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Mobile Database Applications

Mobile Database Applications

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Mobile Database Applications

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  1. Mobile Database Applications Abu Asaduzzaman Michelle Romer ThuNguyet Nguyen COT-6930: Mobile ComputingCSE Dept, FAU, Fall 2003

  2. Mobile Database Applications Project Goals • Study Mobile Database Systems • Survey Existing products to build Mobile DB Applications • Develop Mobile Database Applications MCLab, CSE Department, FAU

  3. Mobile Database Applications Outline • Introduction – Abu • Mobile Database Systems – Abu • Database Design – Michelle • Application Design – Michelle • Mobile Database Application Demo – Thu • Future Directions and Conclusion – Thu MCLab, CSE Department, FAU

  4. Mobile Database Systems Introduction (cont’d) • Fully Connected Information Space • Personal Communication Systems • Architecture, Bandwidth, Frequency • Mobile Database Applications • Architecture • Data and Transaction management • Recovery MCLab, CSE Department, FAU

  5. Fully Connected Info Space MCLab, CSE Department, FAU

  6. Fully Connected Info Space Node Properties • Each node of the information space has some communication capability • Some node can process information • Some node can communicate through voice channel • Some node can do both MCLab, CSE Department, FAU

  7. Fully Connected Info Space System Properties • Wired and wireless communication capability • Complete spatial mobility • Full database system capability • Built on PCS/GSM platform • Distributed system with mobile connectivity MCLab, CSE Department, FAU

  8. Fully Connected Info Space Mobile Connectivity A mode in which a client or a server can establish communication with each other whenever needed. Intermittent connectivity: A mode in which only the client can establish communication whenever needed with the server but the server cannot do so. MCLab, CSE Department, FAU

  9. Personal Communication Systems • Architecture • Bandwidth limitations • Frequency reuse • Mobile Cells MCLab, CSE Department, FAU

  10. Personal Communication Systems Architecture A system where wired and wireless networks are integrated for establishing communication PSTN AC HLR AC Access Channel BS Base Station EIR Equipment Identify Register HLR Home Location Register MSC Mobile Switching Center MTSO Mobile Tel Switching Office MU Mobile Unit (MS, MH) PSTN Public Switched Network VLR Visitor Location Register VLR MSC/MTSO MSC/MTSO EIR MU BS MU Wireless components MCLab, CSE Department, FAU

  11. Personal Communication Systems Bandwidth limitations NMT: Nordic Mobile Telephone PDC: Pacific Digital Cellular PACS: Personal Access Communications System PHS: Personal Handyphone System PACS-UB: PACS Unlicensed Band JCT: Japanese Cordless Telephone MCLab, CSE Department, FAU

  12. Personal Communication Systems Frequency reuse The same radio frequency is used for communication by more than one cell sessions. Frequency reuse is achieved from the fact that the entire wireless coverage area is divided into (mobile) cells. MCLab, CSE Department, FAU

  13. Personal Communication Systems D = distance between cells using the same frequency R = cell radius N = reuse pattern (the cluster size, which is 7) Thus, for a 7-cell group with cell radius R = 3 miles, the frequency reuse distance D is 13.74 miles Frequency reuse MCLab, CSE Department, FAU

  14. Personal Communication Systems Mobile cells The entire coverage area is a group of a number of cells. The size of cell depends upon the power of the base stations. MCLab, CSE Department, FAU

  15. Personal Communication Systems Problems with cellular structure • How to maintain continuous communication between two parties in the presence of mobility? Solution: Handoff, Roaming • How to locate of a mobile unit in the entire coverage area? Solution: Location management MCLab, CSE Department, FAU

  16. Personal Communication Systems Handoff and Roaming Handoff is a process, which allows users to remain in touch, even while breaking the connection with one BS and establishing connection with another BS. Roaming is a facility, which allows a subscriber to enjoy uninterrupted communication from anywhere in the entire coverage space. MCLab, CSE Department, FAU

  17. Personal Communication Systems Location Management Two-tier scheme A HLR stores user profile and the geographical location. A VLR stores user profile and the current location (of a user) who is a visitor to a different cell than its home cell. MCLab, CSE Department, FAU

  18. Mobile Database Systems • Architecture • Data Management • Transaction Management • Recovery MCLab, CSE Department, FAU

