science and technology

Each generation of mobile communications has been based on a dominant technology, which has significantly improved spectrum capacity. Until the advent of IMT-2000, cellular networks had been developed under a number of proprietary, regional and national standards, creating a fragmented market.

First Generation:

1) Advanced Mobile Phone System (AMPS) was first launched in the US. It is an analog system based on FDMA (Frequency Division Multiple Access) technology. Today, it is the most used analog system and the second largest worldwide.

2) Nordic Mobile Telephone (NMT) was mainly developed in the Nordic countries. (4.5 million in 1998 in some 40 countries including Nordic countries, Asia, Russia, and other Eastern European Countries)

3) Total Access Communications System (TACS) was first used in the UK in 1985. It was based on the AMPS technology.

There were also a number of other proprietary systems, rarely sold outside the home country.


Second Generation:

1) Global System for Mobile Communications (GSM) was the first commercially operated digital cellular system. It was first developed in the 1980s through a pan-European initiative, involving the Eureopean Commission, telecommunications operators and equipment manufacturers. The European Telecommunications Standards Institute was responsible for GSM standardization. GSM uses TDMA (Time Division Multiple Access) technology. It is being used by all European countries, and has been adopeted in other continents. It is the dominant cellular standard today, with over (45%) of the world’s subscribers at April 1999.

2) TDMA IS-136 is the digital enhancement of the analog AMPS technology. It was called D-AMPS when it was fist introduced in late 1991 and its main objective was to protect the substantial investment that service providers had bmade in AMPS technology. Digital AMPS sevices have been launched in some 70 countries worldwide (by March 1999, there were almost 22 million TDMA handsets in circulation, the dominant markets being the Americas, and parts of Asia)

3) CDMA IS-95 increases capacity by using the entire radio band with each using a unique code (CDMA or Code Division Multiple Access) . It is a family of digital communication techniques and South Korea is the largest single CDMA IS-95 market in the world.

4) Personal Digital Cellular (PDC) is the second largest digital mobile standard although it is exclusively used in Japan where it was introduced in 1994. Like GSM, it is based on the TDMA access technology. In November 2001, there were some 66.39 million PDC users in Japan.

5) Personal Handyphone System (PHS) is a digital system used in Japan, first launched in 1995 as a cheaper alternative to cellular systems. It is somewhere in between a cellular and a cordless technology. It has inferior coverage area and limited usage in moving vehicles. In November 2001, Japan had 5.68 million PHS subscribers.

Sources: www.itu.int