2G digital cellular systems were introduced at the end of the 1980s, the major improvements and characteristic are:
· Not only digitized the control link but also the voice signal
· Introduction of advanced and fast phone to network signaling
· Better battery technologies and lower power electronics
· Provide better quality and higher capacity at lower cost

In the 1990s, GSM, IS-136 ("TDMA"), iDEN and IS-95 ("CDMA") began to be introduced.

The first digital cellular phone call was made in the US in 1990, and the first GSM network were opened in Europe in 1991.

At the same time, the introduction of 2G were meant that the larger "bricks phones" disappeared and replaced by the tiny hand-held devices.

2.5G refers to a standard of cellular wireless technologies that lies between 2G and 3G. It was prompted by the demand for better data services and access to the Internet.

2.5G provides some of the benefits of 3G like packet-switched and can use the existing 2G infrastructure in GSM and CBMA networks.The commonly known 2.5G technique is GPRS.