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IT 644: Mobile Computing

IT 644: Mobile Computing. Instructor: Sridhar Iyer http://www.it.iitb.ernet.in/~sri Course Page http://quark.it.iitb.ernet.in/~it644 Lecture Hours Tue: 9:30, Thu: 10:30, Fri: 8:30. Course Outline. Wireless Networks Cellular networks Wireless LANs Ad hoc networks Satellite systems, …

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IT 644: Mobile Computing

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  1. IT 644: Mobile Computing Instructor: Sridhar Iyer http://www.it.iitb.ernet.in/~sri Course Page http://quark.it.iitb.ernet.in/~it644 Lecture Hours Tue: 9:30, Thu: 10:30, Fri: 8:30

  2. Course Outline • Wireless Networks • Cellular networks • Wireless LANs • Ad hoc networks • Satellite systems, … • Mobile Applications • Client-Server adaptations • Disconnected operations • Mobile agents • Data broadcasting • Wireless application protocol • Other Issues • Security • Energy efficiency • Impact of mobility on algorithms

  3. Wireless Networks • Need: Access computing and communication services, on the move • Infrastructure-based Networks • traditional cellular systems (base station infrastructure) • Wireless LANs • Infrared (IrDA) or radio links (Wavelan) • very flexible within the reception area; ad-hoc networks possible • low bandwidth compared to wired networks (1-10 Mbit/s) • Ad hoc Networks • useful when infrastructure not available, impractical, or expensive • military applications, rescue, home networking

  4. Limitations of Mobile Environments • Limitations of the Wireless Network • heterogeneity of fragmented networks • frequent disconnections • limited communication bandwidth • Limitations Imposed by Mobility • lack of mobility awareness by system/applications • route breakages • Limitations of the Mobile Computer • short battery lifetime • limited capacities

  5. Effect of Mobility on Protocol Stack • Application • new applications and adaptations • Transport • congestion and flow control • Network • addressing and routing • Link • media access and handoff • Physical • transmission errors and interference

  6. Mobile Applications • Vehicles • transmission of news, road condition etc • ad-hoc network with near vehicles to prevent accidents • Emergencies • early transmission of patient data to the hospital • ad-hoc network in case of earthquakes, cyclones • military ... • Traveling salesmen • direct access to central customer files • consistent databases for all agents • mobile office

  7. Mobile Applications • Web access • outdoor Internet access • intelligent travel guide with up-to-datelocation dependent information • Location aware services • find services in the local environment, e.g. printer • Information services • push: e.g., stock quotes • pull: e.g., nearest cash ATM • Disconnected operations • mobile agents, e.g., shopping • Entertainment • ad-hoc networks for multi user games

  8. Application Adaptations for Mobility • System-transparent, application-transparent • the conventional, “unaware” client/server model • System-aware, application-transparent • the client/proxy/server model • the disconnected operation model • System-transparent, application-aware • dynamic client/server model • data broadcasting/caching • System-aware, application-aware • the mobile agent model

  9. World Wide Web and Mobility • HTTP/ HTML have not been designed for mobile applications/devices • HTTP Characteristics • stateless, connection oriented overheads • big protocol headers, uncompressed content transfer • HTML Characteristics • designed for computers with “high” performance, color high-resolution display, mouse, hard disk • typically, web pages optimized for design, not for communication; ignore end-system characteristics • Adaptations for Mobile WWW • Enhanced browsers and/or servers • Client proxy: pre-fetching, caching, off-line use • Network proxy: adaptive content transformation for connections • Client and network proxy • New protocols/languages: WAP/WML

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