NEED FOR WIRELESS COMMUNICATION

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12 Δεκ 2013 (πριν από 3 χρόνια και 11 μήνες)

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INTRODUCTION


NEED FOR WIRELESS COMMUNICATION


DIFFERENCE BETWEEN WIRELESS AND CORDLESS
COMMUNICATON


EARLIER DEVELOPMENTS


GENERATIONS OF THE WIRELESS COMMUNICATION


FIRST GENERATION(1G)


SECOND GENERATION(2G)

o
2G TECHNOLOGIES


THIRD GENERATION(3G)

o
3G TECHNOLOGIES

o
FUTURE GENERATION(4G)


APPLICATIONS AND FUTURE ASPECTS





Wireless communication

is the transfer of information over a
distance without the use of enhanced electrical conductors or
"wires
".

The distances involved may be short (a few meters as in
television remote control) or long (thousands or millions of kilometers
for radio communications). When the context is clear, the term is often
shortened to "wireless". Wireless communication is generally
considered to be a branch of

telecommunications.

It encompasses various types of fixed, mobile, and portable

two
-
way
radios,

cellular telephones,

personal digital assistants

(PDAs),
and

wireless networking. Other examples of

wireless
technology

include

GPS

units,

garage door openers and or garage doors,
wireless

computer mice,

keyboards

and

headsets,

satellite
television

and cordless

telephones.

Wireless networking

(i.e. the various types of unlicensed 2.4

GHz
Wi
-
Fi
devices) is used to meet many needs. Perhaps the most common use is
to connect laptop users who travel from location to location. Another
common use is for mobile networks that connect via satellite. A wireless
transmission method is a logical choice to network a LAN segment that
must frequently change locations. The following situations justify the
use of wireless technology:

To span a distance beyond the capabilities of typical cabling,

To provide a backup communications link in case of normal network
failure,

To link portable or temporary workstations,

To overcome situations where normal cabling is difficult or financially
impractical, or

To remotely connect mobile users or networks.

The term "wireless" should not be confused with the term
"cordless", which is generally used to refer to powered electrical or
electronic devices that are able to operate from a portable power
source (e.g. a battery pack) without any cable or cord to limit the
mobility of the cordless device through a connection to the mains
power supply. Some cordless devices, such as cordless telephones,
are also wireless in the sense that information is transferred from
the cordless telephone to the telephone's base unit via some type
of wireless

communications link. This has caused some disparity
in the usage of the term "cordless", for example in

Digital
Enhanced Cordless Telecommunications.

In the last fifty years, wireless communications industry
experienced drastic changes driven by many technology
innovations.

The term "wireless" came into public use to refer to a radio receiver or

transceiver

(a dual
purpose receiver and transmitter device), establishing its usage in the field of wireless
telegraphy early on; now the term is used to describe modern wireless connections such as in
cellular networks and wireless broadband Internet. It is also used in a general sense to refer to
any type of operation that is implemented without the use of wires, such as "wireless remote
control" or "wireless energy transfer", regardless of the specific technology
(e.g.

radio,

infrared,ultrasonic) that is used to accomplish the operation. While

Guglielmo
Marconi

and

Karl Ferdinand Braun

were awarded the 1909

Nobel Prize for Physics

for their
contribution to wireless telegraphy.

In 1885,

T. A. Edison

used a vibrator magnet for induction transmission. In 1888, Edison
deployed a system of signaling on the Lehigh Valley Railroad. In 1891, Edison obtained the
wireless patent for this method using inductance (U.S. Patent 465,971).

In the

history of wireless technology
, the demonstration of the theory of

electromagnetic
waves

by

Heinrich Hertz

in 1888 was important
.

The theory of electromagnetic waves was
predicted from the research of

James Clerk Maxwell

and

Michael Faraday. Hertz demonstrated
that electromagnetic waves could be

transmitted

and caused to travel through space at straight
lines and that they were able to be

received

by an experimental apparatus
.

The experiments were
not followed up by Hertz.

Jagadish Chandra Bose

around this time developed an early wireless
detection device and help increase the knowledge of millimeter length electromagnetic
waves.
Practical applications of wireless radio communication and radio remote control technology
were implemented by later inventors, such as

Nikola Tesla.

