CSE-302: Mobile Computing

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