Mobile DatabaseMobile DatabasePrepared byPrepared by Ali M. AlrazgiAli M. Alrazgi
SupervisorSupervisor
Dr. Hassan NajadatDr. Hassan Najadat
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Wireless Characteristics
Mobile Computing Architecture
Mobile Problems .
Characteristics of Mobile Environments
Data Management Issues
Wireless CharacteristicsWireless Characteristics
Data Rates. Range. Interference. Support for packet switching . locality of access Seamless roaming (Phone ). Wi-Fi , Bluetooth :use unlicensed frequency .
Interference
Mobile Computing ArchitectureMobile Computing Architecture
Infrastructure-based mobile platform
A general architecture of an infrastructure-based mobile platform
high-speed wired network
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.
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Mobile Computing Architecture: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 ArchitectureMobile Computing Architecture::
Mobile ProblemsMobile Problems
Software problems
Data managementQuery & Transaction processingSecurityTransaction management Database recovery
Hardware problems are more difficult.Limited & intermittent of Connectivity .Battery Life .Changes in network topology.Wireless Transmission Speed.
Characteristics of Mobile EnvironmentsCharacteristics 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 EnvironmentsCharacteristics of Mobile Environments
contcont
To compensate for high latencies and unreliable connectivity
Caching frequently used data on the mobile device.Increasing data availability and response timeOrganize data by using the Cluster
A client may be unreachable because handoffProxies for unreachable (proxy can cache updates
intended for the server
Proxy automatically forwards these cached updates to their ultimate destination
Data ManagementData 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 processingTransaction & Query processing
Query processingQuery processing
Pull/push mechanism
Pull-operationPush-operation
(Broadcast Strategy)
On-DemandBroadcast
Periodic Broadcast
Query processing: Awareness of where the data is located is important and affects the cost/benefit analysis of query processing
Transaction & Query processingTransaction & 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 communicationLimitation of Resource preservation is of the utmost importance
Query
Query
Result
Result
Transaction & Query processingTransaction & 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 broadcastPush operation (on-demand broadcast)M
ob
ile C
lien
t Qu
ery
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 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.
ABC
AABC
CBA
CAA
periodic broadcast
Transaction & Query processingTransaction & Query processing
Push operation (periodic broadcast): Refers to periodically broadcast databaseOne 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 modelsTransaction 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 designMobile 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 designMobile database design..Synchronization and Conflict ResolutionEasy Synchronization Deploy Conflict Resolution Techniques
Mobile Database
ResponsivenessIdentify Relevant DataData SummarizationData CompressionData CachingIndexingRestricted Connection High Availability
Automatic BackupsAutomatic Recovery Data Replication
Security User AuthenticationData EncryptionRestrict Access Through Roles
Data Consistency And ConcurrencyManage Online TransactionManage Offline TransactionManage Unplanned Disconnection
Addition FactorsData SizeScreen SizeSlow Transmission SpeedSlow Processing SpeedCost
Database RecoveryDatabase 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
ReferencesReferences
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 Thank you for your attention
Questions ?Questions ?