1G

(or 1
-
G) refers to the first
-
generation
of

wireless

telephone

technology,

mobile

telecommunications. These are
the

analog

telecommunications standards that were introduced in the 1980s and
continued until being replaced by

2G

digital

telecommunications. The main difference
between two succeeding mobile telephone systems, 1G and

2G, is that the radio signals
that 1G networks use are analog, while 2G networks are digital.

Although both systems use digital signaling to connect the radio towers (which listen to
the handsets) to the rest of the telephone system, the voice itself during a call is encoded
to digital signals in 2G whereas 1G is only modulated to higher frequency, typically
150

MHz and up.

One such standard is

NMT

(Nordic Mobile Telephone), used in

Nordic
countries,

Switzerland,

Netherlands,

Eastern Europe

and

Russia. Others
include

AMPS

(Advanced Mobile Phone System) used in the

United
States

and

Australia,

TACS

(Total Access Communications System) in the

United
Kingdom,

C
-
450

in

West Germany,

Portugal

and

South Africa
, Radiocom
2000

in

France, and

RTMI

in

Italy. In Japan there were multiple systems. Three
standards, TZ
-
801, TZ
-
802, and TZ
-
803 were developed by NTT, while a competing
system operated by DDI used the JTACS (Japan Total Access Communications System)
standard.

Antecedent to 1G technology is the

mobile radio telephone, or

0G

2G

(or 2
-
G) is short for second
-
generation

wireless

telephone

technology. Second
generation 2G cellular telecom networks were commercially launched on
the

GSM

standard in

Finland by

Radio linja

(now part of

Elisa Oyj) in 1991. Three
primary benefits of 2G networks over their predecessors were that phone conversations
were

digitally encrypted,

2G systems were significantly more efficient on the
spectrum allowing for far greater mobile phone penetration levels; and 2G introduced
data services for mobile, starting with SMS text messages.

After 2G was launched, the previous mobile telephone systems were retrospectively
dubbed

1G. While radio signals on 1G networks are

analog, and on 2G networks
are

digital, both systems use digital signaling to connect the radio towers (which listen
to the handsets) to the rest of the telephone system.

2G technologies can be divided into

TDMA
-
based and

CDMA
-
based standards
depending on the type of

multiplexing

used. The main 2G standards are:

GSM

(TDMA
-
based), originally from Europe but used in almost all countries on all six
inhabited continents (Time Division Multiple Access). Today accounts for over 80% of
all subscribers around the world. Over 60 GSM operators are also using

CDMA2000

in
the 450 MHz frequency band (CDMA450
).

IS
-
95

aka

cdmaOne

(CDMA
-
based, commonly referred as simply

CDMA

in the US),
used in the Americas and parts of Asia. Today accounts for about 17% of all subscribers
globally. Over a dozen CDMA operators have migrated to GSM including operators in
Mexico, India, Australia and South Korea.

PDC

(TDMA
-
based), used exclusively in Japan

iDEN

(TDMA
-
based), proprietary network used by

Nextel

in the

United
States

and

Telus Mobility

in

Canada

IS
-
136

aka

D
-
AMPS

(TDMA
-
based, commonly referred as simply 'TDMA' in the US), was
once prevalent in the Americas but most have migrated to GSM.

2G services are frequently referred as

Personal Communications Service, or PCS, in the
United States.

2.5G

services enable high
-
speed data transfer over upgraded existing 2G networks.
Beyond 2G, there's

3G, with higher data speeds, and even evolutions beyond 3G, such
as

4G.

International Mobile Telecommunications
-
2000 (IMT
--
2000)
, better known
as

3G

or

3rd Generation
, is a generation of standards for

mobile
phones

and

mobile
telecommunications services
fulfilling specifications by
the

International Telecommunication Union
.

Application services include wide
-
area wireless voice

telephone,

mobile Internet

access,

video calls

and mobile
TV,
all in a mobile environment. Compared to the older

2G

and

2.5G

standards, a 3G
system must allow simultaneous use of speech and data services, and provide
peak data rates of at least 200

kbit/s

according to the IMT
-
2000 specification.
Recent 3G releases, often denoted

3.5G

and

3.75G, also provide

mobile
broadband

access of several

Mbit/s

to laptop computers and

smartphones.

