16 Messages/Procedures and their contents

23.2843GPPLocal Call Local Switch (LCLS)Release 17Stage 2TS

16.1 Messages between (G)MSC servers

16.1.1 General

The BICC messages between (G)MSC servers on Nc interface are specified in 3GPP TS 23.205 [2]. The SIP methods and corresponding responses that shall be supported between (G)MSC servers on Nc interface are specified in 3GPP TS 29.231 [10]. The LCLS related information exchanged in these messages and encapsulated in the corresponding SIP messages is specified below and in 3GPP TS 29.205 [6].

The MAP messages used for inter-MSC handover between Anchor and Target MSC-Server (E-interface) are specified in 3GPP TS 23.205 [2] and 3GPP TS 23.009[9]. The LCLS related information exchanged in these messages is specified below and in 3GPP TS 29.002 [12].

16.1.2 Initial Address

Table 16.1.2.1 indicates the LCLS related information which is exchanged between the MSC servers in the Initial Address (BICC: IAM or SIP-I: INVITE request with encapsulated ISUP IAM) message. Only the Information Elements required by LCLS are shown.

Table 16.1.2.1: LCLS related information in Initial Address message

Message

Message direction

Information element name

Information element required

Information element description

Initial Address (BICC: IAM or SIP-I: INVITE [IAM])

Forward

Global Call Reference

C

This information element identifies the call. This information element shall be included when LCLS is supported in the core network.

LCLS-Negotiation Request

C

This information element indicates the initial negotiation request and LCLS permissions. This information element shall be included when LCLS is supported in the core network.

LCLS-Configuration-Preference

C

This information element indicates the LCLS configuration preference while LCLS is established. This information element shall be included when LCLS is supported in the core network.

16.1.3 Answer

Table 16.1.3.1 indicates the LCLS related information which is exchanged between the MSC servers in the Answer (BICC: ANM or SIP-I: 200 OK final response to initial INVITE request with encapsulated ANM) message. Only the Information Elements required by LCLS are shown.

Table 16.1.3.1: LCLS related information in Answer message

Message

Message direction

Information element name

Information element required

Information element description

Answer

(BICC: ANM or SIP-I: 200 OK-INVITE [ANM])

Backward

LCLS-Status

C

This information element identifies the LCLS connection status. This information element shall be included when LCLS is negotiated in the core network.

16.1.4 Bearer and Codec Information

Table 16.1.4.1 indicates the LCLS related information which is exchanged between the MSC servers in the Bearer and Codec Information (BICC: APM) message. Only the Information Elements required by LCLS are shown.

Table 16.1.4.1: LCLS related information in Bearer and Codec Information message

Message

Message direction

Information element name

Information element required

Information element description

Bearer and Codec Information

(BICC: APM

Backward

LCLS-Negotiation Response

O

This information element indicates the initial negotiation response. This information element shall be included when the APM is related to LCLS negotiation in Bearer and Codec Information messages and LCLS is supported in the core network.

LCLS-Configuration-Preference

C

This information element indicates the LCLS configuration preference while LCLS is established. This IE shall be included if the LCLS-Negotiation Response is included.

16.1.5 Backward LCLS Negotiation

Table 16.1.5.1 indicates the LCLS related information which is exchanged between the MSC servers in the LCLS Negotiation (BICC: APM; SIP-I: 183 Session Progress provisional response with encapsulated APM) message or in the Address Complete (BICC: ACM; SIP-I: 183 Session Progress provisional response with encapsulated ACM) message or in the Call Progress (BICC: CPG; SIP-I: 183 Session Progress provisional response with encapsulated CPG) message. Only the Information Elements required by LCLS are shown.

Table 16.1.5.1: LCLS related information in the LCLS Negotiation message

Message

Message direction

Information element name

Information element required

Information element description

LCLS Negotiation (BICC: APM;
SIP-I: 183 Session Progress [APM])

Backward

LCLS-Negotiation Response

M

This information element indicates the initial negotiation response.

LCLS-Configuration-Preference

M

This information element indicates the LCLS configuration preference while LCLS is established.

Table 16.1.5.2: LCLS related information in the Address Complete message

Message

Message direction

Information element name

Information element required

Information element description

Address Complete

(BICC: ACM;
SIP-I: 183 Session Progress [ACM])

Backward

LCLS-Negotiation Response

O

This information element indicates the initial negotiation response.

LCLS-Configuration-Preference

C

This information element indicates the LCLS configuration preference while LCLS is established. This IE shall be included if the LCLS-Negotiation Response is included.

Table 16.1.5.3: LCLS related information in the Call Progress message

Message

Message direction

Information element name

Information element required

Information element description

Call Progress (BICC: CPG;
SIP-I: 183 Session Progress [CPG])

Backward

LCLS-Negotiation Response

O

This information element indicates the initial negotiation response.

LCLS-Configuration-Preference

C

This information element indicates the LCLS configuration preference while LCLS is established. This IE shall be included if the LCLS-Negotiation Response is included.

