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Content for  TS 22.173  Word version:  17.3.0

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1  Scopep. 10

The present document define the IMS Multimedia Telephony service and the minimum set of capabilities required to secure multi-vendor and multi-operator inter-operability for Multimedia Telephony and related Supplementary Services.

2  Referencesp. 10

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, edition number, version number, etc.) 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.
TR 21.905: "Vocabulary for 3GPP Specifications".
[2]  (void)
[3]  (void)
TS 22.228: "IP multimedia (IM) CN subsystem, stage 1"
ITU-T Recommendation I.210: "Principles of telecommunication services supported by an ISDN and the means to describe them".
TS 22.041: "Operator Determined Barring (ODB)"
TS 24.173: " IMS Multimedia Telephony Communication Service and Supplementary Services; Stage 3"
TS 22.101: "Service principles".
TS 22.182: "Customized Alerting Tones (CAT) Requirements; Stage 1".
TS 22.183: "Customized Ringing Signal (CRS) Requirements; Stage 1".
ITU-T Recommendation F.703: "Multimedia Conversational Services".
TS 22.090: : "Unstructured Supplementary Service Data (USSD); Stage 1".
TS 22.001: "Principles of circuit telecommunication services supported by a Public Land Mobile Network (PLMN)".
TS 22.030: : " Man-Machine Interface (MMI) of the User Equipment (UE)".
ATIS 1000067.2015: "IP NGN Enhanced Calling Name (eCNAM)"
RFC 8224:  "Authenticated Identity Management in the Session Initiation Protocol (SIP)".
ATIS 1000074.2019: "Signature-based Handling of Asserted information using toKENs (SHAKEN)".

3  Definitions, symbols and abbreviationsp. 11

3.1  Definitionsp. 11

Caller Identity Analytics function:
A verification function that analyzes a large set of traffic data to identify fraud and caller identity spoofing trends and make risk recommendations about the originating telephone number based on trend analysis.
Block list:
List of identities or identity ranges that, for one reason or another, are being denied a particular service.
Spoofed call:
A call where caller identity creation, modification or removal in call signalling results in an unauthorized or illegal use of this identity in the call., This typically occurs where the caller intends to defraud the called user or otherwise illegally obscure the real caller identity.
Allow list:
List of identities or identity ranges that are provided particular services. Allow list is also named VIP list.

3.2  Symbolsp. 11


3.3  Abbreviationsp. 11

For the purposes of the present document, the abbreviations given in TR 21.905 and the following apply. An abbreviation defined in the present document takes precedence over the definition of the same abbreviation, if any, in TR 21.905.
Three Party
Anonymous Communication Rejection
Advice Of Charge - Charging
Advice Of Charge - During the communication
Advice Of Charge - at the End of the communication
Advice Of Charge - Information
Advice Of Charge - charging information at communication Set-up time
Customized Alerting Tone
Communication session Barring
Completion of Communication sessions to Busy Subscriber
Communication Deflection
Communication DIVersion
Communication Forwarding Busy
Communication Forwarding on Not Logged-in
Communication Forwarding No Reply
Communication Forwarding on Subscriber Not Reachable
Communication Forwarding Unconditional
COnnected Line identification Presentation
COnnected Line identification Restriction
Customized Ringing Signal
Circuit Switched
Closed User Group
Communication Waiting
Enhanced Calling Name
Explicit Communication Transfer
Flexible Alerting
Communication HOLD
Incoming Communications Barring
Malicious Communication IDentification
Message Waiting Indication
Outgoing Communications Barring
Originating Identification Presentation
Originating Identification Restriction
Public Safety Answer Point
Public User Identity
Signature-based Handling of Asserted information using toKENs
Secure Telephone Identity Revisited
Terminating Identification Presentation
Terminating Identification Restriction

4  Service descriptionp. 12

4.1  General Service characteristicsp. 12

The IMS Multimedia Telephony Service should allow multimedia conversational communications between two or more users. It provides real time bidirectional conversational transfer of speech, video or optionally other types of data.
The IMS Multimedia Telephony communication is point to point between terminals communicating, or a terminal and a network entity. This communication is usually symmetrical, but in special cases the media components present in each direction may be different, or they may be the same but with different bit rates and Quality of Service.
An IMS Multimedia Telephony communication can start with only one type of media and additional types of media may or may not be added by the users as the communication progress. Therefore a particular IMS Multimedia Telephony communication may consist of only one type of media, e.g. speech.
IMS Multimedia Telephony service is different from other IMS based services, such as Push to Talk over Cellular (PoC).
Its characteristics includes the following:
  • IMS Multimedia Telephony is a service where speech, and speech combined with other media components, is the typical usage but the service is not limited to always include speech, it also caters for other media or combinations of media (e.g. text and video).
  • The IMS multimedia telephony service includes supplementary services. The behaviour of these services is almost identical to supplementary services for CS voice (TS 11) and PSTN/ISDN.
  • The anticipated usage model is that of traditional telephony: one user connecting to any other user, regardless of operator and access technology.
  • When a supplementary service is invoked it applies to all media components of an IMS Multimedia Telephony communication. A supplementary service can be activated by the user for one or more types of media components. If one or more of these media components are present in the IMS Multimedia Telephony communication then the supplementary service is invoked.

