3RD SEM MOBILE COMPUTING UNIT_1

History of the mobile communication :

Wireless communication was a magic to our ancestors but Marconi could initiate it with his wireless telegraph in 1895. Wireless Communication can be classified into three eras.

• Pioneer Era (Till 1920)
• Pre Cellular Era(1920-1979)
• Cellular Era (beyond 1979)

The first commercial mobile telephone system was launched by BELL in St. Louis, USA, in 1946. Few lucky customers got the services. Early mobile systems used single high power transmitters with analog Frequency Modulation techniques to give coverage up to about 50 miles and hence only limited customers could get the service due to this severe constraints of bandwidth.

Cellular Era

To overcome the constraints of bandwidth scarcity and to give coverage to larger sections, BELL lab introduced the principle of Cellular concept. By frequency reuse technique this method delivered better coverage, better utility of available frequency spectrum and reduced transmitter power. But the established calls are to be handed over between base stations while the phones are on move.

Even though the US based BELL lab introduced the cellular principle, the Nordic countries were the first to introduce cellular services for commercial use with the introduction of the Nordic Mobile Telephone (NMT) in 1981.

First Generation Systems

All these systems were analog systems, using FDMA technology. They are also known as First Generation (1G) systems. Different systems came into use based on the cellular principle. They are listed below.

Year                            Mobile System

1981                           Nordic Mobile Telephone450

1982                           American Mobile Phone System(AMPS)

1985                           Total Acess Communication System(TACS)

1986                           Nordic Mobile Telephony900

Disadvantages of 1G systems

• They were analog and hence are were not robust to interference.
• Different countries followed their own standards, which were incompatible.

To overcome the difficulties of 1G, digital technology was chosen by most of the countries and a new era, called 2G, started.

Advatanges of 2G

• Lower bit rate voice coding enabled more users to get the services simultaneously.
• Reduction of overhead in signaling paved way for capacity enhancement.
• Good source and channel coding techniques make the signal more robust to Interference.
• New services like SMS were included.
• Improved efficiency of access and hand-off control were achieved.

Name of the Systems	Country
DAMPS-Digital Advanced Mobile Phone System	North America
GSM-Global System for Mobile communication	European Countries and International applications
JDC - Japanese Digital Cellular	Japan
CT-2 Cordless Telephone–2	UK
DECT-Digital European Cordless Telephone	European countries