mobile computing mobile communication systems n.
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  2. What is Mobile Computing? • Wireless Communication Systems • Mobile Communication Systems Architecture • Key Technologies of Mobile Computing • Applications

  3. WHY MOBILE COMPUTING ? • People are mobile

  4. WHY MOBILE COMPUTING ? • Devices are mobile

  5. WHAT IS MOBILITY? • A person who moves • between different geographical locations • between different networks • between different communication devices • between different applications

  6. WHAT IS MOBILITY? • Mobile computing is about both physical and logical computing entities that move • Physical entities • computers change locations • Logical entities • a running user application or a mobile agent migrating over internet

  7. BUZZWORDS – NOMADIC-MOBILE-UBIQUITOUS • Nomadic computing • refers to limited migration • migration is within a building at a pedestrian speed • interleaved pattern of user relocation and indoor connections • users carrying laptop with wireless access are engaged in nomadic computing

  8. BUZZWORDS – NOMADIC-MOBILE-UBIQUITOUS • Mobile computing • requires wireless h/w to support outdoor mobility and handoff from one h/w to the next at a pedestrian or vehicular speed • traveler in car using laptop / smart phone / mobile device connected with a GSM/WCDMA/HSPA phone engaged in mobile computing • Ubiquitous computing or pervasive computing • refers to access to computer network all the time at any location by any person • can not be realized unless mobile computing matures


  10. My Dream of Future • Social Web of Things • Imagine Everything was Linked

  11. HETEROGENEOUS WIRELESS COMMUNICATION WORLD DAB: Digital Audio Broadcast VHE: Virtual Home Environment DVB-T: Digital Video Broadcast Terrestrial UMTS: Universal Mobile Telecommunication System

  12. HETEROGENEOUS WIRELESS COMMUNICATION WORLD • Heterogeneous wireless networks consists of • Cellular networks • WLAN networks • other access technologies • Users should be able to access various services from various networks with varying properties in terms of data rates, SNR, latency, coverage, price etc. • Multiple devices or multi-mode devices may be used to access various services which add to the complexity of the system • Mobile communication in such a scenario requires automatic rearrangement of communication and services • These adaptive services need to be centered around the user since multiple networks and operators may be present

  13. NATURAL EVOLUTION OF COMPUTING More Flexible Resource Usage Freedom from Collocation

  14. CHALLENGE • Physical location of mobile is not the network address (address migration) • existing applications send packets to a fixed network address • need to support dynamically changing“local” addresses as mobile device moves through network • how do we route the message to a mobile host

  15. Internet community • Mobile IP deals with location of mobile host • Mobile IP assumes connectionless, packet switching scenario • Mobile IP specification: home environment tracks mobile device’s current location through registration procedure • Cellular community • based on location management of cellular phone users • it deals with connection oriented communication (motivated by issues in call-setup in telephony)

  16. trade-off between searching and informing • informing is a responsibility of the mobile unit when it migrates • extreme situations • mobile unit never informs - works for units receiving few messages and for units which don't move during receiving • mobile unit always informs - works well for units receiving messages frequently

  17. CHALLENGE • Ad hoc routing algorithms • Ad hoc networks arise in rapid deployment scenarios • emergency disaster management • military operation in remote sites • business meeting venues without infrastructure support • Routing algorithms • AODV, DSR, DSDV, TORA, FSR, LAR, ABR, etc.

  18. CHALLENGE • Harsh communications environment • lower bandwidth / higher latency • good enough for video conferencing? • variable bandwidth: applications adaptation to changing quality of connectivity • high bandwidth, low latency • high bandwidth, high latency • low bandwidth, high latency • higher error rates: congestion, interference, etc. • more frequent disconnection • performance depends on density of nearby users but frequency reuse architecture helps • network failure is common

  19. CHALLENGE • Two modes of information dissemination • Publish • data is filtered by client, server provides directory information for assisting the filtering • advantages • hot spots can be broadcast frequently - which saves energy at client, avoid congestion. • Provide on demand

  20. CHALLENGE • Services providing issues • Interoperability and adaptability to h/w environments ranging from high to low bandwidths and wireless communication links • Energy efficient data access • Support for mobility and disconnection

  21. CHALLENGE • Handoff management • a mobile host moves from one cell to another while being connected • undesirable features • call dropping • ping-pong handoffs • vertical handoff among heterogeneous networks

  22. HETEROGENEOUS WIRELESS COMMUNICATION WORLD DAB: Digital Audio Broadcast VHE: Virtual Home Environment DVB-T: Digital Video Broadcast Terrestrial UMTS: Universal Mobile Telecommunication System

  23. CHALLENGE • Security concerns • Authentication is critical • normal network point of attachment is a wall tap • wireless access makes network attachment too easy • Exposure to over-the-air wiretapping • any transmitter can also be a receiver! • some wireless networks provide secure airlinks (e.g., CDPD) • made more difficult by spread spectrum technologies • Mobile agent security