Content for TS 24.173 Word version: 18.0.0

4.1 General 4.1A Roles 4.2 Overview of basic communication part 4.3 Overview of supplementary services part 5.1 IMS communication service identifier 5.2 Session control procedures 5.3 Interworking 5.4 Call progress indications
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4 Overview of multimedia telephony communication service and associated supplementary services in the IP Multimedia (IM) Core Network (CN) subsystem p. 10

4.1 General p. 10

In accordance with the service definition and requirements in TS 22.173, the IMS multimedia telephony communication service specified herein allows multimedia conversational communication between two or more end points. An end point is typically located in a UE, but can also be located in a network entity.

As for traditional circuit-switched telephony, the protocols for the IMS multimedia Telephony communication service allow a user to connect to any other user, regardless of operator and access technology.

The IMS multimedia Telephony communication service consists of two principal parts: a basic communication part, and an optional supplementary services part.

4.1A Roles p. 10

4.1A.1 Multimedia telephony participant p. 10

A UE shall implement the role of a multimedia telephony participant.

4.1A.2 Multimedia telephony application server p. 10

An application server shall implement the role of a multimedia telephony application server. Various application server usages are called out by references to the various supplementary services, see clause 4.3. It is an implementation decision on how to allocate the functionality to one or more application servers.

4.2 Overview of basic communication part p. 10

The basic communication part of an IMS multimedia telephony communication service session is realised by a single SIP session. It utilises media capabilities and flexibility provided by the SIP protocol and the 3GPP IMS specifications. In accordance with the service definition in TS 22.173, media capabilities include RTP-based transfer of voice, real-time video, real-time text and data, and UDPTL-based transfer of fax (RFC 3362), as well as TCP/MSRP-based transfer of text, arbitrary files and sharing of media files with predefined formats.

To ensure interoperability, media handling (including codecs and formats) is fully specified for RTP-based and MSRP-based transfer in:

TS 26.114 for 3GPP systems;
3GPP2 C.S0055-A [21] for 3GPP2 systems; and
ETSI TS 181 005 [22] (codecs) and TS 26.114 (formats and other media handling) for fixed-broadband accesses.

The service is highly dynamic in terms of media component usage: the protocols allow a communication session to start with one or more media components, and components can then be added and/or removed during the communication session. The protocols allow both one-way and two ways transfer between end points. Full duplex speech, and speech combined with other media components, are typical media cases but the protocols do not mandate the use of speech in all sessions.

4.3 Overview of supplementary services part p. 11

The supplementary services part of the IMS multimedia telephony communication service consists of a number of specified supplementary services. These are fully standardized to ensure interoperability between multiple end points, and between end points and network control entities. The behaviour of supplementary services is similar to supplementary services specified for CS speech (TS 11). Supplementary services uses SIP as enabling protocol. Configuration of supplementary services by the user should:

take place over the Ut interface using XCAP as enabling protocol as described in TS 24.623; or
use SIP based user configuration as described in TS 24.238 ;

The "SS_domain_setting" leaf in TS 24.167 provides a mechanism to:

instruct the UE to only use the PS domain for SS setting control;
instruct the UE to only use the CS domain for SS setting control; or
instruct the UE to use the PS domain for SS setting control when the PS domain is being used by the UE for voice services, and to use the CS domain for SS setting control when the CS domain is being used by the UE for voice services.

If one of the restrictions described in the bullets a) or c) applies, then the "PS_domain_IMS_SS_control_preference" leaf in TS 24.167 provides a mechanism to:

restrict the UE to use the Ut interface with XCAP as enabling protocol as described in TS 24.623; or
restrict the UE to use SIP based user configuration as described in TS 24.238.

5 Basic Communication p. 11

5.1 IMS communication service identifier p. 11

URN used to define the ICSI for the IMS Multimedia Telephony Communication Service:

urn:urn-7:3gpp-service.ims.icsi.mmtel. The URN is registered at http://www.3gpp.com/Uniform-Resource-Name-URN-list.html.

Summary of the URN:

This URN indicates that the device supports the IMS Multimedia Telephony Communication Service.

The URN is intended primarily for use in the following applications, protocols, services, or negotiation mechanisms:

This URN is most useful in a communications application, for describing the capabilities of a device, such as a phone or PDA.

Examples of typical use:

Indicating that a mobile phone can support the IMS Multimedia Telephony Communication Service.

