Content for TS 23.172 Word version: 18.0.0

1… 4… 4.2.2… 4.2.3 4.2.4 4.2.5… 4.2.5.2 4.3… 4.3.2… 4.3.3… 4.3.3.1.3 4.3.3.1.4 4.3.3.1a… 4.3.4 4.3.5… 4.3.5.2 4.3.6…

1 Scope p. 6

The present document describes the Service Change and UDI Fallback (SCUDIF) feature. This service is available to UDI/RDI multimedia calls and allows users to achieve successful call establishment when end to end circuit-switched (CS) multimedia is not possible (fallback to speech) or when signalling of the feature is not possible in the network (fallback to preferred service or speech). Furthermore, it allows the users to swap between a multimedia service and basic speech during an established call.

2 References p. 6

The following documents contain provisions, which, through reference in this text, constitute provisions of the present document.

References are either specific (identified by date of publication and/or edition number or version number) or non-specific.
For a specific reference, subsequent revisions do not apply.
For a non-specific reference, the latest version applies. In the case of a reference to a 3GPP document (including a GSM document), a non-specific reference implicitly refers to the latest version of that document in the same Release as the present document.

[1]

TR 21.905: "Vocabulary for 3GPP Specifications".

[2]

TS 23.153: "Out of Band Transcoder Control; Stage 2".

[3]

TS 24.008: "Mobile Radio Interface Layer 3 specification; Core network protocols; Stage 3".

[4]

TS 26.103: "Speech Codec List for GSM and UMTS".

[5]

TS 27.001: "General on Terminal Adaptation Functions (TAF) for Mobile Stations (MS)".

[6]

TS 29.007: "General requirements on interworking between the Public Land Mobile Network (PLMN) and the Integrated Services Digital Network (ISDN) or Public Switched Telephone Network (PSTN)".

[7]

TS 29.205: "Application of Q.1900 series to bearer-independent circuit-switched core network architecture; Stage 3".

[8]

TS 22.101: "Service aspects; Service principles".

[9]

TS 33.106: "3GPP Security; Lawful Interception Requirements".

[10]

TS 23.018: "Basic Call Handling; Technical realization".

[11]

TS 23.003: "Numbering, adressing and identification".

[12]

TS 29.232: "Media Gateway Controller (MGC) - Media Gateway (MGW) Interface; Stage 3".

[13]

TS 26.102: "Mandatory Speech Codec; AMR Speech Codec; Interface to Iu, Uu, Nb".

[14]

TS 23.078: "Customised Applications for Mobile network Enhanced Logic (CAMEL) ; Stage 2".

[15]

TS 23.082: "Call Forwarding (CF) supplementary services, Stage 2".

[16]

TS 22.078: "Customised Applications for Mobile network Enhanced Logic (CAMEL); Service description, Stage 1".

[17]

TS 25.413: "UTRAN Iu interface RANAP signalling".

[18]

RFC 4040: "RTP Payload Format for a 64 kbit/s Transparent Call"

3 Definitions and abbreviations p. 7

3.1 Definitions p. 7

For the purposes of the present document, the terms and definitions given in TR 21.905 and the following apply:

fallback:

when two services (multimedia and speech) are proposed but only one of them is available or wanted, only the service available (preferred or less preferred) is selected, and the other one is discarded

service change:

when two services (multimedia and speech) are available during the active state of a call, users may request a service change to switch between the two services

3.2 Abbreviations p. 7

For the purposes of the present document, the abbreviations given in TR 21.905 and the following apply:

Bearer Capability

BC1

First Bearer Capability in a message (preferred service)

BC2

Second Bearer Capability in a message (less preferred service)

BCa

Bearer Capability of the currently selected service

BCb

Bearer Capability of the service to switch to

BCmm

Bearer Capability multimedia

BCSM

Basic Call State Model

BCsp

Bearer Capability speech

CAMEL

Customised Applications for Mobile network Enhanced Logic

Detection Point

Information Element

MMI

Man-Machine Interface

O-MSC

Originating MSC

OoBTC

Out-of-Band Transcoder Control

O-UE

Originating UE

Repeat Indicator

SCUDIF

Service Change and UDI/RDI Fallback

T-MSC

Terminating MSC

T-UE

Terminating UE