CSE-302: Mobile Computing

mashpeemoveΚινητά – Ασύρματες Τεχνολογίες

24 Νοε 2013 (πριν από 3 χρόνια και 11 μήνες)

101 εμφανίσεις

Dr. R. B. Patel

1

CSE
-
302
:

Mobile

Computing


Dr
.

R
.

B
.

Patel

Dr. R. B. Patel

2

Breakthrough

Technology



Wireless

communication

networks




multiple

networks

“covering”

the

globe




world
-

wide

deregulation

and

spectrum

auctions




standard

communication

systems

and

air

link

interfaces



Portable

information

appliances




laptops,

notebooks,

sub
-

notebooks,

and

MNCs




hand
-

held

computers




PDAs

and

smart

phones



Internet
:




TCP/

I
P&

de
-

facto

application

protocols




ubiquitous

web

content

Dr. R. B. Patel

3

New

Forms

of

Computing



Wireless Computing


Nomadic Computing


Mobile Computing


Ubiquitous
Computing


Pervasive Computing


Invisible Computing

Distributed
Computing

(Client/ Server)

Dr. R. B. Patel

4


Mobile

Computing

Mobile

Computing



Using
:


small

size

portable

computers,

handheld,

MNC,

and

other

small

wearable

devices,



To

run

stand
-

alone

or

network

based

applications

via
:


wireless

networks
:

IR,

BlueTooth,

W
-

LANs,

Cellular,W
-

Packet

Data

networks,

SAT,

etc
.


By

:



nomadic

and

mobile

users

(animals,

agents,

trains,

cars,

cell

phones,


.
)


Dr. R. B. Patel

5

Mobile

Computing


An

important

question

to

ask

is

which

technology

drove

mobile

computing

to

where

it

is

today?



Is

it

the

wireless

network

technology

or

the

miniaturization

and

portable

computing

technology?



Unfortunately,

there

is

no

easy

answer
.

An

individual

with

a

Palm

Pilot

will

probably

answer

in

favor

of

the

portable

technology,

whereas

a

UPS

package

delivery

worker

will

be

more

thankful

to

the

wireless

technology
.



Whatever

the

right

answer

might

be,

more

important

questions

need

to

be

answered
:

where

are

we

now?



And

what

are

the

challenges

and

impediments

facing

mobile

computing?


Dr. R. B. Patel

6

Mobile

computing


Mobile

computing

represents

a

shift

in

the

distributed

systems

paradigm
.



The

potential

of

decoupled

and

disconnected

operation,

location
-
dependent

computation

and

communication,

and

powerful

portable

computing

devices

gives

rise

to

opportunities

for

new

patterns

of

distributed

computation

that

require

a

revised

view

of

distributed

systems
.



However,

factors

such

as

weak

network

connectivity,

energy

constraints,

and

mobility

itself

raise

new

concerns

regarding

the

security,

reliability,

and

even

correct
-
ness

of

a

mobile

computing

system
.


Dr. R. B. Patel

7

Mobile

Computing



Migration

is

important

for

survival


Mobility

originated

from

the

desire

to

move

either

toward

resource

or

away

from

scarcity


Mobile

computing

about

both

physical

and

logical

computing

entities

that

move


Physical

entities

are

computers

that

change

locations


Logical

entities

are

instances

of

running

user

application

or

a

mobile

agent


Mobile

agents

can

migrate

any

where

over

the

Internet
.



But

applications

can

only

move

to

a

local

cluster

of

computers


Dr. R. B. Patel

8

Buzzwords



Mobile,

ubiquitous,

nomadic,

un
-
tethered

(unsecured),

pervasive

and

any

time,

any

where,

any

person

computing

are

used

by

the

researchers

to

refer

to

computing

that

uses

small

portable

devices

and

wireless

communication

network
.


Nomadic

computing

refer

to

limited

migration


Migration

is

within

a

building

at

a

pedestrian

speed


Interleaved

pattern

of

user

relocation

and

indoor

connections


In

the

same

vein,

users

carrying

laptop

with

Dialup

modems

are

engaged

in

nomadic

computing

Dr. R. B. Patel

9

Buzzwords

(contd
...
)



Mobile

Computing

requires
:

Wireless

network

to

support

outdoor

mobility

and

handoff

from

one

network

to

the

next

at

a

pedestrian

or

vehicular

speed


Traveler

in

car

using

laptop

connected

with

a

GSM

phone
-

engaged

in

mobile

computing


Ubiquitous

computing

or

pervasive

computing

refers

to

access

to

computer

network

all

the

time

at

any

location

by

any

person
.


