems and mobile
  computing
• Problems solved in distributed systems
• Remote communication
• Fault tolerance
• High availability
• Remote information access
• Security
• Key constraints of mobility forced the
  development of specialized techniques
• Four areas of research in ubiquitous computing

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How Did We Get Here?
Smart spaces Invisibility Localized
scalability Uneven conditioning
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Problems and Issues of Ubiquitous Computing

• Areas of research
• Effective use of smart spaces context-aware
  space
• Invisibility minimal user distraction
• Localized scalability
• Masking uneven conditioning smartness of
  environments vary
• First requirement for any application is
  proactivity
• All technologies for implementing the scenario is
  available
• Whole is much greater than simply the sum of its
  parts
• Requires seamless integration of component
  technologies
• Problems lie in the architecture, component
  synthesis and system level engineering

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Problems and Issues of Ubiquitous Computing

• User
• Immersed in a PC environment
• Adaptable and reconfigurable
• Client
• May take the role of a server
• A multilayered architecture
• Environment
• Smart space
• Server

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The structure of an Aura Client
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Problems and Issues of Ubiquitous Computing

• Problems that need to be solved
• User intent needs to be established
• A number of research questions need to be
  answered
• Deal with the conflicting requirement of higher
  functionality and limited resources
• Use available resources in the smart space
• Cyber foraging and surrogate of mobile computing
• Cyber foraging living off the land exploit
  wired hardware infrastructure
• Hardware starts playing the role of surrogate of
  the mobile computer

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Problems and Issues of Ubiquitous Computing

• Areas to explore
• Cyber foraging
• Adaptation strategies
• High level energy management
• Client thickness
• Context awareness
• Balancing proactivity and transparency
• Privacy and trust
• Impact on layering

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Problems and Issues of Ubiquitous Computing

• Cyber foraging gives rise to a number of research
  problems
• Discover the presence of surrogates
• Level of trust with a surrogate
• Load balancing
• Time to stage
• Effect of scalability
• System support needed for seamless and minimally
  intrusive surrogate

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Problems and Issues of Ubiquitous Computing

• Adaptation strategies
• Client may guide the application to reduce
  fidelity
• Use reservation based Quality of Service
• Client may suggest the user a corrective action
• Unanswered questions
• Factors that affect the decision to choose
  between the adaptation strategies
• Is reservation based QoS the best strategy?
• Multiple and competing requests for reservations
• Practicality of adaptation using corrective
  actions
• Methods of lowering fidelity

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Problems and Issues of Ubiquitous Computing

• High level energy management
• High level system should get involved for energy
  management
• Energy aware memory management
• Unanswered questions
• Methods of managing energy
• Impact on invisibility
• Can knowledge of user intent be exploited in
  energy management?
• Use of smart spaces and surrogates to reduce
  energy demand
• Remote execution to extend battery life

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Problems and Issues of Ubiquitous Computing

• Client thickness
• The clients need to be as thin as possible but
  should be thick enough to fulfill the
  requirements
• Research questions are
• Quantify client thickness and environmental
  conditioning
• Can the system alert a user when it migrates to a
  less hospitable environment?
• Is transparent migration from a thinner to a
  thicker client possible?
• Can computers be reconfigured to serve as optimal
  mobile clients under diverse environmental
  conditions?
• Can semi-portable infrastructure be carried with
  a user to augment less hospitable environments?

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Problems and Issues of Ubiquitous Computing

• Context awareness
• Required for a minimally intrusive computing
  system
• Issues
• How is context represented internally?
• How frequently does context information need to
  be consulted?
• Minimal services that the environment needs to
  provide
• What are the relative merits of various
  location-sensing technologies?

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Problems and Issues of Ubiquitous Computing

• Balancing proactivity and transparency
• Both are important requirements
• Proactive systems may not always work well
• Transparency is especially important in
  distributed systems with scarce resources
• Unanswered questions
• How are individual user preferences and
  tolerances specified and taken into account?
• How is it possible to determine the balance?
• Can the existing balancing mechanisms be used to
  provide a systematic design guideline to
  application designers?

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Problems and Issues of Ubiquitous Computing

• Privacy and trust
• System contains detailed information related to a
  user
• User trust is achieved by keeping the information
  strictly confidential and private
• Research issues
• Balance between seamless system behavior and the
  need to alert users to potential loss of privacy
• What are the authentication techniques best
  suited to pervasive computing?
• How is access control enforced using the identity
  of users?

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Problems and Issues of Ubiquitous Computing

• Impact on layering
• Layering techniques help solve large problems
• Helps hiding some details but exposes others that
  are required to solve a problem
• Issues are
• Preserving the benefits of layering while
  accommodating the needs of ubiquitous computing
• Are existing layers best extended for pervasive
  computing by broadening their primary interfaces
  or creating secondary interfaces?
• What is the complexity involved in design and
  implementation of layers for ubiquitous computing?

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Areas explored recent publications

• Research areas (2005-2006)
• Internet suspend/resume (ISR)
• VM technology and Distributed File systems
• Same hardware architecture at least to ISA level
• Remote execution
• Cyber foraging
• Resource monitoring and predicting resource
  demands

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Conclusion

• Challenging research problems exist in the field
  of Mobile and Ubiquitous Computing
• Integration of technologies is the main issue
• HCI, Software agents, AI are other areas that are
  integrated in the field
• A lot has been achieved
• More to be explored

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• Thank you