  19. Mobile Database Systems Architecture (Client-Server Model) BS Base Station BSC Base Station Center DB Database DBS Database System HLR Home Location Register MSC Mobile Switching Center MU Mobile Unit (MS, MH) PSTN Public Switched Network VLR Visitor Location Register MCLab, CSE Department, FAU

  20. Mobile Database Systems Traditional Databases Data transfer Distributed Databases Bandwidth and Power Mobile Databases R2/Q2 Client R1/Q1 Gateway Server MCLab, CSE Department, FAU

  21. Mobile Database Systems Data Management Possible schemes • Semantic data caching: The cache contents is decided by the results of earlier transactions or by semantic data set. • Data broadcast: A set of most frequently accessed data is made available by continuously broadcasting it on some fixed radio frequency on wireless channels. MCLab, CSE Department, FAU

  22. Mobile Database Systems DataManagement Data classification • Location Dependent Data (LDD) • Examples: Hotel rates, etc. • What is the problem here? • Location Independent Data (LID) • Examples: Person name, etc. MCLab, CSE Department, FAU

  23. Mobile Database Systems DataManagement Location Dependent Data (LDD) • LDD must be processed under the location constraints. • Location binding or location mapping can be achieved through database schema or through a location mapping table. MCLab, CSE Department, FAU

  24. Mobile Database Systems Data Management Query types • Location dependent query • What is the distance of Boca Airport from “here”? • Continuous monitoring of the longitude and latitude of the origin of the query. GPS can do this. • Location independent query MCLab, CSE Department, FAU

  25. Mobile Database Systems Transaction Management ACID (Atomicity, Consistency, Isolation, and Durability) too rigid for MDS. A part of the transaction can be executed and committed independent to its other parts. User issues transactions from MU and the final results comes back to the same MU. The user transaction may not be completely executed at the MU so it is fragmented and distributed among database servers for execution. This creates a Distributed mobile execution. (example: Kangaroo Transaction, Clustering) MCLab, CSE Department, FAU

  26. Mobile Database Systems Transaction Management Serialization of concurrent execution - Two-phase locking based (commonly used) is not good for MDS. New schemes based on timeout or multi-version may work. Efficient database update scheme to maintain global consistency. Transaction commit - In MDS a transaction may be fragmented and may run at more than one nodes (MU and DBSs). 2PC or 3PC is no good because of their generous messaging requirement. A scheme which uses very few messages, especially wireless, is desirable. MCLab, CSE Department, FAU

  27. Mobile Database Systems Transaction Management Transaction commit One possible scheme is “timeout” based protocol. MU and DBSs guarantee to complete the execution of their fragments of a mobile transaction within their predefine timeouts. Thus, during processing no communication is required. At the end of timeout, each node commit their fragment independently. MCLab, CSE Department, FAU

  28. Mobile Database Systems Transaction and database recovery Complex for the following reasons • Some of the processing nodes are mobile • Limited wireless channels • Limited power supply • Disconnected processing capability MCLab, CSE Department, FAU

  29. Mobile Database Systems Database recovery Desirable recovery features • Independent recovery capability • Efficient logging and check-pointing facility • Log duplication facility Possible approaches • Partial recovery capability • Use of mobile agent technology MCLab, CSE Department, FAU

  30. Mobile Database Systems Summary • Wireless network is becoming a commonly used communication platform • It provides a cheap/easy way to get connected • In some cases this is the only way to reach people • It has a number of easy and difficult problems MCLab, CSE Department, FAU

  31. Mobile Database Systems Summary The emerging trend is to make all service providing disciplines, such as web, E-commerce, workflow systems, etc., fully mobile so that any service can be provided from any place at any time. MCLab, CSE Department, FAU

  32. Mobile Database Systems Summary Customer can surf the information space from any location at any time and do their shopping, make flight reservations, do bank transactions, attend lectures, and so on. This is what the mobile database technology driving us to. MCLab, CSE Department, FAU

  33. Mobile Database Applications Fields of usages • Medical Fields (Doctors, Nurses) • Financial Services • Retail and Customer Services • Educational Institutions MCLab, CSE Department, FAU

