Msc,Ran,vlr,gmsc,hlr,cn,auc,bss,ms introduction

MSC – the mobile service switching centre (MSC) is the core switching entity in the network.
The MSC is connected to the radio access network (RAN);

the RAN is formed by the BSCs and
BTSs within the Public Land Mobile Network (PLMN). Users of the GSM network are registered
with an MSC; all calls to and from the user are controlled by the MSC. A GSM network has
one or more MSCs, geographically distributed.

• VLR – the visitor location register (VLR) contains subscriber data for subscribers registered in
an MSC. Every MSC contains a VLR. Although MSC and VLR are individually addressable,
they are always contained in one integrated node
.
• GMSC – the gateway MSC (GMSC) is the switching entity that controls mobile terminating
calls. When a call is established towards a GSM subscriber, a GMSC contacts the HLR of that
subscriber, to obtain the address of the MSC where that subscriber is currently registered. That
MSC address is used to route the call to that subscriber.

• HLR – the home location register (HLR) is the database that contains a subscription record for
each subscriber of the network. A GSM subscriber is normally associated with one particular
HLR. The HLR is responsible for the sending of subscription data to the VLR (during registration)
or GMSC (during mobile terminating call handling).

• CN – the core network (CN) consists of, amongst other things, MSC(s), GMSC(s) and HLR(s).
These entities are the main components for call handling and subscriber management. Other
main entities in the CN are the equipment identification register (EIR) and authentication centre
(AUC). CAMEL has no interaction with the EIR and AUC; hence EIR and AUC are not further
discussed.

• BSS – the base station system (BSS) is composed of one or more base station controllers (BSC)
and one or more base transceiver stations (BTS). The BTS contains one or more transceivers
(TRX). The TRX is responsible for radio signal transmission and reception. BTS and BSC are
connected through the Abis interface. The BSS is connected to the MSC through the A interface.

• MS – the mobile station (MS) is the GSM handset. The structure of the MS will be described in
more detail in a next section.
A GSM network is a public land mobile network (PLMN). Other types of PLMN are the time
division multiple access (TDMA) network or code division multiple access (CDMA) network. GSM
uses the following sub-division of the PLMN: