Download Mobile Computing

University of Turkish Aeronautical Association
Computer Engineering Department
CENG 453 Mobile Computing
Tansel Dökeroglu, Ph.D.
[email protected]
Room 169
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Books
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Android Books
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Mobile Computing
• Mobile computing refers to computing in a distributed
system in which some processes or processors can
move.
– Moving processes  logical mobility, realized by agents.
– Moving processors  physical mobility, realized by moving
devices.
• Mobile computing extends a distributed computing
environment with a new dimension of mobility.
– Most existing mobile computing systems are based on clientserver computing systems.
– Recent mobile computing solutions consider general distributed
computing, namely, peer-to-peer computing environments.
– Mobility generalizes the network reconfiguration problem.
• Many mobile computing techniques have their root in
distributed systems.
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Mobile Computing vs. Others
• Mobile computing relies on wireless networking and
communications and extends distributed computing
– new issues of client movement, location
management and context-awareness, not to
mention the limitations of devices.
• Pervasive computing extends mobile computing, making
use of small equipment and sensors.
– The number of devices and volume of data can
increase several orders of magnitude
– new issues like data streaming need to be handled.
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Mobile Computing vs. Others
• Networking is the base layer, with communication
primitives.
• Wireless networking and communications extends
networking protocols to cover lack of link and movement
of devices
– GPRS, 3G , IPv6, WLAN.
• Distributed computing covers fundamental issues to utilize
computers over a network.
– coordination mechanism to make the solutions work
– general problem solving approaches
• Internet computing is more on the practical issues of
developing programs and applications that work over
internet.
– using Java and related technology.
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– can be considered a case of distributed computing.
Mobile Computing is
• Taking a computer and all necessary files and software
out into the field.
• Being able to use a computing device even when being
mobile and therefore changing location. Portability is one
aspect of mobile computing.
• The ability to use computing capability without a predefined location and/or connection to a network to
publish and/or subscribe to information.
• A variety of wireless devices that has the mobility to
allow people to connect to the internet, providing
wireless transmission to access data and information
from wherever location they may be.
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The Era of “Mobile Computing”
Mobile Computing
Mobile/Wireless Network
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GSM Base Stations
Ericsson RBS 2000
Nokia PrimeSite
19979
Motorola Marco
Specs
• 1995
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1995
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Newton OS 1.3
4MB ROM
687KB Flash RAM
320x240 Monochrome LCD resistive
touchscreen
RS422 serial port
Localtalk support
1 PCMCIA Slot (5V or 12V)
1 Sharp ASK infrared port
4 AA batteries, rechargeable NiCd batteries
First released January 1995
It weighs 1.8 pounds and is 7.5 inches high,
5.8 inches wide and 1.4 inches deep
USD 900-1400
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The Nokia 9000 Communicator
1996
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Laptops, Notebook, Sub Notebooks
& Netbooks
Laptops: 1991
Notebooks: 1996
Netbooks: 2006
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Wearable Computers
Oculus Virtul Reality
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Wireless Helmet?
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The Projection Keyboard
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Today
Andriod
The iphone
MyVu
The iPad
Plastic Logic QUE
22Moo
Portable projectors
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Tablet
2010-2011
2010
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Sensors
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Burada
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Sensors
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Accelerometers
An accelerometer is a device that measures proper acceleration
("g-force").
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Accelerometers
Accelerometers have multiple applications in industry and
science. Highly sensitive accelerometers are components of
inertial navigation systems for aircraft and missiles.
Accelerometers are used to detect and monitor vibration in
rotating machinery.
Accelerometers are used in tablet computers and digital cameras
so that images on screens are always displayed upright.
Accelerometers are used in drones for flight stabilisation.
Pairs of accelerometers extended over a region of space can be
used to detect differences (gradients) in the proper accelerations
of frames of references associated with those points.
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Hardware side of a typical smart phone
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Software side of a typical smart phone
The bootrom (called "SecureROM" by Apple) is the first significant
code that runs on an iDevice.
