by : Shilpa Chaturvedi 07 Supriya Ghatkar 12 Nikhila Rane 22 Kshitija Raut 23 Rupali Maeen 39 Kanchana Nayakkar 41 Lekha Pedamkar 50

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.

Information can be synchronized with a server database at a later time.

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 Vehicle Location systems).

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 through modes

replicate data on centralized database server and mobile device;

synchronize data on centralized database server and mobile device;

capture data from various sources such as Internet;

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 stations)

Mobile host may be able to communicate with wired network through a wireless digital communication network

Network Infrastructure for mobile computing consists of two technologies :

1. Wireless local-area networks (within a building)E.g. Avaya’s Orinico Wireless LAN

• packet-based cellular telephony networks• early cellular system-Analog Technology• 2G – voice application• 3G and 2.5 G –Packet Based network

FIXED NETWORK

PDA

FIXEDHOSTBASE

STATION

BASESTATION

BASESTATION

Mbps to Gbps

MOBILE HOST

WIRELESS LAN CELL2Kbps - 15Mbps

WIRELESS RADIO CELL9Kbps - 14Kbps

BASESTATION

PDA

A model for mobile communicationMobile 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 another.

Direct communication, without going through a mobile support station is also possible between nearby mobile hostsSupported, 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 transmitted• Energy (battery power) is a scarce resource and its usage must be minimized

Mobile user’s locations may be a parameter of the query•GIS (Geographic Information Systems )queries• Techniques to track locations of large numbers of mobile hosts

Broadcast data can enable any number of clients to receive the same data at no extra cost leads to interesting querying and data caching issues. Users may need to be able to perform database updates even while the mobile computer is disconnected.

• e.g., mobile salesman records sale of products on (local copy of) database.• Can result in conflicts detected on reconnection, which may need to be resolved manually.

Must consider these competing costs:

User time

Communication cost• Connection time - used to assign monetary charges in some cellular systems.•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-peak periods

Energy - optimize use of battery power by minimizing reception and transmission of data. Receiving radio signals requires much less energy than transmitting radio signals.

Mobile support stations can broadcast frequently-requested data

Allows mobile hosts to wait for needed data, rather than having to consume energy

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 schedule or a changeable schedule:

FIXED SCHEDULE: The mobile host uses the known fixed schedule to determine when the relevant data will be transmitted. CHANGEABLE SCHEDULE: The broadcast schedule must itself be broadcast at a well-known radio frequency and at well-known time intervals.

The need for Data Broadcast:

Data should be organized and presented to the users based on its need.

Data Broadcast can be used to manage sending (pushing) the same data interest to the listening clients .

Problems created if the user of the mobile host issues queries and updates on data that resides or is cached locally: This situation creates several problems, in particular:

•RECOVERABILITY: Updates entered on a disconnected machine may be lost if the mobile host fails.

•CONSISTENCY : Cached data may become out of date, but the mobile host cannot discover this until it is reconnected.

Partitioning via disconnection is the normal mode of operation in mobile computing.

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 conflict.

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.

VERSION-NUMBERING-based schemes guarantee only that if two hosts independently update the same version of a document, the clash will be detected eventually, when the hosts exchange information either directly or through a common host.

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