2 Network functions for basic service provision

03.013GPPNetwork FunctionsTS

2.1 Call handling

This set of functions enables the establishment of communications between a mobile subscriber and another network subscriber in one of the following types of network PSTN, ISDN, PSPDN, CSPDN and other PLMNs.

2.1.1 Call from a mobile subscriber registered in VLR

This is the normal case where the call is routed according to the dialled number. After the call, the MSC will send the charging information to the HLR, a billing entity and/or store the charging data on tapes or discs as described in Technical Specification GSM 12.05.

2.1.2 Call from a mobile subscriber not registered in VLR

When the VLR receives a request for call set-up parameters from an MSC for an MS originating call, where the MS is not registered in the VLR, the VLR shall initiate a location updating procedure towards the HLR and in response parameters are given concerning category, services and restrictions. The call is then set up as in 2.1.1. This case only happens when a VLR or an MS failure has occurred.

2.1.3 Call to a mobile subscriber

The call is routed (re-routed or forwarded) according to location data obtained from the HLR to the actual MSC and the MS is paged over the standardised radio interface.

For MSs in mode of operation A and B the paging may be performed via SGSN. This optional network function is further described in the Technical Specification GSM 03.60.

Table 1: Overview of network functions

Class of Network

Network Function

Network

Interworking

Function (NF)

Support

with MAP

NF for basic

Call Handling (Note 3)

M

X

service provision

Packet Handling (Note 4)

M

X

Subscriber Authentication

M

X

Emergency calls (Note 3)

M

Supplementary Services

M

X

Voice group services (Note 3)

O

X

Short Message Service (SMS)

M

X

Signalling information element confidentiality

M

X

NF for

Location registration

M

X

supporting:

Handover (Note 3)

– in the same BSS

M

– in the same MSC

M

– in the same PLMN

M

X

Call re-establishment (Note 3)

M

Additional NF

Queueing

O

for

call handling

OACSU (Note 3)

O

Security related services

M

X

Discontinuous reception

M

Discontinuous Transmission

M/O

Note 2

DTMF (Note 3)

M

Network

management

M

X

oriented NF

(Note 1)

NOTE 1: The function will not be fully specified by GSM (national specifications will complement).

NOTE 2: Only the receiver requirements are mandatory, the transmitter requirements support are optional.

NOTE 3: Only applicable for circuit switched services

NOTE 4: Only applicable for packet switched services

2.1.4 Call handling functions in HLR

The HLR should also support control functions for handling of supplementary services as described for each service in the GSM 03.8x series of Technical Specifications.

The HLR should provide information to the gateway MSC to allow it to route calls directed to a mobile subscriber: either a Mobile Station Roaming Number (MSRN) to allow the call to be routed to the visited MSC or a forwarding number if the call is to be forwarded to a destination different from the original one.

The HLR should provide the identity of the visited MSC to the SMS gateway MSC to allow it to route short messages directed to a mobile subscriber; further detail is given in Technical Specification GSM 03.40.

2.1.5 Call handling functions in VLR

The VLR must provide subscriber parameters to the MSC as required for call handling.

The VLR must also support control functions for handling of supplementary services as described for each service in the GSM 03.8x series of Technical Specifications.

For a MS in mode of operation A or B, the VLR may optionally support establishment and maintenance of an association with an SGSN. This allows paging for a circuit switched call to be performed via SGSN.

2.1.6 Call handling functions in MSC

The MSC must perform normal call routing and call control functions. The MSC will obtain subscriber parameters from its associated VLR.

The MSC must also be capable of performing handover as defined in section 3.2.

In some cases, the MSC must be able to act as a gateway MSC to provide an interface to other circuit-switched networks.

2.1.7 Call handling functions in SGSN

For a MS in mode of operation A or B, the SGSN may optionally support establishment and maintenance of an association with a VLR. This allows paging for a circuit switched call to be performed via SGSN.