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Firmware
In electronic systems and computing, firmware is a type of software
that provides control, monitoring and data manipulation of engineered
products and systems. Typical examples of devices containing firmware
are embedded systems (such as traffic lights, consumer appliances,
and digital watches), computers, computer peripherals, mobile phones,
and digital cameras. The firmware contained in these devices provides
the low-level control program for the device.
A remote control is a very simple example of an
engineered product that contains firmware.
The firmware monitors the buttons, controls the
LEDs, and processes the button presses in order
to send data in a format the receiving device (a
TV set, for example) can understand and process.
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Properties of a typical smart phone
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Properties of a typical smart phone
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Mobile Computing
• Motivations
– Availability of wireless network at reducing communication cost.
– Widespread use of handheld devices with increasing computing
power and lower cost.
– Integration of communication and computing devices (Tablet
computer, SmartPhones).
– Detection of the physical or logical location of a device.
– Making use of wireless network to access information and
perform data processing, resource sharing at high capacity
servers.
– Extend the ability and usefulness of handheld devices.
• Goal
– Access to information anywhere, anytime, anyway.
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Mobile Computing vs. others
• Related concepts
– Wireless computing
• computing without a wire.
• the most primitive form, e.g. using 802.11b, 802.11g or bluetooth.
– Nomadic computing
• computing on the move.
• clients or users are moving.
• physically mobile computing, perhaps prolonged disconnection.
– Ubiquitous computing
• invisible computing or subconscious computing.
• computers and their functionality available to users without being
noticed.
– Pervasive computing
• immersive computing (virtual reality).
• use of wearable computers.
• a current name for ubiquitous computing.
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Mobile Computing vs. Others
• built upon distributed computing discipline
• closely related to
– networking and wireless communications,
– internet computing and cloud computing,
– pervasive computing.
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Pervasive computing
also called ubiquitous computing is the
growing trend towards embedding
microprocessors in everyday objects so they
can communicate information.
The words pervasive and ubiquitous mean
"existing everywhere."
Pervasive computing devices are completely
connected and constantly available.
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Pervasive Computing
• Industry revolution vs information revolution
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Pervasive Computing
• Devices
Pervasive Computing
• Principles
– Decentralization
• based on distributed systems.
• with information synchronization.
• devices and applications are embedded into wireless
networking infrastructure.
– Diversification
• should target on different users with different needs.
• must be able to manage the diversity.
– Connectivity
• boundless connectivity.
– Simplicity
• convenient and intuitive to use.
• good and mature human computer interface.
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Pervasive Computing
• The wearable computer project
MicroOptical display
IR tag reader
Internet appliance
Body bus junction
802.11 bridge
Battery
single
Board computer
Body network hub
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Fueled by advances in mobile computing, wearable robotics are
growing more sophisticated and finding use in medicine, manufacturing,
and the military.
The engineers behind the suit had developed a system that appears to
read the brain’s intentions courtesy of electroencephalographic, or
EEG, sensors
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Distributed Systems
• A distributed system is a system supporting distributed
computing.
• There is no universal definition.
• It is generally a collection of autonomous computers,
connected together by some communication media, usually
a network.
• They are capable of sharing resources and capable of
providing service for one another.
• The processors cooperate to achieve an overall goal.
• Users may view the resulting environment as a single
computing facility.
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Distributed Systems
• Distributed hardware
– Processors and memory are physically separated, connected
only via communication media.
• Distributed control
– Each processor is autonomous, running its own program.
– They cooperate together in a voluntary manner.
• Distributed data
– Data for a program may scatter around and need to be
exchanged to carry out a task.
• Resource sharing
– Expensive resources can be shared among different users.
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Distributed Systems
• Openness
– System is visible to user, and can be modified and extended
when needs arise.
– For example, Unix is an open system and IBM PC has an open
architecture.
• Concurrency
– Processors are autonomous and running concurrently.
– Several jobs may be executed simultaneously.
• Scalability
– It is relatively easy to build a large system using similar approach
to build a small system.
– For example, Internet is built from smaller networks.