Ubiquitous

computing

cannot

be

realized

unless

mobile

computing

matures
.

Dr. R. B. Patel

10


Ubiquitous

Computing

=

Nomadic

Computing

+

Mobile

Computing



No
Network

Fixed
Network

Fixed
Wireless
Network

Wireless
Network

(A)

Wireless
Network

(B)

Nomadic Computing

Mobile Computing



Ubiquitous computing

Dr. R. B. Patel

11

Nomadic

computing


It is another name for mobile computing, is the use
of portable computing devices (such as laptop and
handheld computers) in conjunction with mobile
communications technologies to enable users to
access the Internet and data on their home or work
computers from anywhere in the world.


People using such a system are sometimes referred
to as
technomads
, and their ability to use that
system as nomadicity.

Dr. R. B. Patel

12

Continued …


Nomadicity is the tendency of a person, or group of
people, to move with relative frequency.


The need to support today's increasingly mobile workers
with nomadic computing, the use of portable computing
devices and, ideally, constant access to the Internet and
data on other computers.


The goal of nomadic computing is to enable a consistent
experience for users anywhere in the world, including as
they travel from one place to another.

Dr. R. B. Patel

13

Continued …


A nomadic environment is said to be one that is transparent
to the user, regardless of location, the device and platform
they're using, the available bandwidth, and whether or not
they are in motion at any given time.


Standards such as the Internet Engineering Task Force’s
(IETF) Mobile IPv6 standards and Dynamic Host
Configuration Protocol (DHCP) can be said to support
nomadic computing.

Dr. R. B. Patel

14

Ubiquitous Computing


Ubiquitous computing names the third wave in
computing, just now beginning.


First were mainframes, each shared by lots of
people. Now we are in the personal computing era,
person and machine staring uneasily at each other
across the desktop.


Next comes ubiquitous computing, or the age of
calm technology
, when technology recedes into
the background of our lives.


This is also called "Third Paradigm" computing.

Dr. R. B. Patel

15

Sentient

computing


Sentient computing

is a form of ubiquitous
computing which uses sensors to perceive
its environment and react accordingly.


A common use of the sensors is to construct
a world model which allows location
-
aware
or context
-
aware applications to be
constructed.

Dr. R. B. Patel

16

Mobile

Environment


High
-
speed wire
-
line network

Fixed
host

Fixed
host

Fixed
host

Fixed
host

Fixed
host

Fixed
host

Satellite
link

Wireless
radio Cells

Wireless
LAN

Base
station

Mobile
host

Wireless
link

Comm.
cell

Dr. R. B. Patel

17

Wireless

Telecommunication

Networks



Dr. R. B. Patel

18

Emerging

Portable

Information

Devices



Subscriber Identification


Module (SIM)

Motorola
marco

Motorola Envoy

The Pocket PC

The Nokia 9000 Communicator

The Sharp Zaurus

The
Vadem
Clio

Fujitsu Stylistic
2300/ 3400
The First Wrist PC: Ruputer

Japan’s PHS
Phone, Year
2001

Wearable
Computers
The Power
Ring

Dr. R. B. Patel

19

Applications

for

mobile

computing


There

are

several

applications

for

mobile

computing

including

wireless

remote

access

by

travelers

and

commuters,

point

of

sale,

stock

trading,

medical

emergency

care,

law

enforcement,

package

delivery,

education,

insurance

industry,

disaster

recovery

and

management,

trucking

industry,

intelligence

and

military
.



Most

of

these

applications

can

be

classified

into
:

(
1
)

wireless

and

mobile

access

to

the

Internet,

(
2
)

wireless

and

mobile

access

to

private

Intranets,

and

(
3
)

wireless

and

adhocly

mobile

access

between

mobile

computers
.


Dr. R. B. Patel

20

Beneficiaries

of

ubiquitous

computing




Commuters


Travelers


Stock traders


Medical


Law enforcement


Education


Insurance


Emergency


Trucking


Intelligence


Military

Internet

Intranet

Ad
-
hoc network

Servers

Clients

Dr. R. B. Patel

21

Limitations

of

the

Mobile

Environment




Limitations

of

the

Wireless

Network



H
eterogeneity

of

fragmented

networks



F
requent

disconnections



L
imited

communication

bandwidth



Limitations

Imposed

by

Mobility



Limitations

of

the

Mobile

Computer

Dr. R. B. Patel

22


Continued



Frequent

Disconnections



Handoff

blank

out

(>
1
ms

for

most

cellular

system)



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

Dr. R. B. Patel

23



Continued


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)




Asymmetric

duplex

bandwidth




Limited

communication

bandwidth

exacerbates

the

limitation

of

battery

lifetime
.