  34. Mobile Database Applications Application - Capabilities • Can physically move around without affecting data availability • Can reach to the place data is stored • Can process special types of data efficiently • Not subjected to connection restrictions • Very high reachability • Highly portable MCLab, CSE Department, FAU

  35. Mobile Database Applications Application – Limitations • Limited wireless bandwidth • Wireless communication speed • Limited energy source (battery power) • Less secured • Vulnerable to physical activities • Hard to make theft proof MCLab, CSE Department, FAU

  36. Mobile Database Applications Available products • Sybase SQL Anywhere • Oracle 9i Lite • MS SQL Server 2000, Windows CE • IBM's DB2 Everyplace 7 • Pocket PC, Palm OS, etc. MCLab, CSE Department, FAU

  37. Mobile App. Environment Wireless Network PDA • Check Availability • Check-Out Book CellPhone PocketPC Palm OS Laptop Access Point • Base Station Wired Infrastructure Network Desktop • Clerk Local Database Server • Synchronization Central Database Server • Synchronization MCLab, CSE Department, FAU

  38. Mobile Database Environment MCLab, CSE Department, FAU

  39. Mobile Database Applications Wireless Access Point • Bluetooth or 802.11 • Contact point for wireless Network • Wide range (100-300 feet) • Portable • Connect up to 7 mobile devices at a time MCLab, CSE Department, FAU

  40. PDA Pocket PC, Palm OS • Light • Inexpensive • Small • Convenient • Small amount of memory • Small Database MCLab, CSE Department, FAU

  41. PDA (Cont’d) • Color screen is 160x160 - 320x320 pixels • Text input is done using stylus or keyboard • Power Consumption • PDAs are battery powered • Current PDAs are based on ARM or OMAP • Device circuitry designed specifically to save power MCLab, CSE Department, FAU

  42. PDA (Cont’d) Three modes of operation to minimize power usage • Running Mode • Doze/Idle Mode • Sleep Mode MCLab, CSE Department, FAU

  43. PDA (Cont’d) Memory • Some devices allow user to expand the amount of memory • Amount of RAM is 32MB-64MB or more • Memory Split into two heaps • Dynamic Heap • Used by Operating System • Storage Heap • Data organization and storage MCLab, CSE Department, FAU

  44. PDA (Cont’d) • Can be written in different languages • Pocket PC has the Window File system • A palm application is a Database • Two types of database • Resource • Record • Neither can be larger than 64K in size MCLab, CSE Department, FAU

  45. Project Overview • Students use Palm for wireless access to Library information anywhere, anytime • Palm connects through access point set-up in Mobile Computing Lab to Local Database Server • Local Database Server connected to Central Relational Database through the network MCLab, CSE Department, FAU

  46. Project Challenges • Write Program for Palm OS Platform • Set Up Wireless Access Point • Wireless Connection to Local Area Network • Select/Update Information from Relational Database • Data Synchronization Between Palm Database and Library Database MCLab, CSE Department, FAU

  47. Data Flow Start • PDA • Server Update Relational Database Connect Send Library DB Request Send Updated Database Disconnect Check Book Availability Check-Out/ Hold Book Connect MCLab, CSE Department, FAU

  48. Relational Database Books p*ISBN Vchar(15) u*Title Vchar(100) *Authors Vchar(100) *Publishers Vchar(100) u*Call_Num Vchar(25) *Category_ID Num(2) *Location_ID Num(1) *Status_ID Num(1) Loaner_ID Vchar(11) Loan_Exp_TS Date Num_Renew Num(1) Holder_ID Vchar(11) Hold_Exp_TS Date . Categories p*Category_ID Num(2) *Description Vchar(55) Statuses p*Status_ID Num(1) *Description Vchar(55) Loaners p*Loaner_ID Vchar(11) First_Name Vchar(55) *Last_Name Vchar(55) *St_Address Vchar(25) . MCLab, CSE Department, FAU

  49. Palm Database • Special format of data that Palm OS understands • Not a traditional database • Provides faster response time, low energy consumption • Avoid overwhelming central database on the server MCLab, CSE Department, FAU

  50. Project Assumptions • Library is equipped with the hardware to support wireless access to the network and the mobile DB applications. • Students have access privilege to the library DB (scan his/her ID card) • Students can self-check (check in/out) books MCLab, CSE Department, FAU