Transcript Mobile Computing

MOBILE COMPUTING &
MOBILE COMMUNICATION
SYSTEMS
What is Mobile Computing?
 Wireless Communication Systems
 Mobile Communication Systems Architecture
 Key Technologies of Mobile Computing
 Applications
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WHY MOBILE COMPUTING ?
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People are mobile
WHY MOBILE COMPUTING ?
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Devices are mobile
WHAT IS MOBILITY?
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A person who moves
between different geographical locations
 between different networks
 between different communication devices
 between different applications
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WHAT IS MOBILITY?
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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
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BUZZWORDS –
NOMADIC-MOBILE-UBIQUITOUS
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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
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BUZZWORDS –
NOMADIC-MOBILE-UBIQUITOUS
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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
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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
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RELATIONSHIP –
NOMADIC-MOBILE-UBIQUITOUS
My Dream of Future
http://www.youtu.be/ujk1cprLpD8
 Social Web of Things
http://www.youtu.be/i5AuzQXBsG4
 Imagine Everything was Linked
http://youtu.be/igsJxXMssGA
http://www.youtu.be/__pkZ4-kNvY
http://www.youtu.be/tvpRJrQ8Z2c
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HETEROGENEOUS WIRELESS COMMUNICATION
WORLD
DAB: Digital Audio Broadcast
VHE: Virtual Home Environment
DVB-T: Digital Video Broadcast Terrestrial
UMTS: Universal Mobile Telecommunication System
HETEROGENEOUS WIRELESS COMMUNICATION WORLD
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Heterogeneous wireless networks consists of
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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
NATURAL EVOLUTION OF
COMPUTING
More
Flexible
Resource
Usage
Freedom from Collocation
CHALLENGE
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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
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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)
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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
CHALLENGE
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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.
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CHALLENGE
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Harsh communications environment
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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
CHALLENGE
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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
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CHALLENGE
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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
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CHALLENGE
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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
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HETEROGENEOUS WIRELESS COMMUNICATION
WORLD
DAB: Digital Audio Broadcast
VHE: Virtual Home Environment
DVB-T: Digital Video Broadcast Terrestrial
UMTS: Universal Mobile Telecommunication System
CHALLENGE
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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
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