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Mobile Database ,alrazgi

Mobile Database ,alrazgi







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    Mobile Database ,alrazgi Mobile Database ,alrazgi Presentation Transcript

    • Mobile Database
      • Prepared by
      • Ali M. Alrazgi
      • Supervisor
      • Dr. Hassan Najadat
      • Wireless Characteristics
      • Mobile Computing Architecture
      • Mobile Problems .
      • Characteristics of Mobile Environments
      • Data Management Issues
    • Wireless Characteristics
      • Data Rates.
      • Range.
      • Interference.
      • Support for packet switching .
      • locality of access
      • Seamless roaming (Phone ).
      • Wi-Fi , Bluetooth :use unlicensed frequency .
              • Interference
      • Goal : Access Information Anywhere, Anytime, and in Any Way.
      • Aliases: Mobile, Nomadic, Wireless, Pervasive, Invisible
      • Distinction:
            • Fixed wired network: Traditional distributed computing.
            • Fixed wireless network: Wireless computing.
            • Wireless network: Mobile Computing.
      • Applications:
            • Vertical : tracking , point of sales
            • Horizontal : mail application , filter information provision
            • new massive markets in conjunction with the Web
            • Mobile Information Appliances - combining personal computing and consumer electronics
      Mobile and Wireless Computing & applications
    • Mobile Computing Architecture Infrastructure-based mobile platform A general architecture of an infrastructure-based mobile platform high-speed wired network Base Station Base Station Base Station Wireless LAN Cell 2kbps - 15 mbps Wireless Radio Cell 9kbps-14 kbps Wireless Ethernet Cell Mbps - Gbps
      • Mobile Ad-Hoc Network (MANET):
        • In a MANET , mobile units do not need to communicate via a fixed network such as Bluetooth.
        • In a MANET , mobile units are responsible for routing their own data
        • MANET must be robust enough to handle changes in network topology.
          • Such as arrival or departure of mobile unites.
      • Sample applications for MANET application
            • Multi-user games
            • Battle information sharing
            • shared whiteboards,
            • distributed calendars,
      • Characteristics of (MANET):
        • Frequent disconnections.
        • Frequent network partitions.
        • Centralized control is difficult .
        • Peer Heterogeneity.
      Mobile Computing Architecture: Infrastructure-less Mobile Platform (MANET )
      • MANET can fall under Peer-to-Peer architecture .
      • Peer-to-Peer : means that mobile units is simultaneously a client and server .
      • Kinds of Peer-to –Peer :
            • Hybrid P2P Network : Central server can provide the information to all peers (Napster)
            • Fully p2p network : No central servers
      • First generation : routing and querying through broadcasting ,
      • Causing flooding in the network .
      • Second generation : routing and querying are based on distributed hash tables
      Mobile Computing Architecture:
    • Mobile Problems
      • Software problems
        • Data management
        • Query & Transaction processing
        • Security
        • Transaction management
        • Database recovery
      • Hardware problems are more difficult.
        • Limited & intermittent of Connectivity .
        • Battery Life .
        • Changes in network topology.
        • Wireless Transmission Speed.
    • Characteristics of Mobile Environments
      • High communication latency
        • Latency :
            • Increases the time to service each client request
            • The server can handle fewer clients.
      • broadcasting data whenever possible
      • Intermittent wireless connectivity
            • unIntentional :signals cannot reach,
            • intentional :takeoff of an airplane prerogatives
      • limited battery life
      • Changing client location
    • Characteristics of Mobile Environments cont
      • To compensate for high latencies and unreliable connectivity
            • Caching frequently used data on the mobile device.
            • Increasing data availability and response time
            • Organize data by using the Cluster
        • A client may be unreachable because handoff
              • Proxies for unreachable (proxy can cache updates intended for the server
      • Proxy automatically forwards these cached updates to their ultimate destination
    • Data Management
      • MDB can be distributed under two possible scenarios:
          • The entire database is distributed mainly among the wired components
              • A base station or fixed host manages its own database
              • query and transaction management of mobile environments.
          • The database is distributed among wired and wireless components
              • Data management responsibility is shared among BS or FH and mobile units.
      • Additional considerations and variations:
              • Query processing.
              • Data distribution and replication.
              • Transaction models.
              • Recovery and backup.
              • Mobile database design.
              • Location based service.