5.2 Session control procedures p. 12

The IMS multimedia telephony communication service can support different types of media, including media types listed in TS 22.173. The session control procedures for the different media types shall be in accordance with TS 24.229 and TS 24.247, with the following additions:

Multimedia telephony is an IMS communication service and the P-Preferred-Service and P-Asserted-Service headers shall be treated as described in TS 24.229. The coding of the ICSI value in the P-Preferred-Service and P-Asserted-Service headers shall be according to clause 5.1.
The multimedia telephony participant shall include the "+g.3gpp. icsi-ref" header field parameter equal to the ICSI value defined in clause 5.1 in the Contact header field in initial requests and responses as described in TS 24.229.
The multimedia telephony participant shall include an Accept-Contact header field containing the "+g.3gpp.icsi-ref" header field parameter containing the ICSI value defined in clause 5.1 in initial requests. If the multimedia telephony participant supports the IMS data channel usage as specified in TS 26.114, then the multimedia telephony participant may include an Accept-Contact header field containing the "sip.app-subtype" media feature tag defined in RFC 5688 with a value of "webrtc-datachannel" in a request for a new dialog or standalone transaction. If the user requests capabilities other than multimedia telephony and IMS data channel, the Accept-Contact header field may contain other feature parameters and feature parameter values, and other Accept-Contact header fields may be added to express user preferences as per RFC 3841.

NOTE 1:
How the user indicates other feature parameters and the feature parameter values is outside of the scope of this document.
The multimedia telephony application server shall include the "+g.3gpp.icsi-ref" header field parameter equal to the ICSI value defined in clause 5.1 in a Feature-Caps header field in requests sent to the terminating user and in 1xx or 2xx responses to requests from the originating user as described in TS 24.229 and RFC 6809.
The multimedia telephony participant may use the presence of a "+g.3gpp.icsi-ref" header field parameter equal to the ICSI value defined in clause 5.1 in a Feature-Caps header field in requests and responses as described in RFC 6809 to determine that a multimedia telephony application server is participating in the session and multimedia telephony is the IMS communication service supported for use in the dialog.

NOTE 2:
ICSI values with subclass identifiers are considered equal to the value defined in clause 5.1 when determining that the multimedia telephony application server is participating in the session.
The multimedia telephony application server may insert a Response-Source header field in accordance with the procedures in clause 5.7.1.0 of TS 24.229, where the "role" header field parameter is set to "tas" when initiating a failure response to any received request.

5.3 Interworking p. 12

The multimedia telephony participant could receive initial requests that do not contain the ICSI value defined in clause 5.1 in the Accept-Contact header but still invoke the IMS multimedia telephony communication service application.

5.4 Call progress indications |R14| p. 12

The UE shall support the UE procedures specified in TS 24.628.

6 Supplementary services and enhancements p. 13

6.1 High level requirements p. 13

Actions by an application server in support of supplementary services related to an MPS priority session should be given priority treatment.

Content for TS 24.173 Word version: 18.0.0

4 Overview of multimedia telephony communication service and associated supplementary services in the IP Multimedia (IM) Core Network (CN) subsystem p. 10

4.1 General p. 10

4.1A Roles p. 10

4.1A.1 Multimedia telephony participant p. 10

4.1A.2 Multimedia telephony application server p. 10

4.2 Overview of basic communication part p. 10

4.3 Overview of supplementary services part p. 11

5 Basic Communication p. 11

5.1 IMS communication service identifier p. 11

5.2 Session control procedures p. 12

5.3 Interworking p. 12

5.4 Call progress indications |R14| p. 12

6 Supplementary services and enhancements p. 13

6.1 High level requirements p. 13

6.2 Originating Identification Presentation (OIP) p. 13

6.3 Originating Identification Restriction (OIR) p. 13

6.4 Terminating Identification Presentation (TIP) p. 13

6.5 Terminating Identification Restriction (TIR) p. 13

6.6 Communication Diversion (CDIV) p. 13

6.7 Communication Hold (HOLD) p. 13

6.8 Communication Barring (CB) p. 13

6.9 Message Waiting Indication (MWI) p. 13

6.10 Conference (CONF) p. 13

6.11 Explicit Communication Transfer (ECT) p. 13

6.12 XCAP over Ut interface for Manipulating NGN Services p. 14

6.13 Advice Of Charge (AOC) |R8| p. 14

6.14 Closed User Groups (CUG) |R8| p. 14

6.15 Three-Party (3PTY) |R8| p. 14

6.16 Flexible Alerting (FA) |R8| p. 14

6.17 Communication Waiting (CW) |R8| p. 14

6.18 Completion of Communications to Busy Subscriber (CCBS) Completion of Communications by No Reply (CCNR) |R8| p. 14

6.19 Customized Alerting Tones (CAT) |R8| p. 14

6.20 Customized Ringing Signal (CRS) |R9| p. 14

6.21 Personal Network Management (PNM) |R11| p. 14

6.22 Unstructured Supplementary Service Data (USSD) |R11| p. 14

6.23 Enhanced Calling Name (eCNAM) |R15| p. 15

6.24 Multi-Device and Multi-Identity (MuD/MiD) |R16| p. 15