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Mobile Computing
Apr 10, 2023 1
History of mHistory of mobile obile computing?computing?
Apr 10, 2023 2
By 2012 the number of mobile subscribers throughout the world will reach 5 Billion, of which close to 1.5 Billion will use wireless communicators (3G) as gateways to the Internet
Apr 10, 2023 3
World wide Internet penetration rate increases rapidly.
25% of the world population access to the Internetby 2012, >1 billion of Internet users will use mobile as their only access means
What is mobile What is mobile computing?computing?
Today, access to information and computing services is necessary everywhere◦ not only from our "home base," but also while we
are traveling and when we reach a different location.
Mobile computing ◦ Techniques that allow mobile users to use portable
computing devices to run stand-alone applications and / or to access remote ones via wireless networks.
Apr 10, 2023 4
Mobile computing = mobile + computing, another wave in computing evolution.
◦ Different kinds of mobility Terminal mobility: movement of processors / devices -
caused by mobile devices. User mobility: movement of users – caused by traveling
people. Logical mobility: movement of processes - caused by
mobile codes.◦ Different modes of computing
Small office: take the service/application with users - computing is offline
Home office: maintain the access to the same service/application at different places – computing is online
Mobile office: move to different places and the service/application follows – computing is moving (follow-me)
Apr 10, 2023 5
Evolution of computing Evolution of computing paradigmparadigm
Apr 10, 2023 6
2010Unwired
Enterprise
1980
Branch
Age of DistributedComputing
Client/Server
1990
Office
Age of Personal
Computing
Personal Computer
2000
Remote Office
Age of NetworkedComputing
Internet
2003
Mobile Workplace
Age ofMobile
Computing
Mobile Internet
1960
Fixed Location
Age of Centralized Computing
Mainframe
Synonym of mobile Synonym of mobile computingcomputingMobile computing often uses wireless
and mobile networks as access technologies.
◦Wireless and mobile networks extend networking capacity to cover the areas of lack of wired link and support movement of devices
Wireless communication plays an important role in mobile computing. But, mobile computing does not necessarily mean wireless.
Apr 10, 2023 7
Today’s applications Today’s applications Internet, Wireless Networks & Mobile Computing
◦ Mobile users use wireless communications to access to the Web information and services
WAP GatewayMerchant 1
WAP / Agent Server
Merchant n
Internet
ProviderNetwork
WAP Terminal
SQL
SQL
SQL
- WML pages- list of merchants
Products
Products
Corporations◦ M-business / M-office (working remotely - job dispatch, calendar,
email, workflow, etc)◦ M-commerce (logistics, inventory control)
Consumers◦ M-commerce (shopping, banking, payment, etc)◦ Mobile web access / mobile email / SMS◦ Mobile P2P (file sharing, gaming, etc.)
Government / Public services / Militaries◦ M-healthcare (emergency with in-time patient condition info.)◦ Transportation◦ Tourism (navigation with maps, location-aware travel hints, etc)◦ Intelligent home◦ Environment monitoring◦ Battle field communications
Apr 10, 2023 9
Enabling factorsEnabling factorsMotivations and driving forces
◦Increasing demands on access to information, communication, and cooperation anywhere, anytime, anyway.
◦Technology reality may support such demands Increasing availability of wireless networks at
reduced cost. Widespread use of handheld devices with increasing
computing power and lower cost. Integration of communication and computing
devices (PDA, i-Phone, smart phone, intelligent sensor).
Advances in techniques of detecting location of a device – location based services.
Apr 10, 2023 10
Device VisionDevice VisionMobile phones
◦ 1973: First cellphone call
◦ 2007: ~ 3.3 billion mobile phone subscribers
◦ 2009: ~ 4.6 billion
Smart phones ◦ are mobile phones◦ have operation systems◦ can connect to the internet: web browsing, email, etc◦ have advanced computing ability: send and receive
text & multimedia messages (SMS, MMS), take pictures, etc
Mobile computing means Mobile computing means more…more…
Mobile computing is also closely related to Internet computing technologies◦ Mobile computing uses Internet computing
technologies The layered protocol stack and client/server
paradigm◦ Mobile computing allows the application not to
connect the network all the time Mobile Internet, Wireless Internet
HTTP client / server protocols => WAP
XML, HTML => WML, XHTML
J2SE/J2EE, .Net => J2ME/J2EE, .Net MobileApr 10, 2023 12
Forthcoming applicationsForthcoming applicationsExample: Vehicle Networks
transmission of news, road condition, traffic information, weather, music via DABpersonal communication using mobile phone networkspositioning via GPSlocal ad-hoc network with vehicles close-by to prevent accidents, report traffic jams, guidance system, etcvehicle data (e.g., from busses, high-speed trains) can be transmitted in advance for maintenance busses, trucks, and trains can transmit logistic information for, e.g., fleet management.
ad ho
cUMTS, WLAN,GSM, cdma2000, DAB, ...