              • Division of labor.
              • Security
    • Transaction & Query processing Query processing Pull/push mechanism Pull-operation Push-operation (Broadcast Strategy) On-Demand Broadcast Periodic Broadcast
      • Query processing: Awareness of where the data is located is important and affects the cost/benefit analysis of query processing
    • Transaction & Query processing
      • Pull: PDAs demand , servers respond
      • Pull operation: mobile clients establish
      • a connection with the server via a dedicated link or channel.
      • poor match for asymmetric communication
      • Limitation of Resource preservation is of the utmost importance
      Query Query Result Result
    • Transaction & Query processing
      • Push operation (on-demand broadcast)
            • send queries through dedicated channel, monitors to retrieve result.
      • very large number of request initiated by clients
      • The queries are processed in a group
      • Broadcast is the increase of bandwidth when the client sends the request to the server.
      • The congested channel which that affect on query
      • performance and power consumption of mobile clients.
    • Push operation (on-demand broadcast ) Mobile Client Query Broadcast Channel Query Query Query Result Result Result
            • Send queries through dedicated channel, monitors to retrieve result.
      • very large number of request initiated by clients
    • Broadcast Approach
      • Broadcasting: It is the process in which one node sends a packet to all other nodes in the network .
      • Broadcast Approach :
        • Flat : broadcast the union of the requested data cyclic
        • Skewed : broadcast different items with different frequencies
      • Broadcast : well reduces the load on the server, as clients do not have to maintain active connections to it.
      C B A C A A C B A C B A A
    • Transaction & Query processing periodic broadcast
      • Push operation (periodic broadcast): Refers to periodically broadcast database
      • One or more broadcast channels, a mobile client capture and select data items which it interested in.
      • Access to data is sequential.
    • Push operation (periodic broadcast) cont
      • Main challenge :
        • minimize query response time (reduce the length of broadcast cycles.)
          • Selection of Data Items to be Broadcast
          • Distribution of Data Items over Multiple Channels (split data)
          • Organization of Data items
    • Transaction models
        • Transaction models: A mobile transaction is executed sequentially through several BS and possibly on multiple data sets depending upon the movement of the MU.
      • a mobile transaction is expected to be long-lived because of disconnection in mobile units
            • properties of transactions (ACID) :
              • Atomicity
              • Consistency Preservation
              • Isolation
              • Durability
    • Mobile database design
      • Mobile database design
            • Only the most frequently used data should be stored
            • Minimal the transferred between MU and central-DB
      • Division of labor: In some cases, the client must function independent of the server.
    • Mobile database design.
      • Synchronization and
      • Conflict Resolution
      • Easy Synchronization
      • Deploy Conflict Resolution
      • Techniques
      Mobile Database
      • Responsiveness
      • Identify Relevant Data
      • Data Summarization
      • Data Compression
      • Data Caching
      • Indexing
      • Restricted Connection
      • High Availability
      • Automatic Backups
      • Automatic Recovery
      • Data Replication
      • Security
      • User Authentication
      • Data Encryption
      • Restrict Access Through
      • Roles
      • Data Consistency
      • And Concurrency
      • Manage Online Transaction
      • Manage Offline Transaction
      • Manage Unplanned
      • Disconnection
      • Addition Factors
      • Data Size
      • Screen Size
      • Slow Transmission Speed
      • Slow Processing Speed
      • Cost
    • Database Recovery
      • Mobile Database System Recovery Process : is a mechanism to restore an intermediate consistent state of the system
      • Factors that affect the recovery process:
        • Failure rate of the host
        • Communication / Mobility Ratio
        • Message Size
        • Memory constraints
        • Recovery time
      • Recovery Problem Specifications:
        • Location is not fixed
        • Disconnection
        • Batteries have limited power
        • Different types of failures
              • Hard failure ( broken or is lost or stolen .)
              • soft failure ( memory contents are lost, OS crashes )
        • Random Handoff
        • Weak wireless link
    • References
      • Elmasri/Navathe ‘Mobile Database’ Ch 30
      • Agustinus Borgy Waluyo , Bala Srinivasana and David Taniar ‘Research in mobile database query optimization and processing’
      • Ruchika Dua and Saurabh Bhandari ‘Recovery in Mobile Database System’
      • Weider D . Yu, Tamseela Amjad, Himani Goel, Tanakom Talawat ‘An Approach of Mobile Database Design Methodology for Mobile Software Solutions’
    • Thank you for your attention
    • Questions ?