The
Core Network (CN) contains the functional units described in the following
sections.
Mobile Services Switching Center (MSC) / Mobile Services
Switching
Center (MSC) Server
The
MSC (Server) is responsible for setting up, routing, and supervising calls to
and from the mobile subscriber (mobility management, handover,…). Short
messages, routed from the SMSGMSC or sent from the Mobile Station (MS) / User
Equipment (UE), are relayed in the MSC.
Gateway MSC (GMSC) / Gateway MSC (GMSC) Server
The
GMSC is an MSC serving as an interface between the mobile network and other
networks, such as the Public Switched Telephony Network (PSTN), Integrated
Services Digital Network (ISDN)
and other Public Land Mobile Networks (PLMN) for mobile terminating calls. It
contains an interrogation function for retrieving location information from the
subscriber’s HLR. The GMSC contains functions for rerouting a call to the
Mobile Subscriber according to the location information provided by the HLR.
Visitor Location Register (VLR)
The
VLR temporarily stores information about the MS/UE currently visiting its
service area.
In
an Ericsson’s WCDMA Systems network, the VLR is integrated with the MSC
Media Gateway (MGW)
The
Media Gateway acts as an interface between the Core Network and ATM based networks
(WCDMA RAN and ATM Backbone ).
Combined MSC Server/Media Gateway (MSC Server/MGW)
The
MSC Server and the MGW can be co-located in the same physical GSM MSC/VLR node.
Home Location Register (HLR)
The
HLR database stores and manages all mobile subscriptions belonging to a
specific operator. The HLR stores permanent data about subscribers, including
subscriber's supplementary services, location information, and authentication
parameters. When a person buys a subscription, it is registered in the operator’s
HLR. The HLR can be implemented with the MSC/VLR or as a standalone database.
The
HLR uses Mobile Application Part (MAP) signaling towards the other nodes
(Except for PC-based AUC).
Flexible Number Register (FNR)
FNR
was introduced with Ericsson’s release to provide a flexible number function,
which enables mobile operators to allocate subscriber MSISDN freely without
restricting it to the MSISDN series, held in the HLR where the corresponding
IMSI series is held.
FNR
is modified to provide the function of number portability with GSM R7 in
addition to flexible numbering. Number portability is a network feature that
allows the subscribers
to
retain their MSISDN when they change their service provider within one country,
based on the agreement between different network operators.
FNR
is a database, which stores all the information needed to perform SCCP message
translation before rerouting an incoming call to the correct HLR. The FNR has
the same platform as HLR. It can be implemented as a standalone node or can be
co-located with the other Ams (Application Module).
Authentication Center (AUC)
The
AUC database is connected to the HLR. The AUC provides theHLR with
authentication parameters and ciphering keys by generating triplets or quintuplets
depending on GSM or WCDMA SYSTEMS Release. Using these triplets or quintuplets,
ciphering of speech, data, and signaling over the air-interface is performed. Both
provide system security.
The
AUC is available as a PC or VAX-based system or as an integrated AUC. The
PC-based version is connected to the Input/Output Group 20 (IOG20) similar to
an operator terminal.
The
VAX-based version uses MAP signaling and is connected via S7 signaling links.
The integrated AUC is implemented on an RPD within the AXE 10 and can be
co-located with a MSC/VLR. There is also support for RPG/RPG2 (apart from RPD):
a new and more powerful RP built for the new building practice BYB 501. The RPG/RPG2
is also more than ten times more powerful than RPD. It is smaller and contains
fewer boards.
Equipment Identity Register (EIR)
The
EIR database validates mobile equipment. The MSC/VLR can request the EIR to
check if a MS/UE has been stolen (black listed), not type-approved (gray
listed), normal registered (white listed), or unknown.
The
EIR is connected to the VLR via the S7 network and uses MAP signaling.
The
EIR is implemented as a UNIX operating system or as a VAX computer platform.
Short Message Service - Gateway MSC (SMS-GMSC)
The
SMS-GMSC routes MS/UE-terminated short messages. For signaling to GSM and WCDMA
Systems entities, MAP signaling is used. For signaling to an Ericsson SC, an
Ericsson variant of MAP is used.
Any
MSC/GMSC can be implemented as an SMS-GMSC.
Serving GPRS Support Node - SGSN
The
Serving GPRS Support Node is a primary component in the GSM and WCDMA Systems
network using GPRS. It forwards incoming and outgoing IP packets addressed
to/from a MS/UE that is attached within the SGSN service area.
The
SGSN handles packet routing and serves all subscribers that are physically
located within the geographical SGSN service area. The (packet-switched)
traffic is routed from the SGSN to the BSC/RNC, via the BTS/node B to the User
Equipment.