The following standards are typically branded 3G:

the

UMTS

system, first offered in 2001, standardized by

3GPP, used primarily in
Europe, Japan, China (however with a different radio interface) and other regions
predominated
by GSM

2G

system infrastructure. The cell phones are typically
UMTS and GSM hybrids. The original and most widespread radio interface is
called

W
-
CDMA. The latest release
, HSPA
+, can provide peak data rates up to 56
Mbit/s in the downlink in theory (28 Mbit/s in existing services) and 22 Mbit/s in
the uplink.

the

CDMA2000

system, first offered in 2002, standardized by

3GPP2, used
especially in North America and South Korea, sharing infrastructure with the

IS
-
95

2G standard. The cell phones are typically CDMA2000 and IS
-
95 hybrids. The
latest release

EVDO

Rev B offers peak rates of 14.7 Mbit/s
downstream.

The above systems and radio interfaces are based on kindred

spread
spectrum

radio transmission technology. While the

GSM EDGE

standard
("2.9G"),

DECT

cordless phones
and Mobile
WiMAX

standards formally also
fulfill the IMT
-
2000 requirements and are approved as 3G standards by ITU,
these are typically not branded 3G, and are based on completely different
technologies.

4G

refers to the fourth generation of cellular wireless standards. It is a successor
to

3G

and

2G

families of standards. The nomenclature of the generations generally
refers to a change in the fundamental nature of the service, non
-
backwards
compatible transmission technology and new frequency bands. The first was the
move from 1981 analog (1G) to digital (2G) transmission in 1992. This was followed, in
2002, by 3G multi
-
media support,

spread spectrum

transmission and at least
200

kbit/s, soon expected to be followed by 4G, which refers to all
-
IP

packet
-
switched

networks, mobile ultra
-
broadband (gigabit speed) access and

multi
-
carrier

transmission
.

Pre
-
4G technologies such as

mobile WiMAX

and first
-
release
3G

Long term evolution

(LTE) have been available on the market since
2006

and
2009

respectively

A new generation of cellular standards has appeared approximately every tenth year
since

1G

systems were introduced in 1981/1982. Each generation is characterized by
new frequency bands, higher data rates and non backwards compatible transmission
technology.

4G

systems are expected to appear in 2011
-
2013 (pre
-
4G systems
like

LTE

and mobile WiMAX have already appeared), and

fifth generation

systems
after 2020. The first release of the

3GPP Long Term Evolution

(LTE) standard does
not completely fulfill the ITU 4G requirements called IMT
-
Advanced. First release
LTE is not backwards compatible with 3G, but is a pre
-
4G or

3.9G

technology,
however sometimes branded "4G" by the service providers.

Security systems

Wireless technology may supplement or replace hard wired implementations in
security systems for homes or office buildings.

Television
remote control

Modern televisions use wireless (generally infrared) remote control units. Now radio
waves are also used.

Cellular
telephone (phones and modems)

Perhaps the best known example of wireless technology is the

cellular
telephone

and

modems. These instruments use radio waves to enable the operator to
make phone calls from many locations worldwide. They can be used anywhere that
there is a cellular telephone site to house the equipment that is required to transmit
and receive the signal that is used to transfer both voice and data to and from these
instruments.

Wi
-
Fi

Wi
-
Fi is a wireless

local area network

that enables portable computing devices to
connect easily to the

Internet. Standardized as

IEEE 802.11

a,b,g,n, Wi
-
Fi approaches
speeds of some types of wired

Ethernet. Wi
-
Fi hot spots have been popular over the
past few years. Some businesses charge customers a monthly fee for service, while
others have begun offering it for free in an effort to increase the sales of their goods
.

Wireless energy
transfer

Wireless energy transfer is a process whereby electrical energy is transmitted from a
power source to an electrical load that does not have a built
-
in power source, without
the use of interconnecting wires.

Computer
Interface Devices

Answering the call of customers frustrated with cord clutter, many manufactures of
computer peripherals turned to wireless technology to satisfy their consumer base.
Originally these units used bulky, highly limited transceivers to mediate between a
computer and a keyboard and mouse, however more recent generations have used
small, high quality devices, some even incorporating

Bluetooth. These systems have
become so ubiquitous that some users have begun complaining about a lack of wired
peripherals
.

Wireless devices tend to have a slightly slower response time than their
wired counterparts, however the gap is decreasing. Initial concerns about the security
of wireless keyboards have also been addressed with the maturation of the
technology.

Many scientists have complained that wireless technology interferes with their
experiments, forcing them to use less optimal peripherals because the optimum one
is not available in a wired version
.

This has become especially prevalent among
scientists who use

trackballs

as the number of models in production steadily
decreases.