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The evolution of cellular communication systems is commonly known by 1G, 2G and 3G designations. We are currently in the third generation (3G). See also wireless LAN, wireless glossary and cellular vs. Wi-Fi.

1G - Analog Voice
Introduced in the late 1970s, the first cellular systems were analog and used for voice calls. Years later, 1G systems were occasionally used for data when traveling by adapting the cellphone to connect to the dial-up modem in the laptop. Even when it worked, data transfer was only about 15 Kbps. See AMPS, TACS and NMT.

2G - 2.5G (2G+) - Digital Voice and Data
The second generation refers to the digital systems deployed in the 1990s, which were based on GSM, TDMA or CDMA. Data services were added and commonly called 2.5G or 2G+ technologies, enabling Internet access and e-mail with downstream speeds from 64 to 200 Kbps. See GPRS, EDGE and IS-95.

3G - Higher Speed Data
Launched after the turn of the century, the third generation supports more voice callers on the same system but primarily features faster access to the Internet with downstream speeds from 300 Kbps to 1 Mbps. The predominant 3G technologies on the GSM side are WCDMA and HSPA with CDMA2000 on the CDMA side (see WCDMA, HSPA and CDMA2000). 3G also embraces worldwide roaming for global travelers (see GAN).

3G Convergence - LTE
Both GSM and CDMA carriers are expected to converge their technologies with Long Term Evolution (LTE), an IP-based platform with higher speeds defined in the 3GPP's Release 8 specification in 2008. See LTE and 3GPP.

4G - LTE-Advanced (LTE-A)
In the 2013-2015 time frame, the LTE-Advanced technology for GSM and CDMA carriers is expected to offer higher speeds and automatic roaming to Wi-Fi, satellite and other wireless networks. It embodies the design goals of the IP Multimedia Subsystem (IMS), which integrates all types of communications based on the IP protocol (voice, video, e-mail, Web, messaging, etc.). See LTE and IP Multimedia Subsystem.








Dual Support
If an iPhone 3G is in range of a 3G cell tower, it uses the higher speed of HSDPA. However, it throttles down to the lower-speed EDGE (E) channel if a 3G HSDPA channel is not available. See HSPA.