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Second generation wireless telephony technology (2G) refers to telecom network technologies that were launched on the Global System for Mobile Communications (GSM) standard in 1991 by Radiolinja in Finland.
The most notable upgrade of 2G over its predecessor is the digital encryption of telephone conversations, and considerably higher efficiency on the spectrum, which allows for greater penetration level for mobile phones. 2G also introduced mobile data services, beginning with SMS text messaging.
Second generation wireless is a set of standards made for mobile telecommunication which are maintained and described by the International Telecommunication Union (ITU). This technology uses CODEC (compression-decompression) algorithms to compress and multiplex voice data. Because of this technology, 2G can bundle more calls per amount of bandwidth and it offers services like SMS and email. There is error checking and voice quality can be improved by lowering the noise floor.
2G is primarily divided into two technologies. Time division multiple access (TDMA) standards include GSM which is predominant worldwide, the Japan-exclusive PDC, iDen which is used in some parts of the US and Canada, and D-AMPs which is a predecessor to GSM. The other 2G slice is code division multiple access (CDMA), which is now in lesser use compared to TDMA because of GSM. The most well-known CDMA technology is IS-95 or cdmaOne, used in parts of Asia and the Americas.
The downside of 2G is that it is very dependent on proximity and location to towers, and its digital nature will only compound that problem. Analog signals degenerate over distance, consistently resulting in static until the signal becomes unintelligible, while digital signal cuts off or loses and distorts dramatically because of its jagged, on-off nature. This means that as 2G signal becomes lesser, the frequency of dropped calls and robotic-sounding voice becomes more prevalent.