1. CPET 565 Mobile Computing Systems Data Dissemination and Management (1) Lecture 7 Hongli Luo Indiana University-Purdue University Fort Wayne

2. Data Dissemination and Management - Topics Introduction Introduction Challenges Challenges Data Dissemination Data Dissemination Mobile Data Caching Mobile Data Caching Mobile Cache Maintenance Schemes Mobile Cache Maintenance Schemes Mobile Web Caching Mobile Web Caching Summary Summary

3. Data Dissemination and Management – Topics (cont.) Introduction Introduction Pull (On-Demand) ModePull (On-Demand) Mode Push (Publish-Subscribe) ModePush (Publish-Subscribe) Mode Information CachingInformation Caching Challenges Challenges Architecture-basedArchitecture-based Architecture-lessArchitecture-less Data Dissemination Data Dissemination Bandwidth Allocation for PublishingBandwidth Allocation for Publishing Broadcast Disk SchedulingBroadcast Disk Scheduling

4. Data Dissemination and Management – Topics (cont.) Mobile Data Caching Mobile Data Caching Caching in Traditional Distributed SystemsCaching in Traditional Distributed Systems Cache Consistency MaintenanceCache Consistency Maintenance Performance and Architecture IssuesPerformance and Architecture Issues Mobile Cache Maintenance Schemes Mobile Cache Maintenance Schemes A Taxonomy of Cache MaintenanceA Taxonomy of Cache Maintenance Cache Maintenance for Push-based Information DisseminationCache Maintenance for Push-based Information Dissemination Broadcasting Invalidation ReportsBroadcasting Invalidation Reports Disconnected OperationDisconnected Operation Asynchronous Stateful (AS) SchemeAsynchronous Stateful (AS) Scheme To Cache or Not to CacheTo Cache or Not to Cache Mobile Web Caching Mobile Web Caching Handling DisconnectionsHandling Disconnections Achieving Energy and BandwidthAchieving Energy and Bandwidth

5. Data Dissemination and Management - Introduction Mobile Information Content and Applications Mobile Information Content and Applications Email, Messaging, NewsEmail, Messaging, News Public Transportation, Traffic, Flight StatusPublic Transportation, Traffic, Flight Status Business Info, Financial Info, Banking, Stock quotes, SalesBusiness Info, Financial Info, Banking, Stock quotes, Sales Events, ParkingEvents, Parking Tourism, Hotel, Restaurants, WeatherTourism, Hotel, Restaurants, Weather MedicalMedical Consumer Services, Yellow pagesConsumer Services, Yellow pages

6. Data Dissemination and Management – Introduction (cont.) Mobile Information Servers Mobile Information Servers EmailEmail Web PortalWeb Portal Calendar, Tasks, and ContactsCalendar, Tasks, and Contacts etcetc Possible Combinations Possible Combinations HardwareHardware Network Protocols (Wireless Access Protocols, GSM/Circuit, TDMA/CDPD, TDMA/Circuit)Network Protocols (Wireless Access Protocols, GSM/Circuit, TDMA/CDPD, TDMA/Circuit) BrowsersBrowsers GatewaysGateways

7. Data Dissemination and Management - Introduction (cont.) Mobile Application Server Architecture (Data & Information) Mobile Application Server Architecture (Data & Information) 1 st Tier – Thin clients1 st Tier – Thin clients 2 nd Tier – Communications & Business Applications2 nd Tier – Communications & Business Applications 3 rd Tier – Database Systems (ERP, CRM, etc)3 rd Tier – Database Systems (ERP, CRM, etc)Referenceshttp://www.mobileinfo.com/application_servers.htm

8. Data Dissemination and Management - Introduction (cont.) Wireless Communication Problems Wireless Communication Problems Physical MediumPhysical Medium Signal Fading Signal Fading Path Loss Path Loss Interference Interference Time dispersion Time dispersion Lower bandwidthLower bandwidth Higher error ratesHigher error rates Higher communication latencyHigher communication latency

9. Data Dissemination and Management – Introduction (cont.) Mobile Communication Infrastructures Mobile Communication Infrastructures Wi-FiWi-Fi Wi-MaxWi-Max CDMA (Code Division Multiple Access)CDMA (Code Division Multiple Access) GPRS (General Packet Radio Service; for data packet service on GSM network)GPRS (General Packet Radio Service; for data packet service on GSM network) EDGE (Enhanced Data GSM Evolution, up to 384 Kbps)EDGE (Enhanced Data GSM Evolution, up to 384 Kbps) 3G (3 rd Generation Wireless Technology include enhanced multimedia, and upwards of 2 Mbps throughput)3G (3 rd Generation Wireless Technology include enhanced multimedia, and upwards of 2 Mbps throughput) Bluetooth, IrDA, IrFM, OMA (Open Mobile Alliance) Device ManagementBluetooth, IrDA, IrFM, OMA (Open Mobile Alliance) Device Management