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Distributed Systems
• Fault tolerance
– Processors more available (high availability), independent failure
mode and preferably graceful degradation.
– System can still function when some parts are down.
• Transparency
– User should not perceive the system as being composed of
different parts and the lower level of functionality must be
concealed.
– For example, send/receive using a socket should not be
concerned with data link and network connections.
– Forms of transparency include access, location, concurrency,
replication, failure, migration, performance, scaling.
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New Features in Mobile Computing
• Limited asymmetric bandwidth and high latency
– Wireless channels are of limited bandwidth and asymmetric.
– Perhaps of speed of grade of modems.
• Weak connectivity and low reliability
– Disconnection to channels can easily occur (planned or unplanned)
and can be prolonged.
– Messages may be lost with much higher probability.
• Low processing power and energy
– Battery is expensive and limited.
– Screen or display is small.
• Mobility of devices
– Need to track location of devices and to provide proper services.
– Invalidation to data upon change of location.
• Low physical security
– Mobile devices are easily lost, broken or stolen.
• High degree of heterogeneity
– Devices are very different in nature, e.g., Palm and Pocket PC are
programmed differently, worse for embedded systems and devices.
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Objectives of Mobile Computing
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To run existing distributed applications
To provide distributed services
To share data and resources
To maintain efficiency
To keep communication and operational cost down
To conserve energy
To achieve consistency among views of different users
To be scalable in supporting numerous users
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New Solutions to Old Problems
• Solve problems in distributed systems
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Hardware and computer architecture
Communication architecture and protocols
Distributed operating systems
Synchronization need
File systems
Databases systems
Real-time processing
Multimedia support with QoS
Dynamic system reconfiguration
Security
Application requirement and design
User interfaces design (on mobile devices)
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Mobile Computing Architecture
• Fixed network can be dedicated special network for
the mobile system.
• Fixed network can also be the Internet or Intranet.
• Infrastructured Systems
– MSS (mobile support station, or base station) +
– MU (Mobile unit, mobile station, mobile client)
– WLAN, Cellular Net., etc.
• Ad hoc systems
– Mobile nodes + mobile nodes
– Mobile Adhoc NETwork (MANET), WSN (Wireless
Sensor Network), VANET (Vehicular Ad Hoc Networks),
etc.
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VANETs (Vehicular Ad Hoc Networks)
• Like MANETs:
– They self-organize over an evolving topology
– They may rely on multi-hop communications
– They can work without the support of a fixed
infrastructure
• Unlike MANETs:
– They have been conceived for a different set of
applications
– They move at higher speeds (0-40 m/s)
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– They do not have battery and storage constraints
VANETs
• Communication modes:
– Vehicle-to-Vehicle (V2V) among vehicles
– Vehicle-to-Infrastructure (V2I), between vehicles
and Road-Side Units (RSUs)
– Vehicle-to-X (V2X), mixed V2V-V2I approach
V2V
RSU
V2I
V2I
V2V
RSU
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Mobile Computing Architecture
Server
MU
(mobile unit)
MSS
Fixed network
(mobile support station)
Wireless radio
cell (19.2Kbps)
WLAN
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Mobile Computing Architecture
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Mobile Applications
• Personal applications
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Web and email access.
Personal information management.
Personalized use of computer resources.
Weather and traffic report.
Network games.
• Commercial applications
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personal/tourism
personal
logistics/tourism
personal
finance
Stock price quotation.
Inventory control for traveling salesperson. e-commerce/finance
finance
Banking activities.
tourism
Bus-stop information kiosk at major bus terminals.
Push-based advertisement on vehicle.
e-commerce/tourism
e-coupon.
e-commerce
Generic M-commerce applications.
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Radio-frequency identification (RFID)
is the wireless use of electromagnetic fields to
transfer data, for the purposes of automatically
identifying and tracking tags attached to
objects.
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Location Tracking
• Active badge/RFID card with sensor technology
– An early application of sensor technology in location tracking,
developed by AT&T Cambridge Lab, for tracking and
locating of individuals within a building.
