CSE 302-Mobile Computing Challenges - PowerPoint

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					CSE-302: Mobile Computing

  Dr. R. B. Patel

                    Dr. R. B. Patel   1
Breakthrough Technology
• Wireless communication networks
–     multiple networks “covering” the globe
–     world- wide deregulation and spectrum auctions
–         standard communication systems and air link
• Portable information appliances
–     laptops, notebooks, sub- notebooks, and MNCs
–     hand- held computers
–     PDAs and smart phones
• Internet:
–     TCP/ IP& de- facto application protocols
                         Dr. R. B. Patel             2
–     ubiquitous web content
New Forms of Computing
                                 Wireless Computing
                                 Nomadic Computing
  Distributed                    Mobile Computing
  Computing                      Ubiquitous
  (Client/ Server)               Computing
                                 Pervasive Computing
                                 Invisible Computing

                     Dr. R. B. Patel                    3
Mobile Computing
Mobile Computing
• Using:– small size portable computers,
  handheld, MNC, and other small wearable
• To run stand- alone or network based
  applications via:– wireless networks: IR,
  BlueTooth, W- LANs, Cellular,W- Packet Data
  networks, SAT, etc.
•By : – nomadic and mobile users (animals,
  agents, trains, cars, cell phones, ….)
                   Dr. R. B. Patel          4
Mobile Computing
• An important question to ask is which technology drove mobile
  computing to where it is today?
• Is it the wireless network technology or the miniaturization and
  portable computing technology?
• Unfortunately, there is no easy answer. An individual with a Palm
  Pilot will probably answer in favor of the portable technology, whereas
  a UPS package delivery worker will be more thankful to the wireless
• Whatever the right answer might be, more important questions need to
  be answered: where are we now?
• And what are the challenges and impediments facing mobile

                               Dr. R. B. Patel                          5
Mobile computing
• Mobile computing represents a shift in the distributed
  systems paradigm.
• The potential of decoupled and disconnected operation,
  location-dependent computation and communication, and
  powerful portable computing devices gives rise to
  opportunities for new patterns of distributed computation
  that require a revised view of distributed systems.
• However, factors such as weak network connectivity,
  energy constraints, and mobility itself raise new concerns
  regarding the security, reliability, and even correct-ness of
  a mobile computing system.

                           Dr. R. B. Patel                    6
Mobile Computing
• Migration is important for survival
• Mobility originated from the desire to move either toward
  resource or away from scarcity
• Mobile computing about both physical and logical
  computing entities that move
• Physical entities are computers that change locations
• Logical entities are instances of running user application or
  a mobile agent
• Mobile agents can migrate any where over the Internet.
• But applications can only move to a local cluster of
                           Dr. R. B. Patel                    7
• Mobile, ubiquitous, nomadic, un-tethered (unsecured),
  pervasive and any time, any where, any person computing
  are used by the researchers to refer to computing that uses
  small portable devices and wireless communication
• Nomadic computing refer to limited migration
   – Migration is within a building at a pedestrian speed
   – Interleaved pattern of user relocation and indoor
• In the same vein, users carrying laptop with Dialup
  modems are engaged in nomadic computing
                          Dr. R. B. Patel                   8
Buzzwords (contd...)
• Mobile Computing requires: Wireless network to support
  outdoor mobility and handoff from one network to the next
  at a pedestrian or vehicular speed
• Traveler in car using laptop connected with a GSM phone-
  engaged in mobile computing
• Ubiquitous computing or pervasive computing refers to
  access to computer network all the time at any location by
  any person.
• Ubiquitous computing cannot be realized unless mobile
  computing matures.

