2G – GSM an Overview

During the early 80s, analog cellular telephone systems were experiencing rapid growth. Each country developed its own system, which was incompatible with everyone else's in equipment and operation.

In 1982 the Conference of European Posts and Telegraphs (CEPT) formed a study group called the Groupe Spécial Mobile (GSM) to study and develop a pan-European public land mobile system. In 1989, GSM responsibility was transferred to the European Telecommunication Standards Institute (ETSI), and phase I of the GSM specifications were published in 1990. Commercial service was started in mid-1991, and GSM systems exist on every continent, and the acronym GSM now aptly stands for Global System for Mobile communications.

The GSM core network consists of several kinds of nodes. The important nodes are the

Base Transceiver Station (BTS),

Base Station Controller (BSC),

Mobile Switching Center (MSC)

Visitor Location Register (VLR)

Home Location Register (HLR)

The Base Transceiver Station and the Base Station Controller, forming together the access network of the GSM/GPRS network. The Mobile Switching Center (MSC), responsible for the routing of the calls, the tracking of the mobile users and security functions. The Visitor Location Register a database storing actual user related information of the users currently served by the MSC is often closely located to an MSC. The Home Location Register holds further user information, like the actual location and the subscription data of the users