Today's networks in use across the globe are commonly referred to as second-generation (or 2G) networks. Built out in the 1980's, first-generation networks were exclusively analog networks (based on the AMPS standard in the U.S.) and basically included one feature: voice communications. While voice is arguably the most useful feature for any mobile device to have, analog networks offer limited bandwidth and scalability as user numbers increase. Second generations are based on three major digital technologies (CDMA, GSM, and TDMA) and enable the carrier (that is, your wireless telecommunications provider, such as Verizon, AT&T, Sprint PCS, BT, DoCoMo, etc.) to deliver value-added personal communications services (PCS). Examples of PCS-class features include two-way messaging (using either SMS or other, more proprietary technologies), voice mail, and paging. 2G technologies also offer superior voice quality and system scalability when compared to their analog ancestors.
Each of the primary 2G technologies mentioned above has unique advantages. TDMA (Time Division Multiple Access) is most popular in North America (and is used by carriers such as BellSouth Wirelessnow Cingularand AT&T). TDMA splits the frequency bands into distinct time slots and cycles users across a time slot at regular intervals. The GSM standard grew out of TDMA technology and currently dominates Europe and much of Africa, and is growing in popularity in the U.S. (used by carriers such as VoiceStream, Digiph, and Powertel). GSM supports roaming and data services along with the ability to load data on a personal "SIM" card installed on the phone. Unfortunately, GSM is currently operating at three different frequencies around the world: 900 MHz in Europe, 1800 MHz in Europe, and 1900 MHz in the U.S. and Canada, which requires the use of a "tri-mode" phone (referring to the support for the three frequencies) for roaming between networks. Work is underway to support roaming between TDMA and GSM networks as well, and these two technologies are designed to merge in the future. The final widely used technology, Code Division Multiple Access (CDMA)also known as cdmaOnewas developed by Qualcomm and has been shown to deliver superior voice clarity, security, and spectrum efficiency. CDMA is widely used in the U.S. by Sprint PCS, Verizon, and others.