                         Dr. R. B. Patel                   9
Ubiquitous Computing = Nomadic
Computing + Mobile Computing
  No       Fixed     Fixed             Wireless   Wireless
Network   Network   Wireless           Network    Network
                    Network              (A)        (B)

    Nomadic Computing                  Mobile Computing

              Ubiquitous computing

                     Dr. R. B. Patel                         10
Nomadic computing
• It is another name for mobile computing, is the use
  of portable computing devices (such as laptop and
  handheld computers) in conjunction with mobile
  communications technologies to enable users to
  access the Internet and data on their home or work
  computers from anywhere in the world.
• People using such a system are sometimes referred
  to as technomads, and their ability to use that
  system as nomadicity.
                      Dr. R. B. Patel              11
                  Continued …
• Nomadicity is the tendency of a person, or group of
  people, to move with relative frequency.
• The need to support today's increasingly mobile workers
  with nomadic computing, the use of portable computing
  devices and, ideally, constant access to the Internet and
  data on other computers.
• The goal of nomadic computing is to enable a consistent
  experience for users anywhere in the world, including as
  they travel from one place to another.

                          Dr. R. B. Patel                     12
                    Continued …

• A nomadic environment is said to be one that is transparent
  to the user, regardless of location, the device and platform
  they're using, the available bandwidth, and whether or not
  they are in motion at any given time.
• Standards such as the Internet Engineering Task Force’s
  (IETF) Mobile IPv6 standards and Dynamic Host
  Configuration Protocol (DHCP) can be said to support
  nomadic computing.

                          Dr. R. B. Patel                   13
       Ubiquitous Computing
• Ubiquitous computing names the third wave in
  computing, just now beginning.
• First were mainframes, each shared by lots of
  people. Now we are in the personal computing era,
  person and machine staring uneasily at each other
  across the desktop.
• Next comes ubiquitous computing, or the age of
  calm technology, when technology recedes into
  the background of our lives.
• This is also called "Third Paradigm" computing.

                      Dr. R. B. Patel            14
Sentient computing
• Sentient computing is a form of ubiquitous
  computing which uses sensors to perceive
  its environment and react accordingly.
• A common use of the sensors is to construct
  a world model which allows location-aware
  or context-aware applications to be

                   Dr. R. B. Patel          15
       Mobile Environment
                                                                        radio Cells

                         host                  Fixed
               Fixed                            host

                          High-speed wire-
                            line network
               Fixed                                     host

                          Mobile             Wireless           Comm.
               Base        host               link               cell

                           Dr. R. B. Patel                                   16
Wireless   Telecommunication

           Dr. R. B. Patel   17
            Emerging Portable Information Devices
                                                                         The First Wrist PC: Ruputer
                      The Nokia 9000 Communicator



The Power                                  Subscriber Identification
Ring                                          Module (SIM)

      The Pocket PC   Motorola Envoy             Sharp B. Patel
                                             The Dr. R. Zaurus                                                    18
                                                                       Fujitsu Stylistic   Japan’s PHS       Wearable
                                                                       2300/ 3400          Phone, Year       Computers
Applications for mobile computing

• There are several applications for mobile computing
  including wireless remote access by travelers and
  commuters, point of sale, stock trading, medical
  emergency care, law enforcement, package delivery,
  education, insurance industry, disaster recovery and
  management, trucking industry, intelligence and military.
• Most of these applications can be classified into: (1)
  wireless and mobile access to the Internet, (2) wireless and
  mobile access to private Intranets, and (3) wireless and
  adhocly mobile access between mobile computers.

                          Dr. R. B. Patel                   19
Beneficiaries of ubiquitous computing


            Stock traders
            Law enforcement


                Ad-hoc network
 Servers                                           Clients

                      Dr. R. B. Patel                        20
Limitations of the                 Mobile
–   Limitations of the Wireless Network
–   Heterogeneity of fragmented networks
–   Frequent disconnections
–   Limited communication bandwidth
–   Limitations Imposed by Mobility
–   Limitations of the Mobile Computer

                 Dr. R. B. Patel        21
Frequent Disconnections
– Handoff blank out (>1ms for most cellular
– Drained battery disconnection
– Battery recharge down time
– Voluntary disconnection (turned off to
  preserve battery power, also off overnight)
–    Theft and damage (hostile environment)
–    Roam-off disconnections
                     Dr. R. B. Patel          22
Limited Communication Bandwidth
–       Orders of magnitude slower than fixed
–    Higher transmission bit error rates (BER)
–    Uncontrolled cell population
–    Difficult to ensure Quality of Service (QoS)
–    Asymmetric duplex bandwidth
–             Limited communication bandwidth
  exacerbates the limitation of battery lifetime.
                     Dr. R. B. Patel           23
Limitations of the Mobile Computer

