Concepts and abbreviations of the GSM system
Parts of the GSM system:
MSC - Mobile Switching Centre
Provides connections from GSM to other network (normal telephone networks
, ISDN network etc.)
BSS - Base Station System
Consists of one BSC and several BTSs.
BSC - Base Station Controller
Controls BTSs
BTS - Base Tranceiver Station
Handles radio traffic towards and from the MSs
MS - Mobile Station
For example, a hand-held cellular phone
HLR - Home Location Register
Contains information of all the subscribers of the network operator
VLR - Visitor Location Register
Contains information of all the roaming subscribers currently in
MSC's area. 'Roaming' is using MS elsewhere that its 'home' MSC
area, such as using a Finnish MS in New Zealand.
Protocols of the GSM system:
CM - Connection Management
Applicaton prtocol; contains e.g. CC protocol
CC - Call Control
Protocol for controlling flow of a call
MM - Mobility Management
Takes charge of the mobility of an MS
RR - Radio Resources
Manages radio resources in MS, BTS and BSC. This prtocol takes
charge of signalling between the network and mobile phones.
BSSAP - BSS Application Part
Contains BSSMAP and DTAP
BSSMAP - BSS Management Application sub-Part
Protocol for signalling between MSC and BSC
DTAP - Direct Transfer Application sub-Part
Protocol for data transfer between MS and MSC
BTSM - Base Tranceiver Station Management
Protocol for signalling between BSC and BTS
Radio interfaces of the GSM system:
A-interface - between MSC and BSC
Abis-interface - between BSC and BTS
Lm-interface - between BTS and MS
Additional abbreviations:
GSM - Global System for Mobile communications
SIM - Subsciber Identity Module
A smart card idenifying a mobile subscriber
PLMN - Public Land Mobile Network
A GSM network of a network operator
IMEI - International Mobile Equipment Identity
A unique number identifying a single mobile phone
IMSI - International Mobile Subscriber Identity
A unique number identigyinf a single mobile subscriber
TMSI - Temporary Mobile Subscriber Identity
A temporary identifier for a mobile subscriber; used for
authentication purposes
ASN.1 - Abstract Syntax Notation One
A formal language used for describing information contents