2G

2G

Discussion
Ask a question about '2G'
Start a new discussion about '2G'
Answer questions from other users
Full Discussion Forum
 
Encyclopedia
2G is short for second-generation wireless
Wireless
Wireless telecommunications is the transfer of information between two or more points that are not physically connected. Distances can be short, such as a few meters for television remote control, or as far as thousands or even millions of kilometers for deep-space radio communications...

 telephone
Telephone
The telephone , colloquially referred to as a phone, is a telecommunications device that transmits and receives sounds, usually the human voice. Telephones are a point-to-point communication system whose most basic function is to allow two people separated by large distances to talk to each other...

 technology
Technology
Technology is the making, usage, and knowledge of tools, machines, techniques, crafts, systems or methods of organization in order to solve a problem or perform a specific function. It can also refer to the collection of such tools, machinery, and procedures. The word technology comes ;...

. Second generation 2G cellular telecom networks were commercially launched on the GSM standard in Finland
Finland
Finland , officially the Republic of Finland, is a Nordic country situated in the Fennoscandian region of Northern Europe. It is bordered by Sweden in the west, Norway in the north and Russia in the east, while Estonia lies to its south across the Gulf of Finland.Around 5.4 million people reside...

 by Radiolinja
Radiolinja
Radiolinja was a Finnish GSM operator founded on September 19, 1988. On March 27, 1991, the world's first GSM phone call was made on Radiolinja's network...

 (now part of Elisa Oyj
Elisa Oyj
Elisa Oyj is a Finnish telecommunications company founded in 1882 that was known until July 2000 as HPY. Elisa Oyj employs about 3000 people and in 2007 had revenue of about €1.57 billion...

) 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
SMS
SMS is a form of text messaging communication on phones and mobile phones. The terms SMS or sms may also refer to:- Computer hardware :...

 text messages.

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

. While radio signals on 1G networks are analog
Analog signal
An analog or analogue signal is any continuous signal for which the time varying feature of the signal is a representation of some other time varying quantity, i.e., analogous to another time varying signal. It differs from a digital signal in terms of small fluctuations in the signal which are...

, radio signals on 2G networks are digital
Digital
A digital system is a data technology that uses discrete values. By contrast, non-digital systems use a continuous range of values to represent information...

. Both systems use digital signaling to connect the radio towers (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
3G
3G or 3rd generation mobile telecommunications is a generation of standards for mobile phones and mobile telecommunication services fulfilling the International Mobile Telecommunications-2000 specifications by the International Telecommunication Union...

, and 4G
4G
In telecommunications, 4G is the fourth generation of cellular wireless standards. It is a successor to the 3G and 2G families of standards. In 2009, the ITU-R organization specified the IMT-Advanced requirements for 4G standards, setting peak speed requirements for 4G service at 100 Mbit/s...

; however, 2G networks are still used in many parts of the world.

2G technologies


2G technologies can be divided into TDMA
Time division multiple access
Time division multiple access is a channel access method for shared medium networks. It allows several users to share the same frequency channel by dividing the signal into different time slots. The users transmit in rapid succession, one after the other, each using its own time slot. This...

-based and CDMA
Code division multiple access
Code division multiple access is a channel access method used by various radio communication technologies. It should not be confused with the mobile phone standards called cdmaOne, CDMA2000 and WCDMA , which are often referred to as simply CDMA, and use CDMA as an underlying channel access...

-based standards depending on the type of multiplexing
Multiplexing
The multiplexed signal is transmitted over a communication channel, which may be a physical transmission medium. The multiplexing divides the capacity of the low-level communication channel into several higher-level logical channels, one for each message signal or data stream to be transferred...

