Mobile and Wireless Computing - Computer Science - University of ...

inexpensivebossesΚινητά – Ασύρματες Τεχνολογίες

12 Νοε 2013 (πριν από 3 χρόνια και 8 μήνες)

69 εμφανίσεις

Mobile And
Wireless
Computing

Dr. Michael Katchabaw

The University of Western Ontario

Department of Computer Science

Outline


Introduction


Motivating Factors


Mobile and Wireless Technology


Problems and Issues


Wireless at Western


Concluding Remarks

Introduction


Wireless communication systems

have existed for over 100 years now.


It all began with Marconi’s wireless

telegraph in 1896.


In modern times, it has grown to

include satellite, cellular, and a

variety of wireless local area

networking (LAN) technologies.

Introduction


Growth in the past 10 years in

particular has been phenomenal.


In cellular networks alone, subscribers

have increased from 34 million in 1993

to more than 1 billion in 2003.


There are now more subscribers

to cellular networks than to

wired telephone networks!

Introduction


Wireless LAN adoption has been

staggering as well.


It is estimated there are now 100,000

wireless hot spots with public access

in the U.S. alone, and rapidly growing.


Not to mention all of the private

home, corporate, and

institutional networks!

Introduction


Why is there such a push towards

wireless and mobile technologies?


What are the different wireless

and mobile technologies?


What problems/issues are there?


We will answer all of these

questions very shortly!

Motivating Factors


Wireless users are free to be

relatively mobile.


Wireless service basically allows

anywhere, anytime computing and

communications, which is a very

attractive feature to some.

Motivating Factors


Wireless users are able to join

and leave wireless networks

relatively easily.


There is no physical point of

connection or cabling required,

which makes this attractive for

public network access.

Motivating Factors


Wireless service can be deployed

almost anywhere in the world.


Wired service can be quite difficult

to roll out in some parts of the world,

if not impossible.


Wireless service depends on less

physical infrastructure, and

can target remote areas.

Motivating Factors


Wireless service can be deployed

more quickly and cheaply than

wired service in most cases.


No cabling or other physical

infrastructure required with wireless.


All you need is a wireless

interface, and you can be on

the network in no time.

Mobile and Wireless

Technology


There are a wide variety of mobile

and wireless technologies used

in the world today.


In the end, there are two main

types of wireless networks.

Mobile and Wireless

Technology


Satellite
-
based networks:


A satellite
-
based antennae in a stable

orbit above the Earth relays

communications between two or more

stations on or near the Earth.


Common types include low earth

orbit, medium earth orbit, and

geostationary configurations.

Mobile and Wireless

Technology


Satellite
-
based networks:


Huge coverage areas.


Very high data rates possible.


Can have enormous deployment costs.


Delays in signal propagation due to

the distance it must travel.


Quality of transmission decent.

Mobile and Wireless

Technology


Terrestrial networks:


All network devices and users are

located on Earth.


There tend to be two main kinds of

terrestrial wireless networks: wide

area networks (cellular networks)

and local area networks

(802.11, Bluetooth, and so on).

Mobile and Wireless

Technology


Terrestrial networks:


Coverage areas relatively small.


Data rates vary with the technology.


Deployment costs vary, but usually

much cheaper than satellite networks.


Propagation delays negligible.


Interference can be common.

Mobile and Wireless

Technology


Wireless wide area networks:


Mobile users communicate through

a base station managed by a service

provider and within tens of kilometers.


Global access is provided through the

wireless network, usually as an

add
-
on service provided by the
telecommunications provider.

Mobile and Wireless

Technology


Wireless wide area networks:


1G: Analog, for voice only. (FDMA)


2G: Digital, voice. (TDMA, GSM, CDMA)


2.5G: Digital, data service built on

existing 2G services. (GPRS, EDGE)


3G: Digital, higher speed data

and voice (UMTS, CDMA
-
2000)


4G: Next generation?

Mobile and Wireless

Technology


Wireless local area networks:


Mobile users communicate directly

with each other (ad hoc mode) or

indirectly through an access point

within a few tens of metres.


Global access is provided by a

wired connection from the

access point.

Mobile and Wireless

Technology


Wireless local area networks:


IEEE 802.11 standards (802.11a,

802.11b, 802.11g, etc.) for true

wireless local area network access.


Bluetooth for lower power, shorter

range personal area network

access (in other words, it is a

desktop cable replacement).

Problems and Issues


Wireless networks may be cheaper

to deploy in some cases, but they

can also incur usage fees.


Cellular service is still NOT cheap!

Problems and Issues


Wireless networks tend to have

more security problems.


Most people and organizations do not

secure their private wireless networks!


Many wireless security protocols

(WEP) are seriously flawed,

even if they were used.

Problems and Issues


Wireless networks do not support

the same high speed data rates as

wired networks with the same

reliability and robustness.


Wireless broadband is not here (yet).


Problems of interference, signal

strength, and multipath issues.

Problems and Issues


Too many incompatible standards.


Technology is moving forward. (Great!)


Each new technology is incompatible

with previous technologies, and with

each other. (Bad!)


Older technologies going obsolete

really fast. (Very bad!)

Problems and Issues


Mobile devices often have software

and hardware limitations.


Screens too small. (If they get too

big, they’re not mobile!)


Slower processors, less memory,

and so on.


We can’t always do everything

we want to with them.

Wireless at Western


The University of Western Ontario

was one of the first universities in

Canada to roll out wireless access.


Available to all students, faculty, and

staff in many areas of campus.


Provides wireless LAN access

using the 802.11b standard.

Wireless at Western


Many interesting issues in this:


The large number of potential users

of the network (30,000+).


The extremely large area to cover.


Potentially sensitive areas where

radio signals must be blocked.


Lots of sources of interference

and signal blocking.

Wireless at Western


Security has also been an issue:


The overly simplistic WEP method was

of little use in this setting.


Account names and passwords were

used to restrict access initially,

without any encryption in place.


An encrypted service is now

being rolled out (802.11x).

Wireless at Western


Wireless technology is used in a few

courses in Western’s Department of
Computer Science.


Advanced topics in networking

develops software for mobile phones.


Video games development builds

games for Java enabled mobile

phones and game systems.

Wireless at Western


Western Computer Science also has

many research projects in mobile

and wireless computing.


Performance and benchmarking

of mobile and wireless devices.


Pervasive computing.


Development of wireless

communications protocols.

Concluding Remarks


Wireless and mobile technologies

will continue to revolutionize

computing and communication.


Since these technologies are still

relatively immature, there will be

challenges for some time to come.


The future will be quite interesting!