cellular generations

(redirected from 2.5G wireless)

cellular generations

The evolution of cellular communications networks is commonly known by 1G, 2G, 3G and 4G designations. We are currently in the fourth generation (4G). See also wireless LAN, wireless glossary and cellular vs. Wi-Fi.

4G - LTE
Starting in the 2011 time frame, GSM and CDMA carriers embraced LTE, which offers higher speeds than 3G networks. LTE embodies the design goals of the IP Multimedia Subsystem (IMS), which integrates all communications using the IP protocol (voice, video, email, Web, messaging, etc.). See LTE and IP Multimedia Subsystem.

4G - WiMAX
Sprint was the first carrier to offer a 4G cellular network in the U.S. Using the WiMAX technology, 4G service was rolled out to major cities in 2009, providing faster downloads than Sprint's 3G service. See WiMAX.

4G - HSPA+
In late 2010, the ITU officially designated HSPA+ as a 4G technology, having previously defined it as 3G. See HSPA.

Launched after the turn of the century, the third generation features faster access to the Internet with downstream speeds up to 1 Mbps and more depending on the 3G version. The predominant 3G technologies on the GSM side are WCDMA and HSDPA with CDMA2000 on the CDMA side (see WCDMA, HSPA and CDMA2000). 3G also embraces worldwide roaming for global travelers (see GAN).

The second generation refers to the digital voice systems of the 1990s, replacing analog phones and based on the TDMA and CDMA air interfaces. First deployed in Europe, GSM became the predominant TDMA-based cellular system worldwide. Data networks (GPRS, EDGE, IS-95B) were added and commonly called 2.5G technologies, enabling Internet access and email with slow downstream speeds up to approximately 200 Kbps. See GSM, CDMA, GPRS, EDGE and IS-95.

1G - Analog Voice
Introduced in the late 1970s, the first cellular systems were analog voice. Years later, some 1G cellphones occasionally provided wireless data service to a laptop by connecting them to the laptop's dial-up modem, but hookups were precarious, and when it worked, the data transfer rate was minuscule. See AMPS, TACS and NMT.

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.

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.
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