–   Short battery lifetime (max ~ 5 hours)
–    Subject to theft and destruction =>
–   Highly unavailable (normally powered-off to
  conserve battery)
–     Limited capability (display, memory, input
  devices, and disk space)
–       Lack of de- facto general architecture:
  Handheld, communicators, laptops, and other
                   Dr. R. B. Patel           24
Limitations Imposed by Mobility
Lack of mobility- awareness by
–      inherently transparent programming
  model (object-,components- oriented,
  but not aspect- oriented)
–     lack of environment test and set API
                  Dr. R. B. Patel       25
Lack of mobility- awareness by the system

–       network: existing transport protocols are
  inefficient to use across heterogeneous mix
  of fixed/wireless networks
–     session and presentation: inappropriate for
  the wireless environment and for mobility
–        operating systems: lack of environment
  related conditions and signals
–                client/server: unless changed,
  inappropriate and inefficient
                     Dr. R. B. Patel           26
Mobile and Wireless Networking Issues
–   Mobile IP
–   Wireless Transport
–   Ad- Hoc Networks
–   Location Management
–   Wireless Network Benchmarking
–   Ad- Hoc Network Simulation
–   Wireless Link Simulation

                   Dr. R. B. Patel      27
Wireless and Mobile Computing Models
–         Mobility- aware Client/ Server using
–    Disconnected Operations
–    Application- aware Adaptations
–    Mobile Agents and Objects
–    Thin Client/ Server
–    Mobile Caching and Replication
–    Broadcast Disks
–    Service Advertisement and Brokering
–    Smart Pones
                  Dr. R. B. Patel          28
Mobile file and Database Systems
–   Wireless File System Access
–   Disconnected File Systems
–         Mobile Access to C/ S or Distributed
–   Ad- Hoc Database Systems
–   Checkpointing
–   Database recovery
–   Mobile Database Design
                   Dr. R. B. Patel          29
Mobile Transaction and Workflow
–   ACID Relaxation
–   Mobile Transaction Models
–   Optimistic Data Replication
–   Semantic- based Conflict Resolution
–   Consensus in Mobile Environment

                 Dr. R. B. Patel      30
Wireless and Mobile Applications and Services
–    Application Design for Wireless networks
–    Application Design for Mobility
–    Wireless WWW Access
–    Active Badges (Teleporting)
–    Wireless Classroom (Wireless Campus!)
–    Mobile Groupware
–    Location- sensitive Yellow Service
–    Pervasive Computing and Smart spaces
–    •.....

                   Dr. R. B. Patel          31
Performance and QoS
–       QoS Measures in Wireless and Mobile
–    QoS Guarantees
–    Simulators and Emulaors of Wireless Links
–          Simulators of Mobile and Ad- hoc
–    Wireless Networking Benchmarking
                   Dr. R. B. Patel          32
Emerging Standards
–   The 802.11b
–   The BlueTooth Standard
–   The Wireless Application Protocol (WAP)
–   The CompactHTML
–          The Network Computer Reference
–   Telecom Standards: UMTS
–   …              Dr. R. B. Patel          33

             Commuters                    Internet
             Stock traders
             Law enforcement
             Intranet                     Intranet

