radiowaves

GSM services:

– tele services, voice calls

– bearer or data services

– supplementary services, call holding, call waiting, call forwarding, multi party call conferencing

GSM architecture:

– MS Mobile station, consists of mobile equipment and subscriber identity module

– BSS, base station subsystem, consists of base station transreceiver and base station controller

-NSS, network and switching subsystem, consists of mobile switching center, home location register, visitor, location register, equipment identity register and authentication center

– OSS, operational subsystem

GSM Channel Types:

– Traffic channels, full rate and half rate

– control channels, broadcast, common control and dedicated control

 

Frame structure of GSM

1 Hyper frame = 2048 super frames

For speech

1 supper frame = 51 multiframe

1 multiframe = 26 frames

For signalling

1 superframe = 26 multiframes

1multiframes = 51 frames

1 frame = 8 time slots

1 time slot = 0.577ms

GSM Signalling process:

signalling—->

voice —–>speech coding ->channel coding->interleaving->burst formatting->ciphering->modulation->RF

and reverse process

Digital Enchanced Cordless Telecom