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 ?