20-03-2017, 04:40 PM
2G (or 2-G) is the abbreviation of second generation wireless telephony technology. Second generation 2G cellular telecommunications networks were commercially launched by Radiolinja (now part of Elisa Oyj) in Finland by the GSM standard in 1991. Three main benefits of 2G networks over their predecessors were that telephone conversations were digitally encrypted; 2G systems were significantly more efficient in the spectrum allowing penetration levels of much larger mobile phones; And 2G introduced mobile data services, starting with SMS text messages. 2G technologies enabled different mobile phone networks to provide services such as text messaging, picture messaging and MMS (multimedia messaging). All text messages sent over 2G are digitally encrypted, allowing the transfer of data in such a way that only the receiving recipient can receive and read it. After 2G was launched, the previous mobile phone systems retroactively folded 1G. While the radio signals in 1G networks are analog, the radio signals in 2G networks are digital. Both systems use digital signage to connect radio towers (listening to headphones) to the rest of the telephone system. 2G has been replaced by new technologies like 2.5G, 2.75G, 3G and 4G; However, 2G networks are still used in most of the world.
2G Technologies
2G technologies can be divided into time division multiple access (TDMA) and code division multiple access (CDMA) standards based on the type of multiplexing used. The main 2G standards are:
• GSM (based on TDMA), originally from Europe but used in most of the world outside of North America. More than 60 GSM operators were also using CDMA2000 in the 450 MHz (CDMA450) frequency band in 2010.
• IS-95 also known as cdmaOne (CDMA-based, commonly referred to simply as CDMA in the US), used in the Americas and parts of Asia, accounted for about 17% of all global subscribers. [Citation needed] More than a dozen CDMA operators have migrated to GSM, including operators in Mexico, India and Australia.
• PDC also known as JDC (Japanese Digital Cellular) (based on TDMA), used exclusively in Japan
• The iDEN (TDMA-based) proprietary network used by Nextel in the United States and Telus Mobility in Canada
• IS-136 a.k.a. Digital AMPS or D-AMPS (based on TDMA, commonly referred to simply as "TDMA" in the United States) were once predominant in the Americas, but most have migrated to GSM.
2G services are often referred to as Personal Communications Service, or PCS, in the United States.