Third Generation (3G) cellular systems were developed with the aim of offering high-speed data connectivity to mobile customers. Conceived during the early stages of the Internet explosion, a clear need was established for consumers to be able to access data and multimedia services at a suitable rate. In many parts of the world, the spectrum required to run the new 3G services was auctioned to cellular operators for fees ranging in the multi-billions of dollars.
3G systems are defined by the International Telecommunications Union initiative IMT-2000, as being capable of supporting high-speed data rates in the range of 144 Kbps to >2 Mbps, depending on the conditions and mobile speed. A number of different technologies can fulfill the requirements of the ITU, including some variations of 2G technology, commonly referred to as 2.5G. Development of GSM technology has lead to GPRS and EDGE, while CDMAone (IS95a) systems have born a number of evolutionary systems, which collectively are grouped and classified under the term CDMA2000.
There is general confusion over exactly what constitutes a 3G system and what is a 2.5G system. While technically, many CDMA2000 systems are modifications to existing 2G architectures, they are now widely sold and marketed as 3G systems. The GSM variant on the other hand, while theoretically capable of 3G performance are generally classified as 2.5G systems. This is primarily because a new standard was specifically developed by GSM manufacturers and operators to fulfill the 3G requirements that used a completely different technology to the incumbent GSM system. It is called Wideband-CDMA (W-CDMA), and is destined to be deployed by existing GSM network operators.
