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