第1章 移动计算简介
§1.1 基本概念
§1.2 相关概念分析
§1.3 移动应用
The Era of “Mobile Computing”
Mobile Computing
Mobile/Wireless Network
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Mobile Computing Architecture
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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 where ever location they may be. "
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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 client-server
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.
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.
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
a term coined by Mark Weiser in 1991.
invisible computing or subconscious computing.
computers and their functionality available to users without being noticed.
Pervasive computing
immersive computing.
use of wearable computers.
a current name for ubiquitous computing.
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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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 (WCDMA), 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.
can be considered a case of distributed computing.
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 again 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.
Pervasive Computing
 Industry revolution vs information revolution
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.
Pervasive Computing
 The MIT wearable computer project
PolyU ITC is doing something similar now.
MicroOptical display
IR tag reader
CerfBoard (developin
Internet appliance)
Body bus junction
802.11 bridge
Battery
BSEV core (single
Board computer)
Body network hub
Recap on 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.
Recap on 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.
 Resources sharing
Expensive resources can be shared among different users.
Recap on 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.
Recap on 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.
New Features in Mobile Computing
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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.
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
New Solutions to Old Problems
 Solve problems in distributed systems
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)
Mobile Computing Architecture
 Fixed network can be dedicated proprietary 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
MANET, WSN, VANET, etc.
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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Applications
 Personal applications
Web and email access.
ICQ.
Personal information management.
Personalized use of computer resources.
Weather and traffic report.
Network games.
 Commercial applications
personal/tourism
personal
logistics/tourism
personal
finance
Stock price quotation.
e-commerce/finance
Inventory control for traveling salesperson.
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.
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.
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
Emergency vehicle routing to caller of 999.
Deliver me a pizza as I am hungry!
Deliver value-added information based on current position.
Targeted advertisement to customer: E-coupon.
Logistics arrangement can be made based on location.
Send the goods to an alternative location if traffic jam is out-of-control
for receiving the goods.
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?
M-commerce
Example of three stages???
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
Killer App. of Mobile Computing
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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.
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Mobile games?
$9 billion sold in 2004.
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Mobile web access?
WAP, iMode, WWW
How to resolve the bandwidth problem? 3G?4G?
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Location-dependent services?
Sensor network infrastructure cost?
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Context-aware services?
Locating a best restaurant closest by sensing e-cash in e-wallet and dining
preference.
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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.
Bandwidth Requirement
3G
wireless
LAN
current
Ethernet
Summary
 Concept of mobile computing
 Mobile computing vs. related concepts
Pervasive computing
 Mobile applications
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