– Each building office is equipped with one or more networked
sensors to detect these transmission signals.
• Biometrics cards with
bluetooth and RFID deployed
at US Homeland Security
Office May 2005.
– Requirement: strong resistance
to terrorist exploitation and rapid
electronic authentication.
– Could Hong Kong smart ID do
that?
– Problem: signal could be
detected.
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Location-Awareness
• Location and mobility are the two major factors to be
capitalized in a mobile application.
• Applications can be based on the current location of a
user.
• Example
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Emergency vehicle routing to caller of 999.
Deliver me a pizza as I am hungry!
Deliver value-added information based on current position.
Logistics arrangement can be made based on location.
• Send the goods to an alternative location if traffic jam is out-ofcontrol for receiving the goods.
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Context-Awareness
• A context-aware application is an application that adapts
its behavior to a changing environment.
• It needs to gather contextual information about its
environment, usually through the use of sensors.
• User does not need to give all information and the
application should try to figure out the rest.
• The follow-me type of applications:
– Application knows the location of a user:
• Smart map (Telenor Research) that always maintain the current user
position at center.
• Nearest restroom/toilet depends on gender.
– When in a room, system can look up user profile for preferred room
setting, or mode of operation for a speaker.
Context vs. Location?
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Intelligent Home
• Intelligent home networking system with general technology
– Use mobile phone technology to instruct a home control
computer for home automation equipment.
WiMAX (802.16), 802.11, Bluetooth etc.
Transmit signal and control electronic devices via power line.
Smart TV
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Intelligent Home
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Master here
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Intelligent Home
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Applications of Mobile Computing
• Instant messaging?
– 10 million iMode users in Japan since 18 months of introduction,
also used by Greece Olympics.
– 15.6 billion SMS messages in China January 2004.
• Mobile games?
– $9 billion sold in 2004.
• Mobile web access?
– WAP, iMode, WWW
– How to resolve the bandwidth problem? 3G?4G?
• Location-dependent services?
– Sensor network infrastructure cost?
• Context-aware services?
– Locating a best restaurant closest by sensing e-cash in e-wallet
and dining preference.
• How can the communication infrastructure match with the
application functionality and bandwidth / mobility requirement?
– High bandwidth can be resulted, using pico-cells, but the client
movement speed must be limited.
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Bandwidth Requirement
3G
wireless
LAN
current
Ethernet
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Asynchronous Transfer Mode
Asynchronous Transfer Mode (ATM) is
"a telecommunications concept defined by ANSI and ITU
standards for carriage of a complete range of user traffic,
including voice, data, and video signals".
ATM was developed to meet the needs of the Broadband
Integrated Services Digital Network (ISDN), as defined in the
late 1980s, and designed to unify telecommunication and
computer networks.
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Asynchronous Transfer Mode
It was designed for a network that must handle both traditional
high-throughput data traffic (e.g., file transfers), and real-time,
low-latency content such as voice and video.
The reference model for ATM approximately maps to the three
lowest layers of the ISO-OSI reference model:
network layer,
data link layer,
and physical layer.
ATM is a core protocol used over the backbone of
 The public switched telephone network (PSTN) and
 Integrated Services Digital Network (ISDN)
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WiMAX
(Worldwide Interoperability for Microwave Access)
is a family of wireless communications standards
initially designed to provide 30 to 40 megabit-persecond data rates, with the 2011 update providing
up to 1 Gbit/s for fixed stations.
The name "WiMAX" was created by the WiMAX
Forum, which was formed in June 2001 to promote
conformity and interoperability of the standard.
The forum describes WiMAX as "a standards-based
technology enabling the delivery of last mile
wireless broadband access as an alternative to cable
and DSL".
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Smartphone OS Market Share
2009
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Smartphone Operating System Market Share
The largest shareholder is the Android Operating System
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Smartphone OS Market Share
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Android 6.0 Marshmallow
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Java Platform, Micro Edition, or Java ME,
is a Java platform designed for embedded systems
(mobile devices are one kind of such systems).
