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:
- AMPS (Advanced Mobile Phone System), which appeared in 1976 in the United States, was the first cellular network standard. Used primarily in the Americas, Russia and Asia, this first-generation analogue network had weak security mechanisms which allowed hacking of telephones lines.
- TACS (Total Access Communication System) is the European version of the AMPS model. Using the 900 MHz frequency band, this system was largely used in England, and then in Asia (Hong-Kong and Japan).
- ETACS (Extended Total Access Communication System) is an improved version of the TACS standard developed in the United Kingdom that uses a larger number of communication channels.
The first-generation cellular networks were made obsolete by the appearance of an entirely digital second generation.
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:
- GSM (Global System for Mobile communications), the most commonly used standard in Europe at the end of the XXth century, and supported in the United States. This standard uses the 900 MHz and 1800 MHz frequency bands in Europe. In the United States, however, the frequency band used is the 1900 MHz band. Portable telephones that are able to operate in Europe and the United States are therefore called tri-band.
- CDMA (Code Division Multiple Access), using a spread spectrum technique that allows a radio signal to be broadcast over a large frequency range.
- TDMA (Time Division Multiple Access), using a technique of time division of communication channels to increase the volume of data transmitted simultaneously. TDMA technology is primarily used on the American continent, in New Zealand and in the Asia-Pacific region.
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:
- high transmission data rate:
- 144 Kbps with total coverage for mobile use,
- 384 Kbps with medium coverage for pedestrian use,
- 2 Mbps with reduced coverage area for stationary use.
- world compatibility,
- compatibility of 3rd generation mobile services with second generation networks,
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|