10. Data Dissemination and Management - Introduction (cont.) Mobile Application (Data & Information) Mobile Application (Data & Information) Enterprise Resource Planning (ERP)Enterprise Resource Planning (ERP) Customer Resource Management (CRM)Customer Resource Management (CRM) Sales Force AutomationSales Force Automation Financial Accounting SystemFinancial Accounting System Manufacturing SystemsManufacturing Systems Field ServicesField Services

11. Data Dissemination and Management – Introduction (cont.) Examples of Mobile Application Servers Examples of Mobile Application Servers IBM Websphere Application ServerIBM Websphere Application Server Oracle Mobile Application ServerOracle Mobile Application Server Sybase Mobile Application StudioSybase Mobile Application Studio Nokia WAP Application GatewayNokia WAP Application Gateway Microsoft Mobile Information ServerMicrosoft Mobile Information Server http://technet.microsoft.com/en- us/library/bb676815.aspx http://technet.microsoft.com/en- us/library/bb676815.aspx

12. Data Dissemination and Management – Introduction (cont.) Other Related Tasks and/or Modules Other Related Tasks and/or Modules Mobile Data/Information IntegrationMobile Data/Information Integration Global Mobile Information SystemGlobal Mobile Information System Mobile Information Protection & SecurityMobile Information Protection & Security Mobile Information CenterMobile Information Center Unified Data ModelUnified Data Model Middleware for Mobile Information AccessMiddleware for Mobile Information Access

13. Data Dissemination and Management – Introduction (cont.) Mobile Information Delivery Methods Mobile Information Delivery Methods Push (Publish-Subscribe) ModePush (Publish-Subscribe) Mode Information broadcasting when its available Information broadcasting when its available Resource-efficient Resource-efficient Scalable Scalable Pull (On-Demand) ModePull (On-Demand) Mode User send query for particular information to an information source (server or peer) User send query for particular information to an information source (server or peer) Reply Reply Information CachingInformation Caching Document, files Document, files

14. Data Dissemination and Management – Introduction (cont.) Issues of Mobile Information Services Issues of Mobile Information Services Publication Content: Which itemsPublication Content: Which items Publication Frequency: How oftenPublication Frequency: How often Bandwidth Allocation:Bandwidth Allocation: Uplink channels Uplink channels Downlink channels Downlink channels Adaptive to usage pattern in a cell Adaptive to usage pattern in a cell How can mobile users access services transparently?How can mobile users access services transparently? Broadcast channels, directory channel Broadcast channels, directory channel

15. Data Dissemination and Management – Introduction (cont.) How can mobile users access services transparently? How can mobile users access services transparently?

16. Data Dissemination and Management – Introduction (cont.) How can their energy consumption be minimized? (Energy efficient Info services)How can their energy consumption be minimized? (Energy efficient Info services) CPU in “doze mode” CPU in “doze mode” Low-power radio circuit – matching a predefined set of packet address Low-power radio circuit – matching a predefined set of packet address Store data in a low-energy buffer Store data in a low-energy buffer Wake-up the CPU after a certain time interval Wake-up the CPU after a certain time interval Run CPU clock in a low-power mode Run CPU clock in a low-power mode

17. Data Dissemination and Management – Introduction (cont.) Publish-subscribePublish-subscribe Conserves battery power since no uplink query is needed Conserves battery power since no uplink query is needed More scalable – access time independent of the number of mobile hosts requesting the data More scalable – access time independent of the number of mobile hosts requesting the data More useful in asymmetric environments More useful in asymmetric environments

18. Data Dissemination and Management – Introduction (cont.) Information cachingInformation caching Caching to avoid frequent access Caching to avoid frequent access Replenish on an as-needed basis or in a predictive manner Replenish on an as-needed basis or in a predictive manner Hoarding items that are in short supply and become available only occasionally Hoarding items that are in short supply and become available only occasionally How to guarantee the consistency of cached information How to guarantee the consistency of cached information

19. Data Dissemination and Management - Challenges Challenges Challenges Architecture-based Architecture-based Architecture-less Architecture-less Environment Challenges Environment Challenges Intermittent Power Intermittent Power Intermittent Connectivity Intermittent Connectivity Long Travel Times Long Travel Times Variable Population Density Variable Population Density Lack of Secure Storage Lack of Secure Storage User Challenges User Challenges Mobile Workforce Mobile Workforce User Education Levels User Education Levels

20. Data Dissemination and Management - Challenges Architecture-Based Cellular Mobile Networks Architecture-Based Cellular Mobile Networks 1.Weak Connectivity 2.Severe Resource Constraints 3.Asymmetric Communication Links 4.Location and Time (context) Dependent Architecture-less Mobile Ad Hoc Network (MANET) Architecture-less Mobile Ad Hoc Network (MANET) 1.Weak Connectivity 2.Severe Resource Constraints

21. Data Dissemination and Management - Challenges 1. Architecture-Based Cellular Mobile Networks - Weak Connectivity 1. Architecture-Based Cellular Mobile Networks - Weak Connectivity How to ensure high data availability in mobile computing environment where frequent disconnections may occur because the clients and server may be weakly connected? How to ensure high data availability in mobile computing environment where frequent disconnections may occur because the clients and server may be weakly connected?

