2.5G is a sometimes used term that refers to
GPRS class wireless data connectivity. It is not a
formal standard.
3G, or Third Generation, is a somewhat generic
term for network technologies that the ITU
classifies as part of their IMT-2000 specification.
Generally, wireless network technologies must be
able to provide a mobile device with a downlink
connection speed of 384kbps in order to be
considered a 3G technology. The most used 3G
technologies are WCDMA, CDMA 1xEV-DO, and,
technically, EDGE and CDMA 1xRTT.
Also known as: "third generation"
2G is short for Second Generation, the name
usually given to original GSM, CDMA, and TDMA
networks. 1G, a term rarely used, would refer to
the original analog (AMPS) type mobile networks
first used in the early 1980s.
Also known as: "second generation"