Mobile Computing

jiggerbarnacleMobile - Wireless

Nov 24, 2013 (3 years and 4 months ago)

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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

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The Era of “Mobile Computing”

Mobile Computing

Mobile/Wireless Network

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 pre
-
defined 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.

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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
.

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


Devices

Pervasive Computing

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

Body bus junction

802.11 bridge

CerfBoard (developing

Internet appliance)

Battery

Body network hub

BSEV core (single

Board computer)

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


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


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.

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Mobile Computing Architecture

Server

MU

(mobile unit)

MSS

(mobile support station)

Fixed network

Wireless radio
cell
(19.2Kbps)

WLAN

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Mobile Computing Architecture

Applications


Personal applications

Web and email access.

ICQ.

Personal information management.

Personalized use of computer resources.

Weather and traffic report.

Network games.


Commercial applications

Stock price quotation.

Inventory control for traveling salesperson.

Banking activities.

Bus
-
stop information kiosk at major bus terminals.

Push
-
based advertisement on vehicle.

e
-
coupon.

Generic M
-
commerce applications.

finance

e
-
commerce/finance

finance

logistics/tourism

tourism

e
-
commerce/tourism

e
-
commerce

personal/tourism

personal

personal

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.


A
pplications 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


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.

Bandwidth Requirement

3G

current

Ethernet

wireless

LAN

Summary


Concept of mobile computing


Mobile computing vs. related concepts

Pervasive computing


Mobile applications


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