22. Data Dissemination and Management - Challenges 2. Architecture-Based Cellular Mobile Networks - Severe Resource Constraints 2. Architecture-Based Cellular Mobile Networks - Severe Resource Constraints How to minimize resource consumption (e.g. energy and bandwidth) for data management while ensuring a desired level of data consistency? How to minimize resource consumption (e.g. energy and bandwidth) for data management while ensuring a desired level of data consistency?

23. Data Dissemination and Management - Challenges 3. Architecture-Based Cellular Mobile Networks - Asymmetric Communication Links 3. Architecture-Based Cellular Mobile Networks - Asymmetric Communication Links How can the asymmetric nature of wireless connectivity be exploited to ensure low data access latency and resource consumption? How can the asymmetric nature of wireless connectivity be exploited to ensure low data access latency and resource consumption?

24. Data Dissemination and Management - Challenges 4. Architecture-Based Cellular Mobile Networks - Location and Time (context) Dependent 4. Architecture-Based Cellular Mobile Networks - Location and Time (context) Dependent A mobile user ↔ Query database periodically to retrieve location dependent and time-dependent informationA mobile user ↔ Query database periodically to retrieve location dependent and time-dependent information Traveler ↔ restaurants, hotelsTraveler ↔ restaurants, hotels Salesman ↔ up-to-date product priceSalesman ↔ up-to-date product price Caching and pre-fetching can be an effective technique to reduce the impact of Caching and pre-fetching can be an effective technique to reduce the impact of Low-bandwidthLow-bandwidth Intermittent wireless linksIntermittent wireless links

25. Data Dissemination and Management - Challenges 4. Architecture-Based Cellular Mobile Networks - Location and Time (context) Dependent 4. Architecture-Based Cellular Mobile Networks - Location and Time (context) Dependent The decision to cache or replace a data item also depends on the context (location) of the mobile node in addition to the temporal or spatial localityThe decision to cache or replace a data item also depends on the context (location) of the mobile node in addition to the temporal or spatial locality How do you enhance existing cache management technique for context- dependent data? How do you enhance existing cache management technique for context- dependent data?

26. Data Dissemination and Management - Challenges Architecture-less Mobile Ad Hoc Network (MANET) Architecture-less Mobile Ad Hoc Network (MANET) 1.Weak Connectivity 2.Severe Resource Constraints Data availability and bandwidth/energy efficiency still need to be addressed Data availability and bandwidth/energy efficiency still need to be addressed Can the data management schemes used developed for an Cellular Mobile Networks be used directly to solve problems in a MANET? Can the data management schemes used developed for an Cellular Mobile Networks be used directly to solve problems in a MANET?

27. Data Dissemination and Management - Challenges Gateways of MANET/Cellular Mobile Networks Gateways of MANET/Cellular Mobile Networks Gateways (MANET) – unreliable mobile computing devicesGateways (MANET) – unreliable mobile computing devices Base Stations – reliable dedicated networking devicesBase Stations – reliable dedicated networking devices MANETs Remote Communication LinksMANETs Remote Communication Links Unreliable, Low Bandwidth Links: Radio Frequency Wireless Links Unreliable, Low Bandwidth Links: Radio Frequency Wireless Links High-latency, unreliable Links: Satellite channels High-latency, unreliable Links: Satellite channels Base Stations Remote Communication LinksBase Stations Remote Communication Links High-speed wired networks High-speed wired networks

28. Data Dissemination and Management - Challenges Network Architectures of MANET/Cellular Mobile Networks Network Architectures of MANET/Cellular Mobile Networks Peer-to-peer (P2P) networks – MANETsPeer-to-peer (P2P) networks – MANETs Client-Server – Cellular Mobile NetworksClient-Server – Cellular Mobile Networks Data Management ApproachesData Management Approaches Cooperative Caching Cooperative Caching Caching hierarchy – backbone caches Caching hierarchy – backbone caches Hyper Text Transfer Protocol (HTTP) Hyper Text Transfer Protocol (HTTP) Internet Caching Protocol (ICP) Internet Caching Protocol (ICP)

29. Data Dissemination and Management - Challenges Internet Cache Protocol, RFC 2187 Internet Cache Protocol, RFC 2187 Hypertext Transfer Protocol, http://www.w3.org/Protocols/ Hypertext Transfer Protocol, http://www.w3.org/Protocols/ http://www.w3.org/Protocols/