Target devices range from industrial controls to mobile
phones (especially feature phones) and set-top boxes.
Java ME was formerly known as Java 2 Platform,
Micro Edition (J2ME).
Dalvik is a process Virtual Machine (VM) in Google's
Android operating system that executes applications
written for Android. Dalvik is used on mobile devices
and more recently on devices such as smart TVs and
weRbles.
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Objective-C
Objective-C is a general-purpose, object-oriented
programming language that adds Smalltalk-style
messaging to the C programming language.
It is the main programming language used by Apple
for the OS X and iOS operating systems, and their
respective application programming interfaces (APIs):
Cocoa and Cocoa Touch.
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New Forms of Computing
• Distributed
Computing
(Client/Server)
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•
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Wireless Computing
Nomadic Computing
Mobile Computing
Ubiquitous Computing
Pervasive Computing
Invisible Computing
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Mobile Computing
• Using:
– small size portable computers, hand-helds, and other
small wearable devices,
• To run stand-alone applications (or access
remote applications) via:
– wireless networks: IR, BlueTooth, W-LANs, Cellular, WPacket Data networks, etc.
• By:
– nomadic and mobile users (animals, agents, trains, cars,
cell phones, ….)
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Nomadic, Mobile & Ubiquitous
No
Fixed
Network
Network
Fixed
Wireless
Network
Nomadic Computing
Wireless
Network
(A)
Wireless
Network
(B)
Mobile Computing
Ubiquitous Computing
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Impressive Wireless
Infrastructure!
Global
Satellite
Suburban
Urban
In-Building
Micro-Cell
Macro-Cell
Pico-Cell
dik ©
In-Room
(BlueTooth)
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Wireless Network Convergence
Mobility
2G/3G Mobility-Bandwidth Trade-off
Global
National
1-7 GHz
GSM
0.1-2 GHz
D-AMPS/IS-95
UMTS
0.1-2.3 GHz
Regional
2-4 GHz
Metropolitan
Campus
Office
2-7 GHz
DECT
WLAN
>2 GHz
Room
DECT
10K
20-50 GHz
100K
1M
10M
100M
1G
Bandwidth
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UMTS: Universal Mobile Telecomm. Standard
• Global seamless operation in multi-cell
environment (SAT, macro, micro, pico)
• Global roaming: multi-mode, multi-band, low-cost
terminal, portable services & QoS
• High data rates at different mobile speeds:
144kbps at vehicular speed (80km/h), 384 kbps at
pedestrian speed, and 2Mbps indoor (office/home)
• Multimedia interface to the internet
• Based on core GSM.
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Wireless Network Overlay
Global
Satellite
Suburban
Urban
In-Building
Micro-Cell
Macro-Cell
Pico-Cell
dik
©
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Beneficiaries of Ubiquitous
Computing
Internet
Intranet
• Commuters
• Travelers
• Stock traders
• Medical
• Law enforcement
• Package delivery
• Education
• Insurance
• Emergency
• Trucking
• Intelligence
• Military
Adhoc network
Servers
Clients
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Limitations of the Mobile Environment
 Limitations of the Wireless Network
 heterogeneity of fragmented networks
 frequent disconnections
 limited communication bandwidth
 Limitations Imposed by Mobility
 Limitations of the Mobile Computer
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Frequent Disconnections
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Handoff blank out (>1ms for most cellulars)
Drained battery disconnection
Battery recharge down time
Voluntary disconnection (turned off to
preserve battery power, also off overnight)
 Theft and damage (hostile environment)
 Roam-off disconnections
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Limited Communication Bandwidth
 Orders of magnitude slower than fixed network
 Higher transmission bit error rates (BER)
 Uncontrolled cell population
 Difficult to ensure Quality of Service (QoS)
 Availability issues (admission control)
 Asymmetric duplex bandwidth
 Limited communication bandwidth exacerbates
the limitation of battery lifetime.