Personal Travel Assistant,DAB, PDA, laptop, GSM, UMTS, WLAN, Bluetooth, ...
What’s the future What’s the future picture?picture?
Apr 10, 2023 14
Wireless: ConvergenceWireless: Convergence
Apr 10, 2023 15
Challenges of mobile Challenges of mobile computingcomputingWhere do the challenges come from?
◦Distinct characteristics of mobile and wireless computing: Wireless communications
Mobility
Portability
Apr 10, 2023 16
ChallengesChallengesWired channel
◦ Wired channel can be easily engineered Too many noises? – use shell to protect against
electromagnetic noise Large signal attenuation? - use repeaters to amplify the
signal Data rate too low? - upgrade to coaxial cable or optical
fiber Low error rate - Good quality: 10-6; Optical fiber: 10-11 ~
10-12
Wireless channel◦ Wireless channel is hardly be engineered
High background noises Signal strength fluctuates significantly Low data rate High error rate – Radio: 10-2 or worse
Apr 10, 2023 17
ChallengesChallengesWired channel – what if more than one
transmitter?
Apr 10, 2023 18
Switching Center
or
Network Access Point
Every user accesses the network by means of a dedicated channelNew user is served by a new wired-line circuit
Access capacity is guaranteed.
Dedicated Channel
ChallengesChallengesWireless channel – what happens?
Apr 10, 2023 19
Base Station
Shared Channel
Wireless users access the network by means of a shared channel
Access capacity is inherently limited.
MobilityMobilityDifferent modes of mobility
◦ Personal mobility : reaching a mobile user using a logical identity, irrespective of what device he/she is using, current location in the network, or even which network he/she is located in
◦ Session mobility : maintaining access to the same network service / application at different places
◦ Service / application mobility : making a service/application available to mobile user when the user has moved to another location with other but similar resources (e.g., print using the nearest printer) – following me service
Apr 10, 2023 20
ChallengesChallengesDynamic change of physical locations
◦Mobile users may use their phones at different places
Dynamic change of logical addresses◦Users may use their laptops to access
different networksFrequent change of system
configuration◦Mobile users may use PDAs with cellular
networks when outdoor and with WLANs when indoor.
Apr 10, 2023 21
ChallengesChallengesLocation dependency
◦ Location management problem: How does the network know where the intended recipient of a message is currently located? Cellular scenario
Where is 97532468?
Send broadcast messages from every base station.
Portability
• Minimize power consumption - larger battery life, smaller battery size - lesser weight
• Smaller user interface - handwriting, voice recognition, pens, virtual reality screens.
• Small storage capacity - Compressed file systems
Topics in mobile computingTopics in mobile computing Mobile computing models
◦ Mobile C/S Models Simple C/S model, Client/Agent/Server model, Client/Intercept/Server model
◦ Mobile Peer-to-Peer Model Mobile hosts plays the same role and cooperate to
Discover peers and resources Route query requests Perform specified tasks
◦ Mobile Agent Model Code mobility (with computation, data, and state) Autonomous and Asynchronous
Apr 10, 2023 24
Topics in mobile computingTopics in mobile computingMobile C/S model
◦ C/S model can still be used in mobile environment - mobile hosts act as the clients requesting service from server located at fixed network.
◦ However, mobile C/S model deviates from the C/S model used for distributed system in several ways.
◦ Mobile C/S model cannot assume continuous network connectivity and powerful client ability RPC (Remote process control) is not suitable due to
disconnection; Direct message exchange is not good neither due to weak connectivity and slow network.
Need to decouple the communication in synchronous RPC; Use indirection with messages queued at the two ends.
Topics in mobile Topics in mobile computingcomputingMobile P2P model
◦No central server, actually no difference between client and server: All nodes have the same role, serving
as both server and client Relying on collaboration
◦Completely decentralized & asynchronous operations
◦Nodes can communicate with each other directly
Apr 10, 2023 26
Topics in mobile Topics in mobile computingcomputingMobile agent (MA) model
◦ A MA is a “process on the move” – dispatched by one host, encapsulating a thread of execution along with a package of code, data, and execution state Executes at a host for a while, halts execution, dispatches itself
to another host, and resumes execution there - all under its own control
Apr 10, 2023 27
mobile agent X
logic
mobile agent X
logic
Host A Host B
Migratingmobile agent
X
logic
Topics in mobile Topics in mobile computingcomputingMobile agent features
◦Mobility Actively travels across the network, carrying partial /
intermediate results calculated at the previous host Not just alternative to message passing; can perform
additional tasks along its way of traveling
◦Autonomous Decides by itself what to do and how, when and where it
ought to move
◦Asynchrony Mobile agents and users can execute at the same time
without blocking each other
Apr 10, 2023 28
SummaryMobile computing systems have
different constraints and hence different solutions. Main challenges are due to
Wireless - unreliable.Mobility - dynamism of information.Portability - limited resourcesResource list for further information on
mobile computing.
Apr 10, 2023 29
THANK YOUTHANK YOU
04/10/23 30