4.2  Default media handling capabilities of IMS Multimedia Telephony servicep. 12

IMS Multimedia Telephony can support many different types of media.
IMS Multimedia Telephony service includes the following standardized media capabilities:
  • Full duplex speech;
  • Real time video (simplex, full duplex), synchronized with speech if present;
  • Real-Time Text communication;
  • File transfer;
  • Video clip sharing, picture sharing, audio clip sharing. Transferred files may be displayed/replayed on receiving terminal for specified file formats
  • Fax;
  • Data (CS).
The support of each of these media capabilities is optional for a UE.
At least one common standardized format (e.g. JPEG, AMR) shall be supported per media type.
The IMS Multimedia Telephony service shall support the following handling of media
  • Adding, removing and modifying individual media to/from an IMS Multimedia Telephony communication

4.3  Association of Services to Time/Date |R9|p. 13

As a service option, the activation, deactivation and invocation of services may be associated with a time and/or date setting. To support roaming, the time zone may also be included.

4.4  Additional timing information |R9|p. 13

As a service option, additional timing information on current active services may be made available by the network. The content of this information is service dependant.
As a service option, the user may be allowed dynamically extend this timing for the active communication.

4.5  Allow / block list |R9|p. 13

As service provider option, activation/deactivation/invocation services may be associated with a allow/block list. A list may be specific to a service or may be used by several services.

4.6  Multi-device and Multi-Identity |R16|p. 13

4.6.1  General |R17|p. 13

The support of multiple devices is inherent in IMS. In addition, a service provider may allow a user to use any public user identities for its outgoing and incoming calls. The added identities can but do not have to belong to the served user. Identities may be part of different subscriptions and different operators.
The owner (e.g. individual subscriber, operator/company) of the added identity needs to give its permission for others to use the identity.
The owner (e.g. individual subscriber, operator/company) of the identity shall be able to revoke the permission for others to use the identity.
A user shall be able to indicate which of the allowed identities the user wishes to use for each outgoing communication.
The network shall be able to indicate to the user which identity the incoming communication is intended to reach.
The network shall allow users to add and to delete identities asymmetrically, e.g. if an identity belonging to user B is allowed to be used by user A, this does not automatically mean that an identity belonging to user A is allowed to be used by user B.
Synchronization of communication logs between the multiple devices that are registered under the user identity shall be possible, e.g. the list of in- and outgoing calls, as well as when a missed call notification has been read on one device the other devices shall be updated so they are aligned.

4.6.2  User Configuration |R17|p. 14

The 3GPP System shall support a mechanism for an authorised user to set user preferences to indicate which identities are active or inactive on a specific UE
When an identity is activated or deactivated all UEs that can use that identity to either originate or terminate a session shall receive a notification of the change of status.

4.7  Caller Identity Verification Results Delivery to the User |R16|p. 14

The OIP service (including delivery of the calling name) and the eCNAM service deliver identity information based on information generated by the originating network (e.g., telephone number). Caller Identity Verification functions, such as Caller Identity Analytics functions at the terminating network, can modify the originating network's caller identity information in accordance with the terminating operator policy. The modified name is intended to provide information to the end user about the potential risks associated with the caller identity.
Full or partial name string modifications that result from or are performed by the Caller Identity Analytics function shall be delivered to the UE, according to local operator policy.
Example displays:
  • J. Smith
  • "SCAM?" J. Smith
This is primarily intended for situations where the existing device is unable to, otherwise, present new information to the user, such as spoofing indications.
The 3GPP system shall support a mechanism for a user to simply retrieve (e.g., to view or save) the full or partial name string delivered to the UE, including modifications that result from or are performed by the Caller Identity Analytics function.

5  Service Requirementsp. 14

General service requirements as specified for IMS services in TS 22.228 apply.

6  Quality of Servicep. 14

General QoS requirements as specified for IMS services in TS 22.228 apply.

7  Interworking requirementsp. 14

7.1  Interworking with CS domainp. 14

Standardisation of interworking between the IMS domain and the CS domain for multimedia telephony communications is provided as specified in TS 22.228.

7.2  Interworking with external networksp. 15

General interworking requirements with external networks as specified for IMS services in TS 22.228 apply.

7.3  Media Aspects on Interworking |R8|p. 15

End to end codec negotiation shall be supported. When the codec negotiation fails, transcoding should be provided as an operator option.
When transcoding applies, the quality degradation and additional latency due to decoding/encoding operation shall be minimized.
When the media plane is locally broken-out and/or locally broken-in within a visited network, the home network may instruct the visited network to perform transcoding.
To optimize the end-user experience, during the codec negotiation and subject to operator policy, a wideband codec should be preferred over a narrowband codec, subject to the capabilities of both ends.

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