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Limitations of the Mobile Computer
 Short battery lifetime (max ~ 5 hours)
 Subject to theft and destruction => unreliable
 Highly unavailable (normally powered-off to
conserve battery)
 Limited capability (display, memory, input
devices, and disk space)
 Lack of de-facto general architecture: handhelds, communicators, laptops, and other devices
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Limitations Imposed by Mobility
 Lack of mobility-awareness by applications
 inherently transparent programming model (object-,
components-oriented, but not aspect-oriented)
 lack of environment test and set API support
 Lack of mobility-awareness by the system
 network: existing transport protocols are inefficient to use
across heterogeneous mix of fixed/wireless networks
 session and presentation: inappropriate for the wireless
environment and for mobility
 operating systems: lack of env. related conditions and
signals
 client/server: unless changed, inappropriate and inefficient
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Evolution of Wireless LAN
• In late 1980s, vendors started offering wireless
products, which were to substitute the traditional
wired LAN (Local Area Network) products.
• The idea was to use a wireless local area network to
avoid the cost of installing LAN cabling and ease the
task of relocation or otherwise modifying the
network's structure.
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Evolution of Wireless LAN
• The question of interoperability between
different wireless LAN products became critical.
• IEEE standard committee took the
responsibility to form the standard for WLAN.
• As a result IEEE 802.11 series of standards
emerged.
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Evolution of Wireless LAN
• WLAN uses the unlicensed Industrial,
Scientific, and Medical (ISM) band that
different products can use as long as they
comply with certain regulatory rules
• WLAN is also known as Wireless Fidelity or
WiFi in short
• There are many products which use these
unlicensed bands along with WLAN.
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Evolution of Wireless LAN
• Examples could be cordless telephone,
microwave oven etc.
• There are 3 bands within the ISM bands.
– These are 900-MHz ISM band, which ranges from
902 to 928 MHz;
– 2.4-GHz ISM band, which ranges from 2.4 to 2.4853
GHz; and
– the 5.4 GHz band, which range from 5.275 to 5.85
GHz.
• WLAN uses 2.4 GHz and 5.4 GHz bands.
• WLAN works both in infrastructure mode and
ad hoc mode
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Evolution of Wireless PAN
• Techniques for WPANs are infrared and radio waves.
• Most of the Laptop computers support communication
through infrared, for which standards have been
formulated by IrDA (Infrared Data Associationwww.irda.org).
• Through WPAN, a PC can communicate with another
IrDA device like another PC or a Personal Digital
Assistant (PDA) or a Cellular phone.
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Evolution of Wireless PAN
• The other best known PAN technology standard is
Bluetooth.
• Bluetooth uses radio instead of infrared.
• It offers a peak over the air speed of about 1 Mbps
over a short range of about 10 meters.
• The advantage of radio wave is that unlike infrared it
does not need a line of sight.
• WPAN works in ad hoc mode only
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Mobile computing
• Mobile computing can be defined as a computing
environment over physical mobility.
• The user of a mobile computing environment will be
able to access data, information or other logical
objects from any device in any network while on the
move.
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Mobile computing
• Mobile computing system allows a user to
perform a task from anywhere using a computing
device in the public (the Web), corporate
(business information) and personal information
spaces (medical record, address book).
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Mobile computing
• Mobile computing is used in different contexts with
different names. The most common names are:
– Mobile Computing:
• The computing environment is mobile and moves along with the
user.
• This is similar to the telephone number of a GSM (Global System
for Mobile communication) phone, which moves with the phone.
• The offline (local) and real-time (remote) computing environment
will move with the user.
• In real-time mode user will be able to use all his remote data and
services online.
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Mobile computing
– Anywhere, Anytime Information: This is the
generic definition of ubiquity, where the information
is available anywhere, all the time.
– Virtual Home Environment: (VHE) is defined as an
environment in a foreign network such that the
mobile users can experience the same computing
experience as they have in their home or corporate
computing environment.
• For example, one would like to put ones room heater on
when one is about 15 minutes away from home.
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Mobile computing
– Nomadic Computing: The computing environment
is nomadic and moves along with the mobile user.
• This is true for both local and remote services.
