What is GSM?

Bill Day

Global System for Mobile (GSM) encompases a set of second generation (2G) cellular standards for digitally encoding and transmitting voice over mobile telephony systems. GSM uses frequency, time, and space division multiplexing to conserve radio spectrum.

A key differentiator versus other 2G systems such as TDMA and CDMA is that GSM based systems include a Subscriber Identity Module (SIM), a smart card CPU that provides a globally unique subscriber ID allowing international roaming in 150+ countries.

Many GSM-based 2G and 2.5G handsets (mobile phones) also include a J2ME implementation, and as such are an important target for J2ME developers.

For more information on GSM, please visit the GSM Association:

Many GSM SIMs implement the JavaCard technologies. For more information on JavaCard and its use in GSM SIMs, please refer to the jGuru JavaCard FAQ.