Position: Index > Unclassified >

How the GSM system works?.

2018-02-28 13:49  
Declaration:We aim to transmit more information by carrying articles . We will delete it soon, if we are involved in the problems of article content ,copyright or other problems.


In various countries the frequency bandwidths specified for the GSM services are GSM-400, GSM-800, GSM-900, GSM-1800 and GSM-R.The GSM-900 and the GSM-1800 are the most widely used frequency bandwidths in different parts of the globe.

The GSM-900 has a down link frequency range of 935-960 MHz and an up link frequency of range of 895-915 MHz. This frequency band is partitioned into 124 pairs of simplex channels with separation of 200KHz.A particular range of simplex channels is given to a particular network provider.

The type of interface used in GSM is digital air interface.The analogue voice signals are converted to digital signals before transmission.Up to 8 MS subscribers can be handled by the GSM RF carrier at a time.The rate of transmission is 270 Kbps.

The Gaussian minimum shift keying (GMSK) is used for transmitting the digital signals.In GMSK , a phase change represents the change from a digital “1 ” or a “0 “,occurs over a period of time.The addition of high frequency components to the spectrum is reduced.In GSMK ,the phase change is not constant and it is spread- out.


Schematic of a GSM system.


SIM – Subscriber Identification Module.
MS – Mobile Station.
ME – Mobile Equipment.
BTS – Bare Transceiver System.
MSC – Mobile Services switching Center.
NSS – Network & Switching Subsystem.
PSTN – Public Switched Telephone Network.

Reprinted Url Of This Article: