The first generation of mobile telephony (written 1G) operated using analogue communications and portable devices that were relatively large. It used primarily the following standards:
The second generation of mobile networks (written 2G) marked a break with the first generation of cellular telephones by switching from analogue to digital.
The main 2G mobile telephony standards are:
Thanks to 2G networks, it is possible to transmit voice and low volume digital data, for example text messages (SMS, for Short Message Service) or multimedia messages (MMS, for Multimedia Message Service). The GSM standard allows a maximum data rate of 9.6 kbps.
Extensions have been made to the GSM standard to improve throughput. One of these is the GPRS (General Packet Radio System) service, which allows theoretical data rates on the order of 114 Kbit/s, but with throughput closer to 40 Kbit/s in practice. As this technology does not fit within the "3G" category, it is often referred to as 2.5G
The EDGE (Enhanced Data Rates for Global Evolution) standard, billed as 2.75G, quadruples the throughput improvements of GPRS with its announced theoretical data rate of 384 Kbps, thereby opening the door to multimedia applications. In reality, the EDGE standard allows maximum theoretical data rates of 473 Kbit/s, but it has been limited in order to comply with the IMT-2000 (International Mobile Telecommunications-2000) specifications from the ITU ( International Telecommunications Union).
The IMT-2000 (International Mobile Telecommunications for the year 2000) specifications from the International Telecommunications Union (ITU) defined the characteristics of 3G (third generation of mobile telephony). The most important of these characteristics are:
3G offers data rates of more than 144 Kbit/s, thereby opening the door to multimedia uses such as video transmission, video-conferencing or high-speed internet access. 3G networks use different frequency bands than the previous networks: 1885-2025 MHz and 2110-2200 MHz.
The main 3G standard used in Europe is called UMTS (Universal Mobile Telecommunications System), and uses W-CDMA (Wideband Code Division Multiple Access) encoding. UMTS technology uses 5 MHz bands for transferring voice and data, with data rates that can range from 384 Kbps to 2 Mbps. HSDPA (High-Speed Downlink Packet Access) is a third generation mobile telephony protocol, dubbed "3.5G", which is able to reach data rates on the order of 8 to 10 Mbps. HSDPA technology uses the 5 GHz frequency band and uses W-CDMA encoding.
|GSM||2G||Allows transfer of voice or low-volume digital data.||9.6 kbps||9.6 kbps|
|GPRS||2.5G||Allows transfer of voice or moderate-volume digital data.||21.4-171.2 kbps||48 kbps|
|EDGE||2.75G||Allows simultaneous transfer of voice and digital data.||43.2-345.6 kbps||171 kbps|
|UMTS||3G||Allows simultaneous transfer of voice and high-speed digital data.||0.144-2 Mbps||384 kbps|