Dr. R. B. Patel

24



Continued


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
:

Handheld,

communicators,

laptops,

and

other

devices

Dr. R. B. Patel

25



Continued


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

Dr. R. B. Patel

26

Continued


Lack

of

mobility
-

awareness

by

the

system






networ
k
:

existing

transport

protocols

are

inefficient

to

use

across

heterogeneous

mix

of

fixed/wireless

networks




session

and

presentatio
n
:

inappropriate

for

the

wireless

environment

and

for

mobility




operating

system
s
:

lack

of

environment

related

conditions

and

signals




client/serve
r
:

unless

changed,

inappropriate

and

inefficient



Dr. R. B. Patel

27



Continued


Mobile

and

Wireless

Networking

Issues




Mobile

IP




Wireless

Transport




Ad
-

Hoc

Networks




Location

Management




Wireless

Network

Benchmarking




Ad
-

Hoc

Network

Simulation




Wireless

Link

Simulation



Dr. R. B. Patel

28



Continued


Wireless

and

Mobile

Computing

Models





Mobility
-

aware

Client/

Server

using

Proxies




Disconnected

Operations




Application
-

aware

Adaptations




Mobile

Agents

and

Objects




Thin

Client/

Server




Mobile

Caching

and

Replication




Broadcast

Disks




Service

Advertisement

and

Brokering




Smart

Pones

Dr. R. B. Patel

29



Continued


Mobile

file

and

Database

Systems




Wireless

File

System

Access




Disconnected

File

Systems




Mobile

Access

to

C/

S

or

Distributed

Databases




Ad
-

Hoc

Database

Systems




Checkpointing




Database

recovery




Mobile

Database

Design

Dr. R. B. Patel

30



Continued


Mobile

Transaction

and

Workflow




ACID

Relaxation




Mobile

Transaction

Models




Optimistic

Data

Replication




Semantic
-

based

Conflict

Resolution




Consensus

in

Mobile

Environment

Dr. R. B. Patel

31



Continued


Wireless

and

Mobile

Applications

and

Services





Application

Design

for

Wireless

networks




Application

Design

for

Mobility




Wireless

WWW

Access




Active

Badges

(Teleporting)




Wireless

Classroom

(Wireless

Campus!)




Mobile

Groupware




Location
-

sensitive

Yellow

Service




Pervasive

Computing

and

Smart

spaces






.

.

.

.

.

Dr. R. B. Patel

32



Continued


Performance

and

QoS




QoS

Measures

in

Wireless

and

Mobile

Environments




QoS

Guarantees




Simulators

and

Emulaors

of

Wireless

Links




Simulators

of

Mobile

and

Ad
-

hoc

Networks




Wireless

Networking

Benchmarking

Dr. R. B. Patel

33



Continued


Emerging

Standards




The

802
.
11
b




The

BlueTooth

Standard




The

Wireless

Application

Protocol

(WAP)




The

CompactHTML




The

Network

Computer

Reference

Specification




Telecom

Standards
:

UMTS







Dr. R. B. Patel

34

Continued





Commuters


Travelers


Stock traders


Medical


Law enforcement


Intranet


Education


Insurance


Emergency


Trucking


Intelligence


Military

Internet

Intranet

Ad
-
hoc network

Servers

Clients

Dr. R. B. Patel

35

Challenges



Mobility/context

aware

applications


Naming

and

locating


Routing

data

and

messages


Reliability

in

presence

of

disconnection


Data

management


Transaction

models


Security

Dr. R. B. Patel

36

Continued




Mobile

computing

affects

entire

spectrum

of

issues

in

computing


First

of

all

it

is

distributed

+

mobile

computing


Distributed

computing

as

we

know

works

on

static

wired

network


Node

may

initiate

computation

somewhere

and

migrate

to

another

place
.


So

two

major

problems

that

arise

due

to

mobility



Searching

for

current

location

of

a

mobile

node


To

impose

a

communication

structure

among

nodes

Dr. R. B. Patel

37

Continued



Physical

location

of

mobile

host

is

not

the

network

address,

so

how

do

we

route

the

message

to

a

mobile

host
.