16.1.6 Change of LCLS Configuration

Table 16.1.6.1 indicates the LCLS related information which is exchanged between the MSC servers in the LCLS Configuration Change Request (BICC: APM or SIP-I: INFO request with encapsulated APM) messages.

Table 16.1.6.1: LCLS related information in the LCLS Configuration Change Request message

Message

Message direction

Information element name

Information element required

Information element description

LCLS Configuration Change Request (BICC: APM or SIP-I: INFO [APM]

Both

LCLS-Configuration-Change Request

M

This information element indicates a request to change the requested LCLS configuration preference.

LCLS-Configuration-Preference

M

This information element indicates the LCLS configuration preference to be changed to.

LCLS Configuration Change Request Acknowledge (BICC: APM or SIP-I: INFO [APM]

Both

LCLS-Configuration-Change Result

M

This information element indicates if the LCLS Configuration Change Request is accepted or not.

LCLS-Configuration-Preference

M

This information element has the same value as in LCLS Configuration Change Request.

16.1.7 LCLS Status update

Table 16.1.7.1 indicates the LCLS related information which is exchanged between the MSC servers in the LCLS Status update (BICC: APM or SIP-I: INFO request with encapsulated ISUP APM) message.

Table 16.1.7.1: LCLS related information in LCLS Status update message

Message

Message direction

Information element name

Information element required

Information element description

LCLS Status update

(BICC: APM or SIP-I: INFO [APM])

Both

LCLS-Status

M

This information element indicates the LCLS connection status. This information element shall be included when LCLS connection status has changed in the BSS.

16.1.8 Change of LCLS Status

Table 16.1.8.1 indicates the LCLS related information which is exchanged between the MSC servers in the LCLS Status Change Request (BICC: APM or SIP-I: INFO request with encapsulated ISUP APM) messages.

Table 16.1.8.1: LCLS related information in LCLS Status Change Request message

Message

Message direction

Information element name

Information element required

Information element description

LCLS Status Change Request (BICC: APM or SIP-I: INFO [APM])

Both

LCLS-Status-Change

M

This information element indicates a request to change the LCLS connection status in the BSS.

LCLS Status Change Request Acknowledge (BICC: APM or SIP-I: INFO [APM])

Both

LCLS-Status-Change

M

This information element has the same value as in the LCLS-Status-Change-Request message.

Result Code

M

This information element indicates if the LCLS Status Change request is accepted or not.
NOTE

NOTE: A request to break LCLS shall not be rejected.

16.1.9 MAP_PREPARE_HANDOVER Request

Table 16.1.9.1 indicates the LCLS related information which is exchanged between the Anchor MSC-Server and the Target MSC-Server (E-interface) in the MAP_PREPARE_HANDOVER Request message.

Table 16.1.9.1: LCLS related information in MAP-Prepare-Handover Request message

Message

Message direction

Information element name

Information element required

Information element description

MAP_PREPARE_HANDOVER Request

From Anchor MSC-Server to Target MSC-Server

LCLS GCR

C

This information element identifies the call. This information element shall be included when LCLS is supported in the core network.

LCLS-Negotiation Request

C

This information element indicates request for LCLS. This information element shall be included when LCLS is supported in the core network.

LCLS-Configuration-Preference

C

This information element indicates the LCLS configuration preference while LCLS is established. This information element shall be included when LCLS is supported in the core network.

16.2 Procedures between (G)MSC server and MGW

The (G)MSC server and MGW procedures shall be performed in accordance with 3GPP 23.205 [2] for a BICC based CS core network and in accordance with 3GPP TS 23.231 [3] for a SIP-I based CS core network.

16.3 Messages between MSC server and BSS

16.3.1 General

The procedures used on the Base Station System (BSS) to Mobile-services Switching Centre (MSC) interface for control of GSM services are specified in 3GPP TS 48.008 [7]. The LCLS related information exchanged in these procedures is specified below.

16.3.2 Assignment Procedure between MSC-Server and BSS

Table 16.3.2.1 indicates the LCLS related information which is exchanged between the MSC server and the BSS in the BSSMAP Assignment Procedure. Only the Information Elements required by LCLS are shown.

Table 16.3.2.1: LCLS related information in Assignment Procedure

Procedure

Message direction

Information element name

Information element required

Information element description

Assignment Request

From

MSC-S

Global Call Reference

C

This information element identifies the call. This information element shall be included if local switching is requested by the MSC server.

LCLS-Configuration

C

This information element indicates the LCLS connection preference which shall persist in the BSS while LCLS is established. This information element shall be included if local switching is requested by the MSC server.

LCLS-Connection-Status-Control

C

This information element indicates to BSS whether it is permitted to locally through-connect the call. This information element shall be included if local switching is requested by the MSC server and when the Assignment Request message is sent after Answer.

LCLS-Correlation-Not-Needed

O

This information element indicates to the BSS that call correlation is not needed.

This information element shall be sent if the MSC-Server has detected that the call is not an Intra-BSS call or an Intra-network call.