2.2 Subscriber identity authentication

The purpose of subscriber identity authentication is defined in Technical Specification GSM 02.09.

The authentication mechanism is defined in Technical Specification GSM 03.20 and corresponding procedures on the MS-BSS interface are defined in Technical Specification GSM 04.08.

2.3 Emergency call

2.3.1 General

The land mobile system should be capable of efficient handling of emergency calls fromMS. The signalling procedures on the radio path for emergency calls are given in Technical Specification GSM 04.08.

2.3.2 Routeing

The call should be routed automatically to an appropriate emergency centre based on the geographical location of the MS(e.g. based on the identity of the cell on which the call is established).

2.4 Supplementary services

PLMN may offer supplementary services as shown in Technical Specification GSM 02.04. The support of supplementary services will require control procedures in HLRs, VLRs and MSCs in addition to the control procedure in the fixed network. The technical realisation of supplementary services is given in the GSM 03.8x series of Technical Specifications.

2.5 Voice group services

The PLMN may offer the voice group services. These are the voice group call service (VGCS) and voice broadcast service (VBS), as shown in GSM 02.68 and GSM 02.69, respectively. The support of the voice group call and voice broadcast services will require control procedures in HLRs, VLRs, MSCs and Group Call Register (GCR) and possibly control procedures in the fixed network. The technical realisation of these services is given in GSM 03.68 and GSM 03.69, respectively.

2.6 Short Message Service

This set of functions allows the transfer of short messages i either direction between a mobile station and a short message service centre. More detailed information is given in Technical Specification GSM 03.40.

2.6.1 Short Message Handling functions in the HLR

The HLR should be able to provide information to allow a short message to be routed from the SMS gateway MSC to the visited MSC and/or visited SGSN and then to the required MS.

2.6.2 Short Message Handling Functions in the VLR

The VLR should provide subscriber parameters to the MSC as required for handling short messages.

2.6.3 Short Message Handling Functions in the MSC

The MSC should perform the functions of relaying short messages in both directions between the fixed network of the PLMN and the BSS.

In some cases the MSC should be able to act as an SMS Gateway MSC to relay short messages from a Short Message Service Centre (SC) to a PLMN, or an SMS Interworking MSC to relay short messages from a PLMN to an SC.

2.6.4 Short Message Handling Functions in the SGSN

The SGSN should perform the functions of relaying short messages in both directions between the fixed network of the PLMN and the BSS. The SGSN should also provide subscriber parameters required for handling the short messages relaying function. The SGSN should also download (from HLR or another SGSN) and store subscriber parameters required for handling the short message relaying functions.

2.7 Signalling information element confidentiality

A procedure should be implemented providing for the confidentiality of signalling information elements on the radio path. In Technical Specification GSM 02.09 the signalling information elements which need to be protected are given.

The Encryption Key is calculated in both the MS and the network. Detailed information is given in Technical Specification GSM 03.20.

2.8 Packet Handling

This set of functions enables routing of packets between an MS and a network host in one of the following types of network: PSPDN, networks based on the Internet Protocol (IP) and other PLMNs.

2.8.1 Packet handling functions in SGSN.

The SGSN should perform the functions of routing packets in both directions between one or more GGSN’s and the BSS. The SGSN should also download (from HLR or another SGSN) and store subscriber parameters required for handling the packet routing functions.

2.8.2 Packet handling functions in GGSN

The GGSN should act as a gateway that provides interface(s) to other packet data networks. The GGSN should further perform the functions of routing packets in both directions between these networks and one or more SGSN’s. The GGSN should also download (from SGSN) and store subscriber parameters required for handling the packet routing functions.

2.8.3 Packet switched service functions in HLR

The HLR should provide permanent storage of subscriber data.

The HLR should provide the identity of the visited SGSN to the SMS gateway MSC to allow it to route short messages directed to a mobile subscriber; further detail is given in Technical Specification GSM 03.40.