MOBILE DATABASE : Database than can be connected to by a
mobile computing device over a mobile network.
CACHE : Hold frequent data and transactions
DATABASE : Structured way to organize information
The use of laptops, mobiles and PDAs is increasing and likely
to increase in the future with more and more applications
residing in the mobile systems.
example : MOBILE WORKFORCE.
In this scenario user would require to access and
update information from files in the home directories on a
server or customer records from a database. With the advent
of mobile databases users can load up their smart phones or
PDAs with mobile databases to exchange data remotely
without worrying about time or distance.
Mobile databases let employees enter data on the fly.
Mobile users must be able to work without a wireless
connection due to poor or even non-existent connections.
Applications must provide significant interactivity .
Applications must be able to access local device/vehicle
hardware, such as
printers, bar code scanners, or GPS units (for mapping or Automatic
Bandwidth must be conserved (a common requirement on
wireless networks that charge per megabyte or data transferred).
Users don't require access to truly live data, only
recently modified data.
Functionality required oF mobile dbmS includeS ability to:
communicate with centralized database server
replicate data on centralized database server and
synchronize data on centralized database server and
capture data from various sources such as
manage/analyze data on the mobile device;
create customized mobile applications.
A mobile computing environment consists of :
• mobile computers (mobile hosts)
• a wired network of computers(mobile support
Mobile host may be able to communicate with wired
a wireless digital communication network
Network Infrastructure for mobile computing consists of two
• Wireless local-area networks (within a building)
E.g. Avaya’s Orinico Wireless LAN
2. packet-based cellular telephony networks
early cellular system-Analog Technology
2G – voice application
3G and 2.5 G –Packet Based network
M O B IL E H O S T
W IR E L E S S L A N C E L L
2Kbps - 15M bps
S T A T IO N
F IX E D
W IR E L E S S R A D IO C E L L S T A T IO N
9Kbps - 14Kbps
F IX E D N E T W O R K
S T A T IO N
M b p s to G b p s
S T A T IO N
A model for mobile communication
Mobile hosts communicate to the wired network via
computers referred to as mobile support (or base) stations.
Each mobile support station manages those mobile
hosts within its cell.
When mobile hosts move between cells, there is a
handoff of control from one mobile support station to
Direct communication, without going through
a mobile support station is also possible between
nearby mobile hosts
Supported, for e.g., by the Bluetooth standard
(up to 10 meters, at up to 721 kbps)
New issues for query optimization.
• Connection time charges and number of bytes
• Energy (battery power) is a scarce resource and its
usage must be
Mobile user’s locations may be a parameter of the
•GIS (Geographic Information Systems )queries
• Techniques to track locations of large numbers of
Broadcast data can enable any number of clients to
receive the same data at
no extra cost leads to interesting querying and data
Users may need to be able to perform database
updates even while the
Must consider these competing costs:
• Connection time - used to assign monetary charges in
•Number of bytes, or packets, transferred - used to compute
charges in digital cellular systems
•Time-of-day based charges - vary based on peak or off-
Energy - optimize use of battery power by minimizing
reception and transmission of data.
Receiving radio signals requires much less energy
• Mobile support stations can broadcast frequently-
• Allows mobile hosts to wait for needed data, rather
than having to
There are two reasons for using broadcast data.
= the mobile host avoids the energy cost for
transmitting data requests
= the broadcast data can be received by a
large number of mobile hosts at once,
at no extra cost
The mobile host can cache the broadcast data
For later use.
Broadcast data may be transmitted according to a ﬁxed
or a changeable schedule:
FIXED SCHEDULE: The mobile host uses the known
schedule to determine when the relevant data
CHANGEABLE SCHEDULE: The broadcast schedule
be broadcast at a well-known radio frequency
well-known time intervals.
The need for Data Broadcast:
Data should be organized and presented to the users
based on its need.
Problems created if the user of the mobile
queries and updates on data that resides
or is cached
This situation creates several problems, in
•RECOVERABILITY: Updates entered on a
disconnected machine may be
lost if the
mobile host fails.
•CONSISTENCY : Cached data may become
out of date,
Partitioning via disconnection is the normal mode of operation
For data updated by only one mobile host, it is simple to
propagate update when
mobile host reconnects n other cases data may become
invalid and updates may
When data are updated by other computers, invalidation
reports inform a
reconnected mobile host of out-of-date cache entries
however, mobile host may miss a report.
guarantee only that if two hosts
independently update the same version of a
document, the clash will be detected
eventually, when the hosts exchange
• BUSINESS TRAVELERS : use laptop computers so that
they can work and access data en route
• DELIVERY SERVICES : uses it for packet tracking
• EMERGENCY RESPONSE : uses it at the scene of
disasters ,medical emergencies ,and the like to access
information and to enter data pertaining to the situation
• CELL PHONES : provide not only phone
services but are also mobile computers
allowing email and web access