se standards were based on Time Division Multiple Access (TDMA) technology. One is the Global System for Mobile communications (GSM), and the other is the Digital Advanced Mobile Phone System (D-AMPS). GSM was developed by the European Tele- communications Standards Institute (ETSI) under the auspices of the European Community as a pan-European standard. However, global prominence of several European manufacturers such as Ericsson, Siemens and Alcatel meant that GSM was marketed to operators outside Europe as well and as a result grew to become a global standard. The GSM standardisation process com- menced in the early 1980s, the first set of GSM standards was published in 1990, and the first network commenced operation in 1991. The other TDMA standard, D-AMPS, was developed in North America by the Electronic Industries Alliance (EIA) and the Telecommunications Industry Association (TIA), two Broadband Telecommunications Technologies and Management Time-slot-8 Time-slot-8 Time-slot-8 Time-slot-5 Time-slot-5 Time-slot-5 Time-slot-4 Time-slot-4 Time-slot-4 Time-slot-3 Time-slot-3 Time-slot-3 Time-slot-2 Time-slot-2 Time-slot-2 Mobile 1 PDA 2 Time-slot-1 Time-slot-1 Time-slot-1 Carrier 1 Carrier 2 Carrier in Frequency Mobile 3 Mobile 8 Base station PDA 5 Mobile 4 Figure 10.16 A 2G GSM resource allocation US-based organisations - and is also known by its standard numbers IS-54 and IS-154. The D-AMPS standard was closely based on the Analogue AMPS standard which used 30 kHz for each voice channel. The change from analogue to digital allowed using the 30 kHz channel for 3 users on a TDMA basis, thereby increasing system efficiency by three times. The standards development occurred in the late 1980s, and the relatively minimal evolution meant that a smooth roll-out was carried out in the early 1990s. As noted above, both GSM and D-AMPS use TDMA technology to enable connectivity between several mobile devices and a base station. In TDMA, the same frequency channel is shared among several mobile devices on a time slot bas