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2GFrom Wikipedia, the free encyclopedia

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 Radiolinja (now part of Elisa

Oyj) in 1991.[1]Three primarybenefits 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 greatermobile phone penetration levels; and 2G introduced data services for mobile, starting with SMS text messages.

2G network allows for much greater penetration intensity. 2G technologies enabled the variousmobile phone

networks to provide the services such as text messages, picture messages and MMS (multi media messages).

All text messages sent over 2G are digitally encrypted, allowing for the transfer of data in such a way that only

the intended receiver can receive and read it.

After 2G was launched, the previous mobile telephone systems were retrospectively dubbed 1G. While radio

signals on 1G networks are analog, radio signals on 2G networks are digital. Both systems use digital signaling

to connectthe radiotowers (which listen to the handsets) to the rest of the telephone system.

2G has been superseded by newer technologies such as 2.5G, 2.75G, 3G, and 4G; however, 2G networks are

still used in many parts of theworld.

Contents

1 2G technologies

2 Capacities, advantages, and disadvantages

2.1 Capacity

2.2 Disadvantages

2.3 Advantage

3 Evolution

3.1 2.5G (GPRS)

3.2 2.75G (EDGE)

4 See also

5 References

2Gtechnologies

2G technologies can be divided into Time Division Multiple Access (TDMA)-based and Code Division Multiple

Access (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. 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).[2]

IS-95 akacdmaOne (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 dozenCDMA operators have migrated to GSM including operators in Mexico, India, Australia and South

Korea.

PDC (TDMA-based), used exclusively in Japan
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iDEN (TDMA-based), proprietary network used by Nextel in the United States and Telus Mobility in

Canada

IS-136 a.k.a. 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.

Capacities, advantages, and disadvantages

Capacity

Using digital signals between the handsets and the towers increases system capacity in two key ways:

Digital voice data can be compressed and multiplexed much more effectively than analog voice encodings

through the use of various codecs, allowing more calls to be transmitted in same amount of radio

bandwidth.

The digital systems were designed to emit less radio power from the handsets. This meant that cells hadto be smaller, so more cells had to be placed in the same amount of space. This was possible because

cell towers and related equipment had become less expensive.

Disadvantages

In less populous areas, the weaker digital signal transmitted by a cellular phone may not be sufficient to

reach a cell tower. This tends to be a particular problem on 2G systems deployed on higher frequencies,

but is mostly not a problem on 2G systems deployed on lower frequencies. National regulations differ

greatly among countries which dictate where 2G can be deployed.

A general rule can be applied to make it sound simple. " Frequency is inversely proportional to wavelength ".

Analog has a smooth decay curve, but digital has a jagged steppy one. This can be both an advantage

and a disadvantage. Under good conditions, digital will sound better. Under slightly worse conditions,

analog will experience static, while digital has occasional dropouts. As conditions worsen, though, digital

will start to completely fail, by dropping calls or being unintelligible, while analog slowly gets worse,

generally holding a call longer and allowing at least some of the audio transmitted to be understood.

Advantage

While digital calls tend to be free of static and background noise, the lossy compression they use reduces

their quality, meaning that the range of sound that they convey is reduced. Talking on a digital cell phone,

a caller hears less of the tonality of someone's voice.[citation needed]

Evolution

2G networks were built mainly for voice services and slow data transmission (defined in IMT-2000 specification

documents), but are considered by the general public to be 2.5G or 2.75G services because they are severaltimes slower than present-day 3G service.

2.5G (GPRS)
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2.5G("second and a half generation") is used to describe 2G-systems that have implemented a packet-

switched domain in addition to the circuit-switched domain. It does not necessarily provide faster services

because bundling of timeslots is used for circuit-switched data services (HSCSD) as well. The first major step in

the evolution of GSM networks to 3G occurred with the introduction of General Packet Radio Service (GPRS).

CDMA2000 networks similarly evolved through the introduction of 1xRTT. The combination of these

capabilitiescame to be known as 2.5G. GPRS could provide data rates from 56 kbit/s up to 115 kbit/s. It can

be used forservices such as Wireless Application Protocol (WAP) access, Multimedia Messaging Service

(MMS), and for Internet communication services such as email and World Wide Web access. GPRS datatransfer is typically charged per megabyte of traffic transferred, while data communication via traditional circuit

switching isbilled per minute of connection time, independent of whether the user actually is utilizing the capacity

or is in an idle state. 1xRTT supports bi-directional (up and downlink) peak data rates up to 153.6 kbit/s,

delivering an average user data throughput of 80-100 kbit/s in commercial networks.[3]It can also be used for

WAP, SMS & MMS services, as well as Internet access.

2.75G (EDGE)

GPRS1 networks evolved to EDGE networks with the introduction of 8PSK encoding. Enhanced Data rates

for GSM Evolution (EDGE), Enhanced GPRS (EGPRS), or IMT Single Carrier (IMT-SC) is a backward-compatibledigital mobile phone technology that allows improved data transmission rates, as an extension on top

of standardGSM. EDGE was deployed on GSM networks beginning in 2003initially by Cingular (now

AT&T) inthe United States.

EDGE is standardized by 3GPP as part of the GSM family and it is an upgrade that provides a potential three-

fold increase in capacity of GSM/GPRS networks.

See also

Mobile radio telephone, also known as 0G

1G

3G

4G

2Gspectrum scam, India

References

1. ^"Radiolinja's History" (http://www.elisa.com/english/index.cfm?t=6&o=6532.50). April 20, 2004. Retrieved

December 23, 2009.

2. ^"CDMA Worldwide" (http://www.cdg.org/worldwide/index.asp?

h_area=0&h_technology=999&h_frequency=1). Archived

(http://web.archive.org/web/20100130085408/http://www.cdg.org/worldwide/index.asp?

h_area=0&h_technology=999&h_frequency=1) from the original on 30 January 2010. Retrieved December 23,

2009.

3. ^"CDMA2000 1X" (http://www.cdg.org/technology/cdma20001x.asp). CDG.org. CDMA Development

Group. Archived

(http://web.archive.org/web/20110725231556/http://www.cdg.org/technology/cdma20001x.asp) from the

original on 25 July 2011. Retrieved July 31, 2011.
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Preceded by

1st Generation (1G)

Mobile Telephony

Generations

Succeeded by

3rd Generation (3G)

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Categories: Software-defined radio Mobile telecommunications

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