In the early 1990s, 2G phones deploying GSM technology were introduced. Global System for Mobile communications, or GSM uses digital modulation to improve voice quality but the network offers limited data service.
As demand drove uptake of cell phones, 2G carriers continued to improve transmission quality and coverage. The 2G carriers also began to offer additional services, such as paging, faxes, text messages and voicemail. The limited data services under 2G included WAP, HSCSD and MLS.
An intermediary phase, 2.5G was introduced in the late 1990s. It uses the GPRS standard, which delivers packet-switched data capabilities to existing GSM networks. It allows users to send graphics-rich data as packets. The importance for packet-switching increased with the rise of the Internet and the Internet Protocol, or IP. The EDGE network is an example of 2.5G mobile technology.