                 Ad-hoc network
  Servers                                             Clients

                         Dr. R. B. Patel                        34

•   Mobility/context aware applications
•   Naming and locating
•   Routing data and messages
•   Reliability in presence of disconnection
•   Data management
•   Transaction models
•   Security
                      Dr. R. B. Patel          35
• Mobile computing affects entire spectrum of
  issues in computing
• First of all it is distributed + mobile computing
• Distributed computing as we know works on static
  wired network
• Node may initiate computation somewhere and
  migrate to another place.
• So two major problems that arise due to mobility
   – Searching for current location of a mobile node
   – To impose a communication structure among nodes
                       Dr. R. B. Patel                 36
• Physical location of mobile host is not the network
  address, so how do we route the message to a
  mobile host.
• This question is being addressed by two different
  communities- Internet community and cellular
• Work of Internet community involves Mobile IP
   – Aims at standards that can extend IP in order to deal
     with location of mobile host
   – Mobile IP work assumes connectionless packet
     switching scenario
                        Dr. R. B. Patel                 37
• Cellular community’s effort based on location
  management of cellular phone users
• It deals with connection-oriented communication,
  since it is motivated by issues in call-setup in
• Main problem in mobility management is to find
  an appropriate tradeoff between searching and
• Searching is performed when address of the
  message recipient is not known- at least not
  known precisely     Dr. R. B. Patel            38
•   Informing is a responsibility of the mobile
    host when it migrates
•   Extreme situations can be
    1. Mobile host never informs- works for hosts
       receiving few messages and for hosts which
       do not move during receiving
    2. Always informs – works well for hosts
       receiving messages frequently
                     Dr. R. B. Patel           39
•   Ad hoc network routing is the ultimate challenge
•   Ad hoc networks arise in rapid development scenarios
      1.   Emergency disaster management
      2.   Military operation in remote sites
      3.   Business meeting venues without infrastructure support
•   Many routing algorithms are designed: such as fisheye,
    state routing, dynamic source routing, ad hoc on demand
    routing, etc.
•   There are interesting application of conventional graph
    theoretic problems in ad hoc network routing

                             Dr. R. B. Patel                        40

(a) Infrastructure-based wireless network                     (b) Ad hoc network

                                            Dr. R. B. Patel                        41
• Main cause of loss of packets in wired network is
  congestion because error rates are very low
• In wireless network congestion still remains a
  problem, but the situation is somewhat reversed
• Wired and wireless network require different
  techniques to achieve reliability and flow control
• TCP works is unsuitable for wireless network as it
  interprets errors packets loss

                      Dr. R. B. Patel             42
ITCP (split/indirect TCP) splits TCP into two
  – One between sender and local MSS of the
  – The other between local MSS and recipient
  – If MH switches cell during lifetime of a ITCP
    connection center point of connection moves to
    new MSS sender remains completely unaware
    about it
                    Dr. R. B. Patel             43
• Disconnection/weak connection support is
• CODA file system provides support for this
• It is implemented as client side cache management
• The issue concerns making a file system highly
  available while maintaining consistency
• Caching in mobile environment is quite different.
  MSS cannot keep state information (due to scale)
  for all clients. So invalidation by notification
                      Dr. R. B. Patel            44
•    Categories of information dissemination
    1. Wide area services – such as stock quotes on
       national scale
    2. Macro services- such weather on a regional
    3. Micro services- traffic condition is an
       immediate vicinity
•    Can be extend to even picocells – such
     finding a parking slot
                      Dr. R. B. Patel            45
Proving services will require addressing of following
  new issues

   – Interoperability   and      adaptability   to    network
     environments ranging from high to low bandwidths and
     infrared communication links
   – Energy efficient data access
   – Support for mobility and disconnection
   – Support for active services, triggers (even notification),
     and periodic data delivery.

                          Dr. R. B. Patel                    46
•   Two modes of information dissemination are
    1. Publish
    2. Provide on demand
•   Publish data is filtered by client and server provides
    directory information for assisting the filtering
•   Advantages of information dissemination by publishing
    – Hot spots can be broadcast frequently-which saves
        energy at client, avoid congestion
    – Directory helps client to tune in selectively

                         Dr. R. B. Patel                47
• Handoff management – an MH moves from
  one cell to another while being connected
• Desirable features are
  – Probability of call dropping is minimized
  – Ping-pong handoffs avoided
  – Interruption is minimized

                     Dr. R. B. Patel            48
Mobile Computing Models

• The following models of computing in the
  mobile environment are currently being
  researched and investigated:
  –   Client/Server
  –   Client/Proxy/server
  –   Disconnected Operation
  –   Mobile Agents
  –   The Thin Client Model

                      Dr. R. B. Patel   49

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