Introduction to gsm 2g technology

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Introduction to GSM

• Early 1980s there was analog technologies:

History of Cellular Mobile Radio and GSM(Global Systems for Mobile)

– Advanced Mobile Phone Services(AMPS)in North America.– Total Access Communications System(TACS) in the UK. – Nordic Mobile Telephone(NMT) in Nordic countries.

• Each country developed its own system, which caused problems:
– System worked only withinthe boundaries of each country. – Mobile equipment manufacturers markets were limited by the operating system.

Solution was GSM, which is digital technology and was developed by CEPT(Conference ofEuropean Posts and Telecommunications)

• The Goals of GSM
– Improved spectrum efficiency – International roaming – Low-cost mobile sets and base stations – High-quality speech – Compatibilitywith ISDN and other telephone company services. – Support for new services – QoS

GSM facts(2001)
• Used in over 170 countries • Over 400 GSM network operators • Over 550 million people weresubscribers to GSM

GSM Cell Structure
• The power level of a transmitter within a single cell must be limited to reduce the interference with the neighboring cells.

• Neighboring cells cannot sharethe same channels • Different size of patterns: 4,7,12 or 21 cells in one cluster

Types of Cells
• Macrocells(3 to 35 km)

• Microcells(0,1 to 1 km) - Picocells(0,01 to 1km) - Nanocells(1m to10m)

• Selective cells and tiered cells(two sectors, two frequencies)

• Umbrella cells - covers several microcells

GSM Architecture
• Base Tranceiver Station (BTS)
– serves a single cell –usually placed in the center of a cell – coding – crypting – multiplexing – modulating – synchronizing

• Base Station Controller(BSC)
– translates the 13-Kbps voice to the standard 64-Kbpschannel (used by PSDN or ISDN) – frequency hopping – time and frequency synchronisation – power management – time delay measurements

• The Transcoder and adaptation unit(TRAU)
– (13Kbps speech or...
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