Introduction
Evolution of mobile communication: Early Stages, 1G to 3G
Electromagnetic waves were first discovered as a communication medium at the end of the 19th century. The first systems offering mobile telephone service (car phone) were introduced in the late 1940s in the USA and in the early 1950s in Europe. Those early �Single Cell Systems� were severely constrained by restricted mobility, low capacity, limited service and poor speech quality. The equipment was heavy, bulky, expensive and susceptible to interference. Because of those limitations, less than one million subscribers were registered worldwide by the early 1980s.
First Generation (1G): Analog Cellular
The introduction of cellular systems in the late 1970s/early 1980s represented a quantum leap in mobile communication (especially in capacity and mobility). Semiconductor technology and microprocessors made smaller, lighter weight and more sophisticated mobile systems a practical reality for many more users. These First Generation cellular systems still transmit only analog voice information. The most prominent 1G systems are AMPS (Advanced Mobile Phone System), NMT (Nordic Mobile Telephone) and TACS (Total Access Communication System). With the 1G introduction, the mobile market showed annual growth rates of 30-50%, rising to nearly 20 million subscribers by 1990.
Second Generation (2G): Multiple Digital Systems
The development of 2G cellular systems was driven by the need to improve transmission quality, system capacity and coverage. Further advances in semiconductor technology and microwave devices brought digital transmission to mobile communications. Speech transmission still dominates the airways, but the demands for fax, short message and data transmissions are growing rapidly. Supplementary services such as fraud prevention and encrypting of user data have become standard features that are comparable to those in fixed networks. 2G cellular systems include GSM (Global System for Mobile Communication), D-AMPS (Digital AMPS), CDMA (Code Division Multiple Access) and PDC (Personal Digital Communication).
Today, multiple 1G and 2G standards are used in worldwide mobile communications. Different standards serve different applications with different levels of mobility, capability and service area (Paging Systems, Cordless Telephone, Wireless Local Loop, Private Mobile Radio, Cellular Systems and Mobile Satellite Systems). Many standards are used only in one country or region, and most are incompatible. GSM is the most successful family of cellular standards (GSM900, GSM-R, GSM1800 and GSM1900 and GSM400), supporting some 250 million of the world�s 450 million cellular subscribers with International Roaming in approximately 140 countries and 400 networks.
2G to 3G: GSM Evolution
Phase 1 of the standardization of GSM900 was completed by ETSI in 1990 and included all necessary definitions for GSM network operations. Several Tele- and Bearer-Services have been defined (including data transmission up to 9.6 kbit/s), but only some very basic supplementary services were offered. As a result, GSM standards were enhanced in Phase 2 (1995) to incorporate a large variety of supplementary services that were comparable to digital fixed network ISDN standards. In 1996 ETSI decided to further enhance GSM in annual Phase 2+ releases that incorporate 3G capabilities.
GSM Phase 2+ releases have introduced important 3G features such as Intelligent Network services with CAMEL, enhanced speech codecs EFR and AMR, high data rate services and new transmission principles with HSCSD, GPRS and EDGE. UMTS is a 3G GSM successor standard that is downward compatible with GSM, using the GSM Phase 2+ enhanced Core Network.