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 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.
2G technologies can be divided into TDMA-based and CDMA-based standards depending on the type of multiplexing used.
GSM (TDMA-based), originally from Europe but used in almost all countries on all six inhabited continents
http://en.wikipedia.org/wiki/2G
From: WIKI
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 (IMT-2000) specifications by theInternational Telecommunication Union.[1] Application services include wide-area wireless voice telephone, mobile Internet access, video calls and mobile TV, all in a mobile environment.
http://en.wikipedia.org/wiki/3G
From: WIKI
4G
指的是移動電話系統第四代，也是3G之後的延伸
從營運商的角度看，除了與現有網路的可兼容性外，4G要有更高的數據吞吐量、更低時延、更低的建設和運行維護成本、更高的鑒權能力和安全能力、支持多種QoS等級。
4G意味著更多的參與方，更多技術、行業、應用的融合，不再局限於電信行業，還可以應用於金融、醫療、教育、交通等行業；通訊終端能做更多的事情
http://zh.wikipedia.org/wiki/4G
From: WIKI
In telecommunications, 4G is the fourth generation of cellular wireless standards. It is a successor of the 3G and 2G families of standards. In 2009, the ITU-R organization specified the IMT-Advanced (International Mobile Telecommunications Advanced) requirements for 4G standards, setting peak speed requirements for 4G service at 100 Mbit/s for high mobility communication (such as from trains and cars) and 1 Gbit/s for low mobility communication (such as pedestrians and stationary users).[1]
http://en.wikipedia.org/wiki/4G
From: WIKI
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From: WIKI
In telecommunications, 4G is the fourth generation of cellular wireless standards. It is a successor of the 3G and 2G families of standards. In 2009, the ITU-R organization specified the IMT-Advanced (International Mobile Telecommunications Advanced) requirements for 4G standards, setting peak speed requirements for 4G service at 100 Mbit/s for high mobility communication (such as from trains and cars) and 1 Gbit/s for low mobility communication (such as pedestrians and stationary users).[1]
http://en.wikipedia.org/wiki/4G
From: WIKI
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