 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
    CDMA2000
    CDMA2000 is a family of 3G mobile technology standards, which use CDMA channel access, to send voice, data, and signaling data between mobile phones and cell sites. The set of standards includes: CDMA2000 1X, CDMA2000 EV-DO Rev. 0, CDMA2000 EV-DO Rev. A, and CDMA2000 EV-DO Rev. B...

     in the 450 MHz frequency band (CDMA450).
  • IS-95
    IS-95
    Interim Standard 95 is the first CDMA-based digital cellular standard by Qualcomm. The brand name for IS-95 is cdmaOne. IS-95 is also known as TIA-EIA-95....

     aka cdmaOne
    IS-95
    Interim Standard 95 is the first CDMA-based digital cellular standard by Qualcomm. The brand name for IS-95 is cdmaOne. IS-95 is also known as TIA-EIA-95....

     (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
    Personal Digital Cellular
    Personal Digital Cellular is a 2G mobile telecommunications standard developed and used exclusively in Japan.After a peak of nearly 80 million subscribers to PDC, it had 46 million subscribers in December 2005, and is slowly being phased out in favor of 3G technologies like W-CDMA and CDMA2000...

     (TDMA-based), used exclusively in Japan
  • iDEN
    Iden
    For other uses of the word, see Iden The Iden was an English automobile manufactured from 1904 until 1907. Designed by George Iden, formerly of Daimler, they were four-cylinder 10/17 hp and 25/35 hp shaft-driven cars; each came with "Idens's frictionless radial gearbox"....

     (TDMA-based), proprietary network used by Nextel in the United States
    United States
    The United States of America is a federal constitutional republic comprising fifty states and a federal district...

     and Telus Mobility
    Telus Mobility
    Telus Mobility is a division of Telus Communications which sells wireless services in Canada on its numerous networks. They currently have three different networks based on three different technologies: CDMA and HSPA+ on its mainstream networks, plus iDEN via its Mike division...

     in Canada
    Canada
    Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...

  • 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
Personal Communications Service
At the most basic level Personal Communications Service or PCS describes a set of wireless communications capabilities that allows some combination of terminal mobility, personal mobility, and service profile management...

, or PCS, in the United States.

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 codec
    Codec
    A codec is a device or computer program capable of encoding or decoding a digital data stream or signal. The word codec is a portmanteau of "compressor-decompressor" or, more commonly, "coder-decoder"...

    s, allowing more calls to be packed into the same amount of radio bandwidth
    Bandwidth (computing)
    In computer networking and computer science, bandwidth, network bandwidth, data bandwidth, or digital bandwidth is a measure of available or consumed data communication resources expressed in bits/second or multiples of it .Note that in textbooks on wireless communications, modem data transmission,...

    .
  • The digital systems were designed to emit less radio power from the handsets. This meant that cell
    Cellular network
    A cellular network is a radio network distributed over land areas called cells, each served by at least one fixed-location transceiver known as a cell site or base station. When joined together these cells provide radio coverage over a wide geographic area...

    s could be smaller, so more cells could be placed in the same amount of space. This was also made possible by cell towers and related equipment getting less expensive.

Advantages

  • The lower power emissions helped address health concerns.
  • Going all-digital allowed for the introduction of digital data services, such as SMS and email
    Email
    Electronic mail, commonly known as email or e-mail, is a method of exchanging digital messages from an author to one or more recipients. Modern email operates across the Internet or other computer networks. Some early email systems required that the author and the recipient both be online at the...

    .
  • Greatly reduced fraud
    Fraud
    In criminal law, a fraud is an intentional deception made for personal gain or to damage another individual; the related adjective is fraudulent. The specific legal definition varies by legal jurisdiction. Fraud is a crime, and also a civil law violation...

    . With analog systems it was possible to have two or more "cloned
    Phone cloning
    -Technique:Phone cloning involves placing a computer chip into the target mobile telephone, allowing the electronic serial number of the mobile phone to be modified. The ESN is normally transmitted to the cellular company in order to ascertain whether the mobile phone user is the legitimate owner...

    " handsets that had the same phone number.
  • Enhanced privacy. A key digital advantage not often mentioned is that digital cellular calls are much harder to eavesdrop
    Eavesdropping
    Eavesdropping is the act of secretly listening to the private conversation of others without their consent, as defined by Black's Law Dictionary...

     on by use of radio scanners. While the security algorithms used have proved not to be as secure as initially advertised, 2G phones are immensely more private than 1G phones, which have no protection against eavesdropping.