This

question

is

being

addressed

by

two

different

communities
-

Internet

community

and

cellular

community


Work

of

Internet

community

involves

Mobile

IP


Aims

at

standards

that

can

extend

IP

in

order

to

deal

with

location

of

mobile

host


Mobile

IP

work

assumes

connectionless

packet

switching

scenario


Dr. R. B. Patel

38

Continued



Cellular

community’s

effort

based

on

location

management

of

cellular

phone

users


It

deals

with

connection
-
oriented

communication,

since

it

is

motivated

by

issues

in

call
-
setup

in

telephony


Main

problem

in

mobility

management

is

to

find

an

appropriate

tradeoff

between

searching

and

informing


Searching

is

performed

when

address

of

the

message

recipient

is

not

known
-

at

least

not

known

precisely


Dr. R. B. Patel

39

Continued



Informing

is

a

responsibility

of

the

mobile

host

when

it

migrates



Extreme

situations

can

be

1.
Mobile

host

never

informs
-

works

for

hosts

receiving

few

messages

and

for

hosts

which

do

not

move

during

receiving

2.
Always

informs



works

well

for

hosts

receiving

messages

frequently


Dr. R. B. Patel

40

Continued



Ad

hoc

network

routing

is

the

ultimate

challenge


Ad

hoc

networks

arise

in

rapid

development

scenarios

1.
Emergency

disaster

management


2.
Military

operation

in

remote

sites

3.
Business

meeting

venues

without

infrastructure

support


Many

routing

algorithms

are

designed
:

such

as

fisheye,

state

routing,

dynamic

source

routing,

ad

hoc

on

demand

routing,

etc
.



There

are

interesting

application

of

conventional

graph

theoretic

problems

in

ad

hoc

network

routing


Dr. R. B. Patel

41

Continued



(a) Infrastructure
-
based wireless network

(b)

Ad

hoc

network


Dr. R. B. Patel

42

Continued



Main

cause

of

loss

of

packets

in

wired

network

is

congestion

because

error

rates

are

very

low


In

wireless

network

congestion

still

remains

a

problem,

but

the

situation

is

somewhat

reversed


Wired

and

wireless

network

require

different

techniques

to

achieve

reliability

and

flow

control


TCP

works

is

unsuitable

for

wireless

network

as

it

interprets

errors

packets

loss

Dr. R. B. Patel

43

Continued


ITCP

(split/indirect

TCP)

splits

TCP

into

two

parts


One

between

sender

and

local

MSS

of

the

recipient


The

other

between

local

MSS

and

recipient


If

MH

switches

cell

during

lifetime

of

a

ITCP

connection

center

point

of

connection

moves

to

new

MSS

sender

remains

completely

unaware

about

it


Dr. R. B. Patel

44

Continued



Disconnection/weak

connection

support

is

important


CODA

file

system

provides

support

for

this


It

is

implemented

as

client

side

cache

management

system


The

issue

concerns

making

a

file

system

highly

available

while

maintaining

consistency


Caching

in

mobile

environment

is

quite

different
.

MSS

cannot

keep

state

information

(due

to

scale)

for

all

clients
.

So

invalidation

by

notification

Dr. R. B. Patel

45

Continued



Categories

of

information

dissemination

1.
Wide

area

services



such

as

stock

quotes

on

national

scale

2.
Macro

services
-

such

weather

on

a

regional

scale

3.
Micro

services
-

traffic

condition

is

an

immediate

vicinity


Can

be

extend

to

even

picocells



such

finding

a

parking

slot

Dr. R. B. Patel

46

Continued


Proving

services

will

require

addressing

of

following

new

issues




Interoperability

and

adaptability

to

network

environments

ranging

from

high

to

low

bandwidths

and

infrared

communication

links


Energy

efficient

data

access


Support

for

mobility

and

disconnection


Support

for

active

services,

triggers

(even

notification),

and

periodic

data

delivery
.


Dr. R. B. Patel

47

Continued



Two

modes

of

information

dissemination

are


1.
Publish

2.
Provide

on

demand


Publish

data

is

filtered

by

client

and

server

provides

directory

information

for

assisting

the

filtering


Advantages

of

information

dissemination

by

publishing

are


Hot

spots

can

be

broadcast

frequently
-
which

saves

energy

at

client,

avoid

congestion


Directory

helps

client

to

tune

in

selectively


Dr. R. B. Patel

48

Continued



Handoff

management



an

MH

moves

from

one

cell

to

another

while

being

connected



Desirable

features

are


Probability

of

call

dropping

is

minimized


Ping
-
pong

handoffs

avoided


Interruption

is

minimized

Dr. R. B. Patel

49

Mobile

Computing

Models


The

following

models

of

computing

in

the

mobile

environment

are

currently

being

researched

and

investigated
:


Client/Server


Client/Proxy/server


Disconnected

Operation


Mobile

Agents


The

Thin

Client

Model