GSM / GPRS / EDGE - Mobile Communication Standards
GSM stands for Global System for Mobile Communications (originally Groupe Spécial Mobile) and it is a standard set developed by the European Telecommunications Standards Institute (ETSI) to describe technologies for second generation (2G) digital cellular networks. GSM standard originally described a digital, circuit switched network optimized for full duplex voice telephony and it is the leading cellular phone standard in the world, with networks in most countries.
The standard was expanded over time to include first Circuit Switched Data (CSD, up to 14.4 kbps) transport, then High- Speed Circuit Switched Data (HSCSD, up to 43.2 kbps using more than one time slot) and later General Packet Radio Service (GPRS) This standard with packet data channels on one or several time slots up to 171.2 kbps is used most often nowadays.
GSM is a cellular network. There are five different cell sizes in a GSM network: macro, micro, pico, femto and umbrella cells. The coverage area of each cell varies according to the implementation environment with longest range of 35 kilometers.
GSM networks operate in a number of different carrier frequency ranges, with most 2G GSM networks operating in the 900 MHz or 1800 MHz bands. Where these bands were already allocated, the 850 MHz and 1900 MHz bands were used instead (e.g. in Canada and the USA). The transmission power in the handset is limited to a maximum of 2 Watts in GSM850/900 band and 1 Watt in GSM1800/1900 band. GSM technology is a TDMA (Time Division Multiple Access) system with eight time slots per carrier. The modulation used in GSM is Gaussian Minimum Shift Keying (GMSK).
The evolution path for higher data rates is called EDGE (Enhanced Data rates for GSM Evolution). The objective of the EDGE technology is to increase data transmission rates (up to 473.6 kbps) as well as spectrum efficiency and to facilitate new applications with increased capacity for mobile use. EDGE is a superset to GPRS, utilizing the same bandwidth and frequencies, and can function on any network with GPRS deployed on it, provided the carrier implements the necessary upgrade.