Disadvantages

  • In less populous areas, the weaker digital signal 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.
  • Analog has a smooth decay curve, digital 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
    Dropout (electronics)
    Dropout within the realm of electronics and electrical engineering, has a number of uses.It is the dropping away of a flake of magnetic material from magnetic tape, leading to loss of signal, or a failure to properly read a binary character from data storage...

    . 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 a few words to get through.
  • While digital calls tend to be free of static
    Static
    Static has several meanings:* Static electricity, a net charge of an object** The triboelectric effect, e.g. from shoes rubbing carpet* White noise, a random signal with a flat power spectral density** Noise , a type of radio interference...

     and background noise
    Background noise
    In acoustics and specifically in acoustical engineering, background noise or ambient noise is any sound other than the sound being monitored. Background noise is a form of noise pollution or interference. Background noise is an important concept in setting noise regulations...

    , the lossy compression used by the codecs takes a toll; the range of sound that they convey is reduced. You will hear less of the tonality of someone's voice talking on a digital cellphone, but you will hear it more clearly.

Evolution


2G networks were built mainly for voice services and slow data transmission.

Some protocols, such as EDGE for GSM and 1x-RTT for CDMA2000, are defined as "3G" services (because they are defined in IMT-2000 specification documents), but are considered by the general public to be 2.5G or 2.75G services because they are several times slower than present-day 3G services.

2.5G (GPRS)


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 capabilities came to be known as 2.5G.

GPRS could provide data rates from 56 kbit/s up to 115 kbit/s. It can be used for services such as Wireless Application Protocol
Wireless Application Protocol
Wireless Application Protocol is a technical standard for accessing information over a mobile wireless network.A WAP browser is a web browser for mobile devices such as mobile phones that uses the protocol.Before the introduction of WAP, mobile service providers had limited opportunities to offer...

 (WAP) access, Multimedia Messaging Service (MMS), and for Internet communication services such as email and World Wide Web access. GPRS data transfer is typically charged per megabyte of traffic transferred, while data communication via traditional circuit switching is billed 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. It can also be used for WAP, SMS & MMS services, as well as Internet access.

2.75G (EDGE)


GPRS1 networks evolved to EDGE
Edge
- Aviation :* Leading edge, a line connecting the forward-most points of a wing's profile* Trailing edge, the rear edge of the wing* Zivko Edge 540, an aerobatic aircraft- Mathematics, science and technology :...

 networks with the introduction of 8PSK encoding. Enhanced Data rates for GSM Evolution (EDGE
Edge
- Aviation :* Leading edge, a line connecting the forward-most points of a wing's profile* Trailing edge, the rear edge of the wing* Zivko Edge 540, an aerobatic aircraft- Mathematics, science and technology :...

), Enhanced GPRS (EGPRS), or IMT Single Carrier (IMT-SC) is a backward-compatible digital mobile phone technology that allows improved data transmission rates, as an extension on top of standard GSM. EDGE was deployed on GSM networks beginning in 2003—initially by Cingular (now AT&T) in the 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. The specification achieves higher data-rates (up to 236.8 kbit/s) by switching to more sophisticated methods of coding (8PSK), within existing GSM timeslots.

See also

  • Mobile radio telephone, also known as 0G
  • 1G
    1G
    1G 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...

  • 3G
    3G
    3G or 3rd generation mobile telecommunications is a generation of standards for mobile phones and mobile telecommunication services fulfilling the International Mobile Telecommunications-2000 specifications by the International Telecommunication Union...

  • 4G
    4G
    In telecommunications, 4G is the fourth generation of cellular wireless standards. It is a successor to the 3G and 2G families of standards. In 2009, the ITU-R organization specified the IMT-Advanced requirements for 4G standards, setting peak speed requirements for 4G service at 100 Mbit/s...

  • 2G spectrum scam
    2G spectrum scam
    The 2G spectrum scandal involved officials in the government of India illegally undercharging mobile telephony companies for frequency allocation licenses, which they would use to create 2G subscriptions for cell phones...

    , India