Assignment Complete

From BSS

LCLS-BSS-Status

C

This information element notifies CN of the LCLS connection status in the BSS. This information element shall be included if BSS supports LCLS and both Global Call Reference IE and LCLS-Configuration IE were included in the ASSIGNMENT REQUEST message.

16.3.3 Handover Request Procedure between MSC-Server and BSS

Table 16.3.3.1 indicates the LCLS related information, which is exchanged between the MSC server and the BSS in the BSSMAP Handover Request Procedure. Only the Information Elements required by LCLS are shown.

Table 16.3.3.1: LCLS related information in Handover Request Procedure

Procedure

Message direction

Information element name

Information element required

Information element description

Handover Request

From

MSC-S

Global Call Reference

C

This information element identifies the call. This information element shall be included if local switching is requested by the MSC server.

LCLS-Connection-Status-Control

C

This information element indicates to BSS whether it is permitted to locally through-connect the call. This information element shall be included if local switching is requested by the MSC server.

LCLS-Configuration

C

This information element indicates the LCLS connection preference which shall persist in the BSS while LCLS is established. This information element shall be included if local switching is requested by the MSC server.

Handover Request Ackknowledge

From BSS

LCLS-BSS-Status

C

This information element notifies CN of the LCLS connection status in the BSS. This information element shall be included if BSS supports LCLS and Global Call Reference IE, LCLS-Configuration IE and LCLS-Connection-Status-Control IE were included in the HANDOVER REQUEST message.

16.3.4 Handover Complete Procedure between MSC-Server and BSS

Table 16.3.4.1 indicates the LCLS related information, which is exchanged between the MSC server and the BSS in the BSSMAP Handover Complete Procedure. Only the Information Elements required by LCLS are shown.

Table 16.3.4.1: LCLS related information in Handover Request Procedure

Procedure

Message direction

Information element name

Information element required

Information element description

Handover Complete

From BSS

LCLS-BSS-Status

C

This information element notifies CN of the LCLS connection status in the BSS. This information element shall be included if BSS supports LCLS and if local switching was previously requested for this call leg by the MSC server.

16.3.5 Handover Performed Procedure between MSC-Server and BSS

Table 16.3.5.1 indicates the LCLS related information, which is exchanged between the MSC server and the BSS in the BSSMAP Handover Performed Procedure. Only the Information Elements required by LCLS are shown.

Table 16.3.5.1: LCLS related information in Handover Request Procedure

Procedure

Message direction

Information element name

Information element required

Information element description

Handover Performed

From BSS

LCLS-BSS-Status

C

This information element notifies CN of the LCLS connection status in the BSS. This information element shall be included if BSS supports LCLS and if local switching was previously requested for this call leg by the MSC server.

16.3.6 Internal Handover Command Procedure between MSC-Server and BSS

Table 16.3.6.1 indicates the LCLS related information, which is exchanged between the MSC server and the BSS in the BSSMAP Internal Handover Command Procedure. Only the Information Elements required by LCLS are shown.

Table 16.3.6.1: LCLS related information in Internal Handover Command Procedure

Procedure

Message direction

Information element name

Information element required

Information element description

Internal Handover Command

From

MSC-S

LCLS-Connection-Status-Control

C

This information element indicates to BSS whether it is permitted to locally through-connect the call. This information element shall be included if local switching is requested by the MSC server, and LCLS-Connection-Status-Control indicating "Connect" has not previously been sent to the BSS for this particular call leg.

16.3.7 LCLS Connection Procedure between MSC-Server and BSS

Table 16.3.7.1 indicates the LCLS Connection Procedure and related information, which is exchanged between the MSC server and the BSS. Only the Information Elements required by LCLS are shown.

Table 16.3.7.1: LCLS Connection Procedure between MSC-Server and BSS

Procedures

Message direction

Information element name

Information element required

Information element description

LCLS-Connect-Control

From

MSC-S

LCLS-Connection-Status-Control

O

This information element indicates to BSS whether it is permitted to locally through-connect the call.

LCLS-Configuration

O

This information element indicates the LCLS-Configuration.

LCLS Connect Control Ack

From BSS

LCLS-BSS-Status

M

This information element notifies CN of the LCLS connection status in the BSS.

16.3.8 LCLS Notification Procedure between MSC-Server and BSS

Table 16.3.8.1 indicates the LCLS Notification Procedure and related information, which is exchanged between the MSC server and the BSS. Only the Information Elements required by LCLS are shown.

Table 16.3.8.1: LCLS Notification Procedures between MSC-Server and BSS

Procedures

Message direction

Information element name

Information element required

Information element description

LCLS-Notification

From BSS

LCLS-BSS-Status

C

This information element notifies CN of the LCLS connection status in the BSS. This information element shall be included when BSS changes the LCLS connection status.

LCLS-Break-Request

C

This information element indicates if the LCLS break request is ordered from CN. This information element shall be included when BSS requests to disconnect local switching.

NOTE: Only one of those IE shall be present in the LCLS Notification message.