– Pervasive Computing: A computing environment,
which is pervasive in nature and can be made
available in any environment.
– Ubiquitous Computing: A disappearing (nobody
will notice its presence) everyplace computing
environment. User will be able to use both local and
remote services.
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Mobile computing
– Global Service Portability: Making a service
portable and available in every environment. Any
service of any environment will be available
globally.
– Wearable Computers: Wearable computers are
those computers that may be adorned by humans
like a hat, shoe or clothes (these are wearable
accessories).
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Mobile Computing Functions
• We can define a computing environment as mobile if
it supports one or more of the following
characteristics:
• User Mobility:
– User should be able to move from one physical location to
another location and use the same service.
– The service could be in the home network or a remote
network.
– Example could be a user moves from London to New York
and uses Internet to access the corporate application the
same way the user uses in the home office.
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Mobile Computing Functions
• Network Mobility:
– User should be able to move from one network to
another network and use the same service.
– Example could be a user moves from Hong Kong
to New Delhi and uses the same GSM phone to
access the corporate application through WAP
(Wireless Application Protocol). In home network
he uses this service over GPRS (General Packet
Radio Service) whereas in Delhi he accesses it
over the GSM network.
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Mobile Computing Functions
• Bearer Mobility:
– User should be able to move from one bearer to
another and use the same service.
– Example could be a user was using a service
through WAP bearer in his home network in
Bangalore. He moves to Coimbatore, where WAP
is not supported, he switch over to voice or
SMS(Short Message Service) bearer to access the
same application.
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Mobile Computing Functions
• Device Mobility:
– User should be able to move from one device to
another and use the same service.
– Example could be sales representatives using
their desktop computer in home office. During the
day while they are on the street they would like to
use their Palmtop to access the application.
97
Mobile Computing Functions
• Session Mobility:
– A user session should be able to move from one
user-agent environment to another.
– Example could be a user was using his service
through a CDMA (Code Division Multiple Access)
IX network. The user entered into the basement to
park the car and got disconnected from his CDMA
network. User goes to home office and starts
using the desktop. The unfinished session in the
CDMA device moves from the mobile device to
the desktop computer.
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Mobile Computing Functions
• Service Mobility:
– User should be able to move from one service to
another.
– Example could be a user is writing a mail. To
complete the mail user needs to refer to some
other information. In a desktop PC, user simply
opens another service (browser) and moves
between them using the task bar. User should be
able to switch amongst services in small footprint
wireless devices like in the desktop.
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Mobile Computing Functions
• Host Mobility:
– The user device can be either a client or server.
– When it is a server or host, some of the
complexities change.
– In case of host mobility the mobility of IP needs to
be taken care of.
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Logical Functions of Mobile Computing
The mobile computing functions can be logically
divided into following major segments:
1. User with device:
• The user device, this could be a fixed device like
desktop computer in office or a portable device like
mobile phone.
• Example: laptop computers, desktop computers, fixed
telephone, mobile phones, digital TV with set-top box,
palmtop computers, pocket PCs, two way pagers,
handheld terminals, etc.
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Logical Functions of Mobile Computing
2. Network:
•
•
Whenever a user is mobile, he will be using different
networks at different places at different time.
Example: GSM, CDMA, iMode, Ethernet, Wireless
LAN, Bluetooth etc.
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Logical Functions of Mobile Computing
3.Gateway:
• This is required to interface different transport bearers.
• These gateways convert one specific transport bearer
(transporter) to another transport bearer.
• Example: From a fixed phone (with voice interface) we
access a service by pressing different keys on the
telephone.
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Logical Functions of Mobile Computing
4. Middleware:
•
•
•
This is more of a function rather than a separate
visible node.
In the present, context middleware handles the
presentation and rendering of the content on a
particular device.
It will also handle the security and personalization for
different users
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Logical Functions of Mobile Computing
5. Content:
•
•
•
•
This is the domain where the origin server and
content is.
This could be an application, system, or even an
aggregation of systems.
The content can be mass market, personal or
corporate content.
Origin server will have some means to accessing
the database and the storage devices
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