What is GSM?
Cellular communication is in use throughout the world. The technology behind this is GSM. It is used for mobile to mobile communication mainly for voice/data applications. Data applications include SMS/MMS/Email/Web browsing etc. GSM is the short form of Global System for Mobile Communication.
Let us understand how it works with the help of following simple figure.
When Mobile 1 wants to talk to Mobile 2, Mobile 1 dials Mobile 2's number this will be forwarded to Base Station through signaling channel. Base Station finds out whether the called Mobile 2 is not in use, if so it will send ringing tone to Mobile 2 and once Mobile 2 accepts the call it will establish connection between both the mobiles. One dedicated frequency/time slot is in use for such connection till the call ends. Hence FTDMA is the access scheme used in GSM.
GSM uses 890-915 MHz frequency band from Mobile 1 to Base Station and 935-960 MHz frequency band from Base Station to Mobile 2. This frequency band is divided into RF carriers of 200 KHz bandwidth. Hence there will be 125 RF carriers. Each frequency carrier is divided into 8 logical channels. Hence in GSM each Mobile is allocated one RF carrier and one time slot which will be repetitive in the Frame.
There are various encryption algorithms used to provide secure communication between two mobiles in GSM system.
GMSK modulation scheme is used to modulate the information bits before RF frequency conversion .
Refer our page on GSM tutorial which covers GSM basics,network architecture,network elements,system specifications,applications,frame structure,GSM physical layer or speech processing and network entry procedure.
Refer our page on CDMA and GSM technology comparison.
Refer our page on popular GSM Modem manufacturers.
This page explains what is a GSM technology and provides useful links.