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

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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.

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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)

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Evolution of computing Evolution of computing paradigmparadigm

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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

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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.

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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.

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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

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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

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ChallengesChallengesWired channel – what if more than one

transmitter?

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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.

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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

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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

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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

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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.

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THANK YOUTHANK YOU

04/10/23 30